挫屈束制支撐鋼框補強鋼筋混凝土構架之研究

Seismic Retrofit of Reinforced Concrete Frames with Buckling-restrained Braced Frames

潘冠宇(Kuan-Yu Pan) ； 吳安傑(An-Chien Wu) ； 李昭賢(Chao-Hsien Li) ； 蔡克銓(Keh-Chyuan Tsai)

《結構工程》 30卷4期 (2015/12) Pp. 41-64

https://doi.org/10.6849/SE.201512_30(4).0002

摘要

本研究利用鋼筋混凝土（reinforced concrete, RC）構架角隅處澆置之承壓塊作為RC 構架與補強斜撐系統間力量之傳遞介面，避免高度倚賴傳統補強工法中大量錨栓的使用，同時減少RC 構架與補強系統間之複合效應，斜撐軸力容量亦不直接受錨栓強度所限制。斜撐選用挫屈束制支撐（buckling-restrained brace, BRB）以避免傳統鋼斜撐受壓之挫屈行為，並藉由BRB 高勁度、高韌性與高消能容量的特性，以消散地震輸入之能量，降低結構受震反應。為驗證該補強工法之力量傳遞機制與耐震性能反應，並了解BRB 補強前後整體構架之性能反應差異，本研究設計兩組不同軸力容量之BRB 鋼框補強實尺寸RC 構架及一組安裝裸鋼框之RC 構架進行反覆載重試驗與非線性結構分析。試驗與分析結果顯示，本研究之耐震性能補強工法可使整體側向強度持續成長至3.0%弧度樓層側位移角，所提升之側向強度及勁度分別為安裝裸鋼框試體的2.2 及3.5 倍以上，有效提升既有RC 結構之側向強度、勁度及韌性容量，並藉由BRB 消散大部份的能量。本研究所提出之簡化分析方法及PISA3D 數值模型分析方法可供估計構架各構件之受力反應，有效預測補強構架側向強度，與試驗量測所得之構件受力反應差異均小於13.8%。此外，BRB 鋼框透過RC 構架角隅處承壓塊對梁端及柱端產生額外之局部剪力需求，可利用軟化壓拉桿模型簡算法有效且保守地評估該不連續區域構件之抗剪強度。

關鍵字

耐震補強 ； 鋼筋混凝土結構 ； 挫屈束制支撐 ； 承壓塊 ； 錨栓 ； 軟化壓拉桿模型

並列摘要

Instead of applying the post-installed anchors to transfer the seismic loads, the proposed retrofitting brace system consists of high-strength mortar bearing blocks constructed at the four corners of the existing reinforced concrete (RC) frame to transfer the earthquake forces. In comparison with the traditional retrofitting methods, it avoids the complex on-site anchor installation process. Thus, the brace force capacity is not directly limited by the anchor resisting strength. Buckling-restrained braces (BRBs) are adopted in the proposed retrofitting system to improve the structural strength, stiffness and energy dissipation efficiency. In this study, cyclically increasing lateral displacements were imposed on two RC frames retrofitted with the same WT steel frames for different BRB strength capacities. Cyclic loading test on the third RC frame infilled with the same WT frame only was also conducted to evaluate the strength and stiffness enhancements. Test results indicate that the proposed retrofitting method is efficient in increasing the lateral strength up to the 3% drift ratio while achieving rather good ductility and energy-dissipating capacity. The increased lateral strength and stiffness were more than 2.2 and 3.5 times those of RC frame infilled with WT frame only, respectively. A simplified structural calculation and a detailed PISA3D analysis are proposed to show the effectiveness in predicting member demands to within 13.8% of the test measured test results. Under cyclic lateral loads, the steel braced frame imposes additional shear forces through the bearing blocks to both ends of the RC beam and column member discontinuity regions. In this research, the softened strut-and-tie model was satisfactorily applied in estimating the shear capacities for the discontinuity regions.

並列關鍵字

seismic retrofit ； reinforced concrete frame ； buckling-restrained brace ； bearing block ； post-installed anchor ； softened strut-and-tie model