Comparative experimental study on shaking table test of small radius curved bridge considering different connection types between pier and beam

During the Great Wenchuan Ms 8.0 earthquake, many small-radius curved bridges suffered varying degrees of damage, including Baihua Bridge, Huilan Overpass, and Xiaohuangou Bridge. To understand the damage mechanism, shaking table tests were conducted on two scaled bridge models with different middle pier connection types. In one model, the middle pier and beam were cast monolithically together (CM bridge), while the other had a fixed support installed at the pier-beam connection (FS bridge). Both bridges were subjected to two earthquake ground motions. Visually, damage differed considerably between the bridges. The CM bridge exhibited many horizontal and circumferential cracks at the top and bottom. Meanwhile, the FS bridge concrete was crushed at the top of the middle pier, which must be paid attention to. Amplification factors, maximum drift ratios, residual drift, planar rotation angles, and bearing slip were analyzed for both bridges. For both structures, amplification factors in the X and Y directions decreased with stronger ground motions, while those in the Z direction showed an opposite trend; meanwhile, maximum drift ratios, residual drift, rotation angles, and bearing slip all increased with stronger motions. The acceleration amplification factors of the CM bridge increased with greater ground motion, rising rapidly. The CM bridge saw a maximum drift ratio of 7.07 versus 3.16 for the FS bridge. The trend for the CM bridge was a gradual increase, while the FS bridge had a sudden increase after the maximum drift ratio reached 1.61%. The CM bridge planar rotation angle rose gradually to 0.23 degrees, while the FS bridge angle increased much faster, reaching 0.54 degrees or 2.35 times that of the CM bridge. The FS bridge concrete splitting failure demonstrated vulnerability to seismic events exceeding the design level and the structural measures in this region should be enhanced in the design.