Shaking Table Test for Scale Down Skew Bridge Models with Rubber Bearings
Date Issued
2008
Date
2008
Author(s)
Cheng, Wei-Jin
Abstract
The seismic responses of the skew bridges with rubber bearing are studied. In Taiwan, simply-supported PCI bridges served as the majority of bridge type are widely used with rubber bearing pads as a supporting system. It is common seen that, during the construction practice, the rubber bearing pads have been laid on the cement mortar-made bearing pads without any details of bolting design. This kind of arrangement potentially allows rubber bearing to slide, so as the superstructure when the earthquake occurs. In addition, bridges are usually being skewed to provide transportation service, requiring a further investigation of unseating prevention length to avoid unseating of the superstructure. Therefore, the main topic of this study is to dealing with the seismic behaviors of the skew bridge with rubber bearing. Rather than the existing retrofit approach by utilizing the plastic hinge at end of bridge column, the proposed strategy is to reduce the shear demand of the bridge columns due to the sliding of rubber bearings. To get a better understanding of the frictional force, authors firstly conducted a series of coefficient of friction tests. Furthermore, a scale-down skew bridge model has been constructed to perform the shaking table test. According to the experimental results, the inertial forces from superstructure can be reduced because of the sliding mechanism. After the rubber bearing moved, the horizontal force to be transmitted to substructure from superstructure is just as same as the frictional force of rubber bearing. It represents that the shear demand of bridge columns would be reduced, and provides a new thought differed from plastic hinges. The analytical program, SAP2000N, have been used to simulate the experimental results in this study, and it may obtain the acceptable simulated results. Although it can predict the maximum structural responses effectively, it is essential to discuss the more suitable simulate elements to promote the accuracy of numerical simulation. Finally, the study will discuss that the bridge behaviors with different skew angles and input directions of time histories. The analytical results show that the bridges with skew angle of 20 degree have similar regular responses, but the irregular characteristics of structure will gradually appear when the skew angle is greater than 20 degree. It will cause that the structural behaviors have be predicted difficulty. This thesis suggests that it must consider much more factors to guarantee the structure security when the bridges with greater than 20 degree skew angle will be analyzed.
Subjects
skew bridge
rubber bearing
rubber bearing sliding
shaking table test
frictional force
Type
thesis
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