Experimental study on the post-cracking behavior of preflex beams under cyclic loading

Abstract

Preflex beam composite girders are widely used in the bridge industry. Understanding the post-cracking behavior of preflex beam girders under cyclic loading is essential to improve monitoring and maintenance. The aim of this study was to evaluate the relationship of the deterioration of the lower flange concrete under cyclic loading to the resulting changes in stiffness, neutral axis location, reinforcement bar stress, and steel-lower-flange stresses of the preflex beam. The study also compared the preflex beam behavior with a conventional girder without prestress under cyclic loading. The experimental study included two specimens of the same details, of which one was preflexed and the other was a conventional non-preflexed specimen. The cracking and post-cracking behavior of the specimens were investigated under multiple cyclic loading stages. The study concluded that changes in the concrete crack width can be used to fairly estimate changes occurring in the neutral axis location, rebar stress, and steel-lower-flange stress of the preflex beam under cyclic loading. The smaller width and shorter length of concrete cracks, implying smaller changes in the preflex beam girder, improved its behavior remarkably compared with the non-preflexed girder with wider and longer concrete cracks under cyclic loading. Furthermore, the study concluded that a closer spacing of the shear ribs reduces the crack width. However, the number of cracks would be larger.