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標題: | 桁架圍束式挫屈束制支撐之設計分析與試驗研究 A Study of BRBs using Steel Truss Restrainers |
作者: | Chun Chen 陳雋 |
指導教授: | 蔡克銓(Keh-Chyuan Tsai) |
關鍵字: | 挫屈束制支撐,桁架,圍束單元,變斷面,等效撓曲剛度,等效剪力剛度,整體穩定性,穩定性分析模型,彈性挫屈強度,挫屈破壞強度,反覆加載試驗, buckling-restrained brace,truss,restrainer,varying section,equivalent flexural rigidity,equivalent shear rigidity,global stability,stability analytical model,elastic buckling strength,buckling failure strength,cyclic loading test, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 挫屈束制支撐 (buckling-restrained brace, BRB) 能經濟且有效率地提升建築結構抗震所需之勁度、強度、韌性與消散地震能量的能力,已廣被運用於鋼結構中做為建築的主要制震系統。桁架圍束式挫屈束制支撐 (truss-confined BRB, TC-BRB) 為新型被提出並測試之 BRB。TC-BRB 於圍束鋼管外面再配置一桁架圍束系統,由任意數量、方向與尺寸之剛性桁架構架所構成,並與圍束鋼管一同組成圍束單元來提供 TC-BRB 所需之撓曲剛度;因此其圍束鋼管與內灌水泥砂漿的撓曲剛度與斷面需求將得以大幅下降,更有效率地發揮材料所能以及 BRB 之容許發展強度。當安裝為具長跨與高軸力需求之 TC-BRB 時,將更得以發揮減少材料用量、自重以及初始凹曲等優點。本研究更再提出一全新型 TC-BRB,將桁架圍束系統之斷面高度由原先的等斷面改為沿 BRB 軸向變化,於跨中處最高並以正弦函數曲線向兩端漸縮,有效率地使用材料並獲更優美之外觀。 為推廣此新創型 BRB 使其未來於實際工程應用上更為便利,本研究建立穩定性理論模型與耐震設計方法並進行相關的驗證。先提出桁架圍束系統等效撓曲剛度與剪力剛度的計算方式,再建立穩定性理論模型。在考量剪力效應的前提下計算 TC-BRB 之整體彈性挫屈強度 (Pcr);並再考量初始缺陷與材料非線性行為來計算整體挫屈破壞強度 (Plim)。接下來本研究藉 ABAQUS 建立有限元素模型模擬流程以進行數值驗證,分析結果顯示理論模型在圍束單元其 Pcr 的計算上,誤差皆小於 10%;而於整體 TC-BRB 其 Pcr 的計算上,誤差更皆小於 3%。為了更進一步進行理論驗證並評估 TC-BRB 之實際遲滯消能行為,本研究第一階段先設計並新造兩組具不同桁架圍束系統型態、1/5 縮尺總長 6.3 米、100 噸級之 TC-BRB 試體,並於國家地震工程研究中心的多軸向試驗系統執行反覆加載試驗。在考量殘餘應力的影響後,試驗結果顯示理論模型對於 Plim 的預測誤差皆小於 6%,再次驗證理論模型於穩定性預測上之準確性;更證實本研究所提供之設計方法與相關檢核的可靠性,因此本文提供 TC-BRB 之耐震設計流程供讀者參考。而為觀察 TC-BRB 更為優良的耐震消能與穩定性表現,本研究於第二階段再設計兩組 TC-BRB 試體並提高其整體穩定性容量。 Buckling-restrained brace (BRB) can enhance the stiffness, strength, ductility, and the energy dissipation capability of building structures. Therefore, it has been widely adopted into the lateral force-resisting system in the seismic steel buildings. Recently, a novel type of BRB, namely truss-confined BRB (TC-BRB) with the constant depth of trusses in the restrainer, has been developed and tested. The TC-BRBs’ restrainer is constructed by attaching an additional structural system composed of arbitrary steel open-web truss frames outside a central steel casing to develop the overall restraining rigidity. In this approach, the flexural rigidity and cross-section requirements of the central steel casing and the infilled mortar in the TC-BRB can be significantly lighter than those in a conventional BRB. The initial crookedness caused by the BRBs’ self-weight can also be reduced in the cases of long-span and large axial capacity BRB designs. In this study, a new type of TC-BRB using a varying-depth truss system in the restrainer is analyzed and tested. It allows a more efficient design than the case of using constant-depth trusses on saving the construction material while achieves the structural aesthetic. In order to evaluate the stability performance of these novel BRBs, stability analytical model and seismic design procedures are developed and verified in this study. Key mechanical properties including equivalent flexural rigidity and shear rigidity of the truss system are firstly described. It is illustrated that the TC-BRBs’ elastic buckling strength (Pcr) can be satisfactorily computed by incorporating Timoshenko shear effect into the classical stability theory. In addition, TC-BRBs’ buckling failure strength (Plim) can be further computed by considering different levels of initial imperfections and inelastic material behavior. To numerically verify the proposed analytical model, finite element modeling (FEM) techniques using ABAQUS are introduced. The FEM analysis results demonstrate that the proposed analytical model can satisfactorily predict the restrainers’ Pcr with errors less than 10%; and predict the TC-BRBs’ Pcr with errors less than 3%. To further verify the effectiveness of the proposed design procedures, a cyclic loading test program was conducted. In the first phase, two 1/5-scale TC-BRB specimens, each of 6.3m long with 1016-kN nominal yield strength in the constant- and varying-depth truss designs were tested in NCREE. Test results confirm that the Plim of the two TC-BRB specimens can be accurately predicted using the proposed analytical model with errors less than 6% when the effects of residual stresses in the truss members are considered. The TC-BRBs’ experimental performance also suggests that the proposed design procedures are generally conservative and practical. This study concludes with the recommendations on the seismic design of the proposed constant- and varying-depth TC-BRBs. In order to investigate the hysteretic and stability performance of the TC-BRBs with stronger restrainers, two additional specimens are proposed with significantly increased stability capacities for the second phase study. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/61616 |
DOI: | 10.6342/NTU202001135 |
全文授權: | 有償授權 |
顯示於系所單位: | 土木工程學系 |
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