AMBIENT VIBRATION TESTING OF BRIDGE STRUCTURES

Abstract

The _ ambient vibration testing of the structures is . a . direct and practical method of determining the " dynamic 'characteristics of structure such _ as natural frequencies, _ mode shapes and damping. In. this testing; structure is excited by natural microtremors, - wind, traffic load and machine or man made blast. The cable stayed bridges have proven to be economical for medium - to long spans. ;,Cable stayed bridges posses low weight and -reduced ability to absorb energy by sliding friction. So the inertia force generated in the structure is very low as compared, to external loads. As the cable stayed bridge has complicated -.structural ` systems because of different stiffness structural members, it .is important to carry out elaborate dynamic analysis, and compare with experimental data. This thesis presents the results of ambient vibration testing of " two cable stayed; bridges (i) across Ganga canal at Roorkee, and (ii) across` Ganga canal at Hardwar. The vibration produced were picked up ., by seismometers and recorded in solid state recorder. The experimentally measured time periods _ were compared with the values obtained from mathematical ; models. for the two bridges. A reasonably close agreement - in the fundamental time period between theoretical and experimental values have been observed for both the bridges,