The complexity of the IH-635 Managed Lanes Project,located in Dallas County,Texas,posed several technical and constructive challenges,leading to the adoption of solutions different from the traditional.Two alternative solutions for the pier cap on one of the bridge crossings over IH-35E in the IH-635 project were analyzed in this case study,a cast-in-place post-tensioned concrete cap and an innovative prefabricated steel-concrete composite cap.The approach was to use an estimation of direct costs for material and labor and consideration of construction time schedules.A supplementary numerical modeling confirmed that both alternatives behave elastically under imposed loads.The direct cost of material and labor for the two alternatives were close.However,the composite alternative required 13 days less construction time,resulting in substantial cost savings from traffic closing in the very busy traffic corridor.Traffic closing costs were substantially higher than the direct costs,especially for the post-tensioned cap.The quantification ofthe benefits allows more confidence in the utilization of the composites caps,leading to faster completion of bridge projects and substantial economic savings.
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