Optimal position of outriggers for minimizing the base moment under lateral load

Document Type : Research Article


Department of civil engineering/Islamic Azad University of Torbate jam


In this paper, the optimum position of Outriggers in a structure for minimizing the base moment under lateral loads is investigated. To do so, the base moment and top story displacement are formulated. Then, a Matlab code is employed to find the optimum positions of the Outriggers. Different kinds of lateral loads including concentrated, uniform, triangular and a combination of such loads are taken into account. Moreover, the effects of the variation of structural elements such as columns, Outriggers and core on the base moment and top story displacement are examined. The outcomes indicated that the optimum points of Outriggers get closer when the flexural rigidity of Outriggers increases. Furthermore, it is shown that the greatest decrease in the base moment occurs in a specific range which depends on the structure parameters such as axial rigidity of columns, the distance of columns, the flexural rigidity of Outriggers and height of the structure. The results show that when the wind load intensity increases, the optimum position of the Outriggers will move to the top of the structure.


Main Subjects

[1] M. Wang, S. Nagarajaiah, F. Sun, Optimal design of supplemental negative stiffness damped outrigger system for high-rise buildings resisting multi-hazard of winds and earthquakes, Journal of Wind Engineering & Industrial Aerodynamics, 218 (2021).
[2] B.S. Taranath, Optimum belt truss location for high-rise structures. Structural Engineer, Structural Engineer, 53 (1975) 18-21.
[3] B.S. Smith, I. Salim, Parameter study of outrigger-braced tall building structures, Journal of the Structural Division, 107 (1981) 2001-2014.
[4] B.S. Taranath, Structural analysis and design of tall buildings, CRC Press Llc,  (2011).
[5] Y. Zhu, Inner force analysis of frame–core structure with horizontal outrigger belts, Journal of Building Structures, 10 (1995) 10-15.
[6] B.S. Smith, A. Coull, Tall building structures: Analysis and design, John Willey, New York, 1991.
[7] A. Mijar, C. Swan, J. Arora, I. Kosaka, Continuum topology optimization for concept design of frame bracing systems, J Struct Eng,  (1998) 124-141.
[8] Z. Zhang, X. Fu, J. Wang, Y. Wei, Studies on structural performance of ultra-high rise building with outrigger belts, Journal of Building Structures, 17 (1996) 2-9.
[9] B.S. Taranath, Steel, concrete, and composite design of tall buildings, McGraw-Hill, New York, 1998.
[10] J. Wu, Q. Li, Structural performance of multi‐outrigger‐braced tall buildings, The Structural Design of Tall and Special Buildings, 12 (2003) 155-176.
[11] M. Malekinejad, R. Rahgozar, Free vibration analysis of tall buildings with outrigger-belt truss system, Earthquake and Structures, 2 (2011) 89-107.
[12] J. Zhang, X. Zhao, H. Zhu, C. Zhou, Safety analysis of optimal outriggers location in high-rise building structures, Journal of  Zhejiang University Science A, 8 (2007) 264-269.
[13] R. Rahgozar, Y. Sharifi, An approximate analysis of combined system of framed tube, shear core and belt truss in high‐rise buildings, The Structural Design of Tall and Special Buildings, 18 (2009) 607-624.
[14] Q.Q. Liang, Y.M. Xie, G.P. Steven, Optimal topology design of bracing systems for multi-story steel frames, J Struct Eng, 126 (2000) 823-839.
[15] C.M. Chan, K.M. Wong, Structural topology and element sizing design optimization of tall steel frameworks using a hybrid OC-GA method, Structural and Multidisciplinary Optimization, 35 (2008) 473-488.
[16] L. Stromberg, A. Beghini, W.F. Baker, G.H. Paulino, Application of layout and topology optimization using pattern gradation for the conceptual design of buildings, Structural and Multidisciplinary Optimization,  (2010) 1-16.
[17] K. Shivacharan, S. Chandrakala, N.M. Karthik, Optimum Position of Outrigger System for Tall Vertical Irregularity Structures, IOSR Journal of Mechanical and Civil Engineering, 12 (2015) 54-63.
[18] R. Kamgar, R. Rahgozar, Determination of Optimum Location for Flexible Outrigger Systems in Tall Buildings with Constant Cross Section Consisting of Framed Tube, Shear Core, Belt Truss and Outrigger System Using Energy Method, International Journal of Steel Structures,  (2017) 1-8.
[19] H.S. Park, E. Lee, S. Choi, B.K. Oh, Genetic-algorithm-based minimum weight design of an outrigger system for high-rise buildings, Engineering Structures, 117 (2016) 496-505.
[20] Y. Chen, Z. Zhang, Analysis of outrigger numbers and locations in outrigger braced structures using a multiobjective genetic algorithm, The Structural Design of Tall and Special Buildings, 27 (2017).
[21] L. Xing, Y. Zhou, M. Aguaguana, Optimal vertical configuration of combined energy dissipation Outriggers, The Structural Design of Tall and Special Buildings, 28 (2018).
[22] M. Beltran, G. Turan, O. Dursun, R. Nijsse, Energy dissipation and performance assessment of double damped outriggers in tall buildings under strong earthquakes, The Structural Design of Tall and Special Buildings, 28 (2019).
[23] P. Gunda, V. Anthugari, Optimization of location of outrigger system in tall buildings of different aspect ratios, Materials Today,  (2021).
[24] L. Xing, P. Gardon, Y. Zhou, Optimal outrigger locations and damping parameters for single-outrigger systems considering earthquake and wind excitations, Engineering Structures, 245 (2021).
[25] C. Fang, B. Spencer, J.xu, P. Tang, Optimization of damped outrigger systems subject to stochastic excitation, Engineering Structures, 191 (2019) 280-291.
[26] M. Samadi, N. Jahan, Comparative study on the effect of outrigger on seismic response of tall buildings with braced and Wall Core. II: Determining seismic design parameters, The Structural Design of Tall and Special Buildings 30(9) (2021).