Mid-story Isolation Of Wood-concrete Hybrid Structure Using Wood Isolation Device

To answer the call for prefabricated building,the wood-concrete hybrid building is a new type of structure that in line with China's current conditions,which solves the problem of the low floor area ratio of pure wood structure and fulfill people's requirement for green buildings.However,research shows that the responses of the upper wood structure under earthquake are amplified as known as ‘whiplash effect' because of the stiffness difference between the upper structure and lower structure,which will hinder the proliferation of the hybrid structure.Inspired by Tou-Kung of ancient Chinese wood structure and based on modern structural motion control theories,a wood isolation device which dissipates earthquake energy by friction was designed.And a series of research about the devices and its application in wood-concrete hybrid structure were carried out as follows:(1)the vertical and horizontal monotonous loading test and low frequency cycling load was carried out on the species of the isolation on devices.The Bouc-Wen model of the devices was identified by genetic algorithm based on the hysteric curve obtained from the test.The results show that the Bouc-Wen model can reflect the energy dissipating characteristic of the isolation device precisely.(2)To test the isolation performance of the devices,mid-story isolation layer was installed on wood-concrete hybrid structure.The finite element model of the hybrid structure was established,and the isolation devices was simulated by the Bouc-Wen model identified from the test data.The time history analysis of the structure under frequent and base earthquake intensities shows that the responses of the isolated structure are significantly lower than those of the original structures.(3)the multiple lumped masses model of mid-story isolation structure was established.A program which solve the dynamic equation numerically using RungeKutta method was programmed in Matlab.The responses of the multiple lumped mass model and the finite element model under rare earthquake was compared.The error of the structural response between the multiple lumped mass model between the finite element model is acceptable,but the analysis of the multiple mass model is much less time consuming.(4)In order to find the optimal isolation parameters,the base shear forces,interlayer drift of the upper structure and the acceleration of the lower structure of the three lumped mass model were derived by random vibration analysis.And the isolation parameters of the hybrid structure in this paper was optimized.The optimization shows that lowering the isolation frequency and reduce the base shear force and the displacement of the upper structure,but the acceleration of the lower structure will be amplified.And there is an optimal damping ratio when the isolation frequency is small.The new wooden isolation device has reliable seismic isolation performance by suppressing the whiplash effect of wood-concrete hybrid structure.Thus,it has high application value.