Seismic Mitigation Function Expansion Of Roof Garden Infilled With Silt And Research On Its Simplified Analysis Method

With the increasing frequent occurrence of earthquake disasters,seismic mitigation of structures is of great concern.From earthquake damage investigations and formal research,it is observed that silt liquefaction exhibits inherent energy dissipation property.Subsequently,endowing seismic mitigation function with roof garden considering silt liquefaction results lighter earthquake disaster while achieving environmental green function.In the sense,the project focuses on investigate the energy dissipation property of roof garden based on dynamic behaviors of liquefaction and post-liquefaction of silty soil,with the concept of ensuring roof greening and reflecting rainwater utilization.With the combination of theoretical,numerical and experimental methodologies,the seismic mitigation mechanicm of the Silt Infilled Roof Garden System(SIRGS)is investigated as well as the seismic performance,and subsequently a simplified analysis method is proposed as well as a reasonable design method.The expected results of this project exhibit distinct economic and social value for enhancing urban comprehensive disaster prevention ability and anti-seismic capacity of buildings in villages and towns.Based on existing research,the optimization design is carried out on the SIRGS by considering the the tuning of main structure and seismic mitigation substructure.And then,the energy dissipation property and the seismic mitigation efficiency of the SIRGS is investigated by conducting free-vibration tests and shaking table tests.And subsequently,with the assumption of homogeneous fluid of liquefied silt,the sloshing characteristics of the SIRGS and its influence on the structural dynamics are studied by using ANSYS software.Finally,a simplified analysis method for single-storey buildings with SIRGS on its top is proposed by considering a single degree of freedom system whose damping ratio is calculated by formulation derived from experimental results.The simplified method is validated by MATLAB program,through comparing its results to experimental response under earthquake excitation.Through the research,some conclusions can be obtained as follows,Under the horizontal earthquake action,saturated silt is prone to be liquefied,which indicates that the SIRGS has certain feasibility in engineering application.Free vibration tests show that the SIRGS induces high damping into the structural system,whose seismic mitigation efficiency is favourable.And damping provided by the SIRGS is proportional to the mass ratio between substructure to main structure,which is not relative to the amplitude of ground motion and structural stiffness.Shaking table test shows that the SIRGS exhibits feasible damping property under different seismic excitations.Under sine waves,damping property is higher when the excitation frequency is close to the main structure natural frequency and the sloshing frequency of liquefied silt.Through the finite element simulation,fluid viscous property mainly affect the sloshing amplitude but frequency.In this sense,the Housner model can be extended to calculate the sloshing frequency of the SIRGS.Moreover,it is obtained that higher viscous property induce longer vibration period of the whole system,which is in accordance with experimental results.Numerical simulations shows that structural response calculated by the simplified analysis method is of high agreement with experimental results under earthquake excitation.