Hybrid geotechnical and structural seismic isolation: Shake table tests

Abstract

This paper proposes a hybrid seismic isolation system composed of geotechnical (a layer of sand or gravel as foundation soil) and structural isolation (a low-friction foundation sliding layer), aiming to effectively improve the seismic performance of rural buildings with an economical solution. The isolation system is most suitable for low-rise buildings in high-seismic areas. It is also effective in colder climates as replacing sand or gravel as the foundation soil eliminates frost heave. Shake table testing of three 1/4 scale models of two-story masonry buildings was carried out: an unreinforced brick masonry structure (model MA, without isolation), an identical structure with geotechnical isolation (model MS, with a layer of gravel as the foundation soil), and an identical structure with hybrid geotechnical and structural isolation (model MC). The dynamic characteristics and responses of the three structures were assessed and compared. Test results showed that shear failure of brick walls of model MA occurred at the first story when the input peak ground acceleration reached 0.44g. For model MS, a similar shear failure mode occurred when the acceleration reached 1.02g. Model MC relied on the layer of gravel for isolation before 0.44g, and then several cracks occurred at the foundation sliding layer, which was a sign of sliding. The plastic damage was mainly concentrated in the second story, and model MC showed bending-dominated deformation when the acceleration increased to 1.24g. This study clearly demonstrates the improved seismic performance and technical feasibility of the cost-effective hybrid isolation system.

Study on the strain response of slopes containing cavities under the effect of strong earthquakes

“…Before making the model, a 20 cm thick foundation cushion was laid at the bottom of the model box. To weaken the boundary effect of the model box, a 10 cm thick polyethylene foam plate was placed on both sides of the model as a damping layer 38 . The geometric dimensions of the left and right test models were 75 cm long, 145 cm wide, and 90 cm high, and the dip angle of the rock layer was 20° (bedding slope).…”

“…To weaken the boundary effect of the model box, a 10 cm thick polyethylene foam plate was placed on both sides of the model as a damping layer. 38 The geometric dimensions of the left and right test models were 75 cm long, 145 cm wide, and 90 cm high, and the dip angle of the rock layer was 20 was compacted after each layer was deposited during the production process, and the compactness was controlled by the number of trial tampings of the direct shear material before the model was made. In the test, the "−"-shaped cavity structure was set at different heights on the left side of the model, and the "#"-shaped cavity structure was set at different heights on the right side.…”