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  • 學位論文

國家地震工程研究中心增建案耐震分析

Seismic Analysis of NCREE Office Building Extension

指導教授 : 蔡克銓
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摘要


本研究針對國家地震工程研究中心增建後的結構進行耐震分析。增建案是在既有的六層RC建築上,擴建為十三層RC與鋼構的複合結構;此外建築基地面積也增大以容納一樓至十三樓鋼結構服務核。舊有一樓至六樓的RC建築結構加厚或新增剪力牆,並採複合材料補強RC短梁;為增加結構耐震能力,採用BRB、SPD 及FVD等消能元件。本研究採PISA3D程式,在RC梁、RC柱、RC剪力牆、鋼梁、鋼柱、BRB、SPD、FVD等構件分採雙線性、衰減、硬化等不同材料模型,建置結構分析模型。二至七樓新舊樓板採雙質心雙剛性樓板,並在交界節點採6DOF節點元素來分析新舊樓板交界面受力情形,八至頂樓板採單質心單剛性樓板,進行模態、振動週期、樓層勁度、非線性側推與非線性反應歷時分析。結果顯示前三振動週期相近,分別為長向平移1.24s、短向平移並旋轉1.19s及旋轉1.05s,前三模態之模態質量參與比例各約為60%。樓層勁度在七樓轉換層雖有勁度下降的情形,但不屬在設計規範的軟層範圍內。非線性反應歷時分析採21組三向地震記錄,放大兩水平反應譜的幾何平均以擬合台北二區DBE設計反應譜,放大係數約在2.22~6.35之間。並將DBE三向地震除以3.5或乘以1.3以得SLE、MCE地震危害度下之地震加速度歷時。在21組SLE、DBE、MCE作用下,長向最大屋頂側移角平均值分別為0.303、0.898、1.1%弧度,短向則為0.275, 0.732, 0.935%弧度。長向最大層間側移角發生在七樓且各層側移角最大值分布較為均勻,平均值分別為0.35, 1.21, 1.61%弧度,短向則發生在五樓且七樓以下反應較大,平均值分別為0.34, 1.12, 1.52%弧度。在DBE作用下兩向反應均小於ASCE/SEI 7-10對介於醫院與一般建物重要度建築(Risk3)1.5%弧度的層間側移角限制;在MCE作用下,也小於FEMA 356 Life Safety性能所限制的 2%層間側移角。在DBE、MCE作用下二至七樓板有明顯旋轉反應,短向平均最大角柱層間側移角可高達樓板質心最大層間側移角的1.3倍以上。在三種地震危害度,21個最大基底剪力平均值,依序長向為2040, 5040, 5680噸,短向為1980, 4420, 5020噸。以TAP042地震為例,MCE等級下以RC梁與剪力牆降伏為主,RC短梁雖然有3%弧度的撓曲變形,但只有強度點轉角容量6%弧度的一半。因六、七樓RC棟與服務核的勁度差異,七樓交界有明顯的樓板面內拉壓力,從交界處的受力歷時可看出七樓長向樓層剪力明顯有在交界處發生力量傳遞現象,若七樓柱勁度採用SRC柱桿件模擬,七樓交界樓板長向面內軸拉壓力會比用鋼柱模擬時降低120 tf。另只考慮1.21秒的譜加速度值來擬合台北二區DBE設計反應譜,從前述21組地震的水平地震歷時中選取七組最適者,調整係數在1.96~2.93之間。在三種地震危害度下分別施加在結構長向與短向,所得最大屋頂位移、屋頂加速度與基底剪力的平均值兩向差異在20%以內,性能差異不大。

並列摘要


This study conduct the seismic analysis of NCREE office building extension. Extended NCREE building becomes a composite structure including the original six-story RC structure with RC shear walls and FRP strengthened beams, vertically added seven-story steel structure with BRBs, SPDs and FVDs. In addition, a service core was extended from the first floor to the oof at the north side of the building. PISA3D program was used for conducting the modal, static and nonlinear response history analyses (NRHA). Bilinear, degrading, hardening material models were adopted for RC beam and column, RC shear wall, steel members, BRB and SPD. Maxwell model was applied on FVDs. In order to gain insight into the force transfers between the RC structure and steel service core interfaces, double rigid diaphragms with two separate mass centers and several 6DOF joint elements were incorporated into the lower six floors of the structural model. Single rigid diaphragm and mass center were considered in all other floors. Analysis results showed that the first three modal periods, namely 1.24s (longitudinal translation), 1.19s (transversal translation and rotation) and 1.05s (rotation) respectively, are similar. The first three modes each tribute about 60% of the modal masses, respectively. Using the equivalent later forces, 7th lateral story stiffness is the lowest but still greater than the criterion of a soft story stipulated in the seismic building code. A total of 21 sets of ground accelerations and scaling factors were chosen in fitting the Taipei Zone 2 DBE design spectrum. The scale factors range from 2.22 to 6.35. Under three different earthquake hazard (SLE, DBE, MCE) levels, the averaged maximum roof drifts in the longitudinal (LG) direction are 0.303, 0.898, 1.1% radians and 0.275, 0.723, 0.935% radians in the transversal (TR) direction respectively. The averaged maximum story drifts (SD) occur at the LG 7th floor and TR 5th floor, which are 0.35, 1.22, 1.61% radians and 0.34, 1.12, and 1.52% radians respectively. In the DBEs, the SDs are less than 1.5% radians, and within the ASCE/SEI 7-10 limitation of the risk3 category having an importance between hospital and general buildings. In the MCEs, SDs are less than 2% radians within the FEMA356 performance limitation for life safety. Obvious story rotations occurred from the 2nd to the 7th floor, peak SDs computed at the corner columns are more than 1.3 times of maximum SDs calculated at the mass centers. Maximum base shears in the three earthquake hazards are 2040, 5040, 5680 tf and 1980, 4420, 5020 tf in the LG and TR directions, respectively. During a typical TAP042 MCE as the example, plastic hinges mostly occurred at RC members, and RC short beam rotation developed 3% radians only reached half of the rotational capacity. Due to unsymmetrical lateral stiffness distribution in the TR direction below the 7th floor, results show that the push-pull interface forces in the LG direction are much evident than the interface shear forces observed in the TR direction. During the TAP042 DBE, the maximum axial force of about 165 tf occurred at one of the 7th floor steel beam framed into the RC column. When the SRC column stiffness was incorporated into all columns in the 7th story, the interface beam axial forces could be reduced by about 20%. In order to investigate the building’s seismic performance in the LG and TR directions separately, a total of seven among the 21 sets of ground motions were selected and scaled so that the spectral accelerations at 1.21 seconds match the Taipei Zone 2 DBE spectrum. The scale factors range from 1.96 to 2.93. The NRHA results show that the differences on the peak roof drifts, accelerations and base shears between LG and TR directions are less than 20%.

參考文獻


1. ACI 440.2R-08 (2008). “Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures.”
2. AIJ (2004). “Guidelines for Performance Evaluation of Earthquake Resistant Reinforced Concrete Building.”
3. ASCE/SEI 4-16 (2017). “Seismic Analysis of Safety-Related Nuclear Structures. ” American Society of Civil Engineers, Structural Engineering Institute.
4. ASCE/SEI 43-05 (2005). “Seismic Design Criteria for Structures, Systems, and Components in Nuclear Facilities.” American Society of Civil Engineers, Structural Engineering Institute.
5. ASCE/SEI 7-10 (2010). “Minimum Design Loads for Buildings and Other Structures.” American Society of Civil Engineers, Structural Engineering Institute.

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