Analysis On Seismic Behaviors Of Truss String Structure With Single Or Double Trusses' Prestress Loss

With the rapid development of China,a lot of modern long-span spatial structures have been constructed for years.Truss String Structure(TSS)is one of the typical long-span spatial structures.It is composed of a truss,struts and a prestressed cable,which is a typical combination of rigid and flexible structures.The prestress of cable plays an important role on displacements and internal forces of the structure.However,due to the construction methods and material properties of prestress structure,the prestress of cable will be lost during constructing and using,which influences the usage of structure.Particularly,people always focus on whether the structure keeps its seismic behaviors with prestress loss.Based on the Guangzhou International Convention and Exhibition Center,modeled by the ANSYS Parametric Design Language(APDL),referring to the test results,the effects of prestress loss on seismic behaviors of truss string structure are discussed in this thesis.Hope it can provide some references for design and construction of truss string structure.(1)The process of APDL modeling and the cable force test of the truss string structure are introduced.The initial prestress of cables are 2140kN~2283kN and 3471kN~3776kN in using tested by the frequency method.The initial prestress of cables are 2005kN~2149kN and 3418kN~4100kN in using caculated by ANSYS.Comparing the test results and numerical results of cable forces,it could be found that the prestress of cables have lost during the stage of using.Furthermore,the values,numbers and positions of the prestress loss are unsure in the spatial integral truss string structure.(2)The effects of single or double trusses' prestress loss on structural seismic behaviors are studied by using time-history analysis method under three dimensional seismic actions.The results show that: the structural seismic response will be increased with single or double trusses' prestress loss,leading to a decline of member capacity.Service ability limit state is beyond when 30% prestress lost.The most disadvantageous combination to structure is achieved and the effects of double trusses' prestress loss on structural seismic behaviors are similar to single truss' prestress loss.The prestress loss increases the structural seismic responses,which is disadvantageous to the structure.(3)The structural dynamic stability under seismic actions is discussed.Firstly,the buckling modal and buckling load factor of truss string structure is calculated by eigenvalue buckling analysis.Secondly,considering geometric nonlinearity and material nonlinearity,the critical load of dynamic stability is achieved according to B-R criterion.Finally,the dynamic buckling deformations and buckling stress change of structure are analyzed in detail.