BASIC STUDY ON EVALUATION OF STIFFNESS OF BRIDGE USING INFLUENCE LINE

Abstract

 This study proposed a method for estimating the damage locations and damage levels of bridge girders based on the deflection influence lines. The correction coefficients for flexural rigidities are estimated based on numerical analysis using a bending beam. Two types of objective functions are presented based on the concept of Bayesian inference (MAP estimation). Correction factors for flexural rigidities are estimated for the scenarios of local damage and overall damage. For local damage, the object function that provides prior information on the correction coefficients themselves gave better results. For the overall damage, an object function that provides the prior on the difference between the correction coefficient gave better results. Using Hessian matrices, we evaluated the uncertainty in the estimates and the correlation coefficients among the flexural rigidities, and quantified the estimation accuracy. White noise of 1% or 2% of the maximum amplitude of the influence line was considered as an observation error. The multiple measurements are required to obtain acceptable level of accuracy.