Inelastic Design and Testing of Steel Bridges Comprising Noncompact Sections

Inelastic design procedures allow the designer flexibility and the possibility of more economical designs by decreasing member sizes and eliminating cover plates and flange transitions at negative moment regions. Previous experimental results show that compact girders designed by these procedures perform satisfactorily when subject to design load levels. Current provisions, however, apply only to compact steel bridges. Expanding inelastic design provisions to include noncompact sections is desirable because of the wide use of plate girders with thinner webs. General inelastic provisions applicable to compact and noncompact sections will create designs that are more consistent over the steel bridge inventory. Previous research has shown that noncompact girders have predictable moment-rotation behavior that can be incorporated into inelastic design provisions. However, although the analytical tools exist, large-scale testing is necessary to validate theoretical engineering practice. Inelastic steel bridge design procedures account for the reserve strength inherent in multiple-span steel girder bridges by allowing redistribution of negative pier region elastic moments to adjacent positive moment regions. The redistribution causes a slight inelastic rotation at the interior pier sections, residual moments in the beam, and some permanent residual deflection. After the redistribution, the structure achieves shakedown: deformations stabilize and future loads are resisted elastically.