A Rapid Diagnosis Method Based on the Strain Influence Line for T-beam Bridge Damage

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.