Mechanical Performance And Optimization Of Double Vertical Bar Pierced Truss And Double Vertical Bar Pierced Lattic

Nowadays,in order to improve the utilization rate of urban construction land,the single-layer industrial public building is changed to multi-layer or even high-rise building,which makes the innovative research of large-span floor become the current hot spot.According to the bending moment distribution law of traditional vierendeel truss structural members,double vertical rod vierendeel truss and double vertical rod vierendeel grid floor are proposed.They are suitable for multi-storey building floors of about 32m and 45m respectively.The two new structures are quite different from the traditional vierendeel truss and vierendeel grid in structure,which makes the mechanical performance and economy different.It is of great theoretical significance and engineering application value to analyze their mechanical performance and economy.The main research contents and results are as follows:(1)The first-order elastic theory and finite element method are used to study the mechanical properties of double vertical hollow truss.The formulas of equivalent moment of inertia and equivalent shear stiffness are derived,and the accuracy of the formulas is verified by finite element method.Through the stiffness analysis,the reasonable value range of the vertical bar spacing of the double vertical bar vierendeel truss is determined.The calculation formula of shear deformation ratio is derived,and the parametric analysis of shear deformation ratio is carried out.The variation characteristics of displacement caused by shear deformation of double vertical hollow truss are revealed.After a lot of modeling analysis,the economic parameters of the double vertical hollow truss are obtained.(2)The first-order elastic and double nonlinear finite element method is used to analyze the mechanical performance of the double vertical bar vierendeel grid.The overall deformation,vertical bar deformation and internal force distribution of the double vertical bar vierendeel grid are obtained.The variation rules of internal force,mid-span deflection and maximum equivalent stress are obtained by parametric analysis.The thickness of the grid and the width of the chord section have a great influence on the internal force distribution,mid-span deflection and maximum equivalent stress of the members.The influence of them on the structural stiffness,bearing capacity and economy should be fully considered in the design of the double-vertical-rod open-web grid structure floor.Considering the double nonlinear elastic-plastic analysis,the load-displacement curve has a more obvious horizontal section,the ultimate load is 30 k N/m~2,which is 5 times of the normal load,and the structure has a good safety reserve.When all structural members yield,the mid-span deflection of the structure is 0.514 m,which is about 10 times of the normal service load.(3)The new structure is optimized and compared with the optimized traditional open-web truss and the traditional open-web grid.It is found that the double vertical open-web truss and the double vertical open-web grid floor have higher space utilization rate.Under the premise of meeting the design specifications,the steel consumption of the traditional vierendeel truss is 6.2 t,and the steel consumption of the double vertical bar vierendeel truss is 5.1 t,which is 1.1 t less than that of the traditional vierendeel truss structure,saving about 17.5%.The steel consumption of the traditional open-web grid structure is 150.8 t,and the steel consumption of the double vertical bar open-web grid structure is 131.2 t,which is 20 t less than that of the traditional open-web grid structure,saving about 13.3%.Two new structures have been applied to engineering practice.This research provides a reference and optimization design method for the application of similar projects.