Study On The Structural Performance Of The Complex Long Span Spatial Steel Truss During The Whole Construction Process

Owing to its good mechanical properties,long span spatial steel structure is widely used in industrial plant,exhibition hall,stadium,airport terminal and other buildings.In recent years,due to the need of production and life and the change of aesthetic demand,the requirement for the construction of space steel structure with a huge and complex shape is becoming increasingly tremendous.More complex structural design challenges and engineering implementation are accompanied,in order to ensure the safety of the construction and the requirements of the quality of the engineering,it is necessary to carry out strict analysis and control of the structural performance during the construction period.Based on the construction project of the third waste incineration power plant in Chongqing,using methods that contains field investigation,theoretical analysis and numerical simulation,this paper analyzes the mechanical performance of the three stages during the construction,including truss unit hoisting,truss forming and supporting unloading,and carries out the study of the mechanical properties of the complex long span spatial steel structure during the whole construction process.The main research contents and achievements are as follows:(1)In the discrete time domain,the truss hoisting is analyzed and optimized by using the stepwise modeling and analysis method based on linear elastic time-varying mechanics.Through the analysis of the number of hoisting points,the position of the hoisting point,the division of the truss and the hoisting posture,the structural force and deformation response and stability performance under different parameters are investigated.The variation rule of structural performance with various factors is obtained,which provides a basis for selection of engineering practice.(2)Based on the mechanical theory of time-varying structure and the solution method of nonlinear analysis,the mechanical properties of the simple cantilever beam model and single truss are analyzed by the the element birth and death technology,and then the difference between the analysis of structures that one considering the forming process while another not.The path effect of the construction mechanics is explained,which epmpasis the importance of the analysis containing whole construction process,especially complex lasge-span space steel structure.(3)The whole structure model of roof truss structure and temporary support is established.After all the elements are killed,the truss section is activated gradually to simulate the erection of the truss,the spatial maximum response and internal force redistribution characteristics of each construction step are carefully analyzed,and the characteristics of construction steps which needs more attention in the forming process of the complex steel truss is given.Meanwhile,The time history response of the structure is studied,and the cross influence rule of the construction steps in the multi span structure is presented.(4)On the basis of summarizing the selection of temporary support,the method of unloading and the realization of its simulation,the superiority of the standard section combination tower support,especially the tower crane standard section support,is emphasized,and the displacement method of the support frame with compress-only rod,is put forward.The method reduces difficulty of simulation and improves the efficiency,on the premise of meeting the separation simulation and rebound simulation.(5)Using multi span continuous beam,the unloading sequence of temporary support in different span is analyzed.On the basis of investigating the deformation coRelation of multi span continuous beams,a method for determining the unloading sequence of multi span structures is proposed,according to the deformation coRelation of multi span continuous beams,a method for determining the unloading sequence of multi span structures is proposed,which considers the beneficial effect of inter span deformation.Under the premise of ensuring the continuity of the model,the unloading process analysis of the complex large-span spatial steel truss is carried out.Through the analysis and comparison of the four schemes,the sequence characteristics of the structural unloading are obtained.In order to utilize the advantage of the adjacent odd span,the unloading order of the truss is determined from outside to inside.