Earthquakes and Structures

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Identifying torsional eccentricity in buildings without performing detailed structural analysis

  • Tamizharasi, G. (Department of Civil Engineering, Sardar Vallabhbhai National Institute of Technology) ;
  • Murty, C.V.R. (Department of Civil Engineering, Indian Institute of Technology Madras)
  • Received : 2021.09.27
  • Accepted : 2022.10.11
  • Published : 2022.09.25
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Abstract

Seismic design codes permit the use of Equivalent Static Analysis of buildings considering torsional eccentricity e with dynamic amplification factors on structural eccentricity and some accidental eccentricity. Estimation of e in buildings is not addressed in codes. This paper presents a simple approximate method to estimate e in RC Moment Frame and RC Structural Wall buildings, which required no detailed structural analysis. The method is validated by 3D analysis (using commercial structural analysis software) of a spectrum of building. Results show that dynamic amplification factor should be applied on torsional eccentricity when performing Response Spectrum Analysis also. Also, irregular or mixed modes of oscillation arise in torsionally unsymmetrical buildings owing to poor geometric distribution of mass and stiffness in plan, which is captured by the mass participation ratio. These irregular modes can be avoided in buildings of any plan geometry by limiting the two critical parameters (normalised torsional eccentricity e/B and Natural Period Ratio 𝜏 =T𝜃/T, where B is building lateral dimension, T𝜃 uncoupled torsional natural period and T uncoupled translational natural period). Suggestions are made for new building code provisions.

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References

  1. American Society of Civil Engineers (ASCE) (2017), Minimum Design Loads for Buildings and Other Structures (ASCE7-16), USA
  2. Association of Structural Engineers of the Philippines (2010), National Structural Code of the Philippines 2010, NSCP C101-10, Philippines
  3. Botis, M.F. and Cerbu, C. (2020), "A method for reducing of the overall torsion for reinforced concrete multi-storey rrregular structures", Appl. Sci., 10(16), 1-25. https://doi.org/10.3390/app10165555.
  4. Bureau of Indian Standards (2016), Indian Standard Criteria for Earthquake Resistant Design of Structures, Part 1 General Provisions and Buildings, IS 1893(1), New Delhi, India.
  5. Cheung, W.T.V. (1986), Application of Eccentricity Concept to Multistory Buildings, Ph.D. Dissertation, Civil Engineering and Engineering Mechanics, McMaster University, Hamilton, Canada.
  6. Chopra, A.K. and Goel, R.K. (1991), "Evaluation of torsional provisions in seismic codes", J. Struct. Eng., ASCE, 117(12), 3762-3782. https://doi.org/10.1061/(ASCE)0733-9445(1991)117:12(3762).
  7. Crisafulli, F., Reboredo, A. and Torrisi, G. (2004), "Consideration of torsional effects in the displacement control of ductile buildings", Proceedings of the Thirteenth World Conference on Earthquake Engineering, Vancouver, British Columbia, Canada, Paper No.1111
  8. Das, P.K., Dutta, S.C. and Datta, T.K. (2021), "Seismic behavior of plan and vertically irregular structures: State of art and future challenges", Nat.l Haz. Rev., 22(2), 1-17. https://doi.org/10.1061/(ASCE)NH.1527-6996.0000440.
  9. Disaster and Emergency Management Directorate (AFAD), (2007), Regulations for Buildings in Disaster Regions, Turkey
  10. Duan, X.N. and Chandler, A.M. (1993), "Inelastic seismic response of code-designed multistorey frame buildings with regular asymmetry", Earthq. Eng. Struct. Dyn., 22(5), 431-445. https://doi.org/10.1002/eqe.4290220506
  11. ETABS (2020), Analysis and Design of Building Systems, Version 18.1.1, Computers & Structures Inc. (CSI), USA.
  12. Eurocode 8 (2004), European Standard for Design of Structures for Earthquake Resistance, EN 1998-1: The European Union.
  13. Federal Emergency Management Agency (FEMA) (2003), NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, FEMA 450-1, Building Seismic Safety Council, Washington, DC
  14. Georgoussis, G.K. and Mamou, A., (2018), "The effect of mass eccentricity on the torsional response of building structures", Struct. Eng. Mech., 67(7), 671-682. https://doi.org/10.12989/sem.2018.67.6.671.
  15. Hejal, R. and Chopra, A.K. (1989), "Earthquake analysis of a class of torsionally-coupled buildings," Earthq. Eng. Struct. Dyn., 18(3), 305-323. https://doi.org/10.1002/eqe.4290180302.
  16. Humar, J.L. and Kumar, P. (1998), "Torsional motion of buildings during earthquakes. I. Elastic response", Canadian J. Civil Eng., 25(5), 898-916. https://doi.org/10.1139/l98-031.
  17. International Council of Building Officials, (1997), Uniform Building Code (UBC), Whittier, CA, USA.
  18. Japan Building Code (1) (2001), The Building Standard Law of Japan, Ministry of Land, Infrastructure, Transport and Tourism, Japan
  19. Jarernprasert, S. and Bazan, E. (2008), "Inelastic torsional singlestory systems", Proceedings of the Fourteenth World Conference on Earthquake Engineering, Beijing, China.
  20. Kumar, P. (1998), Torsional Response of Buildings During Earthquake, Ph.D. Dissertation, Carleton University, Ottawa, Canada.
  21. Lin, J.L., Tsai, K.C. and Chuang, M.C. (2012), "Understanding the trends in torsional effects in asymmetric-plan buildings", Bull. Earthq. Eng., 10(3), 955-965. https://doi.org/10.1007/s10518-012-9339-x.
  22. Mehana, M.S., Mohamed, O. and Isam, F. (2019), "Torsional Behaviour of Irregular Buildings with Single Eccentricity", In IOP Conference Series: Materials Science and Engineering, 603(5), 52028. https://doi.org/10.1088/1757-899X/603/5/052028.
  23. Mexico City Building Code (1995), Complementary Technical Norms on Earthquake Resistant Design, Department of Federal District, Mexico
  24. National Building Code (2016), Earthquake Resistant Design, Technical Standard of Buildings E.030, Ministry of Housing, Construction and Sanitation, Peru
  25. National Research Council (2010), National Building Code of Canada (NBCC), Canada
  26. Nepal National Building Code (NBC) (1995), Code of Practice for Seismic Design of Buildings in Nepal, (NBC 105:1995), His Majesty's Government of Nepal, Ministry of Housing and Physical Planning, Department of Buildings, Nepal
  27. Official Chilean Code (1996), Earthquake Resistant Design of Buildings (NCH433.of96), National Institute of Standardisation, INN, Chile
  28. Palermo, M., Silvestri, S., Gasparini, G. and Trombetti, T. (2017), "Corner displacement response spectra for one-storey eccentric structures," Proceedings of the Sixteenth World Conference on Earthquake Engineering, Santiago, Chile, Paper No.2007.
  29. Rutenberg, A. and Pekau, O.A. (1987), "Seismic code provisions for asymmetric structures: a re-evaluation", Eng. Struct., 9(4), 255-264. https://doi.org/10.1016/0141-0296(87)90024-1.
  30. Sedarat, H. and Bertero, V.V. (1990), "Effects of torsion on the linear and nonlinear seismic response of structures", Earthquake Engineering Research Center, UCB/EERC-90/12, University of California, 90(12)
  31. Seismic Design Code for Buildings in Taiwan (2005), Seismic Force Requirements for Buildings in Taiwan, National Center for Research on Earthquake Engineering, Taiwan
  32. Smith, B.S. and Vezina, S. (1985), "Evaluation of centres of resistance in multistorey building structures", Proceedings of the Institution of Civil Engineers, 79(4), 623-635. https://doi.org/10.1680/iicep.1985.761
  33. Standards Association of New Zealand (1992), Code of Practice for General Structural Design and Design Loadings for Buildings, NZS 4203:1992, New Zealand
  34. Tamizharasi, G., Prasad, A.M. and Murty, C.V.R. (2020), "A simple method to identify torsional flexibility in buildings without performing detailed structural analysis", Proceedings of the 17th World Conference on Earthquake Engineering, Sendai, Japan, September, Paper No. C003403.
  35. Tamizharasi, G., Prasad, A.M. and Murty, C.V.R. (2021), "Lateral-Torsional Seismic Behaviour of Plan Unsymmetric Buildings", Earthq. Struct., 20(3), 239-260. https://doi.org/10.12989/eas.2021.20.3.000.
  36. Tso, W.K. (1990), "Static eccentricity concept for torsional moment estimations", ASCE J. Struct. Eng., 116(5), 1199-1212. https://doi.org/10.1061/(ASCE)0733-9445(1990)116:5(1199).
  37. Yiu, C.F., Chan, C.M., Huan, M. and Li, G. (2014), "Evaluation of lateral-torsional coupling in earthquake response of asymmetric multistory buildings", Struct. Des. Tall Spec. Build., 23(13), 1007-1026. https://doi.org/10.1002/tal.1102.