SECOND-ORDER INELASTIC ANALYSIS OF STEEL FRAME STRUCTURES USING IMPROVED FIBER PLASTIC HINGE METHOD

In the realm of inelastic analysis for steel structures, the plastic hinge method is recognized for its computational efficiency but is often criticized for its lower accuracy than the plastic zone method. The present study aims to improve the accuracy of the plastic hinge method by discretizing the cross-section of the plastic hinges located at the element ends. Besides, the proposed fiber plastic hinge method is more efficient than the plastic zone method where each cross-section at the integration points of the element should be discretized. This study utilizes the improved fiber plastic hinge method to compute the initial and full yield surfaces of the cross-section, determine the section spring stiffness, and integrate this method into the second-order inelastic analysis of steel frame structures. Several classic benchmark problems are solved by the present method and the obtained results are compared with results generated by the plastic zone method as implemented in finite element software. The comparison reveals that the proposed fiber plastic hinge method matches the plastic zone method in terms of high accuracy for predicting the inelastic behavior of steel structures, with the added advantage of greater efficiency. Copyright (c) 2025 by The Hong Kong Institute of Steel Construction. All rights reserved.