bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving the Seismic Stability of Concentrically Braced Steel Frames
Authors: Tremblay Robert , Poncet Laure
Published: April 2024

An analytical study was performed to examine the seismic stability of multi-story concentrically braced steel frames. The building height was varied from 4 to 16 stories and three braced frame systems were studied: conventional braced frames, buckling-restrained braced frames, and dual buckling-restrained braced frames. All structures were designed according to Canadian seismic provisions. Different force modification factors were used and both the equivalent static load procedure and the modal response spectrum analysis were considered in design. P-delta effects were accounted for in the design of some of the buildings. The performance of the various structures is evaluated and compared by means of incremental dynamic analysis. The results show that the potential for instability for conventional braced frames is higher for taller structures or when the design loads are reduced. Tall buckling-restrained braced frames were also found to be prone to dynamic instability. Dual buckling-restrained braced frames exhibit a more robust response and represent a promising solution for tall braced steel frames.
Errata: Reliability of the Member Stability Criteria in the 2005 AISC Specification
Authors: Galambos Theodore V.
Published: April 2024

Errata
Geometric Formulas for Gusset Plate Design
Authors: Chambers Janice J. , Bartley Tony C.
Published: April 2024

Common approaches to compute the yield and buckling resistances of gusset plates require knowledge of the lengths yc, ycf , yb, ybf, L1, L2, and L3, (Figures 2 and 7). While numerical values for these resistances have been presented in the literature, formulas for yc, ycf , yb, ybf, L1, L2, and L3 have not been published. This paper presents the derivation and validation of equations to compute these lengths. The equations are summarized in flow charts that can be incorporated into software for practical applications. The formulas provided for yc, ycf, yb, ybf, L1, L2, and L3 enable optimization of gusset plate design.
Improved Flexural Stability Design of I-Section Members in AISC (2005) -- A Case Study Comparison to AISC (1989) ASD
Authors: White Donald W. , Chang Ching-Jen
Published: April 2024

The provisions in the AISC 2005 Specification for Structural Steel Buildings for the flexural stability design of steel I-section members have been updated relative to previous Specifications to simplify their logic, organization and application, while also improving their accuracy and generality. This paper gives a brief overview of the updated provisions, and compares and contrasts their flexural resistance calculations with the corresponding calculations from the previous AISC 1989 Specification for Structural Steel Buildings, Allowable Stress Design and Plastic Design. The relative simplicity and accuracy of the AISC 2005 Specification equations are highlighted.
Capacity Design of Vertical Boundary Elements in Steel Plate Shear Walls
Authors: Berman Jeffrey W. , Bruneau Michel
Published: April 2024

Consistent with capacity design principles, the 2005 AISC Seismic Provisions require that the vertical and horizontal boundary elements of steel plate shear walls be designed to remain essentially elastic while the web plates yield under seismic loading. However, determination of the design loads for vertical boundary elements to reliably achieve capacity design is difficult and a reasonably accurate approximate procedure is needed. This paper presents such a procedure for determining those design loads for the vertical boundary elements of steel plate shear walls so that the desired component yielding sequence is achieved. The procedure combines an assumed plastic collapse mechanism with a linear model of a vertical boundary element to determine the maximum axial forces, shear forces, and moments for vertical boundary elements considering fully yielded web plates and horizontal boundary elements hinging at their ends. Two methods for capacity design given in the commentary of the seismic provisions are also reviewed and their shortcomings are identified. Then, design loads for the vertical boundary elements of two different steel plate shear walls are determined with the proposed procedure and the two current procedures. Results are compared with nonlinear static analysis results. The proposed procedure is shown to give VBE design loads that are significantly closer to the nonlinear static analysis results than the two current procedures.
Investigation of Flange Local Bending Under Flexible Patch Loading
Authors: Carden Lyle P. , Pekcan Gokhan , Itani Ahmad M.
Published: April 2024

The limit state of flange local bending due to applied flexible patch loads was investigated both experimentally and analytically in this study. Analyses showed that an unstiffened beam, supporting a timber or steel post similar to those found in bridge falsework, should be designed for a combination of flange bending and post strength. A series of experiments and finite element analyses were conducted to observe and quantify this limit state and to develop predictive methods for the evaluation of joint capacity. An interaction method was introduced in which both flange bending and timber post crushing capacities are considered. An alternative method that utilizes an effective bearing area of the post was developed, yielding more accurate capacity predictions when a steel post is used. Blocking, sometimes placed between the flanges, increased the capacity of the joint region by up to 70% with a timber post; in contrast, with a steel post, blocking improved the joint capacity by less than 25%. A post eccentricity of up to 6th of the flange width resulted in a reduction of flange-timber post joint strength by 10 to 15%. The effect of a post eccentricity was negligible with a steel post. Finally, equations to calculate the ultimate load for flange local bending are presented in both LRFD and ASD formats.
Current Steel Structures Research No. 13
Authors: Bjorhovde Reidar
Published: April 2024

Current Steel Structures Research
Shear Behavior of A325 and A490 High-Strength Bolts in Fire and Post-Fire
Authors: Yu Liang , Frank Karl H.
Published: April 2024

High strength ASTM A325 and A490 bolts were tested in shear at temperatures up to 800 °C (1,472 °F). The shear strength showed a gradual reduction in both types of bolts as the temperature was increased above 300 °C (572 °F). Strength reduction factors for both types of bolts at elevated temperatures were obtained to provide a means of estimating the bolt shear strength during fire. The residual strength of A325 and A490 bolts after exposure to elevated temperatures was also investigated by both direct shear tests and hardness tests. Significant strength loss occurs on both types of bolts after exposure to temperature higher than the tempering temperature employed in the manufacturing process. The hardness value at 1/2R location on the bolt cross section was found to provide a good estimate of the bolts residual strength. The hardness test provides a simple and practical method to assess the post fire strength of a bolt.
Design of Unstiffened Extended Single-Plate Shear Connections
Authors: Muir Larry S. , Hewitt Christopher M.
Published: April 2024

Extended single-plate shear connections offer many advantages that simplify the construction process. Because the connection to the supported member is moved clear of the support, coping of the supported member is not required and the only fabrication process required for the supported member is drilling or punching. Also, because bolted connections are only used in the connection to the supported member, there is no safety concern over the use of shared bolts through the web of the support. Additionally, in some instances, extended single-plate connections are the only practical solution to a framing problem, such as the case of a member framing into the weak axis of a column with continuity plates. The rigidity of single-plate connections at the support has always been a gray area. Designers have often been concerned about a considerable, unanticipated moment that could be developed in the connection, which could then result in either a moment delivered to the column that the column has not been designed to resist, or a sudden rupture of either the weld or the bolts. Section B3.6a of the AISC Specification for Structural Steel Buildings requires that simple shear connections have sufficient rotational capacity to accommodate the required beam end rotation. This paper will address each of these concerns, and will present a general design procedure for extended single-plate shear connections.
Estimating Inelastic Drifts and Link Rotation Demands in EBFs
Authors: Richards Paul W. , Thompson Brandon
Published: April 2024

When designing eccentrically brace frames (EBFs), the inelastic rotation of the links is estimated to ensure that links will not experience excessive rotations. Typically, design engineers amplify elastic analysis results to estimate EBF link inelastic rotations. Twelve EBF frames of different height (3-, 9-, and 18- story) and strength were designed and two types of analyses performed: static elastic analysis under the design base shear; and non-linear dynamic analysis under ten design-level earthquakes. Roof drifts, story drifts, and link rotations were estimated by amplifying values from the static elastic analyses, and then compared with average values from the dynamic analyses. Poor correlation was observed. For the 3-story frames, estimated link rotations were as much as 63% lower than the rotations observed in the dynamic analyses. For the 9- and 18-story frames, estimated link rotations were as much as two times greater than those observed in the dynamic analyses. Calibrated amplification factors were developed for better estimation of link inelastic rotation. It is demonstrated that amplifying only the shear component of the elastic story deformations will lead to more reasonable estimates.
Design Aspects of Single-Angle Members
Authors: Dumonteil Pierre
Published: April 2024

Used since the very beginning of steel construction, single angle members are found in many different kinds of structures. Nearly all single-angle members are eccentrically loaded in some fashion, yet truss chords, tower legs and similar members not carrying transverse loads are usually designed as centrally loaded members. The ANSI/AISC 360-05 Specification for Structural Steel Buildings prescribes complex design calculations for eccentrically loaded single angles, but also provides simplified equations that adjust the KL/r ratio to account for eccentricities and end restraints. The purpose of this paper is to examine the possibility of simpler calculations and to explore the behavior of single-angle members.
Composite Action in CFT Components and Connections
Authors: Roeder Charles W. , Lehman Dawn E. , Thody Ryan
Published: April 2024

Concrete-filled steel tube (CFT) components provide an attractive alternative to conventional methods of construction. The steel tube serves as formwork and reinforcement to the concrete fill. The fill delays local buckling of the tube and increases the compressive strength, stiffness and ductility of the CFT member if composite action is achieved. As such, the benefits of using CFT components include their efficiency, economy and ability to provide rapid construction. The primary obstacles to using CFT components relate to achieving adequate shear-stress transfer between the two materials needed for composite behavior and to developing robust, constructible connections. There is considerable interaction between this stress transfer and the connections joining CFT members to other structural elements. In many cases, natural bond stress, primarily friction, is adequate to assure good structural performance of the CFT member, but in other cases mechanical interlock or bearing between the steel and concrete is required. While some mechanical transfer elements may supplement the natural bond transfer, others may destroy this beneficial effect. Additionally, natural bond may be dramatically enhanced by bending of the CFT member and by using appropriate connections to join other members to the CFT element. Therefore, proper quantification and understanding of natural, enhanced and mechanical sources of bond stress are needed to develop robust CFT structural components and their connections.
Current Steel Structures Research No. 21
Authors: Bjorhovde Reidar
Published: April 2024

Current Steel Structures Research
Behavior of Vertical Boundary Elements in Steel Plate Shear Walls
Authors: Qu Bing , Bruneau Michael
Published: April 2024

The AISC Seismic Provisions and CSA S-16 Standard require a minimum moment of inertia for the vertical boundary elements (VBEs) in steel plate shear walls (SPSWs) to avoid undesirable VBE behaviors. The equation limiting VBE flexibility has been derived from a flexibility factor, , developed in plate girder theory and the limit on VBE flexibility has been empirically specified based on previous test results. This paper reviews the derivations of the flexibility factor and how that factor was incorporated into current code design requirements for SPSWs. Then, analytical models to prevent VBE shear yielding and to estimate the out-of-plane buckling strength of VBE are developed, followed by a review of past experimental data to investigate if the significant inward VBE inelastic deformation and out-of-plane buckling observed in some instances were due to excessive VBE flexibilities or other causes such as shear yielding at the ends of the VBEs. It is shown that the existing limit on is uncorrelated to satisfactory in-plane and out-of-plane VBE performance. The proposed analytical models predict performance of previously tested SPSWs that correlates well with the experimental observations.
Closure: Limit State Response of Composite Columns and Beam-Columns Part II: Application of Design Provisions for the 2005 AISC Specification
Authors: Leon Roberto T. , Tiziano Perea , Hajjar Jerome F.
Published: April 2024

Closure
Design of Structural Steel Pipe Racks
Authors: Drake Richard M. , Walter Robert M.
Published: April 2024

Pipe racks are structures in petrochemical, chemical and power plants that are designed to support pipes, power cables and instrument cable trays. They may also be used to support mechanical equipment, vessels and valve access platforms. Pipe racks are non-building structures that have similarities to structural steel buildings. The design requirements found in the building codes are not clear on how they are to be applied to pipe racks. Several industry references exist to help the designer apply the intent of the code and follow expected engineering practices. This paper summarizes the building code and industry practice design criteria, design loads and other design consideration for pipe racks.
Bending of Top Plates in Base Chair Connections
Authors: Dowswell Bo
Published: April 2024

In many heavy industrial facilities, column bases must transfer large uplift loads to the foundation, and if the tension load is too large to carry with a standard base plate, chairs are used to transfer the load. The top plate thickness has traditionally been determined using either the elastic one-way bending capacity of a beam spanning the distance between the vertical stiffener plates or the two-way bending capacity based on elasticity theory. These design methods can be used where the nominal stress must be limited to the elastic range, such as structures subject to fatigue. For static loads, a more realistic design model can be achieved by considering the plastic capacity of the plate in two-way bending. In this paper, the author develops a method to calculate the ultimate bending capacity of top plates in base chair connections based on yield line theory. The limit-analysis solution does not rely on the conservative assumptions inherent in calculation methods commonly used in design practice. The proposed equation can be used to calculate the capacity of many different base chair configurations, including those commonly used on plate and shell structures.
Seismic Demand on Column Splices in Steel Moment Frames
Authors: Shen Jay , Sabol Thomas A. , Akbas Bulent , Sutchiewcharn Narathip
Published: April 2024

This study addresses seismic demands on column splices in steel moment-resisting frames. A comprehensive nonlinear analytic investigation was undertaken to evaluate the seismic response analysis of 4-, 9- and 20-story moment-resisting frames subjected to an ensemble of 20 strong ground motions. The outcomes of the study include an analysis of the comprehensive seismic demand on the column splice and recommended guidelines for design requirements for reliable moment frame column splices. The study concludes that the demand on the column splice can approach the nominal design strength of the smaller column when the critical beam-to-column connection reaches its expected maximum deformation capacity. It is reasonable that seismic design provisions for the column splices in special and intermediate moment frames require the column splice to develop the fl exural strength of the smaller column.
Current Steel Structures Research No. 24
Authors: Bjorhovde Reidar
Published: April 2024

Current Steel Structures Research
Experimental Investigation of Shear Transfer in Exposed Column Base Connections
Authors: Gomez Ivan R. , Kanvinde Amit M. , Deierlein Gregory G.
Published: April 2024

Shear transfer mechanisms in exposed column base plate connections are examined through a series of seven full-scale tests. Three mechanisms of shear transfer are investigated, including friction between the base plate and grout support, anchor rod flexure and shear, and shear key (shear lug) bearing. Seven tests were conducted on relatively large-scale specimens that reflect the common base connection configurations as described in the American Institute of Steel Construction's (AISC) Steel Design Guide 1: Base Plate and Anchor Rod Design. A coefficient of friction equal to 0.46 was measured from three tests investigating friction transfer mechanisms between the steel base plate and grout pad, which is comparable to the design value (0.40) specified by the American Concrete Institute for friction between as-rolled steel and concrete. Two tests investigating anchor rod bearing provided data to evaluate the shear resistance provided by a combination of axial tension, shear and flexure, wherein the anchor rods bend in reverse curvature over a distance roughly equal to the base plate thickness plus one-half of the thickness of the welded plate washer. This strength capacity prediction is consistent with a method outlined by the AISC Steel Design Guide 1. Failure of the concrete footing due to edge breakout was investigated as a limit state for shear lug bearing. Data from two tests indicate that for large footings, the current AISC Steel Design Guide 1 procedures, adapted from the American Concrete Institute, may be unconservative due to the size effect in concrete, which reduces the available shear capacity for larger structure geometries. A method that incorporates the size effect is shown to provide a more accurate assessment of the free-edge breakout strength of the concrete. Limitations of the study and future areas of work are outlined.
Effect of Washer Placement on Performance of Direct Tension Indicators with Curved Protrusions
Authors: Cleary Douglas B. , Riddell William T. , Lacke Christopher J.
Published: April 2024

A series of tests was performed to evaluate the effect of a hardened washer placed between the turned element and a direct tension indicator (DTI) with curved protrusions. Configurations with 3/4 in., 7/8 in. and 1.0 in. diameter bolts with and without hardened washers were evaluated. Tests were also performed with Â¾ in. and 7/8 in. bolts using a new type of DTI, where the DTI is staked to a nut. The purpose of these tests was to compare the performance of the various configurations, as measured by the number of gaps open at the specified pretension level, the load required to close at least half of the gaps, and the tensile load on the bolts when all or all but one of the gaps in the DTI are closed. When an ASTM A563 grade DH nut was used for a given bolt diameter, some differences were observed to be statistically significant. However, no consistent trends were observed in these differences, and the actual differences were of the same order of magnitude as the load increments used in testing. Therefore, it was concluded that there are no practical differences between the various configurations considered when grade DH nuts are used. However, the DTI did not perform well without a secondary hardened washer when an ASTM A563 Grade C nut was used.
Technical Note: Effective Length Factors for Gusset Plates in Chevron Braced Frames
Authors: Dowswell Bo
Published: April 2024

Recent earthquakes have exposed the vulnerability of steel plate girder superstructures to seismic forces. Damage has occurred in cross frames and their connections, shear connectors, and steel plate girders. These earthquakes have revealed the shortcomings of U.S. bridge design specifications for these types of bridges. Section 6 of the AASHTO LRFD specifications does not have any seismic design provisions for steel plate girder bridges. Recently these specifications have adopted seismic design provisions that are proposed by the authors for steel superstructures to overcome this shortcoming. The adopted specifications are the result of analytical and experimental investigations by various researchers and work published by many seismic provisions and guide specifications. This paper summarizes the new seismic design provisions and outlines the background behind them.
Satisfying Inelastic Rotation Requirements for In-Plane Critical Axis Brace Buckling for High Seismic Design
Authors: William A. Thornton and Patrick J. Fortney
Published: April 2024

When a vertical brace buckles during a seismic event, its connections must be able to resist the available flexure 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 which 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.
Errata: Fillet Weld Design for Rectangular HSS Connections
Authors: Packer Jeffrey A. , Sun Min
Published: April 2024

Errata
Design of Beam-Columns
Authors: Hooper Ira
Published: April 2024

The design of beam-columns in the 1963 AISC Specification recognizes two important features of structural behavior—frame stability and moment amplification due to lateral deflection. Frame stability may be defined as the ability of a structure to resist sidesway when vertical load is applied. It is not usually a problem for simply connected structures braced against sidesway. Old buildings have heavy masonry walls that provide bracing although no calculations were made for the bracing effect. Modern buildings can no longer afford the cost or wasted space of massive walls. Also, rigidly connected frames have become common. Rigidly connected frames offer several advantages: reduced beam deflections, greater economy and elimination of floor cracks.When rigidly connected frames are not braced against sidesway, the columns and beams must provide the stiffness needed to maintain frame stability in addition to their load resisting function.
Errata: Allowable Loads on Beams without Lateral Support
Authors: Mataya John
Published: April 2024

Errata
Errata: The Behavior of Steel Perimeter Columns in a High-Rise Building Under Fire
Authors: Garlock Maria M. , Quiel Spencer E.
Published: April 2024

Errata
Field Application Case Studies and Long-Term Monitoring of Bridges Utilizing the Simple for Dead--Continuous for Live Bridge System
Authors: Aaron Yakel and Atorod Azizinamini
Published: April 2024

The performance of three bridges constructed using the simple for dead load and continuous for live load (SDCL) bridge system for steel girders was monitored during and after construction to compare actual performance with predicted performance. The structure types were a box-girder bridge, an I-girder bridge and a box-girder bridge built using accelerated construction details. During construction, strains and deflections were monitored so that the degree of continuity over the pier could be determined. The design concept assumes that a simply supported condition exists during casting of the concrete deck. However, to provide lateral bracing, the concrete diaphragm—or turndown—over the pier is cast and cured prior to casting the deck. As expected, encasement of the girders provides some continuity over the pier during casting of the deck. The degree of continuity over the pier can be reduced by lowering the height of the construction joint and through the use of crack-inducing details. Long-term monitoring of the structures showed the behavior to be consistent over time with no significant deviations from the predicted bridge behavior. During the initial time period of approximately 18 months, a slight overall change in strain values was observed in concrete elements. The rate of change slowed during this period and eventually ceased. Subsequently, the response of the structure has been consistent with only small seasonal fluctuations observed. These fluctuations are expected and are generally attributable to changes in ambient temperature, relative humidity, incident solar radiation and ground freeze/thaw conditions.
Effective Weld Properties for Hollow Structural Section T-Connections under Branch In-Plane Bending
Authors: McFadden Matthew R. , Packer Jeffrey A.
Published: April 2024

The 2010 AISC Specification for Structural Steel Buildings has expanded the scope in Chapter K, "Design of HSS and Box Member Connections,"� to include a Section K4, "Welds of Plates and Branches to Rectangular HSS."� An experimental program was undertaken to test various unreinforced HSS-to-HSS 90° T-connections subject to branch in-plane bending moment with the objective of determining the effectiveness of the welded joint. Twelve unique test specimens were designed to be weld-critical, and the results from the full-scale tests revealed that the current equation for the effective elastic section modulus for in-plane bending, Sip, given in Table K4.1 of AISC 360-10, is very conservative. A modification to the current requirement that limits the effective width of the transverse weld elements is proposed, resulting in a safe but more economical weld design method for HSS-to-HSS T-connections subject to branch bending moment. By reanalyzing the data of prior weld-critical tests on HSS-to-HSS T- and X- (cross-) connections subject to branch axial loading, it is shown that the proposed new weld effective length recommendation is applicable to these connections as well. It is also concluded that the fillet weld directional strength enhancement factor, (1.00 + 0.50sin1.5θ), should not be used for strength calculations of welded joints to square and rectangular HSS, with the proposed revision, when the effective length method is used.
Current Steel Structures Research No. 36
Authors: Bjorhovde Reidar
Published: April 2024

Current Steel Structures Research
Panel Zone Deformation Capacity as Affected by Weld Fracture at Column Kinking Location
Authors: Kim Dong-Won , Blaney Colin , Uang Chia-Ming
Published: April 2024

Three full-scale specimens were tested to evaluate the cyclic performance of rehabilitated pre-Northridge steel beam-to-column moment connections. A Kaiser bolted bracket (KBB) was used on the beam bottom flange for all specimens, but different rehabilitation schemes (another KBB, a notch-tough beam flange replacement weld, or a double-tee welded bracket) were used to strengthen the top flange. All specimens were able to sustain an interstory drift angle of 0.04 radian, with large inelastic deformations in the panel zone. Two specimens experienced fracture at the replacement complete-joint-penetration (CJP) welds, mainly due to the large shear deformation in the panel zone. Because it may not be economically feasible to mitigate weak panel zones in seismic rehabilitation, an analytical model was developed to predict the panel zone deformation capacity and the associated strength. In this model, it was postulated that the ultimate panel zone deformation capacity corresponded to that when each column flange was fully yielded and excessive kinking would cause fracture of the beam flange CJP welds. This postulation was verified by the test data of two specimens that experienced weld fracture due to excessive panel zone deformation. It was shown that the deformation capacity is a function of db/tcf (beam depth-to-column flange thickness ratio). The effect of column axial load was also studied.
Recommended Procedures for Damage-Based Serviceability Design of Steel Buildings under Wind Loads
Authors: Aswegan Kevin , Charney Finley A. , Jarrett Jordan
Published: April 2024

This paper provides a recommended procedure for nonstructural damage control of steel buildings under serviceability-level wind loads. Unlike traditional procedures that provide a single drift limit under a given reference load, the recommended procedure provides a decision space that spans a range of wind hazards and associated damage states. Central to the procedure are the use of shear strain in nonstructural components as the engineering demand parameter and the use of component fragility as a reference for limiting damage
Design of Split-Tee Connections for Special Composite Moment Frames
Authors: Fischer Erica C. , Varma Amit H.
Published: April 2024

The beam-to-column connections of special composite moment frames (C-SMFs) serving as the primary seismic force resisting system (SFRS) of a building structure are required to meet the performance criteria specified in the 2010 AISC Seismic Provisions. Chapter K of the Seismic Provisions states that experimental results should be used to provide evidence that the specific beam-to-column connection satisfies the requirements for strength and story-drift angle. This paper focuses on the split-tee connection for C-SMFs with wide flange (WF) beams and rectangular concrete-filled tube (CFT) columns. The paper provides a general description of the split-tee connection identifying its key features and components. This is followed by discussion of expected behavior in the elastic and inelastic ranges of cyclic loading. This discussion is based on prior research and large-scale testing, and it focuses on the various limit states controlling the strength and deformation capacity of the connection. The paper includes the complete design procedure for split-tee connections along with a detailed design example. The information presented in this paper can be used to create a body of evidence to apply for prequalification of similar split-tee connections in C-SMFs.
Connection Design Recommendations for Improved BRBF Performance
Authors: Palmer Keith D. , Roeder Charles W. , Lehman Dawn E.
Published: April 2024

Numerous component tests on buckling-restrained braces (BRBs) have demonstrated their approximately symmetric tension and compressive capacities, stable cyclic behavior and large (component) ductility prior to core fracture. These properties make them suitable ductile fuses for seismic design. Experiments on buckling-restrained braced frame (BRBF) systems show that the inelastic axial deformation capacity of BRBs may be compromised by system performance demands. Damage including significant yielding, local buckling, twisting and fracture of the beams and columns, tearing of the gusset plate welds to framing members, and out-of-plane movement of the BRB have been observed in BRBF tests. Prior test results are reviewed, and an analytical study using high-resolution models, which were validated with prior test results, is used to develop mitigation strategies for the damage. Design recommendations to mitigate damage and improve system performance are developed. The study reveals that damage to the beams and columns at a corner gusset-plate connection is related to the ratio of the component web thickness to the gusset plate thickness, suggesting a modest design change that will significantly improve BRBF performance.
Establishing and Developing the Weak-Axis Strength of Plates Subjected to Applied Loads
Authors: Carter Charles J. , Muir Larry S. , Dowswell Bo
Published: April 2024

When a plate is subjected to applied loads and significant out-of-plane deformation, the demand on the connection may exceed that derived from calculations due to the applied loads only. Where inelastic behavior is acceptable, the intent may be to ensure ductile behavior. For plates with fillet-welded edge connections, this can be accomplished by sizing the fillet welds to develop the strength of the plate. One specific example of this arises when a brace in a special concentrically braced frame (SCBF) is subject to compression and buckles out-of-plane. Bending of the gusset plate may demand more of the gusset plate edge connection than the calculated forces that result on the gusset edge due to the brace force specified in Section F2.6c.2 of AISC 341-16 (AISC, 2016). If not accounted for in the weld size, the uncalculated weak-axis moment on the welds from out-of-plane bending of the gusset plate might cause rupture of the fillet welds to govern the behavior of the system. The method provided in this paper is suitable to determine the minimum size of fillet welds necessary to prevent weld rupture as out-of-plane deformations occur. It can be used for fillet-welded gusset plate edges in SCBFs to satisfy the exception provided in Section F2.6c.4 of AISC 341-16.
Observations from Cyclic Tests on Deep, Wide-Flange Beam-Columns
Authors: Ozkula Gulen , Harris John , Uang Chia-Ming
Published: April 2024

As part of a National Institute of Standards and Technology (NIST) comprehensive research program to study the seismic behavior and design of deep, wide-flange structural steel beam-column members for application in seismic design and construction of steel special moment frames, 25 deep column specimens were subjected to inelastic cyclic loading with three different levels of constant compression axial load (Ca = 0.2, 0.4 and 0.6). The test matrix included five W24 sections (W24×55 to W24×176) to cover a wide range of element slenderness ratios for flange and web local buckling and member slenderness ratios for lateral-torsional buckling and weak-axis flexural buckling. The specimens satisfied AISC 341 requirements for highly or moderately ductile elements. All specimens were subjected to strong-axis bending, except for three specimens that were subjected to weak-axis bending and one specimen that was subjected to biaxial bending. Test results showed that the slenderness ratios had a significant effect on the failure mode—local versus global buckling. The presence of an axial load produced significant local buckling and axial shortening. The level of axial load also affected the plastic rotation capacity. Specimens with weak-axis bending were ductile, showing no local buckling up to a high story-drift ratio. Most of the strong-axis bending specimens were not able to deliver a plastic rotation of 0.03 radian.
Simple-Made-Continuous Steel Bridges with Steel Diaphragms
Authors: Johnson Robert I. , Atadero Rebecca A.
Published: April 2024

Simple-made-continuous (SMC) bridges are a relatively new innovation in steel bridge design. The majority of SMC bridges currently in use are constructed with concrete diaphragms. This article presents the results of numerical analysis and physical laboratory testing of an alternative simple-made-continuous (SMC) connection scheme that uses steel diaphragms in lieu of concrete diaphragms. A bridge using steel diaphragms was constructed by the Colorado Department of Transportation in 2005, and the connections on this bridge serve as the basis for the research discussed herein. The results of the analysis and testing provided information for the development of a design methodology based on the physical behavior of the SMC connection. The paper also compares the steel-diaphragm SMC connection to concretediaphragm SMC connections and demonstrates that the steel-diaphragm design has several desirable features. For a diaphragm cost, which is similar in cost to other SMC schemes, the steel-diaphragm design requires less total construction time. Additionally, because the girder ends are exposed, it is easy to verify that the girders have fully weathered (for weathering steel), they may be easily inspected, and there is no concern about cracking of a concrete diaphragm at re-entrant corners around the steel bridge girders.
Analysis and Design of Cable-Stayed Steel Columns Using the Stiffness Probe Method
Authors: Gurfinkel German , Krishnan Sudarshan
Published: April 2024

The stiffness probe method (SPM) is a new numerical procedure that calculates buckling loads. SPM probes the local stiffness of a given structure at the point of application of a small transverse perturbation force as the applied load is increased. The local stiffness degrades from a maximum for an unloaded structure to zero at the buckling load. An artifice spring is added to the original structure that eventually absorbs the full perturbation force at a prescribed small deflection, thereby keeping structural deformations small as the buckling load is approached. As a result, using an indicator that approaches zero at buckling rather than having to rely on increasingly larger deflections at buckling as in conventional P-? methods, SPM ensures an accurate numerical result for the critical load. The SPM is used herein to study the behavior of one and two cross-arm cable-stayed columns under applied load. A formula is given to calculate the minimum slenderness that justifies converting a tube into a cable-stayed column. Cable-stayed columns may buckle either in a one-lobe symmetrical mode or two-lobe anti-symmetrical mode, the latter case being contrary to conventional thinking. A design example for a given cable-stayed column using the AISC Specification is presented. The effect of optimum cable prestrain to enhance column buckling strengths is discussed. A strength enhancement ratio (SER) is defined that evaluates the additional column strength gained after transforming a given steel tube into a cable-stayed column.
Design Formulation for Critical Buckling Stress of Steel Columns Subjected to Nonuniform Fire Loads
Authors: Memari Mehrdad , Mahmoud Hussam
Published: April 2024

Assessing the stability of steel building frames exposed to fire conditions is challenging due to the need to consider elevated temperature properties of steel, nonuniform heating of structural members, and large deformational demands on the frames. There has been significant progress recently in simulating the response of structural members and systems under fire loads using finite element methods. There is a need, however, for conducting additional analysis while expanding upon previous work to allow for the development of additional design provisions for column buckling while accommodating varying temperature profiles. This study introduces a framework for conducting stability analyses of W-shape steel columns subjected to demands imposed by fire loads considering nonuniform longitudinal temperature profiles. Results from the analyses show good agreement with available strength design equations of steel columns at ambient and elevated temperatures. An equation is proposed to compute the Euler elastic buckling stress in case of nonuniform longitudinal distribution of temperature. In addition, another equation is proposed to calculate the critical buckling stress of steel columns subjected to nonuniform longitudinal temperature demands. The efficiency of the proposed equations is investigated when two additional nonuniform longitudinal temperature profiles are considered.
Post-Buckling Mechanics of a Square Slender Steel Plate in Pure Shear
Authors: Garlock Maria E. Moreyra , Quiel Spencer E. , Yang Peter Y. , Alos-Moya Jose , Glassman Jonathan D.
Published: April 2024

Thin (slender) steel plates possess shear strength beyond the elastic buckling load, which is commonly referred to as the post-buckling capacity. Semi-empirical equations based on experimental tests of plate girders have been used for decades to predict the ultimate post-buckling strength of slender webs. However, several recent studies have shown that the current models for predicting the ultimate shear post-buckling capacity of thin plates are based on some incorrect assumptions regarding their mechanical behavior. As a result, the current design equations provide an approximate estimate of capacity for the range of parameters in the test data upon which they are founded. This paper explores the fundamental behavior of thin plates under pure shear. Such a fundamental examination of shear post-buckling behavior in thin plates is needed to enable design procedures that can optimize a plate’s shear strength and load-deformation performance for a wider range of loading and design parameters. Using finite element analyses, which are validated against available results of previous experimental tests, outputs such as plastic strains, von Mises stresses, principal stresses, and principal stress directions are examined on a buckled plate acting in pure shear. The internal bending, shear, and membrane stresses in the plate’s finite elements are also evaluated. In this study, these evaluations are performed for a simply supported plate with an aspect ratio equal to 1.0 and slenderness ratio equal to 134. Results show that localized bending in the plates due to the out-of-plane post-buckling deformations appear to be a significant factor in the ultimate shear post-buckling capacity of the plate. Also, the compressive stresses continue to increase beyond the onset of elastic buckling in some regions of the plate, contrary to current design assumptions. Overall, this study provides new insights into the mechanics of shear post-buckling behavior of thin plates that can be exploited for design procedures that are consistent with mechanical behavior.
Walking-Induced Vibration of Steel-Framed Floors Supporting Sensitive Equipment
Authors: Davis Brad , Liu Di
Published: April 2024

This paper explains the vibration evaluation methods for floors supporting sensitive equipment in the second edition of the AISC Design Guide 11, Vibrations of Steel-Framed Structural Systems Due to Human Activity. It presents new experimentally verified equations that are simplified for practical implementation. Sensitive equipment tolerance limits are stated in numerous forms, including peak acceleration and various spectral acceleration and velocity. For this reason, response predictions are given in terms of all tolerance limit forms that are commonly used. The most severe responses of lower frequency floors to walking are due to resonant build-ups whereas the most severe responses of higher frequency floors are due to a series of individual footsteps impulses, so equations are given for both. Because the sensitive equipment tolerance limit is objective, each equation includes a calibration factor that results in a high probability that the predicted response will exceed the actual response.
Simplified Method to Determine the Effect of Detailing on Cross-Frame Forces
Authors: Gull Jawad H. , Azizinamini Atorod
Published: April 2024

There are several issues that necessitate the use of steel I-girder bridges with skewed supports. Due to skew supports, the axis of rotation of bearing line cross-frame is not in line with the axis of rotation of girders, and connection points of intermediate cross-frames are either at different elevations or undergo different deflections. The consequence of this behavior is that the cross-frames fit between the girders at one loading stage and do not fit between the girders at other loading stages, depending on the detailing method used to detail the cross-frames. Additional structural responses, henceforth called lack-of-fit effects, are developed when cross-frames do not fit between the girders. These lack-of-fit effects can be estimated by different methods of analysis for different detailing methods. In addition to lack-of-fit effects, fit-up forces are required to fit the cross-frames between their connections to girder during erection, for total dead load (TDL) fit detailing method. Methods of analysis to estimate fit-up forces are not available. The objective of this paper is to introduce different methods that can be used to calculate lack-of-fit effects for the steel dead load (SDL) fit detailing method at the total dead load (TDL) stage and the TDL fit detailing method at the steel dead load (SDL) stage. A comparison of different methods is done to recommend a single simplified method of analysis that can be used to calculate lack-of-fit effects for both SDL fit and TDL fit detailing methods with reasonable accuracy. Analysis methods are proposed to estimate the fit-up forces. The main conclusion of this research is that improved 2D grid analysis can be used to estimate lack-of-fit effects for both TDL fit and SDL fit detailing methods and can also be used to determine fit-up forces for connecting girder and cross-frame detailed with TDL fit.
Reexamination of Shear Lag in HSS Tension Members with Side Gusset Plate Connections
Authors: Bhat Akashdeep A. , Fortney Patrick J.
Published: April 2024

This paper presents an evaluation of the shear lag factor for HSS tension members connected with two side plate gussets with longitudinal welds as given in AISC Specification Table D3.1, Case 6b. The current AISC Specification for Case 6b does not permit weld lengths less than the perpendicular distance between the welds, and has the potential of producing negative shear lag factors. Similar issues previously existed for members given in Case 4 of Table D3.1. However, the AISC Specification has adopted a mathematical model proposed by Fortney and Thornton for Case 4 of Table D3.1. The work presented in this paper offers: (1) a mathematical model for calculating the shear lag factor for Case 6b derived by repurposing the model adopted by AISC for Case 4 of Table D3.1; (2) the results of a parametric study comparing the results of the new mathematical model to the results using the current AISC method, and; (3) discusses the protocols developed for use in finite element analysis to evaluate the effectiveness of the proposed mathematical model. The proposed new mathematical model will permit longitudinal weld lengths less than the perpendicular distance between the welds, and removes the possibility of calculating a negative shear lag factor, while better representing the redistribution of cross-sectional stress near the connection region.
Steel Structures Research Update: Self-Centering Column Base Connections with Friction Dampers
Authors: Liu Judy
Published: April 2024

Recent work on a self-centering column base connection with friction dampers is highlighted. This research is a collaborative effort by Senior Researcher Massimo Latour and Professor Gianvittorio Rizzano from the University of Salerno, Italy, and Professors Aldina Santiago and Luis Simões da Silva of the University of Coimbra, Portugal. The Salerno-Coimbra team has developed an alternative self-centering column base solution to minimize initial costs and economic losses. Specific objectives are to limit damage and residual drifts, with connection components that are easy to repair or replace if needed. The self-centering column base has been validated through quasi-static cyclic testing and pseudo-dynamic testing. The self-centering connection has also been investigated through numerical time-history analyses of moment-resisting frames comparing conventional, fixed column bases to self-centering column bases. Some highlights of the research are presented.