Journal of the Computational Structural Engineering Institute of Korea (한국전산구조공학회논문집)

Computational Structural Engineering Institute of Korea (한국전산구조공학회)
권호 표지
DOI QR코드

DOI QR Code

Capacity Design of Eccentrically Braced Frame Using Multiobjective Optimization Technique

다목적 최적화 기법을 이용한 편심가새골조의 역량설계

  • Hong, Yun-Su (Department of Architectural Engineering, Hanyang Univ.) ;
  • Yu, Eunjong (Department of Architectural Engineering, Hanyang Univ.)
  • Received : 2020.10.05
  • Accepted : 2020.10.13
  • Published : 2020.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

The structural design of the steel eccentrically braced frame (EBF) was developed and analyzed in this study through multiobjective optimization (MOO). For the optimal design, NSGA-II which is one of the genetic algorithms was utilized. The amount of structure and interfloor displacement were selected as the objective functions of the MOO. The constraints include strength ratio and rotation angle of the link, which are required by structural standards and have forms of the penalty function such that the values of the objective functions increase drastically when a condition is violated. The regulations in the code provision for the EBF system are based on the concept of capacity design, that is, only the link members are allowed to yield, whereas the remaining members are intended to withstand the member forces within their elastic ranges. However, although the pareto front obtained from MOO satisfies the regulations in the code provision, the actual nonlinear behavior shows that the plastic deformation is concentrated in the link member of a certain story, resulting in the formation of a soft story, which violates the capacity design concept in the design code. To address this problem, another constraint based on the Eurocode was added to ensure that the maximum values of the shear overstrength factors of all links did not exceed 1.25 times the minimum values. When this constraint was added, it was observed that the resulting pareto front complied with both the design regulations and capacity design concept. Ratios of the link length to beam span ranged from 10% to 14%, which was within the category of shear links. The overall design is dominated by the constraint on the link's overstrength factor ratio. Design characteristics required by the design code, such as interstory drift and member strength ratios, were conservatively compared to the allowable values.

본 연구에서는 철골편심가새골조 시스템을 대상으로 다목적최적화기법을 통해 설계를 수행하고 그 결과를 분석하였다. 최적화 설계를 위해 유전 알고리즘의 일종인 NSGA-II를 활용하였다. 여기서, 목적함수는 이율배반적 관계를 갖는 구조물량과 층간변위로 하여 최소화되고, 제약조건에는 구조기준에서 요구하는 내력비, 링크의 회전각 등을 포함하였다. 제약조건은 최적화 알고리즘 내에서 각 항목을 위반할수록 목적함수 값을 크게 증가시키는 벌금함수의 형태를 가지고 있다. 설계기준에서 EBF 시스템의 설계규정은 링크 부재만 항복이 허용되며 나머지 부재는 링크 항복 시 발생되는 부재력을 탄성상태에서 견디도록 의도한 역량설계법에 기초한다. 그러나 최적화를 통해 도출된 결과 중 일부는 구조기준의 설계조항은 만족하지만 특정층 링크에 소성변형이 집중되어 연약층을 형성함으로써 기준에서 의도하는 역량설계의 원칙을 위배하는 결과가 나타났다. 이를 해결하기 위해 모든 링크의 전단 초과강도계수 중 최대값이 최소값의 1.25배를 넘지 않도록 하는 제약식을 추가하였다. 새로운 제약식을 추가한 경우 모든 최적해는 설계기준과 역량설계의 원칙을 준수하는 것으로 나타났다. 모든 설계안에서 보 경간에 대한 링크의 길이비는 전단링크의 범주에 해당하는 10% ~ 14%였다. 전체적으로 설계안들은 링크의 초과강도 계수비가 가장 지배적인 제약으로 작용하였으며, 구조기준의 요구사항 중 층간변위와 내력비 등의 항목에서 허용치에 비해 매우 보수적으로 설계되었다.

Keywords

References

  1. AISC, A. (2010) Seismic Provisions for Structural Steel Buildings.
  2. ANSI, B. (2016) AISC 360-16, Specification for Structural Steel Buildings, Chicago AISC.
  3. ASCE (2016) Minimum Design Loads and Associated Criteria for Buildings and Other Structures, ASCE Standard ASCE/SEI 7-16 Reston, VA.
  4. Azad, S.K., Topkaya, C. (2017) A Review of Research on Steel Eccentrically Braced Frames, J. Constr. Steel Res., 128, pp.53-73. https://doi.org/10.1016/j.jcsr.2016.07.032
  5. Becker, R., Ishler, M. (1996) Seismic Design Practice for Eccentrically Braced Frames, Structural Steel Educational Council, p.27.
  6. Bosco, M., Rossi, P.P. (2009) Seismic Behaviour of Eccentrically Braced Frames, Eng. Struct., 31(3), pp.664-674. https://doi.org/10.1016/j.engstruct.2008.11.002
  7. Bruneau, M., Uang, C.M., Sabelli, S.R. (2011) Ductile Design of Steel Structures, McGraw Hill Professional.
  8. Deb, K., Pratap, A., Agarwal, S., Meyarivan, T.A.M.T. (2002) A Fast and Elitist Multiobjective Genetic Algorithm: NSGA-II, IEEE Trans. Evolut. Comput., 6(2), pp.182-197. https://doi.org/10.1109/4235.996017
  9. Fathali, M.A., Vaez, S.R.H. (2020) Optimum Performance-based Design of Eccentrically Braced Frames, Eng. Struct., 202, p.109857. https://doi.org/10.1016/j.engstruct.2019.109857
  10. Gong, Y., Xue, Y., Xu, L. (2013) Optimal Capacity Design of Eccentrically Braced Steel Frameworks using Nonlinear Response History Analysis, Eng. Struct., 48, pp.28-36. https://doi.org/10.1016/j.engstruct.2012.10.001
  11. Kaveh, A., Shojaei, I., Gholipour, Y., Rahami, H. (2013) Seismic Design of Steel Frames using Multi-Objective Optimization, Struct. Eng. & Mech., 45(2), pp.211-232. https://doi.org/10.12989/sem.2013.45.2.211
  12. Mohammadi, R.K., Sharghi, A.H. (2014) On the Optimum Performance-based Design of Eccentrically Braced Frames, Steel & Compos. Struct.,, 16(4), pp.357-374. https://doi.org/10.12989/scs.2014.16.4.357
  13. Ohsaki, M., Nakajima, T. (2010) Optimization of Energy Dissipation Property of Eccentrically Braced Steel Frames, In 9th World Congress on Structural and Multidisciplinary Optimization, Shizuoka, Japan.
  14. Popov, E.P., Ricles, J.M., Kasai, K. (1992) Methodology for Optimum EBF Link Design, In Proceedings of the 10th World Conference on Earthquake Engineering, pp.3983-3988.
  15. Whittaker, A.S., Uang, C.M., Bertero, V.V. (1987) Earthquake Simulation Tests and Associated Studies of a 0.3-Scale Model of a Six-Story Eccentrically Braced Steel Structure, Earthquake Engineering Research Center, College of Engineering, University of California.