可變勁度自復位斜撐與樓板自復位碟型彈簧裝置研究

Abstract

本研究共有二個研究重點。首先，許多研究皆指出自復位斜撐構架在地震後有較低的殘餘變形，且遠小於挫屈束制斜撐構架，然而自復位斜撐構架相較於挫屈束制斜撐構架有著較高的初始彈性勁度，導致輸入的地震力增加。為了解決此問題，發展一可調整軸向勁度並增加軸向變形能力的自復位斜撐即為本研究的第一個重點，其中使用碟型彈簧以降低自復位斜撐的初始彈性勁度為本研究所提出的方法。另外，近年來許多學者皆提出預鑄滑動樓板系統的概念，亦有相關實驗證實其能有效地減低結構物受地震力之下的樓板慣性力，然而常見使用來連接樓板與構架的挫屈束制支撐或摩擦耗能裝置儘管能提供飽滿的遲滯消能行為，但在地震發生後樓板與構架間不可避免的殘餘相對位移將導致災後結構物修復的困難，對此本研究的第二個重點即為使滑動樓板系統具有自復位性能，因此提出一新型自復位元件，同樣採用具自復位性能的碟型彈簧來達成此一目的。 本研究提出一新型可變勁度自復位斜撐（AS-SCB）及一樓板自復位碟型彈簧裝置（SCSD），透過將二者首先進行元件測試以驗證預測模型及評估試驗結果之後，將此二裝置安裝於實尺寸三層樓鋼構架系統之中進行振動台試驗，以探討裝置在地震下之真實反應，並分析其耐震性能、消能能力、遲滯穩定性和整體構架系統的行為表現。本振動台試驗分為二個階段，第一階段進行滑動樓板試驗，以SCSD連接預鑄樓板與鋼構架，在MCE等級地震下，其屋頂層之樓板最大滑動量達59.7 mm，而樓板與構架間的殘餘相對位移僅1.9 mm，且有效降低樓板與構架的受力，顯示自復位滑動樓板系統之可行性；第二階段試驗則以足夠剛性之桿件取代SCSD以模擬可變勁度自復位斜撐構架，結果顯示在1.9倍MCE等級地震下，構架屋頂層之殘餘側位移僅14 mm，具有良好的自復位性能，並且斜撐行為與預測模型相符，顯示使用碟型彈簧可以有效降低自復位斜撐之軸向勁度。

This study aims at two main objectives. First, buckling-restrained braces (BRBs) have been verified to provide a stable hysteretic response in steel braced frames, but their residual deformation occurs whenever providing large energy dissipation to frames at large lateral drifts. Self-centering braces (SCBs) have been developed to reduce the residual deformation of frames based on a flag-shaped hysteretic response, but have a much higher initial axial stiffness before the activation, which may result in a higher design base shear when compared to a frame with BRBs. Therefore, this work was aimed to develop a new self-centering brace with adjusted axial stiffnesses and deformation capacity such that the brace response could be designed based on specified yield and ultimate drifts of a frame. Assembling disc springs in the original SCB could achieve a new response characteristic, providing an alternative to tune the SCB structural property. In addition, the concept of precast sliding slab system has been proposed by many scholars in recent years, and some experiments have proved that it can effectively reduce the inertia force of the floor slab under earthquakes. However, even though the common use of BRBs or friction devices to connect the slab with the frame can provide full hysteresis dissipation, the inevitable residual displacement between the slab and the frame will lead to difficulties in repairing the structure after an earthquake. Therefore, the second aim of this study is to provide the sliding slab system with self-centering property; therefore, a new self-centering device is proposed, which also uses disc springs to attain this aim. In this study, a novel adjusted-stiffness self-centering brace (AS-SCB) and a self-centering disc spring device (SCSD) are proposed. The two devices were firstly subjected to component tests to validate the prediction model and to evaluate the test results, and subsequently installed in a full-scale three-story steel frame system for a shaking table test in order to investigate the actual response of the devices under earthquakes and to analyze the seismic performance, energy dissipation capacity, hysteretic stability, and behavior of the overall structural system. The shaking table test is composed of two phases. Phase 1 is the sliding slab testing, which utilized SCSD to connect the precast slab and the steel frame. Under the MCE level earthquake, the maximum sliding in the roof floor reached 59.7 mm, while the residual relative displacement between the slab and the frame was only 1.9 mm. Also, the mechanism effectively reduced the seismic force of the structure, demonstrating the viability of the self-centering sliding slab system. In the phase 2 test, the SCSD was replaced by rigid members to simulate the adjusted-stiffness self-centering brace frame. Test results showed that the residual drift of the roof floor was only 14 mm under 1.9 times MCE level earthquake, which exhibited good self-centering property. The AS-SCB response was also align with the prediction model, indicating that the use of disc springs effectively reduced the axial stiffness of the self-centering brace.