www.springer.com/journal/13296 International Journal of Steel Structures 17(2): 1-10 (2017) DOI 10.1007/s13296- ISSN 1598-2351 (Print) ISSN 2093-6311 (Online) 3-D Finite Element Modeling of Extended Single Plate Shear Connections: Predicting the Mode of Failure Mohamed F. Suleiman 1, *, Bahram M. Shahrooz 2 , Herbert L. Bill 2 , Patrick J. Fortney 3 , and William A. Thornton 3 Department of Civil, Environmental and Geodetic Engineering, Ohio State University, Columbus, OH, 43210, USA Department of Civil and Architectural Engineering and Construction Management, University of Cincinnati, Cincinnati, OH, 45221, USA Cives Steel Company, Roswell, GA, 30076, USA Abstract Twisting and lateral-torsional stability of extended shear-plate connections could be a design issue due to the relatively long distance between the weld and the bolt centroid of the shear tab, and the eccentricity between the thickness of the connection plate and web of the supported beam. The 13 th edition of the Steel Construction Manual did not include checks for determining whether or not twisting would have to be considered as a controlling design limit state. However, the current edition (i.e., the 14 th edition) provides a methodology for evaluating the need for stiffeners (also called stabilizer plates) that based on the amount of twisting of the connection plate. This paper presents the results of three-dimensional non-linear finite element analyses of a number of extended single plate connections in which the floor slab, which braces the top flange of the supported member, was incorporated. The primary goal of the reported research was to examine the need for stabilizer plates, and to investigate twist in extended shear tabs. Keywords: Extended single plate shear connections, Stabilizer plates, Torsional moment, Twist, Shear tab 1. Introduction Single plate shear connections are a common type of connection in which a shear tab is welded to the supporting member and is bolted to the web of the supported beam. Depending on the distance between the weld line and the centroid of the bolt group, the connection is classified as either a conventional or extended single plate shear connection. The extended single plate shear connection, hereafter referred to as EST, is an economical option for beam-beam or beam-column web connections because it eliminates the need for copes, and is easier and safer to erect (Gong, 2010; Yura, 1982). Considering that the connection plate and the beam web are not in the same vertical plane, twisting in the plate can occur. The larger distance between the bolt line and the weld line of an EST connection could make the angle of twist larger relative to a conventional single plate shear connection, Astaneh et al. (1989) and Muir et al. (2011). In a series of tests conducted by Sherman and Ghorbanpoor (Sherman et al., 2002), excessive twisting of some of the EST connections was observed. Floor/roof diaphragms are expected to reduce the lateral twist of the beam and EST by restraining the out-of-plane displacement of the beam’s top flange; however, floor/roof diaphragms were not included in the Sherman and Ghorbanpoor test specimens. Based on the results from these rather simplified test specimens, (Sherman and et al., 2002) concluded that twisting would need to be considered as a potential primary limit state or failure mode in EST connection. Furthermore, they recommended that EST connections not be used unless stiffeners (also called stabilizer plates) are provided in the joint region. The 14 th edition of AISC Steel Construction Manual (2010) provides equations to evaluate the need for stiffeners. These equations were developed based on fundamental concepts of structural mechanics. The main goals of the research reported herein were to (1) better understand the performance of EST connections, (2) examine the possibility of twist as a governing limit state, and (3) study the need for stabilizer plates. To achieve these goals, nonlinear finite element analyses of a number of EST connections were conducted. Received 00000 00, 2016; accepted 00000 00, 2016; published online June 30, 2017 © KSSC and Springer 2017 *Corresponding author Tel: +1-412-805-4610, Fax: +1-877-288-1826 E-mail: suleiman.25@osu.edu, mfozys@hotmail.com