Comparison Of Prestressed Concrete Girders With Debonded Strands And Harped Strands

Abstract

TxDOT standards follow a design that uses depressed strands for the prestressed concrete I-Girders. A new design criteria using debonded strands for prestressed concrete girders that is widely used in Europe is being introduced in Texas. This new design has been proven to be effective and faster to construct since the strands don't need to be harped. The Lyndon B. Johnson (LBJ) Express construction project was located on I-35 and I-635 in North Dallas Texas and required placement of approximately 7,000 girders to complete this extensive project. A typical girder utilized in this project is the Tx54 with a span length of 110 feet; therefore this particular girder design was studied in this research. The testing of the girders were conducted at the precast plants of two different manufacturers: one manufacture constructed prestressed concrete girders with debonded strands and the other only prestressed concrete girders using depressed strands. For the testing, strain gauges were placed along five girders to measure the reaction of the concrete when the strands are released. This study follows the process of construction for the two types of girders. The beams were tested at the precast plants and modeled by a finite element software to allow for comparison with tested results. This comparison will allow the safest and faster girder design for future construction projects.