Alternate Path Analysis of Space Trusses for Progressive Collapse

Abstract

Space trusses of the double‐layer grid type, because of their large degree of static indeterminacy, are often assumed to have sufficient redundancy such that the loss of one member would cause force redistributions that can be accommodated by the remaining structure. However, the results presented in this paper of the analyses performed on a hypothetical space truss and on a constructed space truss show that progressive collapse could occur following the loss of one of several potentially critical members when the structures are subject to full service loading. However, when the structures were evaluated using the American National Standard ANSI A58.1‐1982, the structures were found to survive with a small margin of safety. It is suggested that to improve resistance to progressive collapse the compression members and diagonal members along and adjacent to the column line should be designed with higher factors of safety than those currently used, particularly in the middle half of the span. Further research directions are suggested.