Monolithic reinforced concrete bridge joints under cyclic excitation

Joint regions in monolithic bridge connections often present geometric complexities owing to the structural detailing of the converging members, such as the occasional presence of passages through the body of the connections, the use of relatively high reinforcing ratios and the type of column section (circular or rectangular). An open issue in such circumstances is the definition of the effective joint area mobilized in shear transfer, and the effectiveness of joint reinforcement placed outside the joint panel in the adjacent members. In order to explore the effects of these geometric complexities with particular reference to the adequacy of the Eurocode 8-II (2005) design guidelines for bridge joints an experimental program was carried out on scaled specimens representing bridge monolithic connections under reversed cyclic loading and combined gravity loads. A total of ten specimens were tested. Of those, six represented pier column-superstructure joints, loaded either in the direction transverse to the bridge axis (four specimens) or along the bridge axis (two specimens), at a scale of 1/5. The remaining four specimens represented column-footing connections at a scale of 1/10. Parameters of study were the presence of openings longitudinally or transversally through the joint, the option of decongesting the joint by placing some of the required reinforcement in the adjacent converging members, the shape of the column cross section and the depth of the connection body since these parameters both define the joint volume engaged in shear transfer. The paper summarizes the experimental programme, the primary findings and the implications on established design practice for improved redundancy of force transfer.