Experimental investigation on the damage accumulation of reinforced concrete columns under mainshock-aftershock sequences

This paper presents the details and results of shaking table tests conducted on six 1/3-scaled reinforced concrete columns subjected to mainshock-aftershock (MSAS) ground motions. For each of the two subsets distinguished by the axial compression ratio in the test matrix, one column specimen was subjected to a standard cyclic loading protocol, whereas the second specimen was subjected to a mainshock ground motion record followed by a standard cyclic loading protocol. The third specimen was subjected to MSAS ground motion records followed by a standard cyclic loading protocol. The cyclic loading protocol was used to examine the degradation of the seismic capacity of the specimens. The intensity of the aftershock ground motion record was 0.68 times that of the mainshock ground motion record. The test results indicated that the damage accumulation of columns induced by the MSAS sequence is significant in the shaking table tests, and the MSAS-induced maximum displacement of the specimen with an axial compression ratio of 0.4 was approximately twice as large as that induced by mainshock only. In comparison with the mainshock only case, the aftershock further reduced the structural strength and stiffness of the specimens by 9% and 7%, respectively. The ductility of the specimens tended to decrease with the increase of damage. The damage accumulation of the column with a higher axial compression ratio was more serious than that observed in a column with a lower axial compression ratio.

Automated summary

This study found through shaking table tests that the damage induced by the mainshock-aftershock sequence on columns is significant, and as damage increases, the ductility of the specimens tends to decrease. Columns with higher axial compression ratios showed more severe damage accumulation compared to those with lower axial compression ratios.