強脊結構系統之耐震行為研究

Strong-back systems for enhancing the seismic performance of buildings

郭銘桂(Meng-Kwee Kek)

指導教授 ： 蔡克銓

共同指導教授 ： 林瑞良(Jui-Liang Lin)

國立臺灣大學/工學院/土木工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201801842

摘要

為解決結構受震層間位移角分佈不均之問題，許多學者提出了不同的方法，如利用強脊系統（strongback system）來控制層間位移角，使其均勻分佈。研究顯示，目前對於強脊系統與主構架之間的勁度比並無明確之建議。因此本研究希望利用簡化分析模型對強脊系統進行大量的參數分析，提出有效的設計參數。
本研究以廣義建築模型（generalized building model，GBM）及含強脊系統之廣義建築模型（generalized building model with strongback，GBMSB）作為分析工具，以MATLAB軟體進行計算，探討強脊系統和原構架的適當勁度比及強脊系統的最佳層勁度分配法。研究針對在台北二區，第二類地盤的三、六、九和二十層建築進行參數分析，採用SRSS振態疊加法估算最大彈性層間位移角，並利用層間位移角的標準偏差作為均勻度指標，評估層間位移角分佈之均勻性，使層間位移角的標準偏差為最小之設計為最佳設計。分析結果顯示強脊系統為純剪力型式變形，且其層勁度呈線性遞減，並且於一樓加勁的勁度分配法效果最佳。
　　為了驗證參數分析之有效性，採用SAC研究計畫中的九層鋼構造抗彎矩構架，和國家地震工程研究中心台南實驗室的三層鋼筋混凝土構架試體作為驗證例。將原始結構模型（分別稱為SAC9和T3）、含最佳強脊系統之結構模型（分別稱為SAC9-SB和T3-SB）、及含非最佳強脊系統之結構模型，分別利用PISA3D結構分析程式進行475年回歸期的設計地震和2500年回歸期的最大考量地震的非線性反應歷時分析。結果顯示配置最佳強脊系統之SAC9-SB和T3-SB層間位移角之標準偏差平均值最小，能使層間位移角分佈最為均勻，且各樓層也更趨向於同一瞬間發生最大層間位移角，證明參數分析之有效性。

關鍵字

層間位移角分佈 ； 廣義建築模型 ； 含強脊系統之廣義建築模型 ； 振態疊加法 ； 標準偏差 ； 非線性反應歷時分析 ； PISA3D ； MATLAB

並列摘要

Many researches have attempted to reduce the variations of peak inter-story drifts occurred in earthquakes along the building height. Among various approaches, adding a strongback system into the existing building appears a very effective approach. Nevertheless, these researches show that there seems no clear recommendation on the appropriate stiffness ratio between the strongback system and the target building. Therefore, the key objective of this research is to develop a method of computing the optimal stiffness of the strongback system. The associated parametric study is performed through simplified numerical models. In addition, the effectiveness of the proposed method is verified by investigating one 9-story steel building and one 3-story reinforced concrete (RC) building.
The generalized building model (GBM) and generalized building model with strongback (GBMSB) are employed as the simplified numerical models in the parametric study. The peak inter-story drift ratios along the building height are compute by using the response spectrum analysis method, in which the peak modal responses are combined according to the SRSS method. The optimization objective is to minimize the standard deviation of the peak inter-story drift ratios. The optimal stiffness distribution of a strongback is thus obtained. This study investigated 3, 6, 9 and 20-story buildings. The results of parametric study show that when a pure shear-type strongback, whose first story is stiffened and its story stiffness decreases linearly along the hight, the standard deviation of inter-story drifts is minimized.
The 9-story steel moment resisting frame, designated as SAC9, a prototype building located in Los Angeles adopted in SAC steel research project, was used as an example buildings in this study. In addition, at 3-story RC building, , designated as T3 and tested using shaking table at Tainan Laboratory of National Center for Research on Earthquake Engineering, was also used. Then optimal designs of SAC9 and T3 with the strongbacks are designated as SAC9-SB and T3-SB, respectively.
In order to verify the effectiveness of the proposed method, nonlinear response history analyses (NRHA) of SAC9, T3, SAC9-SB, T3-SB models and the others with different properties of strongback systems were conducted using PISD3D program. Two ensembles each of 20 ground motion records of the 475-year (DBE) return periods were used in the NRHA.
The NRHA result shows that SAC9-SB and T3-SB have smaller standard deviations than those using other strongback properties. The analysis results confirm the effectiveness of the proposed method in proportioning the strongback for buildings.

並列關鍵字

inter-story drift ratio ； generalized building model ； strongback ； nonlinear response history analysis.

參考文獻

 Barbara G. Simpson and Stephen A. Mahin (2017) “Reducing Concentrations of Inelastic Demand with A Strongback.”

 Chen, C.H., Tsai, I.J. and Tang Y. (2017) “Drift Concentration of a Three-Story Special Concentrically Braced Frame with Strongback under Earthquake Loading.” Applied Mechanics and Materials, Vol. 863, pp. 287-292.

 Chopra, A. K.and Cruz, E. F. (1986) ‘‘Evaluation of building code formulas for earthquake forces.’’ J. Struct. Engrg., ASCE, 112, 1881–1899.

 FEMA-355C (2000) State of the art report on systems performance of steel moment frames subject to earthquake ground shaking, prepared by the SAC Joint Venture for the Federal Emergency Management Agency.

 George W. Housner (1963); The behavior of inverted pendulum structures during earthquakes. Bulletin of the Seismological Society of America ; 53 (2): 403–417. doi: