Behavior of Girder-Floor Beam Connections in Prestressed Concrete Pedestrian Bridges Subjected to Lateral Impact Loads

Abstract

Each year a large number of concrete bridges are subjected to impact by overheight vehicles or vehicles carrying overheight objects. Most bridge owners in the United States are concerned with the increasing trend of bridges impacted by overheight vehicles, thereby increasing the urgency to evaluate the resistance of bridges to lateral impact loads. The present integrated numerical and experimental study investigates the behavior of a critical connection, between girders and floor beams, in a type of bridge that is considered to be particularly vulnerable, prestressed concrete through-girder (PCTG) pedestrian bridges. PCTG pedestrian bridges comprise precast, prestressed concrete girders connected by cast-in-place, reinforced concrete floor beams and a cast-in-place deck. The deck is connected to the floor beams only, and the floor beams are joined to the girders using embedded concrete anchors. The investigation combines three-dimensional finite-element analyses with physical testing to elucidate the load-deformation characteristics of the girder-floor beam connections. A series of six girder-floor beam connection subassemblage specimens were built and tested, three of which were subjected to vertical loading, while the other three specimens had a combination of vertical and horizontal load. Three types of anchors were investigated, including two types of loop inserts and one bolt insert. The study revealed that specimen response depends upon the characteristics of the embedded concrete anchors. Deterioration of specimen load capacity was found to be associated with concrete cracking, formation of a cone breakout surface, yielding of the anchors, and fracture of the inserts. The floor beam-girder subassemblages were able to resist large displacements after attaining peak load, even though postpeak load carrying capacity was undermined in most cases.