ASPIRE Spring 11 - Aspire - The Concrete Bridge Magazine

Design and Construction of thei-10 Trinity River Bridgeby Michael D. Hyzak, David P. Hohmann, David Collins,and Brian Merrill, Texas Department of TransportationBy February 2011, traffic was using thewestbound bridge. The total project was75% complete. All photos and drawings:Texas Department of Transportation.A combination ofconcrete solutionsThe Trinity River Bridge carries heavilytraveled I-10 over the Trinity Riverbetween Houston and Beaumont.The existing bridge built in the 1950sconsisted of twin structures with acombined roadway width of 52 ftfor two lanes in each direction. Theexisting bridge also had steep 4%grades to provide for 73 ft of navigationclearance. The main span consisted offracture-critical steel through-girdersystems. The existing bridge representeda choke point for the current trafficvolume of 47,000 vehicles/day. Theroadway to the west had already beenwidened to three or more lanes in eachdirection, and similar work is beingdone to the east. For these reasons, theproject will provide welcome relief to avital route.Design SolutionAn original concept was conceivedusing twin continuous steel plate girderswith piers in the water for the mainriver crossing and precast, prestressedconcrete I-beams on the approaches.On the river crossing, this would havenecessitated a significant amount ofriver access for construction. In addition,construction and maintenance of thepier fender systems would be required.With a river opening of 400 ft andenvironmental and navigational reasonsto span the entire waterway, the mostviable option became a segmental boxgirder bridge built using the balancedcantilever method. To minimize projectcosts, the approach spans remainedprecast, prestressed concrete I-beams.With the resulting reduced lengthof segmental spans, a cast-in-placesegmental box girder cast with formtravelers was the preferred structure type.The project was let to contract in 2006.In February 2011, the project wasapproximately 75% complete. The newTrinity River Bridge has twin structures3636 ft long with approach spansof 72-in.-deep precast, prestressedconcrete I-beams supported onreinforced concrete bents using 18-in.-square, precast, prestressed concretepiles. Twin 990-ft-long segmentalbox girder units carry traffic over thenavigable Trinity River with 50 ft ofvertical clearance. Each cast-in-placeconcrete box girder unit consists of a450-ft-long main span flanked by two270-ft-long end spans. The girder depthvaries between 25 ft at the piers to 10.5ft at midspan. This span arrangementwith a back span-to-main span lengthratio of 0.60 required a nominal amountof shored construction at each end.This was required to avoid conflict withexisting multi-pile footing foundationsfrom the existing structure.The twin cell box girder structures are62 ft wide at the top slab level. The 60ft roadway width provides space forfour lanes plus shoulders for each ofthe twin structures, for a total of eightlanes of capacity. The project phasingdictated the complete construction ofthe westbound bridge. Then, all trafficwas rerouted onto the new structure topermit removal of the existing bridgeprofiletrinity river Bridge/ between houston and beaumont, texasbridge design Engineer: Texas Department of Transportation, Bridge Division, Austin, Tex.segmental construction engineer: Summit Engineering Group, Littleton, Colo.prime contractor: Williams Brothers, Houston Tex.precaster: Valley Prestress Products Inc., Eagle Lake, Tex.post-tensioning contractor: Williams Brothers, Houston, Tex.post-tensioning hardware and services: VSL, Grand Prairie, Tex.22 | ASPIRE, Spring 2011