考虑安装应力的网格结构稳定承载性能试验研究

为研究安装应力对网格结构承载性能的影响，对平面尺寸为7m×12m和5m×12m的两个正交正放四角锥网架进行破坏性试验及有限元分析，结果表明安装应力使网格结构稳定承载力出现较大幅度的降低。对204个平板网架模型和140个双层柱面网壳模型进行参数分析，得到安装应力对稳定承载力的影响系数。采用有限元分析方法研究了38个具有整体失稳可能性的双层球面和双层柱面网壳模型，得到了稳定承载力安全系数K的合理取值范围。结果表明：试验测得的整体变形、刚度和稳定承载力与理想结构存在明显差异；安装应力对稳定承载力的影响系数服从正态分布，平板网架、双层柱面网壳稳定承载力影响系数分别为0.50和0.55；当考虑安装应力初始缺陷，采用Marshall压杆屈曲失稳模型时，建议K取2.0；由于JGJ 7—2010《空间网格结构技术规程》提供的全过程分析方法未考虑杆件初始应力，建议K取3.0。

Experimental study on load bearing behavior of grid structures with assembly stresses

The influence of assembly stresses on the load bearing behavior of grid structures was experimentally and numerically studied. Two orthogonal spatial square pyramid grids with dimensions of 7m×12m and 5m×12m were tested separately and corresponding finite element (FE) analysis was carried out. It is revealed that the ultimate load bearing capacities of grid structures are undermined significantly owing to the assembly stresses. The influence coefficient of assembly stresses on the ultimate load bearing capacity was obtained according to parametric analysis of 204 plate grid models and 140 double-layer cylindrical lattice shells. A total of 38 potentially unstable double-layer spherical reticulated shells and double-layer cylindrical lattice shells were analyzed by means of FE analysis, revealing the reasonable range for the safety factor. It is shown that there are remarkable differences between the structural performances of the perfect models and the tested ones, such as global deformations, structural stiffness, ultimate load bearing capacities. It can be found that the coefficient conforms to a normal distribution. The value of the coefficient is equal to 0.5 for the plate grid, while this value should be taken as 0.55 for the double-layer cylindrical lattice shells. A value of 2.0 is suggested for the safety factor once the initial imperfection of assembly stresses and the Marshall model are introduced. Since the effect of assembly stresses has not been explicitly considered by design provisions in JGJ 7—2010 ‘Technical specification for space frame structures’, a higher value of 3.0 is proposed.