Shaking table test of isolated and non-isolated low-rise masonry structure

To improve the safety and functional retention of masonry structures under moderate to severe earthquakes, a systematic study of the mechanical properties of lead rubber bearings (LRBs) and shaking table tests of seismic isolation masonry models was conducted. Firstly, based on the characteristics of low-rise masonry structure houses and common wall sizes, five small-diameter lead-rubber isolation bearings were designed, and vertical performance and horizontal stiffness tests were carried out. The mechanical performance parameters such as equivalent horizontal stiffness, post-yield stiffness, equivalent damping ratio, and vertical stiffness were obtained. The relationship curve and fitting formula between horizontal displacement, shock absorption coefficient and their influencing factors were calculated. Subsequently, a typical two-story brick structure house without structural columns in a village was selected as the test prototype. A vibration table comparison test with and without seismic isolation layer was designed at a 1:2 scale and full counterweight. Using response spectrum analysis and numerical simulation, three seismic waves were selected for both isolated and non-isolated structures, and sensor placement and loading schemes were designed. Based on the comparison of isolation and non-isolation test phenomena, especially the structural damage of the isolation layer, combined with the dynamic characteristics of white noise sweep frequency, acceleration, displacement, interlayer shear force and interlayer displacement angle, the isolation effect is analyzed and the isolation layer model design is verified. The results show that the vertical compression stiffness of LRB No. 4 is relatively stable, the hysteresis curve is full, the horizontal displacement is less than 60.5 mm, the damping coefficient is less than 0.4, the post-yield stiffness is 149.7 N/mm-167.8 N/mm, and the equivalent horizontal stiffness is 193.9 N/mm-218.65 N/mm. The first two periods of the isolation model are longer and the natural frequency is low, about 25% of the non-isolation model. When the peak acceleration is 0.4 g, the reduction rate of the top layer increases to about 48%, and the reduction rate of the first layer increases to about 40%. The displacement reduction rate of the top floor is about 24% under the action of Tangshan waves, about 36% under the action of Jiangyou waves, and up to 40% under the action of artificial waves. The test results verified the rationality of the low masonry isolation model structure and the isolation effect of lead core rubber bearing(LRB) + Frictionless sliding bearing(FSB).