Study On Progressive Collapse Resistance Of Beam String Structure Based On Improved Configuration Of Bottom Chord And Strut

The traditional beam string structure is often a single vertical strut connecting the upper chord steel bar and the lower chord flexible cable,which makes the redundant degree of the structure not high.If subjected to accidental or extreme load,it is easy to cause progressive collapse and cause significant losses.In order to solve the deficiency of traditional beam string structure,this paper improves the configuration and connection mode of traditional struts,lower chords and other members,and proposes an improved configuration beam string structure.For this structure,the corresponding progressive collapse resistance research is carried out in this paper.The main work is as follows:(1)This paper briefly introduces the research background and significance of the beam string structure,introduces the basic characteristics and engineering application of the beam string structure,summarizes the existing research results on the collapse resistance of the beam string structure,and puts forward a new type of beam string structure which improves the configuration of the lower chord and the strut,and expounds the structural form and connection points of the structure.(2)The practical application project of a traditional beam string structure with a span of 63 m was introduced.A plane beam string structure in the project was taken,and on the basis of it,the structural configuration and member size were improved,and an improved beam string structure with the same span was obtained.Based on the basic principle of force method,the theoretical analysis of the structure was carried out,and the collapse resistance principle after the failure of the lower chord was obtained.(3)An experimental model of an improved beam string structure was designed and manufactured.The local initial failure device based on electromagnetic control was used to simulate the failure of the middle and lower chords of the span.The dynamic test of the model against progressive collapse was carried out.The data in the process of structural collapse test were collected and analyzed.The results show that the improved configuration beam string test model shows good collapse resistance,and it can maintain normal force without collapse under multiple collapse design loads.(4)Based on the ANSYS/LS-DYNA platform,the finite element simulation of the improved beam string structure test model is carried out.The finite element analysis results are compared with the test data,which verifies the correctness of the finite element numerical simulation method described in this paper.The traditional beam string structure and the actual model of the improved beam string structure are analyzed,and the collapse resistance of the two under the same stress conditions is compared.(5)The collapse analysis parameters such as the failure mode of the lower chord,the failure position of the lower chord,the node position of the cross strut and the number of the cross strut in the improved beam string structure are changed.The numerical simulation is carried out in ANSYS/LS-DYNA platform,and the collapse resistance of the structure under different design parameters is obtained.