3-D Finite Element Modeling of Extended Single Plate Shear Connections: Predicting the Mode of Failure

Mohamed F. Suleiman,Bahram M. Shahrooz,Herbert L. Bill,Patrick J. Fortney,William A. Thornton 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.2

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 13th 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 14th 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.

Predicting the Demand of Shear Tab Connections with Composite Beams in Fire

Mohammad A. Hajjar,Elie G. Hantouche 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.3

Shear tab connections are one of the most commonly used simple beam-end framing connections. Simple connections are designed to resist shear forces at ambient temperature. This study aims at identifying the key parameters that aff ect the behavior of composite beams with shear tab connections under fi re. Large axial forces are generated during a fi re event due to the thermal expansion of the materials. These forces, which are not considered in the design, could lead to connection failure. In this study, fi nite element (FE) models are developed in Abaqus and validated against experimental data available in the literature. The strength degradation of the steel material at elevated temperatures is accounted for using retention factors. Concrete damage plasticity is implemented to model the concrete behavior at high temperatures. FE simulations are then performed to investigate the eff ect of diff erent parameters on the behavior of shear tab connections in composite beams subjected to fi re. The main parameters are: load ratio, concrete slab temperature, shear tab thickness, setback distance, bolt diameter, in addition to the creep in the concrete and the partial composite action. This proposed research provides more guidance on the eff ect of thermally induced forces and deformations of shear tab connections with composite beams. It also provides the basis for developing simple methods of analysis.

Progressive Collapse Performance Evaluation of Shear Tab Connection Subjected to Column Loss

Masoud Ghalejoughi,Mohammad Reza Sheidaii 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.5

A shear tab connection is one of the most common simple beam-to-column connections that is widely used in steel structures. In ASCE41-17 (Seismic evaluation and retrofit of existing buildings, American Society of Civil Engineers, 2017) and DoD (UFC 4-023-03, Design of buildings to resist progressive collapse, Department of Defense, Washington, DC, 2009), the plastic rotation capacity of a shear tab connection is purely a function of the connection depth, which is over- and under-estimated, respectively. To address this shortcoming, the present paper tries to provide a better estimation of plastic rotation capacity under the column removal scenario by employing a validated finite element model and conducting a comprehensive parametric study under various effective parameters such as connection depth, adjacent span length, and connection plate thickness. In addition to improving the plastic rotation capacity relationship, since the connection depth and adjacent span length have a significant effect on the plastic rotation capacity of the connection, a new equation has been proposed in terms of these parameters. Also, the axial-shear force–bending moment interaction of the connection is investigated.

Improving seismic performance of eight-bolt extended end plate moment connection

Shahriar Quayyum,Timothy R. Kohany 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.3

The eight-bolt stiffened extended end plate (8ES) connection is one of the connections prequalified for use in special and intermediate moment frames in ANSI/AISC 358. Simulated seismic testing of 8ES connections has generally shown sound performance with ductile failure modes. However, fast fracture of the beam flange at the stiffener toe has been observed in a recent study and was attributed to the high stress concentration in this region. To address this problem, an unstiffened eight-bolt extended end plate connection in which the stress concentration is eliminated by removing the stiffener, and the bolts are rearranged into an octagonal pattern to ensure uniform distribution of bolt forces, has been recently proposed. The study herein performed detailed finite element analyses with octagonal bolt arrangement to demonstrate that despite the improvements, high strain demands at the beam flange to end plate CJP welds may develop when the proposed unstiffened connection is used in conjunction with deep wide flange beam sections (e.g., W-sections of 900 mm nominal depth). Hence, an extended shear tab is used and analytically evaluated for unreinforced eight-bolt extended end plate connections. The extended heavy shear tab relocates the plastic hinge away from flange weld and slightly delays the onset of strength degradation. Systematic analysis results are developed and presented to demonstrate the enhanced seismic performance of the modified EEP connections and to plan future experimentations and design development.

Seismic retrofit of welded steel moment connections with highly composite floor slabs

Kim, Sung-Yong,Lee, Cheol-Ho Elsevier 2017 Journal of constructional steel research Vol.139 No.-

<P><B>Abstract</B></P> <P>In the 1994 Northridge earthquake, connection damage initiated from the beam bottom flange was prevalent in welded steel moment frames. The composite action due to the presence of a concrete floor slab was speculated as one of the critical causes of the prevalent bottom flange fracture. Close review of past experimental studies recently conducted by the authors clearly indicated that conventional steel moment connections with highly composite slabs are much more vulnerable to the bottom flange fracture. In this study, three seismic retrofit schemes are presented for welded steel moment connections with highly composite floor slabs typical of existing steel moment frames in Korea. Because top flange modification of existing beams is not feasible due to the presence of a concrete floor slab, beam bottom flange or web modifications by using welded triangular or straight haunch and heavy shear tab were cyclically tested. Test results of this study showed that all the retrofit schemes used are effective in eliminating the detrimental effect caused by high composite action and can ensure excellent connection plastic rotation exceeding 4% rad. Side effects resulting from retrofit as well as design recommendations are also discussed.</P> <P><B>Highlights</B></P> <P>This experimental study investigates seismic retrofit schemes for PN-type welded steel moment connections with highly composite floor slabs by using the beam bottom flange or beam web modification. The highlights of this study are:<UL> <LI> Reconfirmed the detrimental effects of high composite action for PN-type connections </LI> <LI> Experimentally verified excellent seismic capacity of all the retrofit schemes studied </LI> <LI> Experimentally verified excellent seismic capacity of all retrofit schemes studied </LI> <LI> Analyzed the unique behaviors of the retrofitted connections </LI> <LI> Discussed the side effects that should be considered in retrofit design </LI> </UL> </P>