| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 102 === To investigate the seismic performance provided by the sliding behavior of rubber bearings and rocking mechanism of the spread footing, this study introduced a series of shaking table test about a single span bridge model with different types of bearing system and foundation. The 4 m span bridge model was comprised of a reinforced concrete girder and eighteen massive blocks representing the superstructure. Under the girder, four elastomeric rubber pads (5*7.5*2.5 cm) at left and right end for bridge bearings sustain 6 tf weight of the superstructure. The substructure was composed of two steel pipes which have 0.67 cm thickness, 16.9 cm diameter, 60cm length and two 60*60*10 cm steel footing plate which were put on the 100*100*10cm rubber pads or fixed on the shaking table. The two types of bearing system are simple support and rubber bearing at each end which is allowed for sliding. The footing was embedded by dry silica sand with 50% relatively density for 0 cm and 20 cm, which represents the 0 times and 2 times of the footing thickness. Acceleration records from EL Centro and TCU076 station in Chi-Chi earthquake were chosed as th input ground motions. The peak ground acceleration strarted from 50 gal and achieved 550 gal for various test cases.
Based on the experimental results, the observation demonstrated that the rocking mechanism can reduced the bridge pier bending moment but increase the footing rotation; furthermore, the rocking behavior will become weaker as the soil depth increasing. Otherwise, for fixed base cases, the sliding behavior of rubbering bearings can decline the pier bending moment but increase the girder displacement. However, if the sliding behavior and the rocking bechanism are considered at the same time, the sliding behavior will be reatrain, which means that the seismic behavior will controlled by the footing rocking. In addition, Structural safety issue on the allowable criteria should be addressed and verified from analytical simulations based on relevant designing codes.
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