GRAVITY DISTORTION EFFECT ON SHAKE TABLE TESTS OF CONCRETE FILLED STEEL TUBULAR SINGLE ARCH RIBS

To study the effects of gravity distortion on the seismic responses of concrete filled steel tubular (CFST) bridges, a shake table test was conducted for 1/10-scale CFST single arch ribs based on the theory of hybrid model of artificial mass. Five artificial masses were set up to obtain different degrees of gravity distortion. Several earthquake waves and artificial waves with five time-compressive similarity coefficients were input in both the longitudinal and transverse directions in the test. The test results indicate that the gravity distortion has great effects on the first natural vibration frequency of the model. The greater the gravity distortion, the greater the error between the experimental and theoretical values of the first frequency similarity coefficient of the specimen will be. When the earthquake waves are adopted with a small frequency ratio, the gravity distortion of the model is smaller, the acceleration response is larger, and the time of the peak acceleration is later. The effects of the gravity distortion and frequency ratio of the input waves on the acceleration response in the transverse direction are more significant than those in the longitudinal direction. The effects of the gravity distortion on the acceleration response can be reduced by adjusting the complementary artificial mass of the model and the frequency ratio of the input waves.