The shakedown limit state of slab-on-girder bridges

The purpose of this dissertation is to develop the analytical models to evaluate slab-on-compact steel girder bridges for the shakedown limit state. The two major components that will lead to a more rational and consistent resistance model are the incorporation of the post-elastic strength of redundant steel structures and the structural system analysis in place of the current isolated girder analysis using lateral distribution factors. The result is a structural resistance model for the shakedown limit state of bridge systems.; Two major developments of this work are: (1) the direct method for finding the global shakedown limit load of a bridge system. (2) the inelastic analytical programs to analyze bridge systems in the post-elastic range.; The models were applied to three example bridges. The shakedown limit state showed a significant reserve capacity over that of a first hinge formation (elastic) limit state. This reserve capacity is being ignored in current (1990) ultimate limit states methods. Many of the bridges classified as deficient using current elastic ultimate limits may become sufficient if a true representation of the ultimate strength were considered.; The analytical models were also compared to the experimental results of three full-system bridge tests. Three aspects of bridge behavior were investigated: elastic response, inelastic response, and collapse. The analytical models predicted both the elastic force effects and the deflections of the FHWA-AISI Autostress Bridge Tests with good accuracy. In the inelastic tests of a one-third scale, three-span bridge, the models predicted the inelastic distribution of forces reasonably well when consideration was given for the poorly behaved concrete slab.; The analytical models predicted the ultimate load capacity of the one-third scale bridge test and a Tennessee full-scale bridge test within 5%. The load-deflection behaviors were also in good agreement. The models also predicted that somewhat non-typical failure mechanisms in each of the experimental tests.