Research On Seismic Performance And Fragility Analysis For Hinged Beam-end CFST Frame-Reinforced Concrete Core Wall Structure

In order to promote the development of building industrialization and broaden the scope for application of assembly technology,this paper proposes a hinged beam-end concrete-filled steel tubular(CFST)frame-reinforced concrete core wall structural system so as to solve the problem of introducing assembly technology into high-rise building.This structural system is a new type of lateral force resisting system that modifying the nodes between steel beams and columns or core wall into hinged connections with bolts in the peripheral frame of CFST framecore wall structural system.It reduces the difficulty of peripheral frame design and improves the economic efficiency for the semi-assembled high-rise building.There is still relatively little research on this new structural system.To research on its seismic performance,this paper establishes a nonlinear finite element model verified by the data of earthquake simulation shaking table test to analyze the influence of the common parameters of structure storeys and area ratio of core wall,quantify and compare the seismic demand of hinged beam ends of peripheral frame in the new structure form,the traditional rigid beam ends of the peripheral frame and the rigid beam-end connections with outriggers and belt members.The main research work and results are as follows:(1)A simplified 1:40 reduced scale specimen representing a real supertall building,named Guangxi financial center,was constructed and performed the shaking table tests.The damage phenomena,dynamic characteristics,maximum lateral displacement,maximum inter-storey drift ratio,maximum torsion angle,seismic inertial force,storey shear force,overturning moment and ductility demand of the structure were studied.The experimental results shows that the damage occur at the connection between the concrete slab and the column on the lower storey,the connection between the concrete slab and the core wall,the connection between the concrete slab and the steel beam,and the corner concrete of the core walls.The basic natural vibration periods and damping ratios increase with the increase of the seismic damage,and the dynamic amplification effect decrease.The long-period ground motion response is more significant.The maximum inter-storey drift ratio of the core wall is 1/26,which exceeds 3.8times of the specification collapse limit for the frame-core wall structure system,but the model structure has no collapse.The torsion stiffness of the peripheral rent frame is small,and the structural torsion response is dominated by the core wall.The earthquake inertia force and storey shear force of the structural damage are less affected by the long-period motion components.The ductility demand of storey has a large differences.(2)Based on the experimental data,a full-scale member models was established by the CANNY,a nonlinear finite element analysis software,to perform elasto-plastic time-historey analysis of the CFST column-steel frame-core wall structural system,which comparing the effects of three different connections: hinged connections,rigid connections and strengthened layers(which are defined as storeys equipped with outrigger and belt members to limit interstorey drift)on the overall structural seismic response.The results indicate that the numerical model has high accuracy and computational efficiency.By comparing the differences of interstorey drift ratio,inertia force,storey shear and overturning moment under the three types of connections,it is found that the strengthened layers can reduce the inter-storey drift ratio of the structure more effectively than the rigid connection,and the rigid connection can maintain a large and stable ratio of overturning moment of the peripheral frame at each floor.(3)The seismic performance of the structure was analyzed in terms of energy,base shear and inter-storey drift ratio to explore the influence of core area ratio and number of storeys on the structure.The results show that the total seismic input energy is mainly related to the earthquake intensity and numbers of storeys,and the hysteretic energy dissipation ratio is affected by the peak ground acceleration and frequency spectrum.The core area ratio of the new structure should increase as the number of storeys increases,which complies with the three-level seismic precautionary objectives of current specification.(4)To understand the effect of the connection type on the seismic fragility of CFST framecore wall structures,typical structures with different numbers of storeys(15,30,45 and 60)and different types of beam-end connections(rigid connections,hinged connections,and rigid connections with outriggers and belt members)are designed.The probabilistic seismic demand models(PSDMs)of the structures are obtained using the cloud method,the seismic limit states of the structures are determined by pushover analysis,and the seismic fragility curves based on the mean seismic period and the number of storeys are established.The results show that the differences in the seismic fragilities of structures with the three types of connections can be effectively determined by the harmful interstorey drift ratio(IDR)and the storey ductility,and the determination method with the harmful IDR is relatively simple.The use of beam-end hinges results in advantageous seismic performance in the sub-high-rise structures,with a lower probability of exceeding limit states,and it is still suitable for high-rise and super-high-rise structures with effective seismic measures.