Shaking Table Test Study on Seismic Performance of Hollow Rectangular Piers

Table 6

Failure modes.

Loading conditions (g)	Failure modes
0.25	The specimens had slight vibration, and no visible cracks appeared.
0.5	The vibration of the specimens was obvious, and there were slight cracks at the four bottom corners of the specimens. M7 produced penetrating cracks. There were some horizontal cracks in the middle and lower parts of M5, M8, and M9. Wider cracks occurred at the connection between the bottom of the column and the base of the specimen.
0.75	Shaking of the specimen became increasingly severe, and the specimen was pulled out from the base. Previous cracks on M3 and M4 continued to extend, their widths increased, and new cracks occurred. New penetrating cracks appeared on the M7 specimen.
1.0	The previous crack continued to extend. M3, M4, M5, and M6 had penetrating cracks, the column was pulled out from the base obviously, the new cracks continued to extend upward, and the cover concrete at the root of the pier column began to spall.
1.2	Shaking of the specimen became increasingly severe. All the nine pier specimens had penetrating cracks, the number of cracks increased, and the width of cracks widened. M7 produced four through cracks when the input ground motion was 0.5 g and 0.75 g. With the increase of the peak acceleration of input ground motion, the width of cracks continued to increase, but new cracks did not occur. The cracks of other specimens continued to extend to the upper part of the pier, and the number of cracks increased obviously, but all the specimens had vertical bearing capacity.