實尺寸兩層特殊同心斜撐鋼構架試驗與分析研究

Performance and Analysis of a Full Scale Special Concentrically Braced Frame

蔡青宜(Ching-Yi Tsai)

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(2008年)

https://doi.org/10.6342/NTU.2008.02130

摘要

特殊同心斜撐構架藉由斜撐構件受拉降伏與受壓挫屈兩種力學特性，來抵抗側力與消散外力所輸入之能量。本研究為一國際合作計畫，由美國華盛頓大學西雅圖分校團隊先進行試體設計，而實驗則在國家地震工程研究中心測試。研究動機是希望透過實驗觀察，瞭解特殊同心斜撐構架之受力反應，並建立ABAQUS有限元素分析模型來研究特殊同心斜撐構架之結構行為。目的是希望建立一套有限元素分析程序，以供後續實驗與分析參考。
本研究之試體為一實尺寸兩層特殊同心斜撐鋼構架，試體高度為6.66公尺，寬度為6.7公尺，斜撐排列之幾何形狀為X型。試驗總共進行三次，使用相同梁柱構架，替換不同形式之斜撐與接合板。HSS-8t與HSS-2t兩次試驗之斜撐斷面皆為HSS125x125x9鋼管，但採用不同方式設計接合板。WF-8t試驗則是使用斷面為H175x175x7.5x11作斜撐構件，而接合板設計方式與HSS-8t相同。本研究分別建立三次試驗之有限元素分析模型，進行各試體之反覆側推分析。文中將詳細介紹分析模型之材料、分析元素、邊界條件、初始缺陷與施力方式。
由試驗結果顯示此種同心斜撐系統的確能提供良好的消能能力，頂層位移角容量接近正負3%弧度，而X型配置之斜撐挫屈行為會互相牽動，所有斜撐皆發生挫屈，不會產生弱層現象。結構變形與破壞集中於斜撐與接合板，斜撐最大面外變形可達40cm，但並未對梁柱造成明顯破壞，為一可用之抗側力系統。由有限元素分析結果顯示分析模型可以準確分析特殊同心斜撐構架之斜撐後挫屈行為，對於斜撐挫屈、接合板凹折與斜撐局部挫屈行為皆可模擬。將斜撐與梁柱構架承擔之基底剪力分離後，發現在頂層側位移角小於0.28%弧度之前，斜撐可承擔90%以上之基底剪力，而當頂層位移角大於2%弧度後，斜撐承受之基底剪力約為60%，顯示特殊同心斜撐構架主要仍由斜撐承擔大部分之側力。

關鍵字

有限元素分析 ； 同心斜撐 ； 初始缺陷 ； 斜撐挫屈 ； 接合板

並列摘要

Measuring 6.7 meters wide and 6.66 meters tall, a full scale 2-story special concentrically braced frame (SCBF) was tested in National Center for Research on Earthquake Engineering (NCREE) in Taiwan. This is a cooperative project between researchers from Taiwan and U.S. to investigate the seismic design methods for brace-to-gusset connection details. The objectives of this study are to understand the cyclic behaviors of the SCBF and develop the valid design and analytical procedures.

Tests HSS-8t and HSS-2t were conducted using hollow structural section braces by two different brace-to-gusset details. The WF-8t using the wide-flange section braces was conducted to compare the responses with the HSS-8t. The performances of these three tests are presented in this study, focusing on the investigations of the overall structure and local members. For this purpose, in the beginning this study discusses the setup and the key experimental results of the specimen frame, such as the peak inter-story drifts and buckling of braces. And then nonlinear FEM program ABAQUS was used to simulate the responses of the specimen. This study describes the detailed analytical model and the modeling techniques, such as material model, boundary conditions, initial imperfections, load applying techniques.

Large out-of-plane displacement and local buckling of braces were observed in these three tests. However, except the fracture of some bolts in the beam-web-to-column connections there were no any facture found on beams and columns of specimen. The cyclic base shear versus the story drift relationships obtained from the test and the FEM analytical results are quite agreeable. The analytical results confirm that the magnitude of the severe out-of-plane buckling of the braces can be accurately simulated. Tests show that the ductile brace fractures occurred when the brace has undergone large out–of-plane deformations and developed localized plastic hinge. This local buckling can be observed in the ABAQUS responses. FEM analyses also illustrate that the brace members take about 90% story shear at low level inter-story drifts under 0.0028 radians, but gradually decrease to 60% story shear when the inter-story drift is greater 0.02 radians. This paper concludes with the procedures for finite element analysis of steel SCBFs.

並列關鍵字

FEM ； CBF ； initial imperfections ； buckling of the braces ； gusset plate

參考文獻

[3] AISC (2005b), “Specification for Structural Steel Buildings”, AISC/ANSI Standard 360-05, American Institute of Steel Construction, Chicago, IL.

[4] AISC (2005c), “Steel Construction Manual”, 13th Edition, American Institute of Steel Construction, Chicago, IL.

[7] Chen, C.H., Lai, J.W. and Mahin, S. (2008), “Numerical Modeling and Performance Assessment of Concentrically Braced Steel Frames”, Proceedings, ASCE SEI 2008 Structures Congress, Vancouver, Canada.

[10] Lehman, D. E., Roeder, C. W., Herman, D., Johnson, S. and Kotulka, B. (2008), “Improved Seismic Performance of Gusset Plate Connections”, ASCE, Journal of Structural Engineering, Vol.134, No. 6, Reston, VA, pp.890-901.

[13] Moon, J., Yoon, K.Y., Han, T.S. and Lee, H.E. (2008), “Out of Plane Buckling and Design of X-bracing Systems with Discontinuous Diagonals”, Journal of Constructional Steel Research, Volume 64, Issue 3, pp.285-294.