Quasi-static testing of railway rounded rectangular hollow tall piers having semi-hinged column-base details

Abstract Rounded rectangular hollow tall piers are widely used in high-speed railway bridges in China. However, their oversized sectional dimensions result in the adjacent capacity-protected members (such as the foundation), which are designed to prevent from yielding following an earthquake, likewise having the undesired sizes. To solve this issue, two semi-hinged (SH) base connections aiming at reducing the force transferred to the foundation for this kind of piers were detailed and developed. The only difference between these two SH connections is one of them with the low-strength mortar bed beneath the base. The efficiency of force-reduction for two SH bases was experimentally evaluated by comparison with a conventional fixed-base. Moreover, based on the test data, the seismic performance of bridge piers with the SH and the fixed bases was meticulously compared and analyzed as well. The results demonstrate that rounded rectangular hollow piers incorporating the SH details exhibited stable rocking behavior with a moderate force-reducing capacity, and the employment of the low-strength mortar can further enhance this capacity. Major seismic performance of the SH bases was also comparable to the fixed base; however, the strategies that are prevalent in the controlled rocking systems should be further introduced into the proposed SH bases due to their inherent rocking mechanics.