IDENTIFICATION OF DEGRADED STIFFNESS DUE TO ARBITRARY DAMAGE FOR SLAB BRIDGES UNDER UNKNOWN MOVING LOAD INFORMATION

Abstract

In the present study, the method for detecting of stiffness degradation induced by multiple cracks in plate structures subjected to moving force is proposed. The advantage of the method is that detection is based solely on the response signals in the time domain so that it can overcome the difficulty of a reliable measure of the moving force actions. The proposed method can be effective in economical aspect due to omitting the use of force excitation instrumentation for obtaining response signals in the field of civil engineering excitation and be helpful to identify the damage in bridges in case the information about vehicular force is not known. In this work, the relationship between change of stiffness and multiple cracks is described and formulated by using several modified bivariate Gaussian distribution functions and the time-varying continuous moving force is also formulated by using a quadratic function. The proposed method is particularly efficient when the moving force velocities do not have a sudden change, or, continuous and smooth varying acceleration. In addition, the proposed method utilizes a small number of unknown parameters for detecting of stiffness degradation in comparison with the conventional element-based damage detection method and introduces the inverse technique using hybrid genetic algorithm that can make global solution search possible as opposed to classical gradient-based optimization techniques. Finally, the validity of the technique is numerically verified using a set of dynamic data obtained from a simulation of the actual bridge. The numerical calculations show that the proposed technique is a feasible and practical method which can estimate not only the degraded stiffness distribution but also the velocities and weights of moving force under the unknown information about initial moving force.