Shake table tests to compare the seismic response of concrete frames with conventional and high‐strength reinforcement

Abstract

AbstractReported test results suggest reinforcement grade can have an important effect on the seismic displacement demands of reinforced concrete (RC) structures. Two one‐story one‐bay RC frames (Specimens C1 and H1) were mounted in parallel on the NCREE‐Taiwan shake table and simultaneously subjected to 16 base motions, each representing a horizontal component of recorded earthquakes. The dynamic tests were followed by quasi‐static large‐amplitude cyclic testing. The specimens had the same nominal dimensions and base shear strengths with longitudinal reinforcement that was Grade 60 (60 ksi [420 MPa]) in C1 and Grade 100 (100 ksi [690 MPa]) in H1. Maximum drifts of H1 were 1.3 to 2.3 times larger than for C1. The lateral stiffness of H1 was consistently lower than C1, with stiffness ratios (H1 to C1) ranging from 0.78 after Run 1 to 0.45 after Run 16. Drift estimates using stiffness values based on gross‐section properties provided a reasonable upper bound for C1 but were unconservative for H1. Drift estimates based on the secant‐to‐yield stiffnesses, which were inversely proportional to reinforcement grade, provided an upper bound for both specimens. Preliminary recommendations are made for accounting for these effects in design.