Shaking table test of an RC frame considering horizontal and vertical ground motions

This paper investigates the seismic performance of an RC frame subjected to horizontal ground motions and vertical ground motions (VGMs) through the application of a shaking table test of a two-story, 1/2-scale three-dimensional (X-, Y- and Z-axes) reinforced concrete (RC) frame. The horizontal ground motions and VGMs are input along the X- and Z-axes of the specimen, respectively. The structural responses monitored in the test include the specimen's dynamic properties, displacements, and accelerations. The test results support the following findings: (1) the beams of the frame are heavily damaged due to the vertical load caused by the VGM. The damages to the beams on the second floor are more severe than those on the first floor because the vertical loads of the second story caused by VGMs are larger than those of the first story. (2) The vertical acceleration amplification factor of the slab in the first (second) story generally decreases from 3.54 to 2.93 (2.3-1.93) as the seismic intensity increases. (3) The horizontal frequency (X-axis) after the test is reduced to approximately 40% of the elastic frequency of the structure before the test. The vertical frequency (Z-axis) is reduced to approximately 65% of that of the undamaged structure. The horizontal frequency (Y-axis) after the test is also reduced to approximately 56% of the elastic frequency of the structure, although no seismic excitations are input along the Y-axis.