裝設橡膠支承墊之斜橋縮尺模型試驗

Shaking Table Test for Scale Down Skew Bridge Models with Rubber Bearings

鄭維晉(Wei-Jin Cheng)

指導教授 ： 張國鎮

國立臺灣大學/工學院/土木工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.02050

摘要

國內既有橋梁多屬PCI簡支梁橋，而橡膠支承墊被廣泛運用當作其支承系統。實務上施工方式常將支承墊直接放置於帽梁的砂漿墊之上，並無以剪力鋼棒等構造加以固定。此類支承型式於地震發生時將可能導致支承墊時發生滑動現象。此外，在滿足選線規劃的條件下，許多橋梁必須跨越既有道路及河道，亦使許多橋梁必須以斜交型式設計建造。本文主旨為探討裝設橡膠支承墊之斜橋，在地震作用下的行為反應。有別於既往針對橋柱產生塑鉸機制設計的補強策略，本文冀望能驗證支承系統於初期之滑動損傷，可助於降低橋柱受力的需求。
本研究首先針對橡膠支承墊的磨擦係數進行觀察，發現支承墊在高速滑動下磨擦係數變化並不明顯。再者，建立一座縮尺斜橋模型進行振動台試驗，根據試驗結果顯示，支承墊的滑動將會降低橋梁系統上部結構慣性力的生成。此外，支承墊滑動後之後藉由支承系統傳遞至下部結構的水平力將等同於支承墊的磨擦力，故此效應將有助於降低橋柱受力之需求，提供一個有別於橋柱塑鉸機制的新思維。
本文利用SAP2000N結構分析軟體對於試驗結果進行數值模擬，可求得尚可接受的分析結果，雖可有效預測結構的最大反應，但仍可再研議更適當的模擬元素與方式以提升數值模擬的精確度。最後，本文探討不同斜角角度的橋梁與地震歷時輸入方向對於斜橋結構反應之影響，分析結果顯示，斜角低於20度之橋梁其行為反應較為規律，而斜角高於20度之橋梁其結構不規則特性逐漸顯現，將導致結構行為難以預測，本文建議分析設計斜角高於20度之橋梁時，應考量諸多因素以確保結構安全。

關鍵字

斜橋 ； 橡膠支承墊 ； 支承墊滑動 ； 振動台試驗 ； 磨擦力

並列摘要

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.

並列關鍵字

skew bridge ； rubber bearing ； rubber bearing sliding ； shaking table test ； frictional force

參考文獻

陳皇嘉(2005)，「裝設橡膠支承墊於橋梁縮尺模型之試驗與分析」，國立台灣大學土木工程學研究所碩士論文，張國鎮教授指導。

廖垣銓(2006)，「裝設橡膠支承墊於縮尺雙跨橋梁模型之試驗與分析」，國立台灣大學土木工程學研究所碩士論文，張國鎮教授指導。

陳威逸(2007)，「含功能性支承縮尺橋梁之試驗與分析」，國立台灣大學土木工程學系碩士論文，張國鎮教授指導。

劉光晏(2006)，「橋梁功能性支承系統耐震性能設計與評估補強方法之研究」，國立台灣大學土木工程學研究所博士學位論文，張國鎮教授指導。

張國鎮、吳秉憲、劉光晏(2004)，「橋梁功能性支承系統參數之研究－橡膠支承墊力學行為與摩擦係數之測定」，報告編號：NCREE-04-027，國家地震工程研究中心。