LATERAL-LOAD RESPONSE OF 2 REINFORCED-CONCRETE BENTS

TWO reinforced concrete bridge bents were subjected to large, transver se displacements. The bents contained detailing deficiencies typical o f the 1960s, including minimal transverse reinforcement, short reinfor cing splices, and a lack of top reinforcement in the footings. Spallin g of the concrete cover at the column tops began at a drift ratio of 1 .5%. At this drift ratio, the column displacement ductility was approx imately four, the curvature ductility was eight, and nominal curvature in the plastic hinges corresponded to a nominal maximum concrete stra in of 0.01. In spite of their deficiencies, the bents resisted transve rse loads equal to nearly 40% of the bridge's weight at a drift ratio of 3%. The ductile response was attributed to a low shear demand and t o the influence of the soil in redistributing the rotational demands a way from the column splices. The measured response was reproduced well by an analytical model that considered the nonlinear force-deformatio n relationships of the columns and soil. The results of a parametric s tudy indicated that the soil surrounding the column bases increased th e column shear demand by 25%.