Optimization of Reduced Beam Sections (RBS) for Ductile Detailing of Seismic Joint Connections Using Finite Element Analysis (FEA)

Document Type : Original Article


Department of Civil Engineering, College of Engineering and Architecture, University of the Cordilleras, Baguio City, Philippines


Steel structures used as Special Moment Resisting Frames (SMRF) designed to resist lateral loads (due to wind and seismic) are expected to undergo large inelastic deformations, hence the ductility requirements are explicitly stated in almost all standards. In any given frame, inelastic deformations should occur in the horizontal elements (e.g. beams) in the form of plastic hinges. Most structural analysis can be performed assuming the beam-column joint (nodes) as a fixed (rigid) connection, however, this may mean that hinging may occur at the connection and thus possibly affect the column through the flange or web connection. In order to ensure a ductile system can be achieved, special detailing requirements are necessary. Among the available methods require the use of Reduced Beam Sections (RBS) adjacent to the beam-column connection to warrant the strong-column/weak-beam design philosophy. The main objective of this paper is to optimize the geometry of the RBS using Finite Element Analysis (FEA) in conjunction with the available standards e.g. BS EN 1998-3 and ANSI/AISC 358-16. While standard codes of practice provide the range of values that can be used in determining the geometry of the RBS, it would be beneficial for a designer to come up with basic rules-of-thumb that can be applied in actual design calculations.


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[1]     (FEMA) FEMA. State of the art report on connection performance 2000.
[2]     Youssef NFG, Bonowitz D, Gross JL. A survey of steel moment-resisting frame buildings affected by the 1994 Northridge earthquake. US National Institute of Standards and Technology; 1995.
[3]     Miller DK. Lessons learned from the Northridge earthquake. Eng Struct 1998;20:249–60. doi:10.1016/S0141-0296(97)00031-X.
[4]     Plumier A. Behaviour of connections. J Constr Steel Res 1994;29:95–119. doi:10.1016/0143-974X(94)90058-2.
[5]     Plumier A. New idea for safe structures in seismic zones. IABSE Symp. Struct. Incl. New Mater., 1990.
[6]     Chambers JJ, Almudhafar S, Stenger F. Effect of Reduced Beam Section Frame Elements on Stiffness of Moment Frames. J Struct Eng 2003;129:383–93. doi:10.1061/(ASCE)0733-9445(2003)129:3(383).
[7]     Zhang X, Ricles JM. Experimental Evaluation of Reduced Beam Section Connections to Deep Columns. J Struct Eng 2006;132:346–57. doi:10.1061/(ASCE)0733-9445(2006)132:3(346).
[8]     Montuori R. The Influence of Gravity Loads on the Seismic Design of RBS Connections. Open Constr Build Technol J 2014;8:248–61. doi:10.2174/1874836801408010248.
[9]     Jones SL, Fry GT, Engelhardt MD. Reduced beam section welded steel moment frames. 12th world Conf. Earthq. Eng. Auckland, New Zealand, Pap., vol. 1671, 2000.
[10]   Sofias C, Tzourmakliotou D. Reduced Beam Section (RBS) Moment Connections-Analytical Investigation Using Finite Element Method. Civ Eng J 2018;4:1240. doi:10.28991/cej-0309170.
[11]   British Standards Institution. Eurocode 8: Design of structures for earthquake resistance Part 3: Assessment and retrofitting of buildings. London: British Standards Institution. 11 January 2006 n.d.
[12]   Lee C-H, Jeon S-W, Kim J-H, Uang C-M. Effects of Panel Zone Strength and Beam Web Connection Method on Seismic Performance of Reduced Beam Section Steel Moment Connections. J Struct Eng 2005;131:1854–65. doi:10.1061/(ASCE)0733-9445(2005)131:12(1854).
[13]   American Institute of Steel Construction. ANSI/AISC 358-16. Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications, including Supplement No. 1. Chicago, USA: American Institute of Steel Construction n.d.
[14]   Lee CH, Jeon SW, Kim JH, Kim JH, Uang CM. Seismic performance of reduced beam section steel moment connections: effects of panel zone strength and beam web connection method. 13th World Conf. Earthq. Eng., 2004, p. 1–6.
[15]   American Institute of Steel Construction. ANSI/AISC 341-16. Seismic Provisions for Structural Steel Buildings. Chicago, USA: American Institute of Steel Construction n.d.
[16]   IDEA Statica. General theoretical background. Retrieved from https://www.ideastatica.com
[17]   Landolfo R, Mazzolani FM, Dubina D, da Silva LS, d’Aniello M. Design of Steel Structures for Buildings in Seismic Areas: Eurocode 8: Design of Steel Structures in Seismic Areas. General Rules and Rules for Buildings, ECCS; 2017.