Cyclic performance of steel moment-resisting connections with reduced beamsections experimental analysis and finite element model simulationD.T. Pachoumis, E.G. Galoussis, C.N. Kalfas, I.Z. EfthimiouSteel Structures Laboratory, School of Civil Engineering, Democritus University of Thrace, Xanthi, 67100, Greecea r t i c l e i n f oArticle history:Received 13 May 2009Received in revised form9 April 2010Accepted 28 April 2010Available online 16 June 2010Keywords:Reduced beam section connectionDogboneMoment-resisting connectionCyclic loadingFinite element analysisa b s t r a c tReduced beam section (RBS) moment-resisting connections have been developed in order to provide ahighly ductile response and reliable performance. Recommendations for the design and detailing of theRBS member were prescribed in EC8, Part 3. However, the effectiveness of these recommendations fora European profile is dubious, due to limited existing data from European research. An experimentalprogram was performed in order to evaluate the proposed values of the geometrical characteristics of theRBS, and the results are presented in the present paper. Two full-scale subassemblages were tested undercyclic loading and the results are compared with those obtained from the theoretical model, using thefinite element method. The analysis confirms the need for readjustment of the geometrical characteristicsof the RBS in order to apply to European profiles.' 2010 Elsevier Ltd. All rights reserved.1. IntroductionThe unexpected local brittle damage of beam-to-column con-nections of steel moment-resisting frames in the Northridge (1994)and Kobe (1995) earthquakes generated concerns regarding the re-liability of the current design practise and detailing of connections.Rigorous post-earthquake investigations have revealed many fac-tors contributing to the failure. The high stress concentration atthe welded web and flanges and the vulnerability of the connec-tion to the large ductility demand are considered to be two criticalfactors causing such failures. A natural way to solve the problemis to reduce the ductility demand on the welded areas and allevi-ate the stress concentration level. Numerous solutions to the mo-ment frame connection problem have been proposed [14], manyof which have been shown to exhibit satisfactory levels of ductilityin numerous tests.One of these is the reduced beam section (RBS) configuration.Portions of the beam flanges are trimmed away in the region ad-jacent to the beam-to-column connection. The RBS can be viewedas a ductile fuse that forces the formation of the plastic hinge awayfrom the joint so that much of ductility demand on beams may re-sult from the RBS instead of the welded beam-to-column interface.Extensive experimental [57] and analytical [810] projects havebeen conducted proving the effectiveness of this solution. Appar-ently, the efficiency of the RBS in mitigating the problems relies on Corresponding author. Tel.: +30 6977135683; fax: +30 2541079821.E-mail address: dpachoum@civil.duth.gr (D.T. Pachoumis).the proper design of the RBS, which includes the shape, the locationand flange reduction ratio (the reduced flange area over the origi-nal flange area) of the RBS. Various shaped cutouts were proposed(constant, tapered or radius cut) to reduce the cross-sectionalarea. Experimental investigations have demonstrated that a curvedRBS behaves with the highest rotational capacity with respect topolyline-shaped solutions [11]. The location of the RBS with a givenflange reduction ratio may alter its efficiency. Besides, an RBS withsmall reduction in beam flanges might do little to reduce the stressin the column faces. However, an RBS with excessive reduction inthe beam flanges may result in premature lateraltorsional buck-ling of the RBS.Some design parameters are recommended by FEMA 350 [1]and FEMA 351 [12] regarding the location and reduction rate ofan RBS, based on the local performance of tested beam-to-columnassemblies. In Europe, also, following the spirit of the above-mentioned recommendations, in EC8, Part 3 [13] designs of suchtype of connection are presented. The proposals for the radius cutfrom FEMA 350, which prequalified this shape, and EC8, Part 3 arepresented in Table 1. The values for the geometrical parametersrecommended in EC8, Part 3 are the average of, or even the sameas, those in FEMA 350, due to the lack of experimental studies onEuropean profiles. So, the effectiveness of these recommendationsis questionable. Recent experimental research [14] confirmed theneed for readjustment of the geometrical characteristics for thedesign of a radius-cut RBS.This paper presents an investigation on the cyclic performanceof steel moment-resisting connections with RBS, using European0141-0296/$ see front matter ' 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.engstruct.2010.04.038