Determining critical areas of transmission towers due to sudden removal of members

In this study, the structural susceptibility of a 400 kV power transmission tower subjected to progressive collapse and methods of determining the critical areas of above mentioned structure are investigated. OpenSees program is used for numerical modeling and nonlinear dynamic analysis of the tower which considers the buckling possibility of compression members and the plasticity in the cross sections as well. First, the progressive collapse analysis is performed and the results are reported as time history diagrams. Then, the impact factor of members' removal and the capacity-to-demand ratio are calculated for different failure scenarios of structural members due to the results of preliminary analysis of progressive collapse. The critical areas of the transmission tower through impact factor and capacity-to-demand ratio are determined so that it will be more feasible to propose retrofitting methods for the damaged structure in order to reduce the future risks. For the studied sample transmission tower, impact factors and capacity-to-demand ratios of 41% of APM cases can predict same critical areas.