Shear Behavior and Design of High Strength Concrete Prestressed Bridge Girders

A simple semi-empirical set of equations was developed at the University of Houston (UH) to predict the shear strength of PC I-girders with normal-strength concrete. The UH-developed equation is a function of concrete strength, web area, shear span to effective depth ratio, and percentage of transverse steel. This research intends to validate or modify the UH-developed equation for (1) high-strength concrete and (2) different sizes of PC girders and studying the possibility of premature failure due to local failure in end zone. Ten modified Tx28 PC girders, derived by scaling down an existing TxDOT cross section, were tested in this study for the first objective. The girders were divided into three groups (Groups A, C and F) based on the concrete strength. Each group of the PC girders was tested with different shear span to effective depth ratio. The validity of the proposed UH-developed equations was ascertained using the experimental results. It was found able to predict accurately the ultimate shear strength of PC girders with concrete strength up to 117 MPa (17,000 psi) with enough ductility. Six PC girders of Tx-series with three different sizes were tested for the second objective. The girders were divided into three groups (Groups D, E and G) based on the girder depth. The experimental results ensured the validity of the UH-developed equations for PC girders with different sizes. Also, the experimental data showed that the PC girders of the new Tx-series can reach the maximum shear capacity without a shear-bond failure. The results of testing the 10 modified Tx-28 girders were used to validate a finite element program developed at UH, Simulation of Concrete Structures (SCS), for PC girders with different concrete strength. Analytical results presented in this dissertation proved the validity of SCS to predict the behavior of PC girders with different concrete strength up to 117 MPa (17,000 psi).