۱- Introduction

۲- Methods

۳- Comparison of computer methods to experimental results

۴- Destructive testing

۵- Conclusions

References

Abstract

Currently, there is a limited amount of published information on failures of prestressed concrete bridges subjected to shear and moment. A scale prestressed concrete bridge was constructed to investigate the ultimate behavior of the bridge with particular focus on load distribution after cracking and on contribution of full-depth diaphragms to structural capacity. A point load was applied at the quarter-span point of the bridge over an interior girder. As the loaded girder failed, the diaphragm-girder connection cracked. Torsion was observed to cause cracking in the exterior girder and the end diaphragm rotated away from the bridge as the deck deformed. A punching shear failure ended the test, however damage indicative of two-way slab behavior was observed in the deck. This failure suggests that post girder failure, the diaphragms provide an important means of load transfer, allowing moment redistribution in the deck and potentially increasing capacity. Testing in the elastic range compared favorably with respect to deflections and shear distribution factors from a grillage model, a 2-D finite element model and a 3-D finite element model.

Introduction

There is very little published literature on the ultimate behavior of bridges as a structural system [1,2,3,4,5,6,7,8]. In particular, few tests of prestressed concrete girder and slab bridges have been performed despite this bridge type being extremely common across the United States. Information about failure mechanisms in bridges can provide important guidance to designers and can improve computer modeling techniques to more accurately represent bridge behavior. Since bridges are complex systems, there is no substitute for actual load tests to failure to verify calculations of individual component capacity. A review of concrete bridge tests performed around the world determined that shear failures were particularly hard to predict, non-structural elements (like diaphragms) often contribute to capacity, and that there were fewer tests of prestressed concrete girder bridges than reinforced concrete bridges [9]. This paper details the construction and testing to failure of a roughly half length-scale prestressed concrete girder bridge. The primary goal of the scale bridge testing was to investigate shear behavior of the bridge system with particular attention paid to load distribution and behavior of the middle and end diaphragms. The effects of diaphragms on shear behavior have not been studied extensively and there is conflicting information in the research on their effects on load distribution and behavior at ultimate loads [1,10,11,12,13]. In addition to the bridge test, 2-D and 3-D computer models were built with a goal to determine elastic shear distribution factors (DFs) and compare them with factors derived during bridge testing. Some guidance on developing bridge models to find DFs are given.