Seismic Performance And Failure Mechanism Of Single-layer Spherical Reticulated Shells With Semi-rigid Joints

As a typical spatial structure,the single-layer reticulated shell structure shows advantages in limitness for loading,economical and flexibility of modeling.The singlelayer reticulated shell structures are usually used in landmark structures.Because of the good seismic resistance,this type of structure is usually used as the temporary shelters for people after the earthquake.However,some space structures were damaged or even collapsed in earthquakes,which caused a great economic and social impact.Prefabricated joints have been widely used in many kinds of buildings because of their high construction efficiency,high quality and environmental protection.However,in the past seismic design,prefabricated joints were generally simplified as hinged joints,and the single-layer reticulated shells connected by prefabricated joints are greatly limited in practical engineering applications.In this study,following the research route from joint to structure,the experimental,numerical simulation and theoretical analyses are used to investigate the mechanical performance of semi rigid joints and the seismic performanc and failure mechanism of the semi-rigidly jointed single-layer reticulated structures under the earthquake load.Furthermore,a dynamic failure mode control method for semirigidly jointed single-layer reticulated spherical shells based on joint performance is proposed.The main research contents are as follows:1.The bolt-column joint without initial slip and gear joint with initial slip were chosen to be as the two typical research subject.The behavior of the two joints was studied in both in-plane and out-of-plane directions.The static and dynamic tests of these two joints were carried out and the static moment rotation curves,hysteretic curves and failure modes of column joints and gear joints under pure bending were obtained.2.Refined finite element models of joints were established.The mechanical property of bolt-column joints and gear joints under pure bending,tension and bending,compression and bending and other conditions was analyzed.The performance difference of the jont with asymmetric cross section under bending around different axes was discussed.Based on the theoretical formula of skeleton curves,the damage models of joints with and without initial slip were proposed,the accuracy of which was verified by the experimental results.The damage model can simulate the damage characteristics considering the stiffness and strength degradation and the slip increase.3.Based on ABAQUS,a numerical analysis model of semi-rigid reticulated shell with semi-rigid joints was established,considering the material damage accumulation,three-dimensional seismic action and initial defects.The failure mechanism of the semirigidly jointed single-layer spherical reticulated shells was studied by introducing the joint damage model into the reticulated shell model.Four typical failure modes were obtained: member strength failure,joint strength failure,mixed strength failure,and dynamic instability.The effect of three joint parameters including joint stiffness,joint bearing capacity and joint slip,and three reticulated shell parameters including span,risespan ratio and roof weight on the failure mode of the structure was obtained.Considering the responses of members and joints,based on yield ratio of members,average plastic strain of members,yield ratio of joints and average damage of joints,a failure mode identification method for semi-rigid reticulated shells was proposed.Based on a large number of parameter analysis results,the damage index of semi-rigid single-layer spherical reticulated shell structure was proposed.The influence of different member section,roof span,rise-span ratio,roof weight and other parameters on structural damage index was investigated.The failure mode control method of semi-rigid single-layer spherical reticulated shell based on joint performance was proposed.The effectiveness of the proposed calculation formulas was verified by comparing the results of the experiment.4.The influence of joint stiffness on the seismic performance of single-layer kewitt spherical reticulated shell was obtained.The limit stiffness ratio and limit yield moment of the joints in semi-rigid reticulated shell with different parameters were proposed.The influence of the roof span,roof weight and member section on the two design parameters was obtained and the calculation formula was established.The seismic force coefficient for the single-layer kewitt spherical reticulated shells with semi-rigid joints were obtained.The effectiveness of response spectrum analysis method for seismic design of semi-rigid single-layer reticulated shells was discussed.The results show that this method can be applied for calculating the seismic response of members in semi-rigid single-layer reticulated shell,but it can not reflect the real mechanical response of the joints.