Non-destructive techniques for early damage detection for highway bridges using dynamic response

Abstract

Nondestructive techniques are based on the comparison of the static and dynamic behaviors of intact structures and their behavior in later times. The techniques are based on detection of any damage or deterioration through the structural behavior. One of the effective methods used in damage detection is based on the dynamic response of the structure to random excitation. The random decrement method is used to extract the free vibration response of structural systems subjected to Gaussian random loads with zero mean. The free vibration of the system depends on the mass and stiffness matrices of the system. When the mass and/or stiffness matrices change, the free response will also be changed. The random decrement method identifies the damage through the change of the system properties. The random decrement is usually used for single channel readings. However, in this work it is extended to use multi-channel to extract multi-signature for the structure from the dynamic response of the multi-degree-of-freedom systems. The proposed research aims to apply the random decrement technique as a nondestructive method in identifying the damage existence and location in concrete bridges. Moreover, one of the successfully used methods on data taken from finite element analysis is the modified mode shape difference method. The method can be used to extract the mode shapes of the structure without knowing the exciting force under the condition that excitation force should be stationary with zero-mean Gaussian process. The proposed work will include three models; single span, two-span simply supported bridges and a slab type bridge.  Since bridges are subject to moving dynamic loads, the models will be tested by using different locations to inspect the best places to excite the structures.