SHAKING TABLE TESTS ON THE SEISMIC RESPONSE CHARACTERISTICS OF DOUBLE-COLUMN PIERS WITH SHEAR BEAMS

Shaking table tests were carried out to study the influences of shear beams on the seismic response of double-column piers that were designed to support the girder of a full cable-stayed bridge model. The double-column pier with shear beams included two columns and five shear beams equally installed between the two columns. A full cable-stayed bridge model of 1/70-scale that included the pier (a double-column pier and a double-column pier with shear beams), tower, girder, pile group, and artificial soil was designed and tested on a shaking table array. The seismic response characteristics were compared between the double-column piers with and without shear beams when they were subjected to various earthquake waves of various frequency contents, such as the artificial, El Centro, and Mexico City waves. The experimental results show that the maximum strains at the bottom of the double-column pier with shear beams were less than those of the double-column pier under the artificial, El Centro wave, and Mexico City waves of various shaking amplitudes. The additional shear beams significantly mitigated the strain responses at the bottom of the double-column pier, and decentralized the inner force of the columns. The maximum accelerations at the bottom of the double-column pier with shear beams are 1.4-1.8 times those of the shaking table when the bridge model was subjected to the artificial, El Centro, and Mexico City waves with 0.1 g, 0.15 g, and 0.2 g. The pile-soil-structure interaction significantly affected the seismic response of the double-column pier with shear beams and increased its longitudinal acceleration responses. The seismic responses, such as the acceleration, displacement, and strain responses of the double-column pier with and without shear beams were significantly affected by the frequency spectral characteristics of the various earthquake waves. The extent of the influence was dependent on the relationship between the frequency contents of the earthquake waves and the frequency spectral characteristics of the piers.