| The parts of ultra-thin-walled cold-formed steel building are produced in factories and assembled in layers on site,which meets the requirements of the construction industrialization put forward by the state.Previous studies have shown that low-rise buildings have good seismic performance and can be widely used in high-intensity seismic fortification areas.However,when the structure is used in multi-storey buildings,the horizontal seismic action will increase with the number of stories increasing.It is difficult to ensure the safety of the structure only by strengthening the lateral members and other measures.In view of the obvious characteristics of spatial integrity and axial compression increase caused by multi-member and multi-storey,the seismic performance of components and the seismic design method of structures are studied to ensure the safety and reliability of structural load-bearing capacity.In this thesis,a systematic experimental study and theoretical analysis of multi-storey building system are carried out,including the method of interstorey reinforcement,seismic resistance of composite wall-slab joints,shear resistance of double-storey composite wall with floor joints and seismic design method of structure.The specific work is as follows:(1)Five methods of structural strengthening are put forward in the weak parts of the structure,and they are applied to the structural strengthening measures between the floors of buildings.The mechanical properties of the components were studied,and the bearing capacity and deformation indexes were obtained.The applicability of the strengthened components was determined by considering the limit of inter-story drift ratio and the damage resistance.(2)In this thesis,a study on the shear behavior of 23 full-scale composite wall specimens with floor joints under low-frequency cyclic loading is presented.Considering the form and quantity of anti-pulling anchor bolts,the type and thickness of panel,the axial pressure and the inter-layer strengthening parts,the influence law on the seismic performance of the wall is obtained.The stiffness degradation curves,inter-story drift ratio and failure characteristics of wall layers are abtained,which provides a criteria for the acquisition of Damage-based Seismic Design Methods of structures.The feasibility of adopting component strengthening measures is determined to meet the seismic design principles of "strong connection weak wall".The characteristic values of hysteretic curves and restoring force skeleton curves are obtained,which provide basic data for Damage-based Seismic Design of structures.(3)The comparative aseismic performance of 18 column-floor beams and 7 composite wall-slab spatial joints with diaphragm are studied.The influence of joint type,section height and type of column,axial compression ratio and angle steel thickness on the aseismic performance of the joints is obtained.Since the stiffness of the joints increases after cladding,the self-tapping screws at the floor joints are mostly invalid before the failure of the panel,the failure of the self-tapping screws is the key to the success of the connection.The restoring force skeleton curve eigenvalue of the node is obtained,which provides the basic data for the seismic performance calculation of the structure.The load capacity and stiffness decrease gradually,and damage is the result of cumulative damage.The joints failure modes,the property of hinge or rigid joint are acquired,which provides a criterion for obtaining the simplified mechanical model of th e structure.(4)In view of the decentralized load-bearing and multi-member characteristics of the structure,the concept of structural damage index is introduced,and a Damage-based Seismic Design Method for multi-storey buildings is proposed.Based on the shaking table test of full-scale low-rise buildings carried out by domestic and foreign scholars and combined with the double-deck composite wall and composite wall-slab joint test carried out in this thesis,the allowable damage index,the top floor displacement angle and the allowable limit value of the inter-story drift ratio of different damage grades are analyzed,and the corresponding relationships among the damage characteristics,damage grades and allowable damage index under the five damage grades are established to form the damage criteria for evaluating structures under horizontal earthquake.Simplified mechanical analysis model is established by using the Pivot connection element in SAP2000 is used to simulate the wall and simplify it.A simplified mechanical analysis model is established to calculate the seismic performance of the wall under different earthquake intensity and compare with the relevant formulas to confirm the feasibility of the method.The damage index and the inter-story drift ratio are obtained to characterize the damage state of the structure.The damage grade of the structure is evaluated by the damage criterion obtained in this dissertation.By adjusting eigenvalue of the restoring force skeleton curve of the wall in the Pivot connection element,the aseismic design of the structure is completed under the condition of meeting the requirements of the "three-level" seismic fortification,and the Damage-based Seismic design method is obtained. |
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