Abstract
Bridge damage induces immediate stiffness reductions in bridge structures, manifested as variations in static parameters such as strain and deflection, which pose significant safety risks. This paper presents a rapid damage diagnosis method for T-beam bridges using strain influence lines. The method derives the analytical strain influence line formula for T-beam bridges and examines its variation under transverse and longitudinal damage conditions. By analyzing peak values and envelope area shifts in the strain influence line, a diagnostic difference curve is generated, enabling the development of a qualitative damage assessment system. This system localizes damaged regions and provides transverse/longitudinal positioning and quantitative evaluation methods for T-beam bridge damage. Experimental validation using a scaled T-beam bridge model confirms the method's applicability and feasibility for damaged-state structural assessment.