Statical analysis of progressive collapse in string truss structure

The research of progressive collapse is currently more focused on multistory buildings rather than large-span spacial steel structures which can also accommodate a great deal of people. It is also imperative, however, to investigate possible progressive collapse of large-span spacial steel structures, for example, string truss structures, due to the structural importance factor as well as material nonlinearity. This paper investigated mechanism and evaluated methods of progressive collapse from string truss structures. Based on geometric and material nonlinear analysis of progressive collapse from string truss structures, it was concluded that material nonlinearity affects more on progressive collapse, when compared with geometric nonlinearity. Key structural members were also identified through static analysis of ultimate-state capacity by removal of each structural member. Thereafter, two main stream methods, i.e., concept design and direct structural analysis, for progressive collapse control of large-span spacial structures were evaluated. Pandey´s Sensitivity analysis was regarded as the most effective concept design method to evaluate redundancy. However, because the method is on the basis of linear elastic structure, and moreover estimates the redundancy in accordance with the degree of stress variety of all components, it has some deficiencies regarding the progressive collapse control. As for the direct calculation method, alternate load path measure is most frequently used, which could reflect the ability of progressive collapse, but needs a great number of calculations. Therefore, one simple calculation method pertaining to counter-progressive collapse of spacial structure was put forward through simplification of stress-strain curve of pole and process of progressive collapse. According to statistics, compared with Pandey´s sensitivity analysis method, such a simple way makes less error.