Shaking Table Test And Analysis On Seismic Performance Of Multi Unit Connected Steel Structure

In the past decades,with the rapid development of science and technology and economy,people’s requirements for architecture are not only limited to its architecture function.Higher requirements for its visual function,cultural and artistic function are proposed.On this condition,all kinds of landmark buildings continue to emerge.In order to express their cultural meaning and play their special visual functions,these buildings often use unconventional modeling,and then need to use all kinds of irregular forms of structural design.Chengdu natural museum project is one of the representative projects.The structure is composed of six steel structural units connected with each other.The vertical members are inclined and bent along with the structural facade.The roof of each unit adopts large-span space grid.According to the current code of China,the ultralimit designs of this structure is as follows: there are local discontinuities in the floor slab,irregular concave convex in the plane,irregular torsion in the plane,discontinuities in the vertical lateral force resisting members,asymmetry of each unit connected by different strength connecting structures.In order to ensure the safety of the structure and support the design institute,shaking table test of 1/25 scale model of the main steel structure of Chengdu nature museum is carried out.The acceleration,displacement,strain response and dynamic characteristics of the structure under various intensity conditions are obtained.The key data such as displacement angle and torsion angle are calculated,and the seismic response of the whole structure and each unit is analyzed.Performance analysis is carried out to find out the relatively weak parts.Based on the measured ground excitation and the finite element analysis,the elastic-plastic time history analysis of the prototype structure is carried out.The results of the dynamic characteristics obtained by the analysis are compared with those obtained by the test,and the rationality of the finite element analysis is verified.Finite element analysis is used to analyze the support form selection of the middle weak corridor and the feasibility of the support strengthening measures of the unit with weak lateral stiffness in front of the structure.The main conclusions are as follows:(1)The peak value of story drift angle is 1/303 under 7th intensity frequent earthquake,which is less than the limit value of 1/250 in the current code;the peak value of story drift angle is 1/104 under 7th intensity rare earthquake,which is less than the limit value of 1/50 in the current code,and the structure remains intact in the test.The structure meets the current three-level seismic fortification requirements,and the overall seismic performance is good.(2)There are many irregular forms such as staggered floors and large-area openings in the structural plane,and the stiffness center and mass center of each floor deviate greatly,which leads to obvious torsional of the structure under earthquake.The frequency band of the overall translational response of the structure is close to that of the torsional response,indicating that the lateral-torsion coupled response is visible..(3)Due to the staggered floor and large-area openings in the second floor of the structural hanger unit,the local torsion is strong.(4)The results show that the natural frequency of the structure is close to that of the model test,and the error is in a reasonable range.Under the same ground motion input,the results of the acceleration and displacement of the structure are in good agreement,and the finite element model is reasonable.(5)The analysis of structural energy consumption components shows that the structure starts to enter the elastic-plastic working state under the 8th intensity rare degree rare to 9th intensity rare degree,and the degree of plasticity is deepening,but the degree of plastic development is limited.As a result,the structural damage is small.(6)The analysis of plastic hinge out shows that the column base of the hanger unit is relatively weak.By selecting the one with larger response to analyze the hysteretic curve of plastic hinge in detail,it can be seen that the hinge member is in good working condition and has not been damaged.(7)Through the comparison of finite element analysis,the form of weak corridor support has little influence on the main structure.When the weak corridor support is rigidly connected at both ends,the internal force distribution of the corridor is relatively reasonable.(8)In view of the large response of the front atrium unit roof in the test,the finite element analysis is used to evaluate the strengthening scheme of adding support.The results show that adding support can effectively reduce the acceleration and displacement response of the unit roof,and strengthen the lateral stiffness of the unit.