Comparative Structural Behavior Analysis of a Four-Span Parker Truss Bridge with Two Damaged Members under Vertical Loads

This study investigates the structural response of a four-span Parker truss bridge with two damaged members subjected to vertical loading. The bridge is modeled as a steel Parker truss with four equal spans and variable depth, and a concentrated vertical load is applied at mid-span to represent a typical service load condition. Damage is introduced by reducing the stiffness of two selected members, simulating degradation due to corrosion, fatigue, or prior overloading. A finite element model is developed using beam elements with rigid joints to capture the global behavior of the truss, and linear elastic material properties are assumed for steel. The numerical results show that the simultaneous reduction in stiffness of two members significantly alters the internal force distribution and amplifies the von Mises stress in the adjacent structural elements. The presence of two damaged members leads to increased vertical deflections at the loaded span and modifies the overall deformation pattern compared to the intact and single-damage configurations. These changes indicate a noticeable reduction in global stiffness and structural robustness, as well as a higher susceptibility to serviceability issues. The findings highlight that multiple-member damage can compromise both the safety margin and redundancy of Parker truss bridges, even when the damage is localized. This underscores the necessity of incorporating multi-member damage scenarios in structural assessment, and emphasizes the importance of regular inspection, continuous monitoring, and timely rehabilitation strategies to maintain the long-term performance of truss bridges with variable-depth geometry.

کلیدواژه ها:

Parker steel truss bridge ، load-carrying capacity ، structural behavior