含挫屈束制支撐之新建鋼筋混凝土構架耐震設計與反應分析研究

Seismic Design and Response Analysis of RC Frames with Buckling Restrained Braces

黃潔倫(Jie-Lun Huang)

指導教授 ： 蔡克銓

國立臺灣大學/工學院/土木工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01534

摘要

挫屈束制支撐(BRB) 為一種耐震消能構件，其於受拉及受壓時皆能達降伏而不發生挫屈，擁有飽滿且穩定的遲滯迴圈。近年來許多研究及試驗也都證明BRB能提供結構良好的勁度、強度、韌性及消能機制，實務上已廣泛的被應用於鋼結構中，但將BRB應用於新建鋼筋混凝土結構的技術及研究甚少被著墨。為了探討含挫屈束制支撐之新建鋼筋混凝土構架 (BRB-RCF)受震之行為，本研究以PISA3D建立數值分析模型，預測於NCREE進行之實尺寸兩層樓BRB-RCF擬動態試驗[楊巽閎 2015]反應。擬動態試驗所用之地震歷時，亦經由此數值模型進行分析挑選。分析預測與試驗比對結果顯示，BRB-RCF之受震反應可以PISA3D預測模型合理預測。試驗結束後，本研究進一步利用試驗反應校正PISA3D分析模型，而達到更準確之模擬結果。本文介紹兩種模型的詳細建置方法。
為了更進一步探討BRB實際運用於新建RC結構的可行性，本研究提出六層樓BRB-RCF之設計例，並設計一棟六層樓的韌性抗彎構架(MRF)作為對照，利用前述對兩層樓BRB-RCF試體建立精確模型的方法與經驗，分別對 BRB-RCF及MRF兩系統建立結構模型進行非線性動力歷時分析。此外也針對BRB-RCF的模擬提出簡化模型的建置方法，此模型可大量減少分析時間，達到與複雜模型相近的分析結果。動力分析結果顯示，短向BRB總受力比長向BRB多，按照50/50、10/50、2/50等級地震排列，其短向BRB平均總受力比約為35%、40%、40%，長向BRB平均總受力比約為24%、26%、28%，而MRF與BRB-RCF於2/50等級地震下造成之最大層間側位移角分別為1.8%及1.5%。
為了提高BRB在RC構架中之總受力效益，本研究提出BRB-RCF另一設計方法：將BRBF作為主要抗側力系統，其餘RC梁柱只作為抗重力系統。此設計方法可顯著減少RC重力系統之梁柱尺寸，提高BRB總受力效率。並針對此設計結果之短向一半，建立二維平面結構模型進行非線性動力歷時分析。動力分析結果顯示，此設計能將BRB總受力比提高至75%，而能保持約略相同之最大層間位移角。
本研究已利用試驗証實所設計之預埋鐵件能成功將BRB與RC構架接合，也用6FBRB-RCF設計例確認BRB與RC構架接合之預埋鐵件於真實結構中之可行性。分析結果顯示，底層邊界梁的剪力需求較大，需設計成較寬之梁。此外，本研究所提設計例的BRB採之字形配置，此種BRB配置對梁產生之軸力需求較小。若BRB採單斜平行方式配置，須考慮梁受顯著軸力之容量設計。本研究將BRB應用於較低矮的RC結構，雖可減少層間側位移角。但由於RC結構勁度較大，樓層相對變形較小，BRB尺寸與受力亦較小，因此減震效果較不顯著。

關鍵字

鋼筋混凝土構架 ； 挫屈束制支撐 ； 擬動態試驗 ； 非線性動力歷時分析 ； 簡化模型 ； 二維平面構架分析

並列摘要

The buckling-restrained brace (BRB) has been evolved into a cost-effective energy dissipation member for seismic resistant steel buildings. A BRB can develop full yield strength under both tension and compression through its restraining member by preventing its steel core from undergoing flexural buckling failure. In recent years, many studies and tests have proved BRBs can improve stiffness, strength, ductility and energy dissipation mechanism for structures. BRBs have been widely applied in steel structures in the past decades. However, researches on applying BRBs to new reinforced concrete frames (RCFs) are somewhat limited.
This study consists of two parts. In order to study the performance of RC frame with BRBs (BRB-RCF) under earthquakes, in the first part, an analytical model is constructed using PISA3D for predicting the responses of a two-story BRB-RCF tested at NCREE. The full-scale two-story BRB-RCF has been tested using four hybrid tests and cyclic loading test. Details of the specimen design and test results can be found in Mr. Hsun-Horng Yang’s thesis. Ground motions adopted in the tests are selected by using the prediction model analyses and 60 ground motion records. After the tests, the prediction model is calibrated into a simulation model based on the experimental results. Very satisfactory agreements with the test results can be achieved from the simulation model analyses.
In order to further study the seismic performance of low-rise BRB-RCFs, this study uses six-story building design examples, one BRB-RCF and one RC moment resisting frame (MRF). The six-story BRB-RCF and MRF analytical models are constructed using PISA3D and the proposed modeling methods. For the purpose of saving analysis time while achieving accuracy, a simplified model is proposed for the 6-story BRB-RCF response history analyses. The analytical results show that the ratios of maximum total BRB shear and BRB-RCF shear in transverse direction are about 35% (50/50 hazard level earthquake), 40% (10/50 hazard level earthquake) and 40% (2/50 hazard level earthquake). These are larger than those computed for longitudinal direction with 24% (50/50 hazard level earthquake), 26% (10/50 hazard level earthquake) and 28% (2/50 hazard level earthquake). The maximum story drift in the BRB-RCF and MRF under the 2/50 hazard level earthquake are 1.5% and 1.8%, respectively.
In order to improve the BRB efficiency in the BRB-RCF, this study propose to configure the RC BRBFs as primary lateral force resisting systems, and treat the remaining RC beam and column members as a gravity system. This scheme can significantly reduce the sizes of a number of RC beams and columns and improve the efficiency of BRBs. This study uses the PISA3D to construct the two-dimensional analytical model of one half of the building structure in transverse direction and perform nonlinear dynamic analysis. Analysis results confirm that the RC-BRBF scheme enables the total BRB shear ratio of the RC-BRBF to increase to 75%, while the story drift responses are similar to the aforementioned BRB-RCF system.
This series of experimental and analytical researches has confirmed the effectiveness of the design, fabrication and modeling methodologies for the proposed BRB-RCF. Tests have confirmed that the use of the proposed steel embedment as the interface for the BRB and RC members can be successfully implemented into real RC frames. Analytical results of the 6-story RC-BRBF and BRB-RCF show that a large shear demand exists in the in D-region of the lower floor beams. These beams must be designed wider than those in the upper floor beams. In addition, the BRBs in the proposed RC-BRBF or BRB-RCF are arranged in a zigzag configuration. This should reduce the axial force demand on beams. This paper discusses the axial force demands computed from the response history analyses. Implementing the BRBs into low-rise RC building can somewhat reduce the responses of the structures. However, due the significant stiffness of RC members, the sizes and their effectiveness of the BRBs in reducing the seismic drift response of RC buildings is limited.

並列關鍵字

reinforced concrete frame ； buckling restrained brace ； hybrid test ； nonlinear response history analysis ； simplified model ； two-dimensional analysis

參考文獻

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