Limit Analysis for Evaluation of Compression Diagonal Gusset Plates in Steel Truss Bridges

Abstract

Current standard evaluation procedures for compression gusset plates, the two-fold Whitmore section (Whitmore) buckling and the partial plane shear yielding (PPSY), as specified in The Manual for Bridge Evaluation (MBE), are conservative and may result in unnecessary strengthening and retrofitting. To provide accurate and rational load rating factors for decision-making, the two-strut buckling model, which is based on the lower bound theorem of limit analysis, is developed to evaluate compression diagonal gusset plates in steel truss bridges. The proposed model includes two struts, horizontal and vertical strut plates that are subjected to moments, axial compression, and shear forces, and satisfies equilibrium and the M–P–V interaction equation, where the moment on the vertical or the horizontal strut sections is M, the axial force on the vertical or horizontal strut sections is P, and the shear force on the vertical or horizontal strut sections is V. The predicted results were compared with 116 large-scale experimental and finite-element (FE) analytical tests that were reported in the National Cooperative Highway Research Program (NCHRP) 12-84 project, the MBE refined methods including the basic corner check (BCC) and the truncated Whitmore section (TWS) buckling. Of the three methods, the proposed two-strut buckling (TSB) model had the best professional factor [PF (Ptest/Ppredication)] and the relatively low coefficient of variation (COV). The procedures and concepts in the proposed model combine established engineering principles with simplicity and good engineering intuition to achieve uniformity when evaluating compression diagonal gusset plates in steel truss bridges. To provide accurate and rational load rating factors for decision-making for the bridge owners, the two-strut buckling model that is based on the lower bound theorem of limit analysis is developed to evaluate compression diagonal gusset plates in steel truss bridges. The predicted results were compared with 116 large-scale experimental and finite-element (FE) analytical tests that were reported in the National Cooperative Highway Research Program (NCHRP) 12-84 project, the Manual for Bridge Evaluation (MBE) refined methods, the basic corner check (BCC), and the truncated Whitmore section (TWS) buckling. Of the three methods, the proposed two-strut buckling model had the best professional factor [PF (Ptest/Ppredication)] and a low coefficient of variation (COV). The procedures and concepts in the proposed model combine established engineering principles with simplicity and good engineering intuition to achieve uniformity when evaluating compression diagonal gusset plates in steel truss bridges.