Research On The Overall Jacking Construction Method Of "post-straightening" For Complex Folded Surface Gri

With the improvement of social and economic level,the number of various venues and railway stations is increasing day by day,and a large number of complex spatial structures have emerged in China,which greatly increases the difficulty of construction.Therefore,it is necessary to put forward new construction methods to ensure the safety and speed of construction.Relying on the construction of the quadrangle cone irregular folding grid roof of the National Fitness Center in Tianqiao District of Jinan City,this thesis had done the following work:(1)Based on the construction site and the characteristics of the grid structure,a new construction method of the grid frame--"Post-straightening" overall jacking method was proposed.The jacking frame is used as the temporary support for the assembly of the grid frame,and the jacking frame is extended and assembled from the jacking point to the four sides.During the assembly process,the height of the jacking frame is adjusted so that the new ball nodes are close to the ground.It has the advantages of fast construction speed,saving construction cost and safety.(2)Determine the construction scheme of grid frame 2,which was "first assemble on the ground,then upright and jack up in place,and then reassemble the rods".Midas/Gen was used to establish the finite element model,and the life-and-death unit method was used to simulate the grid frame assembly scheme and compared it with the measured data.The results show that the simulation results are in good agreement with the measured data,and the assembly scheme is safe and feasible.The stress of the rod at the jacking point is large,and the stress state of some rod changes greatly when the jacking frame is unloaded.(3)To simulate the working conditions of maximum non-synchronicity in the assembling process of the grid frame,considered the influence of the stiffness of the jack-up frame,replaced the grid support with spring support and analyzed the jack-up frame with large stress using Ansys.The results show that the stress of the frame does not exceed the limit under the non-synchronous condition.When the stress state of the structure changes and the stress of the bar increases,the flat reaction of the lifting water increases obviously.When the stress of the bar near the jacking point is the largest,when the stress of the belly bar is greater than that of the chord bar and the vertical displacement difference is the largest,the flat reaction of the jacking water and the stress of the bar are the largest.When the jacking frame is bent and deformed and the internal force it receives increases,the force state becomes eccentric compression state,and the top section cross bar and bottom section column bear the greatest force.(4)The method to determine the straightening value of the grid frame and two straightening schemes,step by step and step by step,were proposed,and the finite element software was used to simulate the two schemes.The results show that there is little difference in the vertical reaction and the stress of the grid frame under the two straightening schemes.Compared with the one-step straightening method,the maximum X and Y horizontal reaction on the jacking point under the one-step straightening method decreases by 12.09% and 11.04%,respectively.For structures with regular form or jacking points located at the same height,it is recommended to adopt step by step method.For structures with irregular form and jacking points located at different heights,it is recommended to adopt step by step method.(5)By changing the stiffness of the grid support to simulate the righting process under different heights,the internal force of the grid frame,the internal force of the jacking frame and the tilt of the jacking frame were used to determine the optimal height of the grid frame righting.The results show that changing the upright height can significantly reduce the horizontal reaction at the jacking point,the internal force of the jacking frame and the inclination of the jacking frame,but has little effect on the stress and vertical reaction of the grid frame.Changing the upright height of the grid frame does not change the overall stress mode of the grid frame and the jacking frame,and the overall stress mode of the grid frame is related to the non-synchronous value.When the jack-up frame reaches 6 joints in D1,the maximum tensile stress of the jack-up frame decreases by 2.89%,the maximum high-pressure stress increases by 1.16%,the maximum tensile and compressive stress of the jack-up frame decreases by 5.23% and 6.27% respectively,and the maximum X and Y inclination of the jack-up frame decreases by 34.42% and 36.33%,respectively.(6)The "Post-straightening" overall jacking method was summarized and extended to the three structures of the grid frame.The results show that the "Post-straightening" overall jacking method is suitable for small space structure with complex structure form,large height difference,difficult assembly and its own bearing capacity,or for the partition assembly of large-span structure;The three assembly schemes and the non-synchronous process in the assembly process are safe and feasible and the error between the simulation results and the measured results is small.At the height of D2,the maximum compressive stress of the straightening frame decreases by 6.09%,the maximum tensile stress increases by 2.55%,the maximum tensile and compressive stress of the straightening frame decreases by11.42% and 36.94%,respectively,and the maximum x-direction and Y-direction inclination of the jacking-up frame decreases by 54.59% and 65.26%,respectively."Righting after" integral jacking method has good safety and applicability,and provides experience for the subsequent construction of similar structures.