Abstract： A theoretical diagnosis method is proposed for local separation or uneven loading diseases of bridge rubber supports, using the dynamic responses of bridges under impact loads. The support stiffness reduction ratio is defined as a disease index. The impact responses and their sensitivities to the disease indexes are calculated. The sensitivity equation is established and solved, and the support stiffness is identified by the finite element model updating technique and optimization method. A simply-supported railway box-girder bridge and a simply-supported fabricated roadway box-girder bridge are taken as examples. The results show that the stiffness variations of single or multiple supports can be well identified by the proposed disease diagnosis method, and then the supports can be judged whether locally separated or unevenly loaded. For simply-supported railway box-girder bridges, the impact points and response measurement points should be placed on the bridge flanges with larger torsional vibrations, while for simply-supported fabricated roadway box-girder bridges, they should be placed on axis of each girder.
2013, Vol. 32 
