Shaking table test of self-centering frame structure considering soil-structure interaction

Abstract

Thanks to their resilience, self-centering frame structures are increasingly being utilized in practice. Releasing the fixity at some of the frame joints allows for dissipation of seismic energy through rocking, while un-bonded pre-stressed rebars can be used to enhance the self-centering mechanism. So far, most studies focused on such frames resting on a rigid foundation, not accounting for soil-structure interaction (SSI). This paper presents preliminary results of shaking table tests, recently conducted on the 4 m × 4 m shaking table of Tongji University (China). Two six-floor self-centering frame structures (SCF) made of reinforced concrete (RC) were tested at a 1:10 scale on: (a) fixed-base, with the structure directly connected to the shaking table; and (b) compliant-base, with the structure founded on a pile-group on a layer of sand-sawdust-mixture, filled in a 3 m diameter cylindrical container, thus accounting for SSI. The comparison of the test results allows for quantification of the role of SSI. A tensile anchor was specially designed to apply the prestressing and anchoring of high-strength rebars to the RC columns. The uplifting of the self-centering frame was captured by an NDI Optotrak Certus dynamic measurement system. The experimental results indicate that both self-centering frames can successfully self-center after the earthquake, experiencing only limited uplifting and sustaining limited structural damage of the RC columns. Subjected to successive seismic excitations, the natural frequency of the SSI system was found to decrease, indicating some accumulation of damage, but to a lesser extent than that of the fixed base system. The presented experimental results offer useful preliminary insights for the design of such self-centering structures.