Although truss towers used for telecommunication, electric power transportation, supporting structures for smokestacks in power plants have been designed against wind loads, a higher level of safety is recently required because of the increase of anticipated large seismic inputs. The ultimate strength of these structures is governed by tubular member buckling which is easily led to member fracture. This paper proposes the post-fracture analysis methods for truss structures composed with tubular members of large diameter-to-thickness ratios, and study on the collapse mechanism of such truss towers after the buckling and fracture of main columns and diagonals are investigated, using IDA analyses taking these member fractures into account.
