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Roswell, GA, United States

Thornton W.A.,Cives Engineering Corporation | Muir L.S.,Structural Steel Consultant
Engineering Journal | Year: 2012

Bolted connections subjected to both shear and tension must be checked for prying action and the interaction between tension, and shear must be considered. The 2010 AISC Specification for Structural Steel Buildings (AISC 360-10) presents interaction equations both for bearing connections and for slip-critical connections. This paper demonstrates two methods to account for tension and shear interaction when prying action must be considered in slip-critical connections. The prying action procedure outlined in the 14th edition Steel Construction Manual is assumed. Copyright © 2012 by the American Institute of Steel Construction. Source


Thornton W.A.,Cives Engineering Corporation | Fortney P.J.,Cives Engineering Corporation
Engineering Journal | Year: 2012

When a vertical brace buckles during a seismic event, its connections must be able to resist the available flexural strength of the brace about its critical buckling axis without fracture. This is achieved in most current practice by orienting the brace to buckle out-of-plane and introducing a hinge line in the gusset to permit large inelastic rotations with small out-of-plane flexure demand on the connections and the supporting members. In this paper, the authors introduce a connection configuration that allows the development of a hinge line, which will permit large inelastic rotations for in-plane brace buckling with small flexural demand on the connection and supporting members. Copyright © 2012 by the American Institute of Steel Construction. Source


Fortney P.J.,Cives Engineering Corporation | Thornton W.A.,Cives Engineering Corporation
Engineering Journal | Year: 2016

Single-plate shear connections experience some magnitude of torsional moment, either due to the lateral torsional buckling phenomena or due to the effects of lap eccentricity. When the required torsional strength of the connection exceeds the available torsional strength of the connection, the designer has two options: alter the geometry of the connection to increase the torsional resistance of the connecting plate or provide stabilizer plates. Thornton and Fortney (2011) provide analysis techniques for accounting for the effects of lap eccentricity and lateral torsional buckling strength. Part 10 of the Manual (Steel Construction Manual, 14th ed., 2011) presents a summary of the equations used for such an evaluation. However, no discussion was provided by Thornton and Fortney with regard to the size and detailing of a stabilizer plate when such a plate is required. This paper presents recommendations for the analysis with regard to appropriate stabilizer plate cross-sectional dimensions and the attachment of the stabilizer plate to the connecting material and support. Three different types of stabilizer plates are presented along with recommendations for the design and detailing of the stabilizer plates; the impact that each type has on the design of the single-plate shear connection and the supporting column is presented as well. Source


Fortney P.J.,Cives Engineering Corporation | Thornton W.A.,Cives Engineering Corporation
Engineering Journal | Year: 2015

Vertical braces that connect concentrically to frame beams away from the beam-column joint are referred to as V-type or inverted V-type braced frames, as chevron braced frames or as mid-span braces. The braces are commonly connected to the frame beam using gusset plates. Typically, these gusseted connections are analyzed and designed considering only the effect of the brace forces on the region of the beam within the connection region. This is a reasonable approach when the summation of the vertical components of the brace forces is zero. However, when the vertical components result in a non-zero net vertical force (also referred to as an unbalanced force), analyzing and designing the connection as if it were isolated from the frame may result in a significantly undersized beam, requiring expensive beam web and flange reinforcement. In this paper, the effect of the brace forces on the beam in this type of braced frame configuration is referred to as the chevron effect. This paper presents a method for determining the distribution of brace forces within the connection and also the impact of the brace force distribution on the frame beam. The mechanism analysis required by the 2010 AISC Seismic Provisions for Structural Steel Buildings, AISC 341-10, is presented, and the discussion illustrates the importance of considering the entire frame when evaluating the impact of the brace forces on the beam. Source


Fortney P.J.,Cives Engineering Corporation | Thornton W.A.,Cives Engineering Corporation
Engineering Journal | Year: 2012

Section J2.2b of the 2010 AISC Specification for Structural Steel Buildings requires the length of longitudinal welds, used to connect flat plate tension members, to be greater than the distance between the longitudinal welds. Currently, weld lengths less than the distance between the welds are not permitted for connections of flat plate members. The procedure for the calculation of the shear lag factor, U, for this type of connection is given by Case 4 in Table D3.1 of the AISC Specification, where U is a function of the length of the longitudinal weld and the width of the plate. Although Case 4 is explicitly defined for plates only, the generally accepted practice in the design of similar welded connections of angles, channels, tees and wide flange members is to apply the same limitation on weld length, and calculate the effect of shear lag as 1 - x/l as given by Case 2 in Table D3.1 of the AISC Specification, while ignoring shear lag effects with weld lengths between one and two times the distance between the welds. Furthermore, for connection geometries meeting those for Case 2 or Case 4, there is no guideline for considering connection strengths where the longitudinal welds on each side of the member have unequal lengths (e.g., skewed web members or braces) or weld lengths less than the distance between the welds. This paper presents recommendations for a generalized design procedure for welded connections of plate, angle, channel and tee tension members regardless of the length of the weld or if the length of the longitudinal welds are unequal. A summary of the treatment of various current building codes/specifications (AISC and CSA) on this topic is presented along with the results of several published experimental research projects that evaluated the behavior of these types of connections. Two analytical models are presented, and recommendations for changes to the current AISC Specification are made, followed by an example problem illustrating the practical application of the recommendations. Source

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