Engineering Appendix
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4.0 STRUCTURAL PROJECT FEATURES
4.1 Houma Navigation Canal Lock
4.1.1 Geotechnical
Introduction. This is a summary of the soils investigation and foundation design for the Houma Navigation Canal (HNC) Lock presented in Volume 18. The lock consists of two float-in concrete gravity structures with concrete pile chamber guard walls and tie-in walls. Two alternative gate widths were considered (110 and 200 feet). The foundation design is presented for both alternatives.
Geotechnical Exploration. Available borings were obtained from an A-E soils report entitled "Subsoil Investigation, Houma Navigation Canal Locks, Terrebonne Parish, Louisiana" by Gillen Geotech, Inc. of Metairie, Louisiana, dated January 13,1993. This report was prepared in cooperation with South Terrebonne Tidewater Management & Conservation District for Coastal Engineering and Environmental Consultants, Inc. Fifty-eight (58) 3-inch diameter undisturbed borings were taken to depths ranging from 60 feet to 140 feet below the water surface. Volume 18 shows the location of the borings and the boring logs from the referenced report. They were taken north of the proposed site at a previously considered site. The borings are not within the currently proposed footprint of the lock structure. Site specific boring and testing would be performed in the detailed design phase.
General Geology in the Area of the Lock. Refer to Paragraph 1.4 of this summary report for the general geology of this area. More specific geology information at the lock site is given in Volume 18.
Laboratory Tests. The soil report contained laboratory tests used to classify and determine the physical properties of the soils. Tests presented include Unconfined Compression tests, Unit Densities, Moisture Contents, Atterberg Limits (liquid and plastic), One Point Triaxial (UU) tests and Consolidation tests. The test results are available in Volume 18.
Foundation Conditions. Generalized soil profiles for the lock site and detail descriptions of the foundation conditions are available in Volume 18.
Design Shear Strengths. Using very limited shear testing from the off site borings and ground surface elevations from surveys in the vicinity of the off site borings, design shear strength parameters for the lock design were determined and are shown in Volume 18. The current proposed lock site is located south of the boring locations. The boring information shows a difference between the soil parameters at the north end and at the south end of the boring layout. Therefore the borings located to the south end of the boring layout were used in this study. Also, using the very limited shear testing, design shear strength parameters for the design of the closure dam on Bayou Grand Caillou were determined and are also shown in Volume 18.
Design Analyses. Typical geotechnical analyses were performed for the lock structure and dam embankment.
Stability. The maximum excavation slope and the stability of the concrete gravity structures were determined by the LMVD Method of Planes using the design "Q" shear strengths. A Still Water Level (SWL) of el. +10.0 ft NGVD on the gulf side and el. –1.0 ft NGVD in the chamber was used as the critical hydraulic loading in the stability analysis of the concrete gravity structure. The minimum required factors-of-safety used with respect to the design shear strengths were 1.3 for the excavation slope and 1.5 for the concrete gravity structure. Since the two concrete gravity structures are the same and the south structure has the greatest hydraulic loading, only the south structure was analyzed. The excavation slope analysis and the structure stability analysis is presented in Volume 18. The design mix material to be placed beneath the gravity structures will be designed to give a minimum shear strength of 250 psf for the 200 ft. wide gate structure and 280 psf for the 110 ft. wide gate structure. The stability of the closure dam in Bayou Grand Caillou was determined by the LMVD Method of Planes using the design "Q" shear strengths and a water level of el. +6.0 ft NGVD on one side and el. –1.0 ft NGVD on the other as the critical hydraulic loading. This hydraulic loading can occur to either side of the closure dam. The closure dam stability analysis is presented in Volume 18.
Cantilever Concrete Chamber Guard Walls. The required penetration for the stability of the cantilevered concrete chamber guard walls was determined by the computer program "CWALSHT" using classical soil mechanics procedures. The critical case for the wall design was using the "Q" case design channel shear strengths and a factor-of-safety of 1.5 applied with respect to those shear strengths. The hydraulic loading for the wall was water at el. -1.0 ft NGVD in the chamber and el. +6.0 ft NGVD on the backside. Also, the wall will be subject to the same reverse water elevations and an impact load of 3.9 Kips/foot. A 3-foot high by 10-foot wide riprap berm was added to the backside to give approximately the same design tip for both analyses. The results of these two analyses are furnished in Volume 18.
Braced Concrete Tie-in Walls. The concrete tie-in wall will be braced with batter piles on the protected side. The required penetration and brace force for the stability of the braced concrete tie-in walls were determined by the computer program "CWALSHT" using classical soil mechanics procedures. The critical case for the wall design was using the "Q" case design channel shear strengths for a factor-of-safety of 1.25 applied with respect to those shear strengths for the wave load case. The hydraulic loading for the wall was water to el. +10.0 ft. NGVD with a wave force acting at el. -5.8 ft NGVD on the gulf side and el. -1.0 ft NGVD on the backside. For the reverse load case, the wall was designed using the "Q" case design channel shear strengths for a factor-of-safety of 1.5 applied with respect to those shear strengths. The hydraulic loading for this case was water to el. –1.0 ft NGVD on the gulf side and el. +6.0 ft NGVD on the backside. Riprap berms on both sides of the concrete tie-in wall were used to give approximately the same tip elevation. The results of these two analyses are furnished in Volume 18.
Pile Capacity. Ultimate compression and tension pile capacities versus tip elevation were developed for 24-inch diameter pipe piles. These piles are to be used as braces for the concrete tie-in walls. Tip elevations for cost estimating purposes are based on applying a factor-of safety of 3.0 if no pile test is to be performed and 2.0 with a pile test. The results are presented in Volume 18.
Bearing Capacity for Concrete Gravity Structures. The allowable bearing capacity for the concrete gravity structures was determined using procedures presented in the design manual "Soil Mechanics, Foundations, and Earth Structures" - NAVFAC DM-7 dated May 1982. The allowable bearing capacity was determined for both the unbackfilled and backfilled conditions. The allowable bearing capacity for the unbackfilled condition is 629 psf and for the backfilled condition is 879 psf. The calculations are presented in Volume 18.
Settlement of the Concrete Gravity Structures. The concrete gravity structures will be placed in excavations to el. –40.0 ft NGVD. This excavation will be removing at least 890 psf of overburden pressure (see soil parameter plates in Volume 18). The normal bearing pressure from the structure will be between 400 to 500 psf. Due to the fact that the in-situ soil pressure to be removed is much greater than the normal structure bearing pressure, no significant settlement of the concrete gravity structure is expected.
Seepage.
Concrete Gravity Structures. Seepage was checked beneath the south structure because it will be subjected to greater hydraulic loading (Still Water Level of el. +10.0 ft NGVD on the gulf side and el. –1.0 ft NGVD in the chamber). Seepage was checked using Lane’s Weighted Creep Ratio Method. The results are shown in Volume 18. A sheetpile cutoff wall will be placed on the gulf side to help control seepage and for scour protection.
Tie-in walls. The design tip of the concrete tie-in walls is el. -104.8 ft NGVD. The foundation is all clay. By inspection seepage is not a problem.
Dewatering. There is no requirement for dewatering with the float-in type structure.
Recommendations. Future geotechnical analysis should focus on obtaining complete soil data and surveys that give adequate knowledge of the structure sites. More in-depth investigation is needed to provide adequate structural foundation and dam embankment analyses.
4.1.2 Structural Design
Introduction. The purpose of the Houma Navigation Canal (HNC) lock is twofold. Its primary purpose is to provide hurricane protection, while minimizing impacts to the navigation industry. Salinity control is a secondary benefit of the lock. The proposed lock will have a usable length of 1,200 feet with a clear width opening of 200 feet and a sill elevation of –20 feet NGVD. The structure consists of two single gate bays, each with a set of sector gates, based upon a traditional Corps of Engineers configuration. The gate bays will be separated by a dewatering chamber. Several possibilities have been considered for the dewatering chamber that include, but are not limited to: an earthen chamber; a conventional U-frame; pile supported inverted T-walls with sheetpile cutoff that would form the chamber walls and would be separated by a chamber bottom consisting of rip-rap; and a continuous line of octagonal concrete piles driven to form the chamber walls which again would be separated by a chamber bottom consisting rip-rap. The southern set of the lock’s sector gates would be constructed to a hurricane protection elevation of +15.0 feet NGVD and would tie-in to the adjacent hurricane protection system whereas the northern set of the lock’s sector gates would be constructed to elevation +8.0 ft NGVD. If a storm moves inland and the floodside water falls to a lower elevation than the interior water, the gates would be opened to release water and prevent flooding due to interior drainage.
A summary of the feasibility design considerations for construction of the Houma Navigation Canal Lock is presented. The geotechnical conditions used for this study are site specific, and the cost estimates reflect the feasibility level designs for the lock. Sample feasibility level design calculations for the Houma Navigation Canal Lock are presented in Volume 18.
This study presents two design variations that are referred to as cast-in place and float-in. The float-in structure design consists of float-in prestressed/post-tensioned segmental concrete gate bay structures on pile foundations. The cast-in place alternative consists of conventionally reinforced concrete pile supported gate bay structures constructed within a dewatered cofferdam. The steel sector gate designs are essentially identical for each alternative with only minor differences between the northern and southern sets of gates.
Site Description. The HNC is a man-made navigation channel constructed in 1961 that provides direct access to the Gulf of Mexico from the Gulf Intracoastal Waterway at Houma, Louisiana. The locks would be installed in the HNC approximately 3,000 feet south of its intersection with Bayou Grand Caillou, in Terrebonne Parish, Louisiana.
Navigation During Construction
Cast-In Place Structure. The cast-in place design utilizes a large cofferdam and dewatering system, and would require excavation of a temporary by-pass channel on the west side of the existing Houma Navigation Channel during construction in order to maintain navigation. The cofferdam would allow construction of the lock to take place using in-the-dry conventional methods. Typically, a temporary timber guide wall will be required to protect the cofferdam from impact and as an aid to navigation during construction.
Float-In Structure. The float-in alternative will not utilize a cofferdam. The concrete gate bay structures are constructed at off-site graving yards and towed to the site. Other features are installed in the channel bottom using in-the-wet construction techniques. Construction of the foundation will be staged to allow for maintaining a minimum width for navigation where possible. The channel may be widened or a temporary bypass channel may need to be provided on the west side of the existing channel, in order to maintain acceptable navigation during construction. If a bypass channel is not needed, reduced power will be required for vessels passing through the construction area. This will minimize any damage to the prepared foundation. A navigation closure period will be required for positioning and sinking of the lower hull section and during various subsequent construction work items. Once the structure has been completed to a level that provides adequate stability, navigation could pass during certain times during each day until construction is completed.
Structural Design of Concrete Lock Monoliths
General. The cast in place and float-in structure alternatives, sector gates and the floodwall tie-ins were designed to a level that demonstrates feasibility. Detailed design will be presented in a future Design Report. Miscellaneous structures including control houses, guidewalls, dolphins and cut-off walls were based on existing structures.
Design References
The following list of design references were used as general guidance to formulate design criteria for the design features:
1. EM 1110-2-2200 Gravity Dam Design 2. ETL 1110-2-256 Sliding Stability for Concrete Structures 3. ETL 1110-2-307 Flotation Stability Criteria for Concrete Hydraulic Structures 4. EM 1110-2-2502 Retaining and Floodwalls 5. EM 1110-2-2703 Lock Gates and Operation Equipment 6. ETL 1110-2-338 Barge Impact Analysis 7. EM 1110-2-2104 Strength Design for Reinforced Concrete Hydraulic Structures 8. EM 1110-2-2906 Design of Pile Foundations 9. EC 1110-2-291 Stability Analysis of Concrete Structures 10. Draft EC 1110-2-XXXX Structural Design of Precast and Prestressed Hydraulic Concrete Structures 11. Prestressed Concrete Institute, PCI Design Handbook, Third Edition. 12. ACI Committee 357, ACI 357.2R-88 State-of-the-Art Report on Barge-Like Concrete Structures 13. Gerwick, Ben C., Jr., International Experience in the Performance of Marine Concrete 14. Morganza to the Gulf Feasibility Study, Flood Gate Structures Bush Canal, St. Paul District, September 10, 1999
The above references and the preliminary designs presented herein should not be taken as establishing standard Corps design criteria or construction details. Future assessment and refinement of these designs is planned, but costs are not expected to change appreciably. Design criteria for the sector gate design is discussed separately in Section 2.4.5.
Float–In Structure Alternative
Float-In Structure Design Criteria. Design criteria for the float in design was taken primarily from references 10 through 13 above. The float-in designs include in-the-wet construction, prestressed/post-tensioned concrete and lightweight concrete in marine environments. Criteria are being developed through the Innovations for Navigation Projects Research Program (INP) concurrent with the Corps’ ongoing design efforts. A portion of the information has been developed in the concrete and offshore industry codes. Designs with both normal and light concrete were included in this study for the float in design. The evaluation focused on the effects of weight on draft, floatation stability, and structural considerations. An evaluation of findings regarding suitability or durability of lightweight concrete could not be incorporated into this report. Final determination as to the suitability of lightweight concrete and specific mixes to be used will be addressed by a separate concrete materials design report in the detailed design phase.
a In-the-wet construction. In-the-wet construction has been used for years in the offshore industry and is addressed by the American Concrete Institute. The proposed in-the-wet construction design is based on draft INP recommendations, typical designs and details that were borrowed from the offshore industry. b Transportation Loading. In accordance with reference 10 above, the float-in module is designed for loads encountered during float-in. In accordance with reference 10 and 12 above, three buoyancy conditions are considered: still water level condition (SWL), hogging wave condition, and a sagging wave condition. The design approach generally followed guidance outlined in references 10 and 12 above. In preliminary design, longitudinal hull loads were used for initial sizing of the hull. Longitudinal, transverse and torsional loads should be considered in final designs. c Strength and Serviceability. Strength is based on prestressed/post tension design approach. The ultimate strength requirements were based on load factors from reference 10 above. Load factors are given specifically for float-in type designs. In a marine environment, minimizing or eliminating concrete tensile stress during float-in to improve durability should be a design consideration. d Prestressed/Post Tensioned Concrete Design. The use of prestressed/post-tensioned concrete has existed for float-in type structures since the early 1980’s (Gerwick, 1990). Ultimate strength design was in accordance with reference 11 above and used load factors from reference 10. The floodgate structures are located in a waterway with varying salinity. Allowable stresses considering cracking and cover are important issues.
Float-In Structure Design Features
1 General. The lock’s float-in gate bay structures consist of a float-in precast prestressed/post-tensioned concrete structure with integral wingwalls that will be founded on piles. The concrete structure contains three major features: float-in module, upper wing walls and in-fill concrete. The float-in module includes the lower hull and the lower portion of the wingwalls. The preliminary overall dimensions for each of the float-in gate bay modules is expected to be approximately 435 feet wide by 159 feet long by 20 feet deep.
The float-in modules and upper wing walls are constructed off site in a graving yard. Concurrent with the construction in the graving yard, battered bearing piles will be driven in-the wet and cut off underwater at the proper elevation. Once completed, the lower section is floated to the site and sunk on to landing pads. Hydraulic flat jacks are installed on each landing pad for positioning. Tension piles are then driven through ports formed into the lower hull section. Sheet pile cut-off walls are driven and a temporary skirt is installed to confine underbase concrete. Underbase tremie concrete is placed to provide a seal between the structure and founding soils. It also transfers bearing loads between the structure and the battered piles. Underbase concrete reinforcing and shear transfer should be evaluated during future design phases.
Each gate bay monolith is subdivided into precast concrete panels that are tied together with cast-in-place closure pours. The precast panels are prestressed to resist handling loads and contain conventional reinforcement and post-tensioning ducts. The closure pours are sized to allow adequate room for tie-in reinforcement, post-tensioning ducts and limit reinforcement congestion to ensure concrete consolidation. The lower hull or base slab is continuously post-tensioned after assembly of the precast concrete panels.2 Transportation Design. The lower hull was designed as a prestressed/post-tensioned concrete barge to resist transportation loading. Draft analysis, still water and hogging wave stress analysis were performed. Due to the load distribution in the lower hull, sagging wave stresses will not be a concern. The draft requirement was set at 8 foot maximum. The draft requirements should be verified during future design stages. Temporary auxiliary buoyancy could be used to reduce the draft by 1 to 2 feet, if required. A simple floatation stability was performed as outlined in the Draft EC, Design of Precast and Prestressed Hydraulic Concrete Structures. The large ratio of hull width to draft depth ensures that overall floatation stability will not be a problem. 3 Erection Design. Erection loading includes installation of float-in or lift-in modules and other construction loading. Feasibility of the set down condition was evaluated. The setting load condition addresses the sinking of the lower hull onto the prepared foundation. Temporary pile founded landing pads are required to position the lower hull prior to concreting the base. Landing pads were designed for a set down load that included a 5 percent negative buoyancy load plus the added load when the water elevation drops two feet. 4 Final Configuration Loading. In the final configuration, each load case was analyzed for vertical, lateral, overturning and flotation stability. Vertical resultants for each load case were shown to act through the kern. Vertical tension piles minimized the infill concrete needed in the wing walls to reduce slab moments. The vertical tension piles provided the necessary resistance against flotation. A pile foundation was designed in accordance with EM 1110-2-2906, Design of Pile Foundations. The layout was based on 24 inch diameter steel pipe piles with a design compression capacity of 135 kips. The capacity was based on a factor of safety of 2, which will require pile testing. The dewatered case required tension piles to achieve the 1.3 floatation factor of safety. The tension piles were 24-inch diameter steel pipe piles with a design tension capacity of 102 kips using a factor of safety of 1.5. The bearing piles are battered in both directions to resist lateral movement and modeled as pinned to the base slab. The tension piles are vertical and extend into the base slab and were modeled as fixed. The lower hull is in-filled with a sand lightweight concrete for ballast, which forms the base slab in the final configuration. The in-fill concrete was designed to act as dead load only and not as a structural composite. The uniform pile layout was modeled as an average uniform bearing load evenly distributed under the base. Longitudinal moments and shears were calculated to check sizing of the base slab and post-tension requirements.
Cast-In-Place Structure Alternative
Cast-In-Place Design Criteria
Design criteria for the cast in place design was taken primarily from references 1 through 11 above. The casts in place designs incorporate conventional normal weight reinforced concrete.
Cast-In-Place Structure Design Features
a General. The cast-in-place lock structure consists of cast-in-place concrete founded on bearing piles. The structure is designed monolithically on a continuous mat foundation. Floodwalls will extend from the southern gate bay monolith to the adjacent hurricane protection levee system, maintaining the top of structure elevation. b Construction. Prior to construction of the lock, a by-pass channel would be established on the west side of the proposed lock and construction of a cofferdam would be completed. Once the site is prepared, prestressed concrete piles would be driven. Alternate rows will be battered in alternate directions parallel with the channel. The piles will be imbedded in the concrete mat with steel anchors. After installation of the piles, a reinforced concrete base slab will be cast in place. Reinforced concrete wing walls will be formed on the base slab. The walls are supported by the heavy gate anchorage abutments and intermediate wall buttresses.
Structural Design Loads and Design Data
The float-in and cast-in-place lock structures were designed for the following load cases:
a Transportation Loading. (Float-in Design only) The lower hull for each of the lock’s gate bay structures was designed as a prestressed/post-tensioned concrete barge to resist transportation loading. Draft analysis, still water and hogging wave stress analyses were performed. Due to the load distribution in the lower hull, sagging wave stresses will not be a concern. Each of the concrete lock gate bay float-in structures will draw approximately 15 feet of water (with sector gates and machinery installed). The wave loading assumes that the concrete float-in structure will only be transported within the intracoastal water system. The loading considered two cases: 1. Still water condition with no waves and 2. Hogging waves of 3 feet in height and a period equal to the full length of the floating structure. b Final Configuration (Cast-In and Float-In Designs): The following hydraulic data presents the water elevations.
Water Surface Elevation (NGVD) Load Case Flood Side Protected Side SWL/Wave Height SWL Hurricane, Maximum Head w/o Wave 15.0 3.0 Maximum Reverse Head from Hurricane -2.0 2.0 Operating, Maximum Direct Head 3.0 -1.0 Operating, Reverse Head -1.0 4.0 Hurricane, Maximum Head with Wave 11.0/9.4 -1.0 Maintenance Condition, Dewatered 6.0 6.0
Design data for the structures are listed below:
Typical Flood Gate Structure Elevations (NGVD) Top of Floodgate Structures 15 ft Top of Sector Gates 15 ft Gate Sill -20 ft Top of Guide Walls 15 ft
Sector Gate Design
General. Two movable sector gates are required for each of the lock’s two gate bay structures. Each sector gate consists of three basic parts: An arc-shaped steel damming surface, a pintle, hinge or pivot pin, and the steel framework that connects and transfers water loads between them. The total lock width clear opening width is 200 feet. The sector gates each have a radius of 118 feet- 4 inches.
References. The applicable sections of the following references were used to formulate design criteria for the various structural components.
a EM 1110-2-2105, Design of Hydraulic Steel Structures (March, 1993). b EM 1110-2-2703, Lock Gates and Operating Equipment (June, 1994). c EM 1110-1-2101, Working Stresses for Structural Design (November, 1963) d AISC, Manual of Steel Construction, Allowable Stress Design, Eighth Edition
Sector Gate Configuration and Construction. The sector gates are all steel, welded structures, with the exception of some mechanical parts and timber fenders. Construction of the sector gates will incorporate standard steel fabrication methods. The arc shaped gate damming surface is a hollow steel box structure with watertight ballast compartments. The buoyancy of the sector gates will be controlled by providing a permanent pumping system that will be capable of mitigating any unexpected loss of buoyancy. The operable ballast compartments will be accessible from vertical hatches on the upper deck, in order to facilitate their inspections. The framing for the gates consists of two horizontal frames located roughly at quarter points on the box beam consisting of welded steel tubing. However, the gate design and geometry will be refined and optimized in the detailed design phase. Variations in interior angle, radius and configuration of interior frame members will be investigated. The sector gates’ tube members will be sealed at intersections with welded internal diaphragms to create multiple watertight compartments. External corrosion protection would be achieved by a paint system supplemented by a sacrificial anode cathodic protection system. Internal corrosion protection for the structural tubes would be accomplished by a two step internal treatment of the tubes. The first step will involve flushing the pipes with a degreasing solution, and the second step consists of treating the members with an environmentally approved "floc" coating. Inspection plugs will be provided for internal inspection of buoyant members. Additional buoyancy can be provided by the gate’s supporting tube framework and by a trim compensating tank located near the hub. The size and location of buoyancy features will be determined concurrently with the final design of the gate. The buoyancy will reduce wear and stress on the sector gate, pivot bearing, and associated gate machinery. The sector gate and associated machinery will, however, be designed to demonstrate normal functioning without supporting buoyancy, in case of an emergency.
Sector Gate Design Criteria. The general layout and design of the sector gates was conducted using the criteria of EM 1110-2-2703, Lock Gates and Operating Equipment. EM 1110-2-2105 states that allowable stress design shall be conducted using 83% of the stresses determined from the AISC allowable stress design method. The actual loading considered five load cases as listed below.
CASE DESCRIPTION 1 Maximum Direct Head from Hurricane 2 Maximum Reverse Head from Hurricane 3 Operating, Maximum Direct Head 4 Operating, Reverse Head 5 Maximum Direct Head from Hurricane
In addition to the loading cases listed above, EM 1110-2-2703 requires that a 125 kip boat impact load be applied as a point load on the horizontal beams supporting the gate face and at any panel point on the canal side of the gate framing. Another loading considered in the sector gate design was the closing torque on the gate when it is operated under reverse head. Forces in the gate hinge and anchorage were determined from the gate reactions
Floodwall and Miscellaneous Structures
a Floodwalls. The floodwalls extend from the lock structure to the levee system. The walls were designed as standard sheet pile walls, braced by walers, that transfer the lateral loads into the battered bearing piles b Control and Machinery Houses. A control house is provided to shelter the lock control systems and to provide space for lock operating personnel, as required. A machinery house is provided to shelter the lock machinery from the weather. While the control and machinery houses have not yet been designed, cost estimates for these structures were based upon historical data from similar structures. c Guide walls and Dolphins. Guide walls and dolphins are provided as aids to navigation and to protect the main flood lock structure from impact. The structure designs, wall lengths and cost estimates were based on similar projects. d Cut-Off Walls. A cut-off wall is provided on the flood side of the structure to reduce possible seepage, scouring and reduce uplift. PZ 22 sheet pile sections have been assumed for use in the cut-off walls, and should extend down to the same elevation as those used for the adjacent flood walls.
4.1.3 Mechanical Design
Gate Operation. Gate operation will be two speeds with a time dependent 1 to 4 second speed ramp at start, stop and speed changes. The dual speed and speed ramp will be accomplished electronically by way of a hydraulic proportional valve. A slow gate speed of 3.5 degrees per minute will be used for heads over 1/2 foot and a high speed of 30 degrees per minute will be used for heads of less than 0.5 feet. As with all other sector gates in NOD, the lock operator will open the gates a small amount that permits filling or emptying the chamber without producing undue hawser forces. Once the heads are equalized to within 1/2 foot, the gates will then be fully opened.
Gate Operating Machinery. The gate operating machinery will be a rack and pinion gear drive. The rack will be attached to the gate along the outside radius of the gate's skin plate. A pinion drive gear will be attached to a low speed high torque hydraulic (LSHT) motor mounted on the lock wall. In order to provide clearance, between the LSHT motor and gate, an idler gear will be used. The idler gear has a 29" pitch diameter and the drive pinion has a pitch diameter of 21". A the Series 64 Hagglunds LSHT hydraulic motor operating at 2500 psi was used for design purposes. Arranged in this configuration, the motor can provide a tangential force at the rack of 36,300 lbs. with a differential pressure across the motor of 2500 psi. It is anticipated that between 25,000 and 30,000 lbs. of tangential rack force will be required. Each gate will be equipped with its own hydraulic power supply. The hydraulic power supply for the motor will consist of a variable delivery pressure compensated pump driven by an electric motor. The electric motor will be either 25 or 30 horsepower. A second smaller motor and pump will be provided as an auxiliary supply. The gate operating machinery is shown on Plates M-3 and M-4.
Water System. A water system will be provided for small fires, (i.e. guide wall fire) and for general wash down. The system shall consist of a single 15 horsepower motor driven pump with an operating pressure of 100 psi at 50 gpm. Hose reels with 100' hoses will be placed near each gate bay and at 200-foot increments along the lock walls.
4.1.4 Electrical Design
General
a Scope. The design for the lock includes provisions for power, control, lighting, emergency power and grounding. b Design Criteria. The various sub-systems are designed to use standard equipment, material and products of the electrical industry. In the selection of the materials and equipment, special consideration was given to ease of operation, reliability and maintenance. The standards of the National Manufacturers Association (NEMA), the Institute of Electrical and Electronics Engineers (IEEE), and the American National Standards Institute (ANSI) will be used as guides in the selection of all electrical equipment. The design of circuits, grounding system and conduit systems will conform to the 1999 National Electrical Code and the National Electrical Safety Code.
Power Source. Electric service for the lock will be provided by Local Power Co. and emergency power by a 250kW diesel engine generator set.
Power Distribution
a General. The electrical service should be rated 400 amps, three phase, four wire, 277/480 Volts. Emergency power will be derived from a 250 kW diesel engine generator set installed in the powerhouse. The unit will be of sufficient capacity to operate the gates, supply essential power to the control houses, generator building, shop building, and maintain site lighting. The service will include an automatic transfer switch to control the emergency generator in the event the commercial power supply fails. b Grounding. The lock grounding system will be grounded in accordance with the National Electrical Code. The grounding system will consist of copper ground rods interconnected with copper conductors. All jumpers and grounding electrode conductor connections will be done by exothermic weld. All electrical equipment, machinery, and exposed metal will be bonded to the grounding electrode system. c Emergency Generator. Standby generation will be supplied from a diesel driven generator set located in the lock generator building The fuel supply for the generator will be provided from a main station tank to a skid mounted day tank. Alarms will be locally annunciated on the generator, shop building and within the control rooms. d Voltage Drop Requirements. Conductors will be sized to prevent the voltage drop from exceeding three percent at the farthest utilization point on each circuit.
Control System
The lock will use a Programmable Logic Controller (PLC) with panel mounted touch screens and use a 10 mbs IEEE 802.3 Ethernet protocol for communications between the PLC and Pentium II 450Hz processor. The software will be RS view by Rockwell Automation. The PLC hardware will be the Allen Bradley SLC 5/05 platform. Plc rack will be located in control house #1.
Conduit and Boxes
a Conduit. All wiring will be installed in rigid metal conduit except that motors and other electrical equipment subject to vibration will be connected with liquid-tight flexible metal conduit. b Pull and Junction Boxes. All pull boxes and junction boxes will be of cast metal of sufficient thickness or provided with bosses to accommodate the required threads for the conduit connections of size specified. c Outlet Boxes. All outlet boxes for receptacles, switches, and lighting fixtures will be of cast metal with bosses drilled and tapped or with threaded hubs of sizes specified. The edges will be designed to take a heavy cover gasket with four or more screws for attaching covers or fixtures.
Lighting System
High Intensity Discharge lighting will be used for general site lighting. Lights will be controlled with lighting contractors. Illumination levels will be approximately 5 foot-candles. Navigation lights will be installed on dolphins and guide walls. Interior lights for office spaces will be fluorescent fixtures with t-8 lamps and electronic ballast. Illumination levels will be in accordance with the Illumination Engineering Society of North America (IES).
Ventilation. A small ventilator will be furnished for the restroom.
Communications
An outlet box will be provided in the office walls for telephone connections. A conduit from the outlet box will be stubbed outside of the lock and capped.
Lighting Protection System
The lock will be provided with a lightning protection system that is the standard product of a manufacturer regularly engaged in the production of lightning protection.
4.2 56 foot Wide Channel Closure Floodgates
Introduction. This summary presents the results of the geotechnical analyses for the 56’ wide navigable floodgates located in the project levee alignments. Two types of floodgate structures were analyzed. One using conventional construction methods built in the dry (Cast-In Place Structure) and the other using pre constructed float-in methods (Float-In Structure). Braced steel sheet pile walls will tie the floodgate structure into the adjacent levee. Several structure designs are based on the design for other structures with similar loading and foundations conditions as noted. This summary covers the following floodgates:
Volume 3 Bayou Du Large Floodgate Volume 4 Bayou Grand Caillou Floodgate Volume 5 Bayou Little Caillou Floodgate Volume 6 Bayou Pointe au Chien Floodgate Volume 7 Bayou Petit Caillou & Bayou Terrebonne Floodgate Modification Volume 8 Bayou Petit Caillou Floodgate Replacement Volume 9 Bayou Terrebonne Floodgate Replacement Volume 11 Bush Canal Floodgate Volume 13 Falgout Canal Floodgate Volume 17 Grand Bayou Floodgate Volume 20 Humble Canal Floodgate Note: 1 - Based on designs for Bayou Little Caillou Floodgate 2 - Based on designs for Bush Canal Floodgate 3 - Based on designs for Falgout Canal Floodgate 4 - Volume 7 considers modifications to two existing floodgate structures. A cursory review of the geotechnical reports and pile load test reports presented in Volume 7 reveal that seepage and deep-seated analyses are missing but the existing foundation piling appears adequate. The tie-in floodwalls and brace piles are questioned for adequacy. These aspects will be analyzed in the detailed design phase.
Geotechnical Exploration. Borings used were either previously taken and supplied by the local sponsor, existing Corps borings in the vicinity of the proposed floodgates, or new borings taken by the Corps at the proposed location of the floodgates to provide design data for geotechnical analyses. See the corresponding Volumes listed in Paragraph 4.2.2.1 above for detail descriptions of the available geotechnical explorations at each site. The following floodgates do not have borings located within the proposed footprint of the structure:
Bayou Pointe au Chien Floodgate Bayou Petit Caillou Floodgate Replacement Bayou Terrebonne Floodgate Replacement Grand Bayou Floodgate Humble Canal Floodgate
It is unknown if the available borings used for Falgout Canal Floodgate are located within the proposed footprint of the structure.
General Geology in the Area of Floodgates. Refer to Paragraph 1.4 of this summary report for the general geology of this area. More specific geology information at the floodgate sites is given in the corresponding Volumes listed in Paragraph 4.2.2.1 above.
Laboratory Testing Program. Soil borings were taken at some floodgate locations, where no previous information was available, to determine subsurface deposits and to recover specimens for shear strength tests.
Shear Strength Tests. Specimens from the borings were tested to obtain design values. Visual classifications, water content, Atterberg limits, unconfined compression tests, sieve, and other routine tests were performed during soil processing. Unconsolidated undrained (Q), consolidated undrained (R), direct shear (S) and consolidation (C) tests were performed on select specimens from the Corps borings. Test results are presented in the corresponding Volumes listed in Paragraph 4.2.2.1 above.
Design Shear Strengths. Shear strength data, determined for the proposed floodgate sites, are presented in the corresponding Volumes listed in Paragraph 4.2.2.1 above. Shear strengths used for the design were determined from combining the shear strength data from available borings.
Survey Data. No survey data was available at the proposed floodgate sites. Ground surface elevations were estimated based on field observations and available soil reports furnished by the local sponsor. Boring elevations, where no information was available, were estimated assuming the water surface at Elevation 0 N.G.V.D.
Floodgate Analyses. Typical geotechnical analyses were performed for the floodgate structures.
Pile Foundations. Typical ultimate compression and tension pile capacities versus tip elevations were developed for various pile types and sizes for each of the proposed structures. Typical design parameters used are shown below:
Concrete and Timber Piles Short Term "Q"-Case Long Term "S"-Case f Kc Kt Nc Nq d f Kc Kt Nc Nq d Clay 0° 1.0 0.7 9 1.0 0° 23° 1.0 0.7 0 10.0 23° Silt 15° 1.0 0.7 9 4.5 15° 28° 1.0 0.7 0 17.5 28° Sand 30° 1.25 0.7 0 22.0 30° 30° 1.25 0.7 0 20.0 30° Steel Pipe Piles Short Term "Q"-Case Long Term "S"-Case f Kc Kt Nc Nq d f Kc Kt Nc Nq d Clay 0° 1.0 0.7 9 1.0 0° 23° 1.0 0.7 0 10.0 19° Silt 15° 1.0 0.7 9 4.5 12° 28° 1.0 0.7 0 17.5 23° Sand 30° 1.25 0.7 0 22.0 30° 30° 1.25 0.7 0 20.0 25°
The results of design pile loads versus tip elevations for floodgate structures are presented the corresponding Volumes listed in Paragraph 4.2.2.1 above. The recommended pile tip elevations for cost estimating purposes was based on applying a factor-of-safety as shown below for both compression and tension.
Allowable Pile Capacities Factor-of Safety Without Pile Load Test With Pile Load Test Q-Case 3.0 2.0 S-Case 3.0 (Dead Load Only) 2.0 (Dead Load Only) 1.5 (Total Load) 1.0 (Total Load)
During construction, test piles will be driven and load tested where economically justified in the project area. The results of the pile load tests will be used to determine the length of the service piles where applicable. Sub-grade modulus curves for estimating lateral resistance of the soil at the floodgate structures are shown on the pile capacity plates in the corresponding volumes listed in Paragraph 4.2.2.1 above.
Deep-seated Stability. Conventional stability analyses utilizing a 1.30 factor-of-safety incorporated into the soil parameters were performed for potential failure surfaces beneath the floodgate structures. The net driving forces at the base of the structures are greater than for any other failure surface. Therefore, no additional forces need be applied to the structures because of critical failure surfaces below the base. Summation of horizontal driving and resisting force results are shown in the corresponding volume listed in Paragraph 4.2.2.1 above.
Tie-in Floodwall Stability. The required penetration for the stability of the braced sheet pile tie-in walls was determined by the wedge-type method of analysis using the CWALSHT computer program for both the short term (Q) and long term (S) cases. The walls were analyzed for the short-term case using the soil design "Q" strengths and for the long-term (S) case using the "S" shear strengths of C=0 and f=23° for clay strata and C=0 and f=28° for silt strata. Sand strengths are the same for both cases. Hydraulic loading consists of stillwater plus wave loading conditions. Factors-of-safety of 1.5 for the short term (Q) case and 1.2 for the long term (S) case were applied to the design shear strengths to determine the required tip penetration and moments in the sheeting. A factor-of-safety of 1.0 was used to determine the required brace force. The factors-of-safety were applied as follows: f developed = arctan (tan f available/factor-of-safety) and cohesion developed = cohesion available/factor-of-safety. Using the resulting shear strength, net lateral soil and water pressure diagrams were developed for movement toward each side of the sheet pile. With these pressure distributions, moments about the brace elevation were equated to zero to determine the tip penetrations, and the summation of horizontal forces were equated to zero to determine the brace reaction. Both "Q" and "S" cases were analyzed assuming excavation backfill adjacent to the tie-in floodwall has equivalent strengths as the in situ material. The critical load case results using the free earth method is presented in the corresponding volume listed in Paragraph 4.2.2.1 above. Riprap was used to control scour on each side of the wall and also reduce the overturning moments. The computer runs are also presented in the corresponding volume listed in Paragraph 4.2.2.1 above.
Seepage Cutoff. The required penetration for seepage cutoff was analyzed by utilizing Lane's Weighted Creep Ratio Method. The weighted creep distance was calculated as the sum of the vertical creep path distance plus one-third of the horizontal path distance. Lane's Weighted Creep Ratio is the ratio of the weighted creep distance to the maximum differential head. Seepage calculations are shown in the corresponding volume listed in Paragraph 4.2.2.1 above.
Floodgate Excavation. Excavation slopes were checked by the LMVD Method of Planes using the design (Q) shear strengths and a minimum factor-of-safety of 1.3. See the corresponding volume listed in Paragraph 4.2.2.1 above for the presentation of the stability analyses.
Dewatering. Dewatering for the cast-in place structures will be required to reduce the hydrostatic pressures in the sands and silts existing below the structure base. The dewatering systems will require wells or wellpoints.
Foundation Settlement. The floodgate structures are supported on deep foundation piling and are therefore expected to experience negligible settlement. The levee end of the sheet pile tie-in walls will experience settlements approaching that of the levee. Therefore, at the same time levee maintenance or raising is being performed, it will be necessary to bring up to grade any cantilevered portion of the sheet pile wall.
Recommendations. Future geotechnical investigation should focus on obtaining complete soil data and surveys that give adequate knowledge of the structure sites. More in-depth investigation is needed to determine settlement, structural foundation analysis and dewatering requirements.
4.2.2 Structural Design
Navigation During Construction
Cast-In Place Structure: The cast-in place design utilizes a large cofferdam and dewatering system. The cofferdam would allow the construction of the flood gate structure to take place using in-the-dry conventional methods with little or no disruption to navigation. The waterway width varies at the structure locations. Some are relatively wide which allows for centering of the structure with a by-pass channel within the existing banks. At some locations the channel must be widened or a bypass channel provided. Typically a temporary timber guide wall will be required to protect the cofferdam from impact and as an aid to navigation during construction.
Float-In Structure: The float-in alternative will not utilize a cofferdam. The concrete structure is constructed at an off-site graving yard and towed to the site. Other features are installed in the channel bottom using in-the-wet construction techniques. Construction of the foundation will be staged to allow for a minimum width for navigation where possible. At some locations the channel must be widened or a bypass channel provided. Where a bypass channel is not provided, reduced power will be required for vessels passing through the construction area. This will minimize any damage to the prepared foundation. A navigation closure period will be required for positioning and sinking of the lower hull section and during subsequent construction work items. Once the structure has been completed to a level that provides adequate stability, navigation could pass during certain times during each day until construction is completed.
Structural Design of Concrete Gate Monoliths
General. The cast in place and float-in structure, sector gates and the flood wall tie-in were designed to a level that demonstrates feasibility. Detailed design will be presented in a future Design Report. Miscellaneous structures including control houses, guidewalls, dolphins and cut-off walls were based on existing structures.
Design Criteria and References
The following list of design references were used as general guidance to formulate design criteria for the design features:
1. EM 1110-2-2200 Gravity Dam Design 2. ETL 1110-2-307 Flotation Stability Criteria for Concrete Hydraulic Structures 3. ETL 1110-2-256 Sliding Stability for Concrete Structures 4. EM 1110-2-2502 Retaining and Floodwalls 5. EM 1110-2-2703 Lock Gates and Operation Equipment 6. ETL 1110-2-338 Barge Impact Analysis 7. EM 1110-2-2104 Strength Design for Reinforced Concrete Hydraulic Structures 8. EM 1110-2-2906 Design of Pile Foundations 9. EC 1110-2-291 Stability Analysis of Concrete Structures 10. Draft EC 1110-2-XXXX Structural Design of Precast and Prestressed Hydraulic Concrete Structures 11. Prestressed Concrete Institute, PCI Design Handbook, Third edition., 201 North Wells Street, Chicago Illinois 60606. 12. ACI Committee 357, ACI 357.2R-88 State-of-the-Art Report on Barge-Like Concrete Structures 13. Gerwick, Ben C., Jr., International Experience in the Performance of Marine Concrete
The above references and the preliminary designs presented herein should not be taken as establishing standard Corps design criteria or construction details. Future assessment and refinement of these designs is planned, but costs are not expected to change appreciably. Design criteria for the sector gate design is discussed separately in Section 3.6.
Float–In Structure Alternative
Float-In Structure Design Criteria. Design criteria for the float in design was taken primarily from references 10 through 13 above. The float in designs include; in-the-wet construction, prestressed/post-tensioned concrete and lightweight concrete in marine environments. Criteria are being developed through the Innovations for Navigation Projects Research Program (INP) concurrent with Corps’ ongoing design efforts. A portion of the information has been developed in the concrete and offshore industry codes.
Designs with both normal and light concrete were included in this study for the float in design. The evaluation focused on the effects of weight on draft, floatation stability, and structural considerations. An evaluation of findings regarding suitability or durability of lightweight concrete could not be incorporated into this report. Final determination as to the suitability of lightweight concrete and specific mixes to be used will be addressed in a separate concrete materials design report in the detailed design phase.
a In-the-wet construction. In-the-wet construction has been used for years in the offshore industry and is addressed by the American Concrete Institute. The proposed in-the-wet construction design is based on draft INP recommendations, typical designs and details are borrowed from the offshore industry. b Transportation Loading. In accordance with reference 10 above, the float-in module is designed for loads encountered during float-in. In accordance with reference 10 and 12 above, three buoyancy conditions are considered: still water level condition (SWL), hogging wave condition, and a sagging wave condition. The design approach generally followed guidance outlined in references 10 and 12 above. In preliminary design, longitudinal hull loads were used for initial sizing of the hull. Longitudinal, transverse and torsional loads should be considered in final designs. c Strength and Serviceability. Strength is based on prestressed/post tension design approach. The ultimate strength requirements were based on load factors from reference 10. Load factors are given specifically for float-in type designs. In a marine environment, minimizing or eliminating concrete tensile stress during float-in to improve durability should be a design consideration. d Prestressed/Post Tensioned Concrete Design. The use of prestressed/post-tensioned concrete has existed for float-in type structures since the early 1980’s (Gerwick, 1990). Ultimate strength design was in accordance with reference 11 above and used load factors from reference 10. The floodgate structures are located in a waterway with varying salinity. Allowable stresses considering cracking and cover are important issues.
Float-In Structure Design Features
a General. The float-in structure consists of a float-in precast prestressed concrete structure with integral wingwalls that are founded on piles. The concrete structure contains three major features: float-in module, upper wing walls and in-fill concrete. The float-in module includes the lower hull and the lower portion of the wingwalls. The overall dimensions of the float-in module are 159 feet wide by 71 feet long. Elevations will vary for the different structures.
The float-in module and upper wing walls are constructed off site in a graving yard. Concurrent with the construction in the graving yard, battered bearing piles will be driven in-the wet and cut off underwater at the proper elevation. Once completed, the lower section is floated to the site and sunk on to landing pads. Hydraulic flat jacks are installed on each landing pad for positioning. Tension piles are then driven through ports formed into the lower hull section. Sheet pile cut-off walls are driven and a temporary skirt is installed to confine underbase concrete. Underbase tremie concrete is placed to provide a seal between the structure and founding soils. It also transfers bearing loads between the structure and the battered piles. Underbase concrete reinforcing and shear transfer should be evaluated during future design phases.
The monolith is subdivided into precast concrete panels that are tied together with cast-in-place closure pours. The precast panels are prestressed to resist handling loads and contain conventional reinforcement and post-tensioning ducts. The closure pours are sized to allow adequate room for tie-in reinforcement, post-tensioning ducts and limit reinforcement congestion to ensure concrete consolidation. The lower hull or base slab is continuously post-tensioned after assembly of the precast concrete panels.b Transportation Design. The lower hull was designed as a prestressed/post-tensioned concrete barge to resist transportation loading. Draft analysis, still water and hogging wave stress analysis were performed. Due to the load distribution in the lower hull, sagging wave stresses will not be a concern. The draft requirement was set at 8 foot maximum. The draft requirements will be verified during future design stages. Temporary auxiliary buoyancy could be used to reduce the draft by 1 to 2 feet, if required. A simple floatation stability check was performed as outlined in Draft EC, Design of Precast and Prestressed Hydraulic Concrete Structures. The large ratio of hull width to draft depth ensures that overall floatation stability will not be a problem. c Erection Design. Erection includes installation of float-in or lift-in modules and other construction. The feasibility of the set down condition was evaluated. The setting load condition addresses the sinking of the lower hull onto the prepared foundation. Temporary pile founded landing pads are required to position the lower hull prior to concreting the base. Landing pads were designed for a set down load that included a 5 percent negative buoyancy load plus the added load when the water elevation drops two feet. d Final Configuration. In the final configuration, the structure was analyzed for vertical, lateral, overturning and flotation stability. A typical summary of overall stability results is presented in Volume 14. Vertical resultants for each load case were shown to act through the kern and floatation stability is summarized. Vertical tension piles minimized the infill concrete in the wing walls to reduce slab moments. The vertical tension piles provided the necessary resistance against flotation. The pile foundation was designed in accordance with EM 1110-2-2906, Design of Pile Foundations. The layout was based on 24 inch diameter steel pipe piles with a design compression capacity of 135 kips. The capacity was based on a factor of safety of 2, which will require pile testing. The dewatered case required tension piles to achieve the 1.3 floatation factor of safety. The tension piles were 24-inch diameter steel pipe piles with a design tension capacity of 102 kips using a factor of safety of 1.5. The bearing piles are battered in both directions to resist lateral movement and modeled as pinned to the base slab. The tension piles are vertical and extend into the base slab 12 feet and were modeled as fixed. The lower hull is in-filled with a sand lightweight concrete for ballast, which forms the base slab in the final configuration. The in-fill concrete was designed to act as dead load only and not as a structural composite. The uniform pile layout was modeled as an average uniform bearing load evenly distributed under the base. Longitudinal moments and shears were calculated to check sizing of the base slab and post-tension requirements. An analysis summary is shown in Volume 14.
Cast-In-Place Concrete Structure
Design Criteria. Design criteria for the cast in place design was taken primarily from references 1 through 10 above. The cast in place designs incorporate conventional normal weight reinforced concrete.
Cast-In Place Structure Design Features
a General. The cast-in place floodgate structure is cast-in-place concrete founded on bearing piles. The overall footprint is 132 feet wide by 56 ft long, which is 30 percent smaller than the float-in design. The structure is designed monolithically on a continuous mat foundation. Floodwalls will extend to the levee system maintaining the top of structure elevation. b Construction. Prior to construction of the floodgate structure, a by-pass channel will be established and construction of a 192-foot diameter cofferdam will be completed. Once the site is prepared, 322 prestressed concrete piles (14 inch by 14 inch, 70 feet long) will be driven. Alternate rows will be battered in alternate directions parallel with the channel. The piles will be imbedded in the concrete mat with steel tension anchors. After installation of the piles, a 5 ½ foot thick reinforced concrete base slab will be cast in place. Reinforced concrete wing walls will be formed on the base slab. The walls are supported by the heavy gate anchorage abutments and intermediate wall buttresses.
Structural Design Loads and Design Data
The float-in and cast in place floodgate structures were designed for the following load cases:
a Transportation Loading. (Float in Design only) The lower hull was designed as a prestressed/post-tensioned concrete barge to resist transportation loading. Draft analysis, still water and hogging wave stress analysis were performed. Due to the load distribution in the lower hull, sagging wave stresses will not be a concern. The draft requirement was set at 8 foot maximum. The draft requirements should be verified during future design stages. Temporary auxiliary buoyancy could be used to reduce the draft by 1 to 2 feet, if required. The wave loading assumes that the concrete float-in structure will only be transported within the intracoastal water system. The loading considered two cases: 1. Still water condition with no waves and 2. Hogging wave of 3 feet in height and a period equal to the full length of the floating structure. b Final Configuration (Cast-In and Float-In Designs). The following hydraulic data presents the ranges of water elevations that vary with structure location. Refer to TABLE 2.8.7 HYDRAULIC DESIGN CRITERIA in this Appendix for specific structure criteria.
Water Surface Elevation (NGVD) Load Case Flood Side Protected Side SWL/Wave Height SWL Hurricane, Maximum Head w/o Wave 8.0-9.2 -1.0 Maximum Reverse Head from Hurricane -2.0 6.0 Operating, Maximum Direct Head 3.0 -1.0 Operating, Reverse Head -1.0 4.0 Hurricane, Maximum Head with Wave 9.2-11.0 -1.0 Maintenance Condition, Dewatered 6.0 6.0
Typical Flood Gate Structure Dimensions and Elevations (NGVD) Floodgate Width 56 ft Top of Floodgate Structures (elevation) 11-16 ft Top of Floodgates (elevation) 11-16 ft Gate Sil l Elevation -9 ft Top of Guide Walls (elevation) 11-16 ft
Sector Gate Design
General. This section describes the methods and assumptions used in the design of the sector gates. Two movable sector gates are required for each floodgate. Each sector gate consists of three basic parts: An arc-shaped steel damming surface, a pintle, hinge or pivot pin, and the steel framework that connects and transfers water loads between them. The total floodgate opening width is 56 feet. The sector gates have a radius of 46’-4".
References. The applicable sections of the following references were used to formulate design criteria for the various structural components.
a EM 1110-2-2105, Design of Hydraulic Steel Structures (March, 1993). b EM 1110-2-2703, Lock Gates and Operating Equipment (June, 1994). c EM 1110-1-2101, Working Stresses for Structural Design (November, 1963) d AISC, Manual of Steel Construction, Allowable Stress Design, Eighth Edition
Sector Gate Configuration and Construction. The sector gates are all steel, welded structures, with the exception of mechanical parts and timber fenders. The construction will incorporate standard steel fabrication methods. The arc shaped gate-damming surface is a hollow steel box structure with watertight compartments. The framing for the gates consists of two horizontal frames located roughly at quarter points on the box beam consisting of welded steel tubing. However, the gate design and geometry will be refined and optimized in the next level of study. Variations in interior angle, radius and configuration of interior frame members will be investigated. The tube members will be sealed at intersections with welded internal diaphragms, to create multiple watertight compartments. Corrosion protection will be achieved by a paint system supplemented by a cathodic protection system. Inspection plugs will be provided for internal inspection of buoyant members. Additional buoyancy can be provide by the gate’s supporting tube framework and by a trim compensating tank located near the hub. The size and location of buoyancy features can be determined when the final design of the gate is prepared. The buoyancy will reduce wear and stress on the sector gate, pivot bearing, and associated gate machinery. The sector gate and associated machinery will, however, be designed to demonstrate normal functioning without supporting buoyancy in case of an emergency. A permanent pumping system will also be provided to mitigate any unexpected loss of buoyancy.
Design Criteria. The general layout and design of the sector gates was conducted using the criteria of EM 1110-2-2703, Lock Gates and Operating Equipment. EM 1110-2-2105 states that allowable stress design shall be conducted using 83% of the stresses determined from the AISC allowable stress design method. The actual loading considered five load cases as listed below.
CASE DESCRIPTION 1 Maximum Direct Head from Hurricane 2 Maximum Reverse Head from Hurricane 3 Operating, Maximum Direct Head 4 Operating, Reverse Head 5 Maximum Direct Head from Hurricane
In addition to the loading listed above, EM 1110-2-2703 requires that a 125 kip boat impact load be applied as a point load on the horizontal beams supporting the gate face and at any panel point on the canal side of the gate framing. Another loading considered in the sector gate design was the closing torque on the gate when it is operated under reverse head. Forces in the gate hinge and anchorage were determined from the gate reactions
Floodwall and Miscellaneous Structures
a Floodwalls. The floodwall extends from the flood gate structure to the levee system. The walls were designed as standard sheet pile walls braced by a waler, which transfers the lateral loads into battered bearing piles b Control and Machinery Houses. A control house is provided to shelter the gate control systems and provide space for a gate operator as required. The machinery house is provided to shelter the gate machinery from the weather. These were not designed, cost estimates but were based on historical data from similar structures. c Guide walls and Dolphins. Guide walls and dolphins are provided as aids to navigation and to protect the main flood gate structure from impact. The structure designs and wall lengths and cost estimates were based on similar projects. d Cut Off Walls. A cut-off wall is provided on the flood side of the structure to reduce possible seepage, scouring and reduce uplift. A PZ-22 sheet pile section was assumed for the cut-off wall to extend down to El –32.3, which is the same depth as the flood walls.
4.2.3 Mechanical Design
Gate Operation. Gate operation will be two speeds with a time dependent 1 to 4 second speed ramp at start, stop and speed changes. The dual speed and speed ramp will be accomplished electronically by way of a hydraulic proportional valve. A slow gate speed of 3.5 degrees per minute will be used near the end of gate travel, (1 to 3 feet from fully close or fully open, measured at the skin plate). A higher speed of 30 degrees per minute will be used in between the ends of travel.
Gate Operating Machinery. The gate operating machinery will be a rack and pinion gear drive. The rack will be attached to the gate along the outside radius of the gate's skin plate. A pinion drive gear will be attached to a low speed high torque hydraulic (LSHT) motor mounted on the lock wall. The drive gear has a pitch diameter of 40". A the Series 64 Hagglunds LSHT hydraulic motor operating at 2500 psi was used for design purposes. Arranged in this configuration, the motor can provide a tangential force at the rack of 19,400 lbs. with a differential pressure across the motor of 2500 psi. It is anticipated that between 10,000 and 15,000 lbs. of tangential rack force will be required. Each gate will be equipped with its own hydraulic power supply. The hydraulic power supply for the motor will consist of a variable delivery pressure compensated pump driven by an electric motor. The electric motor will be 10 horsepower. The gate operating machinery is shown on Plates M-1 and M-2.
4.2.4 Electrical Design
General
a Scope. The design for the lock includes provisions for power, control, lighting, emergency power and grounding. b Design Criteria. The various sub-systems are designed to use standard equipment, material and products of the electrical industry. In the selection of the materials and equipment, special consideration was given to ease of operation, reliability and maintenance. The standards of the National Manufacturers Association (NEMA), the Institute of Electrical and Electronics Engineers (IEEE), and the American National Standards Institute (ANSI) will be used as guides in the selection of all electrical equipment. The design of circuits, grounding system and conduit systems will conform to the 1999 National Electrical Code and the National Electrical Safety Code.
Power Distribution
The electrical service will be rated 100 amps, three-phase, four wire, 277/480 volts. Emergency Power will be derived from a 35 kW diesel engine generator set installed in the control house. The unit will be of sufficient capacity to operate the gates, to supply essential power to the control house and maintain site lighting. The service will include a manual transfer switch to control the emergency generator in the event the structure's commercial power supply fails.
Grounding
The site grounding electrode system will include a combination of driven electrodes and connection to the embedded re-enforcing mat in the floor slab of the control structure.
Service Equipment
The main service disconnect will be a 100 amp, 3-pole, circuit breaker disconnect switch. A 50 amp, 3-pole, circuit breaker will provide overcurrent protection for the generator. A manual transfer switch rated 100 amps will be used to select normal or emergency power. A riser diagram of the proposed electric service is shown on the electrical drawings.
Panelboards
A 225 amp, main-lugs-only, 277/480 volt, 3-phase, 4-wire circuit breaker panelboard will be used to distribute power to the sector gate operating machinery, Site lighting, transformer, and 120/208 volt panelboard. The panelboard will be equipped with a UL listed surge arrestor for added protection.
The Control Building Panelboard will include a 60 amp main breaker and space for up to 30 single pole circuit breakers. The panelboard will rate for 120/208 volts, 3-phase, 4-wire operation. "Bolt-on" branch circuit breakers will be used.
Electrical Enclosures
Electrical enclosures installed indoors will be the manufacturer's standard, NEMA 1 design. Enclosures installed in outdoor locations will be NEMA 3R construction.
Wiring
The electrical distribution system will include insulated copper conductors installed in Electrical Metallic Tubing (EMT) indoors and Rigid Galvanized Steel (GRS) conduit outdoors. All wire and cable will be specified in accordance with the Corp's standard guide specification for hydraulic structures.
Lighting
Interior light level for the Control Building operating room will be 30 foot-candles. This is in accordance with recommendations of the Illuminating Engineering Society of North America (IES). Two-tube industrial fluorescent light fixtures with F32T8 lamps and solid- state ballast will be used. Receptacles rated 15/20 amps, 120 volts will be provided for use with hand power tools. Each Receptacle will include integral Ground-Fault protection.
Five pole-mounted 150 watt, high-pressure sodium light fixtures will be mounted on the structure for general site lighting. The lights will be controlled with a lighting contractor, photocell and HAND-OFF-AUTOMATIC switch located in the Control Building. Solar/battery powered Navigation lights and foghorn will be installed, as required, on dolphins, guide walls, and the floodgate structure. Details of navigational aids and lighting are shown on Plate E-2.
4.3 125’ Wide Channel Closure Floodgates
4.3.1 Geotechnical
Introduction. This summary presents the results of the geotechnical analyses for the 125’ wide navigable floodgates located in the project levee alignments. Two types of floodgate structures were analyzed. One using conventional construction methods built in the dry (Cast-In Place Structure) and the other using pre constructed float-in methods (Float-In Structure). Braced steel sheetpile walls will tie the floodgate structure into the adjacent levee. This summary covers the following floodgates:
Volume 15 GIWW Floodgate at Bayou Lafourche Volume 16 GIWW Floodgate at Houma
Geotechnical Exploration. Borings used were either the closest existing Corps borings to the proposed floodgates, or new borings taken by Corps at the proposed levee alignment to provide design data for geotechnical analyses. See the corresponding volume listed in Paragraph 4.3.2.1 above for detail descriptions of the available geotechnical explorations at each site. Neither of the floodgates have borings located within the proposed footprint of the structure.
General Geology in the Area of Floodgates. Refer to Paragraph 1.4 of this summary report for the general geology of this area. More specific geology information at the floodgate sites is given in the corresponding volume listed in Paragraph 4.3.2.1 above.
Laboratory Testing Program.
Shear Strength Tests. Specimens from the borings were tested to obtain design values. Visual classifications, water content, Atterberg limits, unconfined compression tests, sieve, and other routine tests were performed during soil processing. Unconsolidated undrained (Q) tests were performed on select specimens from the Corps borings. Test results are presented in the corresponding volume listed in Paragraph 4.3.2.1 above.
Design Shear Strengths. Shear strength data, determined for the proposed floodgate sites, are presented in the corresponding volume listed in Paragraph 4.3.2.1 above. Shear strengths used for the design were determined from combining the shear strength data from available borings.
Survey Data. No survey data was available at the proposed floodgate sites. Ground surface elevations were estimated based on field observations and limited existing Corps survey data.
Floodgate Analyses. Typical geotechnical analyses were performed for the floodgate structures.
Pile Foundations. Typical ultimate compression and tension pile capacities versus tip elevations were developed for various pile types and sizes for each of the proposed structures. Typical design parameters used are shown below:
Concrete and Timber Piles Short Term "Q"-Case Long Term "S"-Case f Kc Kt Nc Nq d f Kc Kt Nc Nq d Clay 0° 1.0 0.7 9 1.0 0° 23° 1.0 0.7 0 10.0 23° Silt 15° 1.0 0.7 9 4.5 15° 28° 1.0 0.7 0 17.5 28° Sand 30° 1.25 0.7 0 22.0 30° 30° 1.25 0.7 0 20.0 30° Steel Pipe Piles Short Term "Q"-Case Long Term "S"-Case f Kc Kt Nc Nq d f Kc Kt Nc Nq d Clay 0° 1.0 0.7 9 1.0 0° 23° 1.0 0.7 0 10.0 19° Silt 15° 1.0 0.7 9 4.5 12° 28° 1.0 0.7 0 17.5 23° Sand 30° 1.25 0.7 0 22.0 30° 30° 1.25 0.7 0 20.0 25°
The results of design pile loads versus tip elevations for floodgate structures are presented the corresponding volume listed in Paragraph 4.3.2.1 above. The recommended pile tip elevations for cost estimating purposes shall be based on applying a factor-of-safety as shown below for both compression and tension.
Allowable Pile Capacities Factor-of Safety Without Pile Load Test With Pile Load Test Q-Case 3.0 2.0 S-Case 3.0 (Dead Load Only) 2.0 (Dead Load Only) 1.5 (Total Load) 1.0 (Total Load)
During construction, test piles would be driven and load tested. The results of the pile load tests will be used to determine the length of the service piles where applicable. Subgrade modulus curves for estimating lateral resistance of the soil at the floodgate structures are shown on the pile capacity plates in the corresponding volume listed in Paragraph 4.3.2.1 above.
Deep-seated Stability. Conventional stability analyses utilizing a 1.30 factor-of-safety incorporated into the soil parameters were performed for potential failure surfaces beneath the floodgate structures. The net driving forces at the base of the structures are greater than for any other failure surface. Therefore, no additional forces need be applied to the structures because of critical failure surfaces below the base. Summation of horizontal driving and resisting force results are shown in the corresponding volume listed in Paragraph 4.3.2.1 above.
Tie-in Floodwall Stability. The required penetration for the stability of the braced sheet pile tie-in walls was determined by the wedge-type method of analysis using the CWALSHT computer program for both the short term (Q) and long term (S) cases. The walls were analyzed for the short-term case using the soil design "Q" strengths and for the long-term (S) case using the "S" shear strengths of C=0 and f=23° for clay strata and C=0 and f=28° for silt strata. Sand strengths are the same for both cases. Hydraulic loading consists of stillwater plus wave loading conditions. Factors-of-safety of 1.5 for the short term (Q) case and 1.2 for the long-term (S) case were applied to the design shear strengths to determine the required tip penetration and moments in the sheeting. A factor-of-safety of 1.0 was used to determine the required brace force. The factors-of-safety were applied as follows: f developed = arctan (tan f available/factor-of-safety) and cohesion developed = cohesion available/factor-of-safety. Using the resulting shear strength, net lateral soil and water pressure diagrams were developed for movement toward each side of the sheet pile. With these pressure distributions, moments about the brace elevation were equated to zero to determine the tip penetrations, and the summation of horizontal forces were equated to zero to determine the brace reaction. Both "Q" and "S" cases were analyzed assuming excavation backfill adjacent to the tie-in floodwall has equivalent strengths as the in situ material. The critical load case results using the free earth method are presented in the corresponding volume listed in Paragraph 4.3.2.1 above. Riprap was used to control scour on each side of the wall and also reduce the overturning moments. The computer runs are also presented in the corresponding volume listed in Paragraph 4.3.2.1 above.
Seepage Cutoff. The required penetration for seepage cutoff was analyzed by utilizing Lane's Weighted Creep Ratio Method. The weighted creep distance was calculated as the sum of the vertical creep path distance plus one-third of the horizontal path distance. Lane's Weighted Creep Ratio is the ratio of the weighted creep distance to the maximum differential head. Seepage calculations are shown in the corresponding volume listed in Paragraph 4.3.2.1 above.
Floodgate Excavation. Excavation slopes were checked by the LMVD Method of Planes using the design (Q) shear strengths and a minimum factor-of-safety of 1.3. See the corresponding volume listed in Paragraph 4.3.2.1 above for the presentation of the stability analyses.
Dewatering. Dewatering for the cast-in place structures may be required to reduce the hydrostatic pressures if future site specific borings determine sands and silts to be below the structure base. The dewatering systems would then require wells or wellpoints.
Foundation Settlement. The floodgate structures are supported on deep foundation piling and are therefore expected to experience negligible settlement. The levee end of the sheet pile tie-in walls will experience settlements approaching that of the levee. Therefore, at the same time levee maintenance or raising is being performed, it will be necessary to pull up to grade any cantilevered portion of the sheet pile wall.
Recommendations. Future geotechnical studies should focus on obtaining complete soil data and surveys that give adequate knowledge of the structure sites. More in-depth investigation is needed to determine settlement, structural foundation analysis and dewatering requirements.
4.3.2 Structural Design
Introduction and Project Features
The primary purpose of the GIWW floodgates is hurricane protection. Each of the floodgate structures will consist of a single gate bay with a set of sector gates, based upon a traditional Corps of Engineers configuration. The floodgates will typically be closed on a rising tide as an approaching hurricane raises the water in the channel to elevation +3 feet NGVD, or upon imminent flooding.
Navigation During Construction
Cast-In Place Structure. The cast-in-place design utilizes a large cofferdam and dewatering system, and would require excavation of a temporary by-pass channel in the GIWW during construction in order to maintain navigation. The cofferdam would allow construction of the floodgate to take place using in-the-dry conventional methods. Typically, a temporary timber guide wall will be required to protect the cofferdam from impact and as an aid to navigation during construction.
Float-In Structure. The float-in alternative will not utilize a cofferdam. The concrete structure is constructed at an off-site graving yards and towed to the site. Other features are installed in the channel bottom using in-the-wet construction techniques. Construction of the foundation will be staged to allow for maintaining a minimum width for navigation where possible. If a bypass channel is not needed, reduced power will be required for vessels passing through the construction area. This will minimize any damage to the prepared foundation. A navigation closure period will be required for positioning and sinking of the lower hull section and during various subsequent construction work items. Once the structure has been completed to a level that provides adequate stability, navigation could pass during certain times during each day until construction is completed.
Structural Design of Concrete Gate Monoliths
General
The cast in place and float-in structure alternatives, sector gates and the floodwall tie-ins were designed to a level that demonstrates feasibility. Detailed design will be presented in a future Design Report. Miscellaneous structures including control houses, guidewalls, dolphins and cut-off walls were based on existing structures.
Float-In Structure Alternative
Float–In Structure Design Criteria. The float- in designs include; in-the-wet construction, prestressed/post-tensioned concrete and lightweight concrete in marine environments. Criteria are being developed through the Innovations for Navigation Projects Research Program (INP) concurrent with Corps districts’ ongoing design efforts. A portion of the information has been developed in the concrete and offshore industry codes. Designs with both normal and light concrete were included in this study for the float-in design. The evaluation focused on the effects of weight on draft, floatation stability, and structural considerations. An evaluation of findings regarding suitability or durability of lightweight concrete could not be incorporated into this report. Final determination as to the suitability of lightweight concrete and specific mixes to be used will be addressed in a separate concrete materials design report.
a In-the-wet construction. In-the-wet construction has been used for years in the offshore industry and is addressed by the American Concrete Institute. The proposed in-the-wet construction design is based on draft INP recommendations, typical designs and details are borrowed from the offshore industry. b Transportation Loading. The float-in module is designed for loads encountered during float-in. Three buoyancy conditions are considered: still water level condition (SWL), hogging wave condition, and a sagging wave condition. In preliminary design, longitudinal hull loads were used for initial sizing of the hull. Longitudinal, transverse and torsional loads should be considered in final designs. c Strength and Serviceability. Strength is based on prestressed/post tension design approach. The ultimate strength requirements were based on load factors from the PCI Design Handbook. Load factors are given specifically for float-in type designs. In a marine environment, minimizing or eliminating concrete tensile stress during float-in to improve durability should be a design consideration. d Prestressed/Post Tensioned Concrete Design. The use of prestressed/post-tensioned concrete has existed for float-in type structures since the early 1980’s (Gerwick, 1990). The floodgate structure is located in a waterway with varying salinity. Allowable stresses considering cracking and cover are important issues.
Float-In Structure Design Features
a General. The float-in structure consists of a float-in precast prestressed/post-tensioned concrete structure with integral wingwalls that will be founded on piles. The concrete structure contains three major features: float-in module, upper wing walls and in-fill concrete. The float-in module includes the lower hull and the lower portion of the wingwalls. The float-in modules and upper wing walls would be constructed off site in a graving yard. Concurrent with the construction in the graving yard, battered bearing piles will be driven in the wet, and cut off underwater at the proper elevation. Once completed, the lower section is floated to the site and sunk onto landing pads. Hydraulic flat jacks are installed on each landing pad for positioning. Tension piles are then driven through ports formed into the lower hull section. Sheet pile cut-off walls are driven and a temporary skirt is installed to confine underbase concrete. Underbase tremie concrete is placed to provide a seal between the structure and founding soils. It also transfers bearing loads between the structure and the battered piles. Underbase concrete reinforcing and shear transfer should be evaluated during future design phases.
The monolith is subdivided into precast concrete panels that are tied together with cast-in-place closure pours. The precast panels are prestressed to resist handling loads and contain conventional reinforcement and post-tensioning ducts. The closure pours are sized to allow adequate room for tie-in reinforcement, post-tensioning ducts and limit reinforcement congestion to ensure concrete consolidation. The lower hull or base slab is continuously post-tensioned after assembly of the precast concrete panels.b Erection Design. Erection loading includes installation of float-in or lift-in modules and other construction loading. Feasibility of the set down condition was evaluated. The setting load condition addresses the sinking of the lower hull onto the prepared foundation. Temporary pile founded landing pads are required to position the lower hull prior to concreting the base. Landing pads were designed for a set down load that included a 5 percent negative buoyancy load plus the added load when the water elevation drops two feet. c General. The float-in structure consists of a float-in precast prestressed/post-tensioned concrete structure with integral wingwalls that will be founded on piles. The concrete structure contains three major features: float-in module, upper wing walls and in-fill concrete. The float-in module includes the lower hull and the lower portion of the wingwalls. The float-in modules and upper wing walls would be constructed off site in a graving yard. Concurrent with the construction in the graving yard, battered bearing piles will be driven in the wet, and cut off underwater at the proper elevation. Once completed, the lower section is floated to the site and sunk onto landing pads. Hydraulic flat jacks are installed on each landing pad for positioning. Tension piles are then driven through ports formed into the lower hull section. Sheet pile cut-off walls are driven and a temporary skirt is installed to confine underbase concrete. Underbase tremie concrete is placed to provide a seal between the structure and founding soils. It also transfers bearing loads between the structure and the battered piles. Underbase concrete reinforcing and shear transfer should be evaluated during future design phases. d Final Configuration. In the final configuration, each load case was analyzed for vertical, lateral, overturning and flotation stability. Vertical resultants for each load case were shown to act through the kern, and floatation stability is summarized. Vertical tension piles minimized the infill concrete needed in the wing walls to reduce slab moments. The vertical tension piles provided the necessary resistance against flotation. A pile foundation was designed in accordance with EM 1110-2-2906, Design of Pile Foundations. The layout was based on 24 inch diameter steel pipe piles with a design compression capacity of 135 kips. The capacity was based on a factor of safety of 2, which will require pile testing. The dewatered case required tension piles to achieve the 1.3 floatation factor of safety. The tension piles were 24 inch diameter steel pipe piles with a design tension capacity of 102 kips using a factor of safety of 1.5. The bearing piles are battered in both directions to resist lateral movement and modeled as fixed to the base slab. The tension piles are vertical and extend into the base slab and were modeled as fixed. The lower hull is in-filled with a sand light-weight concrete for ballast, which forms the base slab in the final configuration. The in-fill concrete was designed to act as dead load only and not as a structural composite. The uniform pile layout was modeled as an average uniform bearing load evenly distributed under the base. Longitudinal moments and shears were calculated to check sizing of the base slab and post-tension requirements.
Cast-In-Place Structure Alternative
Cast-In-Place Design Criteria
The cast-in-place designs incorporate conventional normal weight reinforced concrete.
Cast-In-Place Structure Design Features
a General. The cast-in-place floodgate structure is cast-in-place concrete founded on bearing piles. The structure is designed monolithically on a continuous mat foundation. Floodwalls will extend to the levee system, maintaining the top of structure elevation. b Construction. Once the site is prepared, prestressed concrete piles will be driven. Alternate rows will be battered in alternate directions parallel with the channel. The piles will be imbedded in the concrete mat with steel anchors. After installation of the piles, a reinforced concrete base slab will be cast in place. Reinforced concrete wing walls will be formed on the base slab. The walls are supported by the heavy gate anchorage abutments and intermediate wall buttresses.
Structural Design Loads and Design Data
The float-in and cast-in-place floodgate structures were designed for the following load cases:
a Transportation Loading. The lower hull was designed as a prestressed/post-tensioned concrete barge to resist transportation loading. Draft analysis, still water and hogging wave stress analyses were performed. Due to the load distribution in the lower hull, sagging wave stresses will not be a concern. Each of the two alternatives for the concrete floodgate float-in structures will draw approximately 13 feet of water (with sector gates and machinery installed). The wave loading assumes that the concrete float-in structure will only be transported within the GIWW system. The loading considered two cases: 1. Still water condition with no waves, and 2. Hogging waves of 3 feet in height with an assumed period equal to the full length of the floating structure. b Final Configuration. The hydraulic design data is presented in TABLE 2.8.7 HYDRAULIC DESIGN CRITERIA for specific structure criteria.
Sector Gate Desgin
General. This appendix describes the methods and assumptions used in the design of the sector gates. Two movable sector gates are required for the floodgate. Each sector gate consists of three basic parts: An arc-shaped steel damming surface, a pintle, hinge or pivot pin, and the steel framework that connects and transfers water loads between them. The total floodgate opening widths are 200 feet and 110 feet for the two alternatives.. The sector gates for the 200 foot alternative have a radius of 118’- 4", and the sector gates for the 110 foot alternative have a radius of 74’ – 0".
References. The applicable sections of the following references were used to formulate design criteria for the various structural components.
a EM 1110-2-2105, Design of Hydraulic Steel Structures (March, 1993). b EM 1110-2-2703, Lock Gates and Operating Equipment (June, 1994). c EM 1110-1-2101, Working Stresses for Structural Design (November, 1963) d AISC, Manual of Steel Construction, Allowable Stress Design, Eighth Edition
Sector Gate Configuration and Construction. The sector gates are all steel, welded structures, with the exception of some mechanical parts and timber fenders. Construction of the sector gates will incorporate standard steel fabrication methods. The arc shaped gate-damming surface is a hollow steel box structure with watertight ballast compartments. The buoyancy of the sector gates will be controlled by providing a permanent pumping system that will be capable of mitigating any unexpected loss of buoyancy. The operable ballast compartments will be accessible from vertical hatches on the upper deck, in order to facilitate their inspections. The Corps is currently in the process of researching alternative methods for use in ballasting the sector gates during removal and replacement operations. The framing for the gates consists of two horizontal frames located roughly at quarter points on the box beam consisting of welded steel tubing. However, the gate design and geometry will be refined and optimized in the next level of study. Variations in interior angle, radius and configuration of interior frame members will be investigated. The sector gates’ tube members will be sealed at intersections with welded internal diaphragms to create multiple watertight compartments. External corrosion protection will be achieved by a paint system supplemented by a sacrificial anode cathodic protection system. Internal corrosion protection for the structural tubes will be accomplished by a two step internal treatment of the tubes. The first step will involve flushing the pipes with a degreasing solution, and the second step consists of treating the members with an environmentally approved "floc" coating. Inspection plugs will be provided for internal inspection of buoyant members. Additional buoyancy can be provide by the gate’s supporting tube framework and by a trim compensating tank located near the hub. The size and location of buoyancy features will be determined concurrently with the final design of the gate. The buoyancy will reduce wear and stress on the sector gate, pivot bearing, and associated gate machinery. The sector gate and associated machinery will, however, be designed to demonstrate normal functioning without supporting buoyancy, in case of an emergency.
Sector Gate Design Criteria. The general layout and design of the sector gates was conducted using the criteria of EM 1110-2-2703, Lock Gates and Operating Equipment. EM 1110-2-2105 states that allowable stress design shall be conducted using 83% of the stresses determined from the AISC allowable stress design method. The actual loading considered five load cases as listed below.
CASE DESCRIPTION 1 Maximum Direct Head from Hurricane 2 Maximum Reverse Head from Hurricane 3 Operating, Maximum Direct Head 4 Operating, Reverse Head 5 Maximum Direct Head from Hurricane
In addition to the loading listed above, EM 1110-2-2703 requires that a 125 kip boat impact load be applied as a point load on the horizontal beams supporting the gate face and at any panel point on the canal side of the gate framing. Another loading considered in the sector gate design was the closing torque on the gate when it is operated under reverse head. Forces in the gate hinge and anchorage were determined from the gate reactions
Floodwall and Miscellaneous Structures
a Floodwalls. The floodwalls extend from the floodgate structure to the levee system. The walls were designed as standard sheet pile walls, braced by walers that transfer the lateral loads into the battered bearing piles b Control and Machinery Houses. A control house is provided to shelter the gate control systems and to provide space for a gate operator, as required. A machinery house is provided to shelter the gate machinery from the weather. While the control and machinery houses have not yet been designed, cost estimates for these structures were based upon historical data from similar structures. c Guide walls and Dolphins. Guide walls and dolphins are provided as aids to navigation and to protect the main flood lock structure from impact. The structure designs, wall lengths and cost estimates were based on similar projects. d Cut-Off Walls. A cut-off wall is provided on the flood side of the structure to reduce possible seepage, scouring and reduce uplift. A PZ 22 sheet pile section was assumed for use in the cut-off walls to extend down to the same cut-off elevation as those used for the adjacent flood walls.
4.3.3 Mechanical Design
Gate Operation. Gate operation will be two speeds with a time dependent 1 to 4 second speed ramp at start, stop and speed changes. The dual speed and speed ramp will be accomplished electronically by way of a hydraulic proportional valve. A slow gate speed of 3.5 degrees per minute will be used near the end of gate travel, (1 to 3 feet from fully close or fully open, measured at the skin plate). A higher speed of 30 degrees per minute will be used in between the ends of travel.
Gate Operating Machinery. The gate operating machinery will be a rack and pinion gear drive. The rack will be attached to the gate along the outside radius of the gate's skin plate. A pinion drive gear will be attached to a low speed high torque hydraulic (LSHT) motor mounted on the lock wall. The drive gear has a pitch diameter of 40". A the Series 64 Hagglunds LSHT hydraulic motor operating at 2500 psi was used for design purposes. Arranged in this configuration, the motor can provide a tangential force at the rack of 19,400 lbs. with a differential pressure across the motor of 2500 psi. It is anticipated that between 10,000 and 15,000 lbs. of tangential rack force will be required. Each gate will be equipped with its own hydraulic power supply. The hydraulic power supply for the motor will consist of a variable delivery pressure compensated pump driven by an electric motor. The electric motor will be 10 horsepower. The gate operating machinery is shown on Plates M-1 and M-2.
4.3.4 Electrical Design
a Scope. The design for the floodgates includes provisions for power, control, lighting, emergency power and grounding. b Design Criteria. The various sub-systems are designed to use standard equipment, material and products of the electrical industry. In the selection of the materials and equipment, special consideration was given to ease of operation, reliability and maintenance. The standards of the National Manufacturers Association (NEMA), the Institute of Electrical and Electronics Engineers (IEEE), and the American National Standards Institute (ANSI) will be used as guides in the selection of all electrical equipment. The design of circuits, grounding system and conduit systems will conform to the 1999 National Electrical Code and the National Electrical Safety Code.
4.4 200’ Wide Channel Closure Floodgate
4.4.1 Geotechnical
Introduction. This summary presents the results of the geotechnical analyses for the 200-foot wide navigable floodgate located in the Houma Navigation Canal. Two types of floodgate structures were analyzed. One using conventional construction methods built in the dry (Cast-In Place Structure) and the other using pre constructed float-in methods (Float-In Structure). Braced steel sheetpile walls will tie the floodgate structure into the adjacent levee.
Geotechnical Exploration. Borings used were either the closest existing Corps borings to the proposed floodgates, or new borings taken by Corps at the proposed levee alignment to provide design data for geotechnical analyses. See the corresponding volume listed in Paragraph 4.3.2.1 above for detail descriptions of the available geotechnical explorations at each site. Neither of the floodgates have borings located within the proposed footprint of the structure.
General Geology in the Area of Floodgates. Refer to Paragraph 1.4 of this summary report for the general geology of this area. More specific geology information at the floodgate sites is given in the corresponding volume listed in Paragraph 4.3.2.1 above.
Laboratory Testing Program.
Shear Strength Tests. Specimens from the borings were tested to obtain design values. Visual classifications, water content, Atterberg limits, unconfined compression tests, sieve, and other routine tests were performed during soil processing. Unconsolidated undrained (Q) tests were performed on select specimens from the Corps borings. Test results are presented in the corresponding volume listed in Paragraph 4.3.2.1 above.
Design Shear Strengths. Shear strength data, determined for the proposed floodgate sites, are presented in the corresponding volume listed in Paragraph 4.3.2.1 above. Shear strengths used for the design were determined from combining the shear strength data from available borings.
Survey Data. No survey data was available at the proposed floodgate sites. Ground surface elevations were estimated based on field observations and existing in-house insufficient survey information.
Floodgate Analyses. Typical geotechnical analyses were performed for the floodgate structures.
Pile Foundations. Typical ultimate compression and tension pile capacities versus tip elevations were developed for various pile types and sizes for each of the proposed structures. Typical design parameters used are shown below:
Concrete and Timber Piles Short Term "Q"-Case Long Term "S"-Case f Kc Kt Nc Nq d f Kc Kt Nc Nq d Clay 0° 1.0 0.7 9 1.0 0° 23° 1.0 0.7 0 10.0 23° Silt 15° 1.0 0.7 9 4.5 15° 28° 1.0 0.7 0 17.5 28° Sand 30° 1.25 0.7 0 22.0 30° 30° 1.25 0.7 0 20.0 30° Steel Pipe Piles Short Term "Q"-Case Long Term "S"-Case f Kc Kt Nc Nq d f Kc Kt Nc Nq d Clay 0° 1.0 0.7 9 1.0 0° 23° 1.0 0.7 0 10.0 19° Silt 15° 1.0 0.7 9 4.5 12° 28° 1.0 0.7 0 17.5 23° Sand 30° 1.25 0.7 0 22.0 30° 30° 1.25 0.7 0 20.0 25°
The results of design pile loads versus tip elevations for floodgate structures are presented the corresponding volume listed in Paragraph 4.3.2.1 above. The recommended pile tip elevations for cost estimating purposes shall be based on applying a factor-of-safety as shown below for both compression and tension.
Allowable Pile Capacities Factor-of Safety Without Pile Load Test With Pile Load Test Q-Case 3.0 2.0 S-Case 3.0 (Dead Load Only) 2.0 (Dead Load Only) 1.5 (Total Load) 1.0 (Total Load)
During construction, test piles would be driven and load tested. The results of the pile load tests will be used to determine the length of the service piles where applicable. Sub-grade modulus curves for estimating lateral resistance of the soil at the floodgate structures are shown on the pile capacity plates in the corresponding volume listed in Paragraph 4.3.2.1 above.
Deep-seated Stability. Conventional stability analyses utilizing a 1.30 factor-of-safety incorporated into the soil parameters were performed for potential failure surfaces beneath the floodgate structures. The net driving forces at the base of the structures are greater than for any other failure surface. Therefore, no additional forces need be applied to the structures because of critical failure surfaces below the base. Summation of horizontal driving and resisting force results are shown in the corresponding volume listed in Paragraph 4.3.2.1 above.
Tie-in Floodwall Stability. The required penetration for the stability of the braced sheet pile tie-in walls was determined by the wedge-type method of analysis using the CWALSHT computer program for both the short term (Q) and long term (S) cases. The walls were analyzed for the short-term case using the soil design "Q" strengths and for the long-term (S) case using the "S" shear strengths of C=0 and f=23° for clay strata and C=0 and f=28° for silt strata. Sand strengths are the same for both cases. Hydraulic loading consists of stillwater plus wave loading conditions. Factors-of-safety of 1.5 for the short term (Q) case and 1.2 for the long-term (S) case were applied to the design shear strengths to determine the required tip penetration and moments in the sheeting. A factor-of-safety of 1.0 was used to determine the required brace force. The factors-of-safety were applied as follows: f developed = arctan (tan f available/factor-of-safety) and cohesion developed = cohesion available/factor-of-safety. Using the resulting shear strength, net lateral soil and water pressure diagrams were developed for movement toward each side of the sheet pile. With these pressure distributions, moments about the brace elevation were equated to zero to determine the tip penetrations, and the summation of horizontal forces were equated to zero to determine the brace reaction. Both "Q" and "S" cases were analyzed assuming excavation backfill adjacent to the tie-in floodwall has equivalent strengths as the in situ material. The critical load case results using the free earth method are presented in the corresponding volume listed in Paragraph 4.3.2.1 above. Riprap was used to control scour on each side of the wall and also reduce the overturning moments. The computer runs are also presented in the corresponding volume listed in Paragraph 4.3.2.1 above.
Seepage Cutoff. The required penetration for seepage cutoff was analyzed by utilizing Lane's Weighted Creep Ratio Method. The weighted creep distance was calculated as the sum of the vertical creep path distance plus one-third of the horizontal path distance. Lane's Weighted Creep Ratio is the ratio of the weighted creep distance to the maximum differential head. Seepage calculations are shown in the corresponding volume listed in Paragraph 4.3.2.1 above.
Floodgate Excavation. Excavation slopes were checked by the LMVD Method of Planes using the design (Q) shear strengths and a minimum factor-of-safety of 1.3. See the corresponding volume listed in Paragraph 4.3.2.1 above for the presentation of the stability analyses.
Dewatering. Dewatering for the cast-in place structures may be required to reduce the hydrostatic pressures if future site specific borings determine sands and silts to be below the structure base. The dewatering systems would then require wells or wellpoints.
Foundation Settlement. The floodgate structures are supported on deep foundation piling and are therefore expected to experience negligible settlement. The levee end of the sheet pile tie-in walls will experience settlements approaching that of the levee. Therefore, at the same time levee maintenance or raising is being performed, it will be necessary to pull up to grade any cantilevered portion of the sheet pile wall.
Recommendations. Future geotechnical studies should focus on obtaining complete soil data and surveys that give adequate knowledge of the structure sites. More in-depth investigation is needed to determine settlement, structural foundation analysis and dewatering requirements.
4.4.2 Structural Design
Introduction and Project Features
The primary purpose of the Houma Navigation Canal (HNC) floodgate is hurricane protection. Two alternatives were evaluated for the floodgate, with the only difference being the clear width opening. One alternative assumes a 110-foot width opening, whereas the other alternative assumes a 200-foot width opening. Each of the alternative floodgate structures would consist of a single gate bay with a set of sector gates, based upon a traditional Corps of Engineers configuration
This report represents a summary of the feasibility design considerations for construction of the Houma Navigation Canal Floodgate. The geotechnical conditions used for this study are site specific, and the cost estimates reflect the site specific feasibility level designs for the floodgate’s two alternatives. Sample feasibility level design calculations for the Houma Navigation Canal Floodgate are presented in Volume 19.
This study presents two design variations for each of the alternatives that are referred to as cast-in-place and float-in. The float-in structure design consists of float-in prestressed/post-tensioned segmental concrete structure on a pile foundation. The cast-in-place variation consists of a conventionally reinforced concrete pile supported structure constructed within a dewatered cofferdam. The steel sector gate designs for each of the two variations (float-in vs. cast-in-place) are essentially identical. However, due to the difference in widths assumed for the two alternatives (110-foot width vs. 200-foot width), the sizes of the gates will differ. The heights for the floodgate structures and their gates will all be the same.
Navigation During Construction
Cast-In Place Structure. The cast-in-place design utilizes a large cofferdam and dewatering system, and would require excavation of a temporary by-pass channel on the west side of the existing Houma Navigation Channel during construction in order to maintain navigation. The cofferdam would allow construction of the floodgate to take place using in-the-dry conventional methods. Typically, a temporary timber guide wall will be required to protect the cofferdam from impact and as an aid to navigation during construction.
Float-In Structure. The float-in alternative will not utilize a cofferdam. The concrete structure is constructed at an off-site graving yards and towed to the site. Other features are installed in the channel bottom using in-the-wet construction techniques. Construction of the foundation will be staged to allow for maintaining a minimum width for navigation where possible. If a bypass channel is not needed, reduced power will be required for vessels passing through the construction area. This will minimize any damage to the prepared foundation. A navigation closure period will be required for positioning and sinking of the lower hull section and during various subsequent construction work items. Once the structure has been completed to a level that provides adequate stability, navigation could pass during certain times during each day until construction is completed.
Structural Design of Concrete Monoliths
General. The cast in place and float-in structure alternatives, sector gates and the floodwall tie-ins were designed to a level that demonstrates feasibility. Detailed design will be presented in a future Design Report. Miscellaneous structures including control houses, guidewalls, dolphins and cut-off walls were based on existing structures.
Float-In Structure Alternative
Float–In Structure Design Criteria
The float- in designs include; in-the-wet construction, prestressed/post-tensioned concrete and lightweight concrete in marine environments. Criteria are being developed through the Innovations for Navigation Projects Research Program (INP) concurrent with Corps districts’ ongoing design efforts. A portion of the information has been developed in the concrete and offshore industry codes. Designs with both normal and light concrete were included in this study for the float-in design. The evaluation focused on the effects of weight on draft, floatation stability, and structural considerations. An evaluation of findings regarding suitability or durability of lightweight concrete could not be incorporated into this report. Final determination as to the suitability of lightweight concrete and specific mixes to be used will be addressed in a separate concrete materials design report.
a In-the-wet construction. In-the-wet construction has been used for years in the offshore industry and is addressed by the American Concrete Institute. The proposed in-the-wet construction design is based on draft INP recommendations, typical designs and details are borrowed from the offshore industry. b Transportation Loading. The float-in module is designed for loads encountered during float-in. Three buoyancy conditions are considered: still water level condition (SWL), hogging wave condition, and a sagging wave condition. In preliminary design, longitudinal hull loads were used for initial sizing of the hull. Longitudinal, transverse and torsional loads should be considered in final designs. c Strength and Serviceability. Strength is based on prestressed/post tension design approach. Load factors are given specifically for float-in type designs. In a marine environment, minimizing or eliminating concrete tensile stress during float-in to improve durability should be a design consideration. d Prestressed/Post Tensioned Concrete Design. The use of prestressed/post-tensioned concrete has existed for float-in type structures since the early 1980’s (Gerwick, 1990). The floodgate structure is located in a waterway with varying salinity. Allowable stresses considering cracking and cover are important issues.
Float-In Structure Design Features
a General. The float-in structure consists of a float-in precast prestressed/post-tensioned concrete structure with integral wingwalls that will be founded on piles. The concrete structure contains three major features: float-in module, upper wing walls and in-fill concrete. The float-in module includes the lower hull and the lower portion of the wingwalls. The overall dimensions of the float-in modules are 435 feet wide by 159 feet long for the 200-foot floodgate alternative, and 261 feet wide by 123 feet long for the 110-foot floodgate alternative. The float-in modules for both alternatives are expected to be approximately 20 feet deep.
The float-in modules and upper wing walls are constructed off site in a graving yard. Concurrent with the construction in the graving yard, battered bearing piles will be driven in the wet, and cut off underwater at the proper elevation. Once completed, the lower section is floated to the site and sunk onto landing pads. Hydraulic flat jacks are installed on each landing pad for positioning. Tension piles are then driven through ports formed into the lower hull section. Sheet pile cut-off walls are driven and a temporary skirt is installed to confine underbase concrete. Underbase tremie concrete is placed to provide a seal between the structure and founding soils. It also transfers bearing loads between the structure and the battered piles. Underbase concrete reinforcing and shear transfer should be evaluated during future design phases.
The monolith is subdivided into precast concrete panels that are tied together with cast-in-place closure pours. The precast panels are prestressed to resist handling loads and contain conventional reinforcement and post-tensioning ducts. The closure pours are sized to allow adequate room for tie-in reinforcement, post-tensioning ducts and limit reinforcement congestion to ensure concrete consolidation. The lower hull or base slab is continuously post-tensioned after assembly of the precast concrete panels.b Transportation Design. The lower hull was designed as a prestressed/post-tensioned concrete barge to resist transportation loading. Draft analysis, still water and hogging wave stress analysis were performed. Due to the load distribution in the lower hull, sagging wave stresses will not be a concern. Temporary auxiliary buoyancy could be used to reduce the draft by 1 to 2 feet, if required. Simple floatation stability was performed as outlined in the Draft EC, Design of Precast and Prestressed Hydraulic Concrete Structures. The large ratio of hull width to draft depth ensures that overall floatation stability will not be a problem. c Erection Design. Erection loading includes installation of float-in or lift-in modules and other construction loading. Feasibility of the set down condition was evaluated. The setting load condition addresses the sinking of the lower hull onto the prepared foundation. Temporary pile founded landing pads are required to position the lower hull prior to concreting the base. Landing pads were designed for a set down load that included a 5 percent negative buoyancy load plus the added load when the water elevation drops two feet. d Final Configuration. In the final configuration, each load case was analyzed for vertical, lateral, overturning and flotation stability. A summary of overall stability results is presented in Volume 19. Vertical resultants for each load case were shown to act through the kern, and floatation stability is summarized. Vertical tension piles minimized the infill concrete needed in the wing walls to reduce slab moments. The vertical tension piles provided the necessary resistance against flotation. A pile foundation was designed in accordance with EM 1110-2-2906, Design of Pile Foundations. The layout was based on 24 inch diameter steel pipe piles with a design compression capacity of 135 kips. The capacity was based on a factor of safety of 2, which will require pile testing. The dewatered case required tension piles to achieve the 1.3 floatation factor of safety. The tension piles were 24 inch diameter steel pipe piles with a design tension capacity of 102 kips using a factor of safety of 1.5. The bearing piles are battered in both directions to resist lateral movement and modeled as fixed to the base slab. The tension piles are vertical and extend into the base slab and were modeled as fixed. The lower hull is in-filled with a sand light-weight concrete for ballast, which forms the base slab in the final configuration. The in-fill concrete was designed to act as dead load only and not as a structural composite. The uniform pile layout was modeled as an average uniform bearing load evenly distributed under the base. Longitudinal moments and shears were calculated to check sizing of the base slab and post-tension requirements.
Cast-In-Place Structure Alternative
Cast-In-Place Design Criteria. The cast-in-place designs incorporate conventional normal weight reinforced concrete.
Cast-In-Place Structure Design Features
a General. The cast-in-place floodgate structure is cast-in-place concrete founded on bearing piles. The structure is designed monolithically on a continuous mat foundation. Floodwalls will extend to the levee system, maintaining the top of structure elevation. b Construction. Prior to construction of the floodgate structure, a by-pass channel will be established on the west side of the proposed lock and construction of a cofferdam will be completed. Once the site is prepared, prestressed concrete piles will be driven. Alternate rows will be battered in alternate directions parallel with the channel. The piles will be imbedded in the concrete mat with steel anchors. After installation of the piles, a reinforced concrete base slab will be cast in place. Reinforced concrete wing walls will be formed on the base slab. The walls are supported by the heavy gate anchorage abutments and intermediate wall buttresses.
Structural Design Loads and Design Data
The float-in and cast-in-place floodgate structures were designed for the following load cases:
a Transportation Loading. The lower hull was designed as a prestressed/post-tensioned concrete barge to resist transportation loading. Draft analysis, still water and hogging wave stress analyses were performed. Due to the load distribution in the lower hull, sagging wave stresses will not be a concern. Each of the two alternatives for the concrete floodgate float-in structures will draw approximately 13 feet of water (with sector gates and machinery installed). The wave loading assumes that the concrete float-in structure will only be transported within the intracoastal waterway system. The loading considered two cases: 1. Still water condition with no waves, and 2. Hogging waves of 3 feet in height with an assumed period equal to the full length of the floating structure. b Final Configuration. The hydraulic data is presented in TABLE 2.8.7 HYDRAULIC DESIGN CRITERIA for specific structure criteria.
Sector Gate Design
General. This appendix describes the methods and assumptions used in the design of the sector gates. Two movable sector gates are required for the floodgate. Each sector gate consists of three basic parts: An arc-shaped steel damming surface, a pintle, hinge or pivot pin, and the steel framework that connects and transfers water loads between them. The total floodgate opening widths are 200 feet and 110 feet for the two alternatives. The sector gates for the 200-foot alternative have a radius of 118’- 4", and the sector gates for the 110-foot alternative have a radius of 74’ – 0".
References. The applicable sections of the following references were used to formulate design criteria for the various structural components.
a EM 1110-2-2105, Design of Hydraulic Steel Structures (March, 1993). b EM 1110-2-2703, Lock Gates and Operating Equipment (June, 1994). c EM 1110-1-2101, Working Stresses for Structural Design (November, 1963) d AISC, Manual of Steel Construction, Allowable Stress Design, Eighth Edition
Sector Gate Configuration and Construction. The sector gates are all steel, welded structures, with the exception of some mechanical parts and timber fenders. Construction of the sector gates will incorporate standard steel fabrication methods. The arc shaped gate-damming surface is a hollow steel box structure with watertight ballast compartments. The buoyancy of the sector gates will be controlled by providing a permanent pumping system that will be capable of mitigating any unexpected loss of buoyancy. The operable ballast compartments will be accessible from vertical hatches on the upper deck, in order to facilitate their inspections. The Corps is currently in the process of researching alternative methods for use in ballasting the sector gates during removal and replacement operations. The framing for the gates consists of two horizontal frames located roughly at quarter points on the box beam consisting of welded steel tubing. However, the gate design and geometry will be refined and optimized in the next level of study. Variations in interior angle, radius and configuration of interior frame members will be investigated. The sector gates’ tube members will be sealed at intersections with welded internal diaphragms to create multiple watertight compartments. External corrosion protection will be achieved by a paint system supplemented by a sacrificial anode cathodic protection system. Internal corrosion protection for the structural tubes will be accomplished by a two step internal treatment of the tubes. The first step will involve flushing the pipes with a degreasing solution, and the second step consists of treating the members with an environmentally approved "floc" coating. Inspection plugs will be provided for internal inspection of buoyant members. Additional buoyancy can be provide by the gate’s supporting tube framework and by a trim compensating tank located near the hub. The size and location of buoyancy features will be determined concurrently with the final design of the gate. The buoyancy will reduce wear and stress on the sector gate, pivot bearing, and associated gate machinery. The sector gate and associated machinery will, however, be designed to demonstrate normal functioning without supporting buoyancy, in case of an emergency.
Sector Gate Design Criteria. The general layout and design of the sector gates was conducted using the criteria of EM 1110-2-2703, Lock Gates and Operating Equipment. EM 1110-2-2105 states that allowable stress design shall be conducted using 83% of the stresses determined from the AISC allowable stress design method. The actual loading considered five load cases: Maximum Direct Head from Hurricane; Maximum Reverse Head from Hurricane; Operating, Maximum Direct Head; Operating, Reverse Head; Maximum Direct Head from Hurricane.
In addition, EM 1110-2-2703 requires that a 125 kip boat impact load be applied as a point load on the horizontal beams supporting the gate face and at any panel point on the canal side of the gate framing. Another loading considered in the sector gate design was the closing torque on the gate when it is operated under reverse head. Forces in the gate hinge and anchorage were determined from the gate reactions
Floodwall and Miscellaneous Structures
a Floodwalls. The floodwalls extend from the floodgate structure to the levee system. The walls were designed as standard sheet pile walls, braced by walers that transfer the lateral loads into the battered bearing piles b Control and Machinery Houses. A control house is provided to shelter the gate control systems and to provide space for a gate operator, as required. A machinery house is provided to shelter the gate machinery from the weather. While the control and machinery houses have not yet been designed, cost estimates for these structures were based upon historical data from similar structures. c Guide walls and Dolphins. Guide walls and dolphins are provided as aids to navigation and to protect the main flood lock structure from impact. The structure designs, wall lengths and cost estimates were based on similar projects. d Cut-Off Walls. A cut-off wall is provided on the flood side of the structure to reduce possible seepage, scouring and reduce uplift. A PZ 22 sheet pile section was assumed for use in the cut-off walls to extend down to the same cut-off elevation as those used for the adjacent flood walls.
4.4.3 Mechanical Design
Gate Operation. Gate operation will be two speeds with a time dependent 1 to 4 second speed ramp at start, stop and speed changes. The dual speed and speed ramp will be accomplished electronically by way of a hydraulic proportional valve. A slow gate speed of 3.5 degrees per minute will be used near the end of gate travel, (1 to 3 feet from fully close or fully open, measured at the skin plate). A higher speed of 20 degrees per minute will be used in between the ends of travel.
Gate Operating Machinery. The gate operating machinery will be a rack and pinion gear drive. The rack will be attached to the gate along the outside radius of the gate's skin plate. A pinion drive gear will be attached to a low speed high torque hydraulic (LSHT) motor mounted on the lock wall. In order to provide clearance, between the LSHT motor and gate, an idler gear will be used. The idler gear has a 29" pitch diameter and the drive pinion has a pitch diameter of 21". A the Series 64 Hagglunds LSHT hydraulic motor operating at 2500 psi was used for design purposes. Arranged in this configuration, the motor can provide a tangential force at the rack of 36,300 lbs. with a differential pressure across the motor of 2500 psi. It is anticipated that between 25,000 and 30,000 lbs. of tangential rack force will be required. Each gate will be equipped with its own hydraulic power supply. The hydraulic power supply for the motor will consist of a variable delivery pressure compensated pump driven by an electric motor. The electric motor will be 20 horsepower. A second smaller motor and pump will be provided as an auxiliary supply. The gate operating machinery is shown on Plates M-3 and M-4.
4.4.4 Electrical Design
a Scope. The design for the lock includes provisions for power, controls, lighting, emergency power and grounding. b Design Criteria. The various sub-systems are designed to use standard equipment, material and products of the electrical industry. In the selection of the materials and equipment, special consideration was given to ease of operation, reliability and maintenance. The standards of the National Manufacturers Association (NEMA), the Institute of Electrical and Electronics Engineers (IEEE), and the American National Standards Institute (ANSI) will be used as guides in the selection of all electrical equipment. The design of circuits, grounding system and conduit systems will conform to the 1999 National Electrical Code and the National Electrical Safety Code.
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