5. Conclusions
Three different designs of precast concrete frame pier specimens are studied both experimentally and numerically. These specimens are based on real bridge applications, and the study is intended to investigate and verify the seismic behavior of the structures. Based on the study, the following conclusions can be drawn: • The seismic behaviors of specimens #1 and #2 are similar, and the bond-slip phenomena in all specimens are observed in later stage of the test, which indicates that the two types of connections are of equivalent performance. Specimen #3 shows lower energy dissipation capability than the other two, which is mainly caused by the design difference. • In addition, the energy dissipation, stiffness ratio, and residual displacement are almost identical for specimens #1 and #2, while specimen #3 retains lower values in the first two indices but similar level of residual displacement. • The columns of specimen #3 experience little damage at the top, which is mainly taken by the tie beam. Thus, the energy dissipation capacity of the columns is not fully exerted. In other words, the overall seismic performance of the frame pier solely with tie beam is not as good as the cap beam structure, and therefore more attention needs to be paid. • Bond-slip behavior is obvious at locations close to the connections. The connections do not experience significant strain increase despite of the embedded locations, indicating that the connections are able to maintain good integrity. • The inactive length of the skin reinforcement applied to consider bond-slip behavior is optimized to be 6% of the column height, which in turn reduces the initial stiffness and improves simulation results. The unique behavior of beam-column joint regions for frame piers is simulated by implementing Pinching4 material, and it also effectively improves the accuracy of the FEM. GSSC modeled using the Reinforcing Steel material with enlarged diameter is proved to be feasible for FEMs.
