Reinforced Concrete Bridge Piers Subjected to Reversed Cyclic Loading

Sixteen large-scale reinforced concrete specimens without web reinforcements were tested to study the behavior of typical bridge piers subjected to deflection reversals that were large enough to cause extensive yielding of the longitudinal reinforcement. The different parameters considered included shear spanto-depth ratio, percentage of longitudinal reinforcement, frequency of the applied load, and axial compressive stresses. Each specimen was SUbjected to a multiple of three cycles of deflection reversals, in increments equal to the yield deflection until failure. Based on parametric studies of the experimental results, a nondimensional factor was introduced to describe the fundamental behavior of such members. The proposed characteristic factor was used to evaluate the ductility, maximum shear stress, energy absorption-dissipation capacities, and the equivalent viscous damping coefficient. The three modes of failure observed were classified according to the range of the proposed factor, and also to the maximum intensity of shear stresses. Based on the experimental results, an expression was introduced to predict the equivalent flexural stiffness in the post-yielding range. Bridge piers are commonly lightly reinforced in both longitudinal and transverse directions. Unlike beams and columns, they fall into different categories in terms of shear span-to-depth ratio, as related to the percentage of reinforcement and level of axial compressive stresses. The main objective of this paper is to study the behavior of typical bridge piers when they are subjected to reversed cyclic deflections large enough to cause extensive yielding of the longitudinal reinforcement. Sixteen large-scale, reinforced concrete specimens without web reinforcements were tested. The specimens were representative of typical bridge piers in terms of material properties, section properties, and construction details. The different parameters considered in this program are the shear span-todepth ratio (a/d), percentage of longitudinal reinforcement (p), frequency of the applied load, and level of axial compressive stresses (a). The exper imental program was divided into three major series, as given in Table 1. The objective for subseries I-A was to examine the effect of shear span-to-depth ratio, aid, on the mode of failure and ductility. For these specimens, the percentage of longitudinal reinforcement was varied to maintain a constant ratio between the shear strength under monotonic load, vc' and the shear stress at yielding of the longitudinal reinforcement, vy • In subseries I-B, seven specimens were tested to examine the effect of the percentage of steel, p. The effect of the load frequency was examined in Ser ies II • Finally, two specimens were tested in Series III with axial compressive force to simulate the actual conditions of the prototype.