Provisions For Structural Steel Buildings Research Articles

Stiffening of I-section MRF beams against degradation due to local buckling

Moment resisting frame (MRF) beams under cyclic loading are vulnerable to local flange and web buckling. The Seismic Provisions for Structural Steel Buildings (AISC341) prescribe width-to-thickness ratio limits, which are contingent on target rotations during predefined cyclic loadings. Some rolled I-sections available in the market cannot be employed in special MRFs since they fall short of satisfying the AISC341 flange slenderness limit. Moreover, local buckling leads to a decrease in both strength and stiffness in cyclically loaded MRF beams, ultimately increasing the risk of frame side-sway collapse. This paper introduces a stiffening method aimed at improving the behavior of I-section MRF beams. The proposed method involves placing a pair of stiffeners at the plastic hinge regions. A two-phase numerical study was conducted to assess the effectiveness of this approach. In the first phase, nine unstiffened beam cross-sections with varying flange and web slenderness were considered. The slenderness limits specified by AISC341 were evaluated based on cyclic analyses of these beams. In the second phase, a parametric study was conducted on the same cross-sections, with the flange width and the placement of the pair of stiffeners considered as variables. The results revealed a substantial improvement in behavior with the addition of a pair of stiffeners. Cross-sections that failed to meet the flange slenderness limit could be used in MRFs when stiffened. The optimal location for the stiffeners was found to be significantly influenced by the flange width. Design recommendations for the ideal stiffener placement are presented in this paper.

Frictional mid‐spliced shear links for eccentrically braced frames

AbstractAccording to the AISC Seismic Provisions for Structural Steel Buildings (AISC341‐16) and EC8, the inelastic rotation demand at the design story drift is limited to 0.08 rad for I‐shape shear links in eccentrically braced frames (EBFs). Numerical studies on EBF archetypes show that the single‐sided inelastic rotation demands can be much higher than the limiting value. In addition, these links can fail due to low‐cycle fatigue (LCF) which depends on the loading history. A mid‐spliced end‐plated detachable replaceable link has recently been developed to promote easy replacement of end‐plated links. In this paper, a frictional mid‐spliced shear link is developed to increase the inelastic link rotation capacity and LCF life of shear links. The proposed link utilizes a splice connection at the mid‐length, where frictional faying surfaces are introduced to dissipate energy. Slip at the mid‐splice connection causes a relative vertical displacement between the link ends which eventually reduces the rotation demands on the I‐shape members. Experimental and numerical studies were conducted to study the proposed link concept. Three conventional and eight frictional mid‐spliced links were tested using a nearly full‐scale test setup. The results showed that the proposed links have a pinched link shear versus link rotation response. The links were able to sustain a link rotation demand of 0.23 rad together with a significant increase in their LCF life. Numerical studies were conducted to investigate the link rotation, interstory drift, and residual interstory drift of EBF archetypes equipped with the proposed frictional link.

Development of a loading protocol for long links in eccentrically braced frames

Loading protocols are generally used for qualification testing of structural members. In eccentrically braced frames (EBFs), the connections of short links attached to columns are evaluated based on the loading protocol given in the AISC Seismic Provisions for Structural Steel Buildings (AISC 341–16). Behavior of many short links without column attachments was also investigated by making use of this loading protocol. The AISC341 loading protocol is suitable for only short links and does not take into account the one-sided nature of link rotation angle (LRA) demands due to mean effects. Long link behavior differs from short link behavior in a sense that long links are subjected to strength and stiffness degradation due to local buckling effects. A nonsymmetrical loading protocol for long links was developed as a part of this study. Twenty-four long link EBF archetypes with variable floor plans, bay widths, number of stories and link length to bay width (e/L) ratios were designed according to the US standards. The responses of EBFs under maximum considered earthquake (MCE) and collapse level earthquake (CLE) were obtained by making use of numerical analysis employing degrading link models. The link rotation angle time histories were reduced and converted into a series of cycles and the peaks of the LRA response were identified by using the rainflow counting algorithm. The nonsymmetrical loading protocol was represented as a function of maximum rotation range, which depends on the seismic hazard and e/L ratio.

Review of Local Buckling Width-to-Thickness Limits

This paper provides a review of local buckling width-to-thickness limits employed in the ANSI/AISC 360-16 Specification for Structural Steel Buildings and ANSI/AISC 341-16 Seismic Provisions for Structural Steel Buildings. The review was conducted by a task group formed to address potential changes in the next and/or future editions of the AISC Specifications. A comprehensive review of existing local buckling limits was completed, including detailing the underlying assumptions and the objectives of the existing limits. In addition, particular attention was given to the potential impact of adopting newer steel materials on the local buckling limits and to considerations of web–flange interaction in local buckling. Further, new methods that have been developed to address local buckling in structural steel design were also examined. It was found that in AISC 360, some lr limits for flexure may not be well aligned with intended objectives, and while all lp limits for flexure ensure the plastic moment may be achieved, rotation objectives are not consistently implemented. Review of lmd and lhd in AISC 341 reveals complications with implementing expected yield stress in the slenderness parameters and highlights the large number of varied objectives for these limits in seismic design, as well as a need for improvements—particularly for deep wide-flange columns. In general, it is found that only minor changes are potentially needed to current width-to-thickness, w/t, limits. Thus, in most cases, it is expected that AISC design can continue unchanged, with the exception of the improved criteria for deep columns. To minimize change while still expanding opportunity, newer local buckling cross-section classification methods could be permitted as alternatives rather than used as replacements to current w/t limits so that advantages of the newer approaches can be utilized when beneficial.

Stability of laterally unsupported shear links in eccentrically braced frames

AbstractI‐shaped links in eccentrically braced frames (EBFs) are susceptible to lateral or lateral torsional buckling when subjected to cyclic link rotations. Lateral bracing should be provided at the ends of the I‐shaped links in order to prevent these failures. Requirements for such braces are available in widely used design specifications such as the AISC Seismic Provisions for Structural Steel Buildings (AISC341‐16) and EC8. These requirements limit the use of I‐shaped links in bridge piers and elevator shafts. A combined experimental and numerical study was undertaken to investigate the behavior of laterally unsupported I‐shaped links under cyclic loading. The experimental study consisted of testing of six nearly full‐scale EBFs where the link length, link length ratio, and presence of lateral supports were considered as the prime variables. The test results demonstrated that short links with link length ratios less than 1.22 can experience inelastic link rotations greater than the codified limit of 0.08 rad even without lateral bracing. A numerical parametric study was conducted to develop more generalized design recommendations for laterally unsupported I‐shaped shear links. Stability of one‐story one‐bay EBFs was studied using geometrically and materially nonlinear finite element analysis including imperfections. The numerical results showed that I‐shaped links without lateral bracing can provide a stable response when the link length ratio is less than 1.15. In addition to this limit, the ratio of the elastic critical buckling capacity to the plastic shear capacity should be greater than 3.5 and 2.5 for links with and without axial force, respectively.

Experimental Validation of Detachable Links for Eccentrically Braced Frames

AbstractEccentrically braced frames (EBFs) subjected to seismic actions dissipate energy through yielding of link members. Other members of the framing are on the other hand designed to remain mainly elastic during a seismic event. The framing can be reused after an earthquake if the link members can be replaced. In line with this, the last decade has witnessed development of replaceable links. However, most of the proposed details are not well suited for replacement under residual drift conditions. Consequently, this paper presents details of an experimental validation of a detachable link concept where a splice connection is introduced at the mid‐length of the link to facilitate replacement under residual frame drift. The concept was studied by conducting six nearly full scale EBF tests under quasi‐static cyclic loading. Different splice details employing bolted connections with vertical slotted or site drilled holes and welded connections were developed. The link length ratio, type of mid‐splice connection and the amount of residual drift were considered as the variables of the testing program. The specimens were subjected to the loading protocol recommended in AISC Seismic Provisions for Structural Steel Buildings (AISC‐341). The experimental results suggested that the detachable links with the proposed connection details can satisfy the link rotation capacity limits of AISC‐341. The detachable links performed similar to conventional links while their replaceability under residual drift was demonstrated.

Design-parameter study on seismic performance of chevron-configured SCBFs with yielding beams

Special concentrically braced frames (SCBFs) designed to meet the 2016 American Institute of Steel Construction Seismic Provisions for Structural Steel Buildings require beams in chevron configurations to develop expected brace forces associated with large lateral deformations. The braces are assumed to fully yield in tension and buckle and deteriorate in compression. These brace forces impose axial forces, shear forces, and bending moments in beams that usually require relatively deep and heavy beam cross sections in comparison to gravity framing and beams in other bracing configurations. A research study was undertaken to develop a new design approach that permits the use of smaller beams engaged as secondary yielding mechanisms. The proposed design approach was developed from previous large-scale experiments and nonlinear response-history analyses. However, the variety of brace sizes and frame geometries used in research to-date is limited. Therefore, two studies were conducted using nonlinear analysis to consider practical design parameters that could impact seismic performance. First, a large parametric study was conducted on three-story chevron SCBFs under static cyclic loading. Second, different methods were used to design typical three-story chevron SCBF buildings for a site in Seattle, WA, which were then subjected to response-history analysis using earthquakes representative of the 2%/50-year hazard level. The studies indicate that low-rise buildings designed by the proposed method have equal or improved seismic performance compared to those designed by conventional design methods, and in conjunction with previous research, they help support future use of the proposed method in practice.

Optimal Design Parameters of Stiffeners for Improving Seismic Performance of Links in EBFs

In eccentrically braced frames (EBFs), the link beam is the main factor determining the behavior of this type of system. In order to enhance the ductility and delaying the web and flange buckling, the link beam is reinforced using intermediate web stiffeners to improve its performance and energy dissipation capacity. The web stiffeners spacing criteria is based on short links under pure shear, which have been applied without considering the bending effect on intermediate links. In this paper, first the effects of stiffener details and section geometry on the link behavior are investigated using finite element modeling, and then by proposing an optimization model, new spacing is proposed for stiffeners of intermediate links that is also consistent with bending distribution, and enhances the performance of intermediate links significantly. To further investigate the results of the optimization model and sensitivity analyses results, the behavior of a total of 52 short, intermediate and long links with different lengths and sections is simulated and investigated under cyclic loading based on ANSI/AISC 341-10 (Seismic provisions for structural steel buildings, Chicago, American Institute of Steel Construction, 2010) using ABAQUS. The results show that the section geometry in W-beams affects the stiffeners spacing and thereby, the behavior of intermediate and long links. According to the obtained results in short links, stiffeners spacing are very conservative and can be increased, and for intermediate links, adjusting the stiffeners spacing based on the proposed optimization model can significantly enhance the performance of the link beam.

Inelastic behavior and seismic design of multistory chevron-braced frames with yielding beams

Chevron or inverted V-braced frames offer numerous architectural and structural advantages, but the current special concentrically braced frame (SCBF) seismic-design requirements in the American Institute of Steel Construction (AISC) Seismic Provisions for Structural Steel Buildings lead to deep, heavy chevron beams; as a result, few chevron SCBFs are built today. Recent research on single-story chevron SCBFs demonstrated that beam yielding can be advantageous at higher demand levels, and design for large, inelastic unbalanced brace-force demands may still result in acceptable seismic performance. However, this prior research did not consider the response of multistory frames. In particular, questions remain as to the potential for concentration of damage, the impacts of composite slabs, and the effects of different beam-to-column connections; these issues can only be investigated using multistory frames. A companion research program was conducted to investigate multistory systems with chevron SCBFs using experimental and computational simulation methods. In the first phase of the research, a three-story chevron SCBF designed to permit beam yielding was tested at the National Center for Research on Earthquake Engineering (NCREE) Laboratory in Taipei, Taiwan. The test results were then used to validate a nonlinear, continuum finite-element model. A limited parametric study was conducted to build upon and further the experiments, specifically to evaluate different beam strengths and stiffnesses. These results were combined to develop design recommendations for chevron SCBFs with yielding beams.

Nonsymmetrical loading protocols for shear links in eccentrically braced frames

SummaryThe AISC Seismic Provisions for Structural Steel Buildings (AISC 341‐16) provide a testing protocol for qualification of link‐to‐column connections in eccentrically braced frames (EBFs). This symmetrical testing protocol was developed by conducting nonlinear time history analysis on representative EBFs designed according to the International Building Code. Although the testing protocol is intended for qualification of link‐to‐column connections, many research programs have employed this recommended protocol for testing of shear links. Recent numerical investigations on constructed EBFs and archetype models showed that links can be subjected to one‐sided loadings with significantly higher link rotation angles than the codified limits. A numerical study has been undertaken to develop nonsymmetrical loading protocols for shear links in EBFs. Pursuant to this goal, 20 EBF archetypes were designed according to the ASCE7‐16 standard. The main parameters investigated were the link length to bay width ratio (e/L), number of stories, type of EBF, and the ground motion level. The archetypes were subjected to maximum considered earthquake and collapse level earthquake as recommended by FEMA P695. The results showed that the history of link rotation is single sided and depends strongly on e/L and the level of ground motion. Nonsymmetrical loading protocols that depend on the aforementioned variables were developed and are presented herein.

Assessment of partial joint penetration welds on bolted end-plate connections

End-plate moment connections are a very common connection type used in today’s metal building industry. Bolted end-plate connections are especially popular because they can be engineered to meet design requirements for moment resisting connections used in seismically active areas. The current industry standard for end-plate moment connections is to use complete joint penetration (CJP) welds when making end-plate to flange welds. An alternative to CJP welds is partial joint penetration (PJP) welds, which leaves some portion of the base metals’ thickness unfused. PJP welds may save time and money in the fabrication of the end-plate connections but the use of PJP welds in this application is currently not considered in the Seismic Provisions for Structural Steel Buildings AISC/ANSI 341-10[1]. The objective of this research was to evaluate the effectiveness of properly detailed PJP flange welds on end-plate connections when subjected to seismic loading by using a pseudo-static loading protocol. Two of the same multiple row extended end-plate moment connection tests were conducted at the University of Oklahoma’s Donald G. Fears Structural Engineering Laboratory. The tested specimens were 44 in. (111.76 cm) deep, cantilevered beams connected to a column via a bolted end-plate. A concentrated load was applied on the beam’s tip creating a moment at the beam to column connection. This created forces acting on the flange to end-plate welds. The specimens were tested in accordance to AISC 341-10’s[1] criteria on cyclic tests for qualification of beam to column connections. Both six-bolt multiple row extended end-plate connections made with PJP welds met AISC 341-10’s[1] requirements for beam to column connection in Intermediate Moment Frames. The specimens’ flanges and webs deformed plastically, while no weld failures were observed during testing. The PJP welds used on the tested beams’ flange to end-plate connections performed favorably. It is the authors’ beliefs that these results may serve as a good starting point for further examination of PJP weld capabilities when subject to seismic loading. Further testing of PJP welds would help to understand their ultimate capabilities. To date the 44 in. (111.76 cm) deep test sections are to our knowledge, the deepest sections that examined PJP flange to end-plate connections subject to seismic loading successfully achieving a 0.02 rad story drift angle.

Development of detachable replaceable links for eccentrically braced frames

SummaryEccentrically braced frames (EBFs) can be repaired after a major earthquake by replacing the links. The link replacement is not a straightforward process and is influenced by the type of the link and the amount of residual frame deformations. The past decade has witnessed the development of different types of replaceable links such as end‐plated links, web connected links, bolted flange and web spliced links, and collector beam and brace spliced links. All of the developed replaceable link details, except the web connected links, are not suitable for link replacement under residual frame drift. In this paper, a detachable replaceable link detail which is based on splicing the link at its mid‐length is proposed. The detail is well suited for installation under residual frame drifts. In addition, the weight and size of the members to be transported and erected are reduced significantly, thereby facilitating the replacement procedure. Performance of this proposed replaceable link is studied by conducting six nearly full scale EBF tests under quasi‐static cyclic loading. The link length ratio, type of end‐plated mid‐splice connection, and the amount of residual drift are considered as test variables. The test results revealed that the inelastic rotation capacity of the detachable replaceable links exceeds the requirements of the AISC Seismic Provisions for Structural Steel Buildings. No failures are observed in the end‐plated mid‐splice connections demonstrating the potential of the proposed details. The detachable replaceable links are investigated by numerical analysis as well to further validate their applicability and to develop design recommendations.

Seismic Design and Performance Evaluation of Long-Span Special Truss Moment Frames

The need for a very-long-span structure in sporting and industrial venues puts steel moment frames and braced frames at a disadvantage. In this regard, special truss moment frames (STMFs) can accommodate a large span by utilizing truss girders to provide high lateral stiffness. However, current seismic provisions for structural steel buildings do not allow STMFs’ span and truss depth to exceed 20 and 1.8 m, respectively. Moreover, when a very long span is used, the high axial forces induced by the gravity load could cause considerable ductility reduction of the chord members in the special segment. This paper presents a study on seismic behavior of long-span STMFs with double-channel truss members, a span length of 27.4 m, and a truss depth of 3.05 m. Plastic hinge models of double-channel sections considering the effect of high axial forces were developed based on experimental and nonlinear finite-element analysis (FEA) for both design basis earthquakes (DBEs) and near-collapse earthquakes or maximum considered earthquakes (MCEs). A design procedure for long-span STMFs using nonlinear pushover analysis is presented. The seismic performance of long-span STMFs was verified using the developed plastic hinge models as well as DBE and MCE ground motions through nonlinear time-history (NTH) analyses. According to the FEA results, a modification to the axial load limit in current seismic provisions for the chord members is recommended.

Re-centering Capability of Inverted-Y Dual Eccentrically Braced Frame

Repair process of structures after a strong earthquake is often governed by the level of permanent deformation experienced by these structures during the shaking event. These phenomena drastically affect the repair cost in addition to the prolonged time needed to accomplish this complex process. In this research the feasibility of utilizing the Re-centering capability of a dual system consisting of steel special moment resisting frame ‘SMRF’ and Inverted-Y geometric configuration eccentric braced frame ‘EBF’ to create an easy-repairable structure after a severe earthquake was examined. In this structural system a removable vertical shear link (i.e. using bolted connection) which is part of the EBF will act as a fuse to dissipate the earthquake input energy while the SMRF will act as a Re-centering system that will force the structure to return to its original position after removing the shear links by intentionally keeping it in the region of elastic behavior. The proposed system’s seismic performance was evaluated through performing series of pushover analyses under different loading patterns, and time history analyses under the action of seven earthquakes. Furthermore, the design provisions provided in the American Code “Seismic Provisions for Structural Steel Buildings” ANSI/AISC 341-10 were verified against the required response and extra recommendations for designing and detailing such structural system were introduced in order to achieve the required behavior. The performed study showed that during severe earthquakes the majority of the inelastic actions were localized within the shear links only while the SMRF behaved almost elastically with few exceptions. In addition, the study provided design and detailing recommendations to create an easy repairable structure after severe earthquakes.

Evaluation of seismic response factors for BRBFs using FEMA P695 methodology

This paper reports the details of a numerical study undertaken to evaluate seismic response factors for steel buckling-restrained braced frames (BRBFs) using the FEMA P695 methodology. In the United States, BRBFs are designed according to Minimum Design Loads for Buildings and Other Structures (ASCE 7) and the Seismic Provisions for Structural Steel Buildings (AISC 341). Twenty-four archetypes were designed according to the U.S. specifications and their behavior was assessed by making use of non-simulated collapse models. The interstory drift, brace axial strain and cumulative brace axial strain demands under collapse level ground motions were determined. The results obtained indicate that the current seismic response factors are adequate in terms of interstory drift and cumulative axial strain demands. On the other hand, large differences between the design level and collapse level axial strains were reported, which can result in undesirable brace behavior. Modified approaches were developed to estimate the axial strains for collapse level ground motions. These include a modification to the deflection amplification factor and a modification to the AISC 341 requirements for expected brace deformations. The archetypes were redesigned using the proposed modifications and reevaluated using the FEMA P695 methodology. The results indicate that the proposed modifications result in axial strain demands that are in close agreement with the calculated demands.

Replaceable links with gusseted brace joints for eccentrically braced frames

Various replaceable link details were developed for use in steel eccentrically braced frames (EBFs) during the past decade. These details include but are not limited to bolted flush end-plated links, bolted extended end-plated links, web connected replaceable links, and bolted flange- and web-spliced links. Another detail which is based on splicing the beam outside the link and braces was recently proposed by the authors. The performance of this detail when used with directly connected braces was studied through experimental testing and acceptable performance was demonstrated. In practice gusseted attachments are widely used for connecting the braces to the beams in EBF systems. In this paper, the proposed detail by the authors is extended to replaceable links with gusseted brace attachments. The use of gusset plates enables to tailor the geometry of the replaceable link and allows different details to be developed. Three replaceable link details are proposed herein. The first detail employs standard gusset plated detail where splicing the beam is performed outside the connection region. The second detail develops a more compact replaceable link by connecting the beam to the link within the brace connection panel. The third detail is a pin connected detail where minimal amounts of bending moments are transferred to the brace member. The proposed details are studied by conducting nine nearly full-scale EBF tests under quasi static loading. The type of replaceable link, link length ratio, connection type, gap size of splice connections, demand-to-capacity ratio of members are considered as the prime variables. The inelastic rotation capacity provided by the replaceable links satisfied the requirements of the AISC Seismic Provisions for Structural Steel Buildings (AISC341-16). The links failed mainly due to fracture of the link web or flange. No failures were observed in the gusseted joints demonstrating the potential of the proposed details.

11.48: An experimental study on welded overlap core: Steel encased buckling‐restrained braces

ABSTRACTBuckling restrained braced frames (BRBFs) can be used as a lateral load resisting system in seismic regions. A typical buckling restrained brace (BRB) is composed of a core segment, debonding material and a buckling restraining mechanism (BRM). The cross‐section of the core segment can be changed along the length to constrain yielding in a limited domain. Most of the BRBs utilize a rectangular core segment which is reduced in width throughout yielding length. The gradual reduction in the width of the core segment produces stress concentrations and employs costly CNC cutting. A novel type of BRB named the welded overlap core steel encased BRB was developed to provide an alternative that does not require CNC cutting of the core plate. This type of a BRB is formed by welding flat bars with different widths to each other. The yielding and non‐yielding segment lengths and areas can be easily tailored to meet the stiffness and strength requirements. An experimental program has been undertaken to study the performance of welded overlap core steel encased BRBs. Pursuant to this goal four BRBs were manufactured and subjected to sub‐assemblage testing. All specimens were tested using the loading protocol recommended in the AISC Seismic Provisions for Structural Steel Buildings (AISC341‐10). Welding detail used to connect the built‐up BRM members was considered as the primary test variable. The experimental results indicated that the proposed core segment concept can be an alternative to more traditional core segment designs. The weld configurations used to connect the buckling restraining mechanisms affected the response significantly. According to the results, properly detailed and inspected welded overlap core BRBs can provide acceptable performance by sustaining cumulative strains in excess of 400 times the yield strain.

Replaceable links with direct brace attachments for eccentrically braced frames

SummaryThis paper reports findings of an experimental study conducted on replaceable links for steel eccentrically braced frames (EBFs). A replaceable link detail which is based on splicing the directly connected braces and the beam outside the link is proposed. This detail eliminates the need to use hydraulic jacks and flame cutting operations for replacement purposes. Performance of this proposed replaceable link was studied by conducting eight nearly full‐scale EBF tests under quasi‐static cyclic loading. The link length ratio, stiffening of the link, loading protocol, connection type, bolt pretension, gap size of splice connections, and demand‐to‐capacity ratios of members were considered as the prime variables. The specimens primarily showed two types of failure modes: link web fracture and fracture of the flange at the link‐to‐brace connection. No failures were observed at the splice connections indicating that the proposed replaceable link detail provides an excellent response. The inelastic rotation capacity provided by the replaceable links satisfied the requirements of the AISC Seismic Provisions for Structural Steel Buildings (AISC341–10). The overstrength factor of the links exceeded 2.0, which is larger than the value assumed for EBF links by design provisions. The high level of overstrength resulted in brace buckling in one of the specimens demonstrating the importance of overstrength factor used for EBF links. Copyright © 2017 John Wiley & Sons, Ltd.

Updates to Expected Yield Stress and Tensile Strength Ratios for Determination of Expected Member Capacity in the 2016 AISC Seismic Provisions

The expected yield stress and expected tensile strength ratios for hollow structural sections (HSS), pipe, and steel reinforcement for steel-concrete composite construction have been updated for the 2016 AISC Seismic Provisions for Structural Steel Buildings. For HSS, each grade of steel, including the new ASTM A1085 specification, has its own Ry and Rt values. Expected yield stress and tensile strength ratios have also been defined for different grades of steel reinforcement. The revisions were based on analysis of mill test data for HSS and pipe from a number of producers and a comprehensive mill survey conducted by the Concrete Reinforcing Steel Institute (CRSI).

Seismic behavior of special truss moment frame with double hollow structural sections as chord members

Research work carried out on steel special truss moment frames (STMFs) with double-angle sections as chord members during the 1990s led to the formulation of design code provisions. Further research results using double-channel specimens resulted in a modified equation for the expected vertical shear strength of the central special segments, Vne, and has been incorporated into the current AISC Seismic Provisions for Structural Steel Buildings. Double hollow structural sections (double-HSS) have the advantages of minimizing lateral torsional buckling and maximizing compactness in the flanges as compared to single HSS with the same flexural capacity. In this research, double-HSS members were proposed for the chord and web members of STMFs instead of double-angle, double-channel, or single-HSS. Double-HSS can effectively delay flange local buckling and enhance rotational ductility due to reduced width-to-thickness ratio (b/t) without increasing the wall thickness of the members. A full-scale STMF subassemblage with double-HSS as truss members was tested under large displacement reversals to simulate a severe earthquake ground motion. Testing results indicate that using double-HSS truss members is a viable alternative for STMFs in high seismic regions. Plastic hinge models are also suggested for computer analysis and design of non-yielding members outside of the special segments.