The Stability Analysis And Experimental Research Of The Bar In Single-layer Reticulated Shell Overall Structure

Single-layer reticulated shell is one of the most used form of space structures. With the development of society, the stability of reticulated shell structure has became a critical factor which restricts its development for the high demanding of span. While compared to overall stability, too little atten tion was paid to the stability of member bars. This paper focus on the stability of single-layer reticulated shell with considering member buckling on the platform of finite element analysis software ANSYS. The influence of effective length coefficient and stability coefficient on the stability of bar was explored, and was verified by testing. The following contents are covered within this paper:For single bar with different cross section, the nonlinear analysis of beam element was applied. The reasonable value for the deficient bar was evaluated comparing FEA results to the calculated value of steel structure specification. The double nonlinear analysis was carried out for the single-layer reticulated shell structure with different cross section considerin g intact bar, only defective nodes or both deficient nodes and bar, respectively. The load-displacement curves of single-layer reticulated shells are obtained and through comparison and analysis, it is conducted that the bearing capacity of bar which consi dered the defects was lower. With the full-process analysis of reticulated shell with different cross section completed, the axial load curves of the unstable members were drawn. It is found that before reaching the ultimate bearing capacity, the member buckling was appeared. And it is also can be conclude that the failure process of reticulated shell structure were mainly caused by one or some bar members. As for circular steel tube cross section, the out-plane instability was basically appeared, while for rectangular section, the in-plane instability around the weak axis was found.The mode experiment and stability test of the reticulated shell with circular section were carried out. According to the test data, it is indicated that combined with stabilization diagram method, the ITD method can be used to identify the modal parameters of the reticulated shell structures. And it also was proved by the numerical simulation of which results were in accordance with the experiment. It can be found that heart-shaped damage of nodes, windmill-like deformation of bars, out of plane buckling of defective bars in outer or secondary outer ring, were presented after shell failure occurred, and the deformation of inner ring bars is smaller. From the testing failure proces s of the latticed shell, it is seen that defective bars buckling were first occurred and then the development of overall damage was formed, and the damage was instantaneous. It can be concluded with the results of test and theoretical analysis that the def iciency bars had a significant impact on bearing performance of reticulated shell structures. Thus taking into account the influence of bar stability, the results can get closer to the actual carrying capacity in the stability analysis.The bar is mainly subjected to axial force in single layer reticulated shell structure, which can be regarded as a compression member. It was found that some assumption were made when calculating effective length coefficient in the code for design of steel structure and tec hnical specification for space frame structures, which has some limitations for application. It seems that it is more reasonable to prevent the bar losing stability from the perspective of the overall structure. The effective length coefficient calculated by the engineering commonly used method tends to be insecure because the structures were still in elastic phase. It is found that the stability coefficient of the member obtained by the nonlinear analysis was lower than code value of the reticulated shell structures. The column curve formula and the Euler formula were adopted to get the effective length coefficient respectively, and the results were more rational with the column curve formula. Therefore, it is viable to control the stability of member bars with adopting the stability coefficient and slenderness ratio in the structure design.