縮尺橋梁模型耐震行為研究

The Study of Seismic behaviors for Small-scale Bridges

李昀叡(YUN-RUEI LI)

指導教授 ： 黃仲偉

中原大學/工學院/土木工程學系/碩士(2022年)

https://doi.org/10.6840/cycu202301009

摘要

目前國內鐵、公路橋梁主要以結構簡單、架設方便的簡支梁橋為主，但由於台灣地狹人稠，兼以斷層眾多，故橋梁無法避免位於斷層附近，甚至是跨越斷層。跨越斷層的簡支梁橋在地震作用下，容易因為斷層線兩側橋柱的相對位移而發生落橋；然而現行規範僅探討近斷層橋梁的耐震行為，對於跨斷層橋梁並沒有明確的耐震要求及設計規範。本研究為探討簡支梁橋在跨越斷層地表運動作用下的反應，建立一組兩跨簡支梁橋的縮尺模型，並另外建立對應的數值模型來驗證縮尺實驗的正確性。首先利用橋柱側推試驗以得到橋柱的非線性側推曲線，並用以擬合非線性纖維元素所需的參數。其次利用位移輸入的振動台進行增量動力試驗，以得到縮尺橋梁在不同強度地震作用下的反應。最後再使用SAP-2000建立有限元素模型進行比較，驗證實驗的正確性，並嘗試回推至原型橋梁。研究結果顯示，橋柱的非線性行為是控制橋梁在地震作用下反應，以及數值模擬與縮尺實驗是否匹配的主要因素。此外，在跨斷層作用下，無論縮尺橋梁是否具備止震塊，縮尺實驗在地震倍率小於1.0時所得之反應會大於數值模擬；但當地震倍率超過1.0之後，縮尺實驗所得之數據會小於數值模擬的結果，且其差距隨實驗倍率越高越明顯。另一方面，在非跨斷層(近斷層)作用下，無論是否有止震塊，數值模擬與縮尺實驗結果則較為相近。推估原因是縮尺模型在跨斷層作用下，橋面板在鉸接點處可以發生剛體旋轉，導致數值模擬與縮尺實驗的結果不同。最後，將縮尺實驗結果反推回原型橋，非跨斷層效應下產生的最大側向位移量為18.3 cm，小於規範的防落長度，代表現行規範規定的防落長度足夠防止近斷層地表運動導致的落橋。

關鍵字

跨斷層 ； 縮尺模型 ； 簡支梁橋 ； 數值模擬 ； 位移輸入

並列摘要

At present, most railway and highway bridges are simply supported bridges with simple structure and convenient construction. Due to Taiwan's dense population and numerous faults, bridges cannot avoid being located near faults, or even crossing faults. Simply supported bridges under crossing-fault ground motions are prone to collapse due to the relative displacement of piers on both sides of the fault line. However, the current seismic design code of bridges only discusses the seismic behaviors of bridges near-fault ground motions, and there are no clear seismic requirements and design specifications for bridges corssing faults. In order to investigate the response of simply supported bridges under the crossing fault ground motions, a 1/50 scale models of two-span simply supported bridges was constructed, and a corresponding numerical model was established to verify the accuracy of the scaled experiments in this study. Firstly, the pushover test is performed to obtain the nonlinear pushover curve of the scaled bridge pier, which is used to fit the required parameters in the nonlinear fiber elements. Secondly, a series of incremental dynamic tests are carried out using the shaking table with displacement input to obtain the response of the scaled bridge under different intensities of earthquakes. Finally, SAP-2000 is used to create a finite element model for comparison, to verify the accuracy of the experiment, and to try to replicate the prototype bridge.
The results of the study show that the nonlinear behaviours of the bridge piers are the main factor controlling the response of the bridge under earthquake action and whether the numerical simulations agree with the scaled experiments. In addition, under the crossing fault ground motions, regardless of whether the scaled bridge has shear keys or not, the responses obtained by the scaled experiments will be greater than those obtained by the numerical simulations when the seismic magnification factor is less than 1.0; but when the seismic magnification factor exceeds 1.0, the data obtained by the scaled experiments will be smaller than those obtained by the numerical simulations, and the differences become more obvious as the magnification factor increases. On the other hand, under the near fault ground motions, the results of the numerical simulations and the scaled experiments are relatively similar, regardless of whether shear keys are present or not. The presumed reason for these result is that under the crossing faults in the scaled model, the rigid body rotation of the bridge deck may occur at the hinge point, resulting in different results between the numerical simulations and the scaled experiments. Finally, the results of the scaled experiments were transferred back to the prototype bridge. The maximum lateral displacement generated under the near fault ground motion was 18.3 cm, which was less than the standard support length, which means that the support length specified in the current design code is sufficient to prevent the unseating under near-fault ground motions.

並列關鍵字

crossing-facult ； simply supported bridge ； scaled model ； numerical simulation ； displacement input

參考文獻

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