【正文】 irders. A deck slab that varies in thickness from 260 to directly supports vehicle loads310 mm. The thicker slab segments will m from each tower in both directions. Recast deck panels will span between the floor beams but will not fully cover the top flanges of the beams. Castinplace (CIP) concrete will be placed on top of the floor beams and the exposed portions of the, flanges to make the concrete deck posite with the steelsupporting frame. A 40 mm thick highperformance concrete overlay will protect the deck from corrosion. To reduce stress in the overlay from Bangkok39。s heavy traffic, the bridge has bee designed to have a 3 percent maximum slope.To ensure bridge longevity and facilitate deck, replacement operations, engineers will use reinforcing bars instead of post tensioning tendons in the deck slab. Reinforcing bars will also be used as ties in the footings to resist lateral thrust between the inclined tower legs. Builtup Ishaped steel beams spaced 4 m apart will form the floor beams and will match the m height of the connecting edge girders. The top flanges of the floor beams will follow the cross, slope of the deck. Three longitudinal beams will provide temporary lateral support for the floor beam top flanges before the CIP concrete strips reach sufficient strength. The top flanges of the longitudinal beams will be wide enough to serve as forms for the CIP concrete strips between precast deck panels.The bridge is designed so that the superstructure of the main span can be erected by delivering the major structural ponents to the deck from the towers. The boxshaped steel edge girders have high tensional strength and are designed to cantilever during floor beam erection. With an inclined outside web and a vertical inside web, this m high, boxshaped steel edge girders will deepen to m as they approach the ends to match the depth of the concrete box girders in the approaches. The top flange will be m wide and the bottom flange will be m wide. To make the concrete deck and steel edge girder posite, shear studs will be welded to the flange. Four rubber bumpers at the deck level of each tower are designed to transfer horizontal wind loads from the superstructure. Bumpers eliminate the use of bearings, which require costly, laborintensive inspections and replacements. The bumpers XX 大學(xué)畢業(yè)設(shè)計(jì)（論文）40are easily accessible for inspection and can be replaced by a single person. Cable anchors are located inside the edge girder, which protects the cabletogirder anchors from the elements. A circular access hole ii1 the inside web and a platform will be constructed at every cable connection between the floor beams to provide easy access to the cable anchors for inspection and main tenancy purposes. For aesthetic reasons, the bottoms of the girders have smooth stay cables consisting of 24 to 77 lowrelaxation, sevenwire welds less strands will support the bridge’s superstructure. The strands are 15 mm in diameter and conform to ASTM International39。s specification A41290a for grade 270 strands. The bridge design incorporates the latest advances for protecting cable strands from corrosion, including galvanizing and coating individual strands with wax or grease and then sheathing them in a layer of polyethylene. The protected strands will be placed in a highdensity polyethylene (HDPE) pipe, which, beingwhite, will reduce heat absorption. Welded beads will be placed in a spiral pattern along the exterior surface of the HDPE pipes to control cable vibrations caused by wind and rain.. Since the long cables (up to 260 m) are prone to largeamplitude vibrations, crosstiesan effective and economical method of controlling cable vibrationwill be installed. The wind ties suppress individual cable resonance by forcing cables withdifferent mode frequencies to vibrate together.The Post Tensioning Institute, based in Phoenix, requires that stay cables be replaceable. The engineers have designed the Chao Phraya River Bridge so that one stay cable can be replaced while traffic continues on two lanes in each direction. The bridge has also been designed to allow for the accidental loss of any one cable without bridge failure.The bridge design includes a large chamber on each tower to house cable anchors. The chamber is by m at the top and 23 by 5 m at the bottom and will provide sufficient space for ladders and platforms to directly access all of the cable anchors. A by m opening in the bottom slab will allow for the lifting of heavy equipment or materials directly from the deck to the chamber. This opening will ease construction, inspection, maintenance, and future cable XX 大學(xué)畢業(yè)設(shè)計(jì)（論文）41replacement. Each anchor pier will consist of double columns. The 4 by 4 m hollow reinforcedconcrete structures have m thick walls to facilitate construction and ensure a long service life. The two columns are tied on top for lateral stability. Cantilever arms will extend from the top of each column longitudinally, carrying the weight of the concrete counterweights before the anchor cables are installed. The cantilever arms will also increase superstructure stiffness and reduce bending moments in the edge girders. The concrete counterweights will eliminate uplift at the anchor piers and, in contrast to such monly used tiedown devices, as steel rods, cables, and pins, require only minimal inspection and no maintenance.The bridge, like much of Bangkok, is located in a floodplain, and there is a 15 m layer of soft clay near the site39。s surface. To properly support the towers and anchor piers, engineers will drill shafts 2 m in diameter to a depth of 50 m. The engineers chose 2 m shafts because they possess the lateral bending capacity required for large foundations in soft soils. To facilitate inspection and maintenance, the designers provided easy access to all of the