Special Moment Frame Connections Research Articles

Special moment frame connections with shear-yielding haunches

Steel special moment frame connections with shear-yielding haunches can be used for seismic retrofit and for new construction. In this study, shear-yielding haunch connections were investigated through experimental testing and finite element analysis. Three specimens were tested, each with a W1000 × 591 beam and W1000 × 554 column. The cyclically loaded specimens completed cycles at 0.04 rad prior to low-cycle fatigue of the haunch plates. The monotonically loaded specimen reached 0.064 rad drift. The experimental specimens had 10 to 15% post-yield stiffness, and the fuses reached the ultimate material strength prior to tearing. M-factors for the connection were determined to be 4.7 for life safety and 6.3 for collapse prevention. Finite element models were used to quantify force transfer through the connection and to investigate the retrofit-specific detail. The experiments and finite element models confirmed that a relatively simple design procedure produced acceptable designs.

An evaluation of slenderness limitations of H-beams for special moment connections

This paper presents the results of seismic connection testing and finite element analyses (FEA) on the slenderness limitations of steel H-beams in special moment-frame (SMF) connections. The effectiveness of FEA models was first validated by the full-scale testing of a reduced-web-section (RWS) connection, and a post-earthquake bolted-web-welded-flange (BWWF) connection. FEA simulations were then performed to study the beam section properties and seismic connection performance. The result shows that if a H-beam has a compact section, the adopted connection will develop strength and ductility meeting the AISC seismic requirements, even though the plastic section modulus ratio between the beam flanges and whole section is less than 70%. The result also suggests the effectiveness of adding a web opening to a BWWF connection. These findings call for a re-examination of the requirements of highly ductile members in SMF connections.

Cyclic behaviour of laterally skewed special moment frame connections having composite concrete slabs

StahlbauVolume 90, Issue 7 p. 527-527 Empfehlungen der Redaktion Cyclic behaviour of laterally skewed special moment frame connections having composite concrete slabs First published: 05 July 2021 https://doi.org/10.1002/stab.202170705Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume90, Issue7July 2021Pages 527-527 RelatedInformation

Cyclic behaviour of laterally skewed special moment frame connections having composite concrete slabs

AbstractThis study presents a numerical investigation into the cyclic performance of skewed special moment frame (SMF) connections that include composite concrete slabs. The study uses advanced finite element simulations to investigate the behaviour of shallow (W14×), medium (W24×) and deep (W33×) steel column sections with three levels of beam skew (10, 20 and 30 degrees) for both bare‐steel and composite (steel‐concrete) construction. To account for complex torsional boundary conditions that may affect the skewed connection response, prequalification‐type analyses were conducted considering the middle storey of a three‐storey, two‐way moment frame configuration. In the analyses, all skewed configurations achieved at least 0.04 rad of connection rotation during the cyclic loading protocol prior to a 20 % reduction in moment capacity. When a composite concrete slab was added, column twisting and column flange yielding increased at large skew angles (30 degrees) during positive moment cycles.

Cyclic behavior of steel moment connections with built-up columns in weak direction

In many countries, due to fabrication restrictions in producing large hollow tubular rolled sections, use of built-up sections is a common practice. One of those built-up sections being a suitable choice as column in two directional steel moment frames is the double-I that attain high moment of inertia about their two main axes. In this study, using a through-plate concept, a new detailing and corresponding design procedure proposed for moment connections with double-I built-up columns in weak axis direction. A series of finite element analyses performed in order to envisage the connection behavior and its load transfer mechanism. To ensure the accuracy of the results, a computer model similar to the experimental prototype assembled and analyzed via finite element method. The numerical results illustrate reasonable agreement with the experimental results. In addition, the influence of the pertinent parameters on the proposed connection such as thickness and height of the column reinforcing plate, and thickness and height of the trough plate examined. The outcome of this research reveals that the proposed connection satisfies the rigidity, strength and ductility criteria according to AISC seismic provisions for special moment frame connections

Column axial load effects on the performance of skewed SMF RBS connections

The selection of an appropriate seismic steel system (braced frame, moment frame, shear wall, etc.) is often influenced by architectural considerations. Moment frame configurations offer the most architectural flexibility, but are somewhat limited by a lack of guidance in the AISC seismic provisions regarding the use of non-orthogonal (skewed) beam-column connections. A recent study investigating laterally skewed moment frame connections indicates adequate seismic performance; however, it was observed that skewed connections increase the potential for column twist and column flange yielding. It is unclear how larger column axial loads present in medium-to-high-rise structures will affect the performance of skewed special moment frame connections.This study investigates the effects of column axial loads on skewed special moment frame connections containing reduced beam sections (RBSs). Detailed finite element analyses are used for all investigations, and several beam-column connection configurations are considered, representing: 3 beam-column geometries (shallow, medium and deep columns); 4 levels of skew at the beam-to-column connection; and 4 levels of applied column axial load. Results indicate that for axial loads less than 50% of the column axial capacity, there is little effect on connection rotation capacity. Beam-skew angle is the main contributor to resulting column twist. With the exception of the deep column geometries that experienced local flange buckling at 50% ΦPn axial load, increased column axial loads have little effect on resulting column flange yielding in skewed RBS moment connections.

Permissible Parameter Ranges of Access Hole Geometries for WUF-W Connections

The welded unreinforced flange-welded web (WUF-W) connection is one of seven prequalified connections for special moment frames (SMF) specified in AISC 358-10 (2010). Previous studies reported that the cyclic behavior of WUF-W connections was strongly affected by weld access hole geometry, and some WUF-W connections did not satisfy the requirements for SMF connections. For investigating in detail the effect of access hole configurations on the cyclic behavior of WUF-W connections, this study conducts three-dimensional nonlinear finite element analyses. This study shows that the seismic behavior of WUF-W connections are strongly affected by two configuration parameters, access hole slope and length of flat portion. To satisfy the requirement for SMF connections, this study proposes a range of the access hole slope and length of flat portion for WUF-W connections considering different span-to-depth ratios, beam depths, and material types.

액세스 홀 형상변수가 WUF-W 접합부 반복거동에 미치는 영향

The welded unreinforced flange-welded web (WUF-W) connection is one of seven prequalified connections for special moment frames (SMF) specified in AISC 358-10 (2010). Previous studies reported that the cyclic behavior of WUF-W connections was strongly affected by weld access hole geometry, and some WUF-W connections did not satisfy the requirements for SMF connections. For investigating in detail the effect of access hole configurations on the cyclic behavior of WUF-W connections, this study conducts three dimensional nonlinear finite element analyses. This study shows that the seismic behavior of WUF-W connections are strongly affected by two configuration parameters, access hole slope and length of flat portion. To satisfy the requirement for SMF connections, this study proposes a range of the access hole slope and length of flat portion for WUF-W connections considering different span-to-depth ratios, beam depths, and material types.

Effects of panel zone yielding on seismic behavior of welded-flange-plate connections

In this study, effects of panel zone yielding on the seismic performance of welded-flange-plate (WFP) connections are investigated. In this work, four full-scale beam-to-column connections were used to run the experiments under cyclic loading. The obtained results can potentially lead to a better understanding of the influence of the panel zone inelastic shear deformation on the cyclic behavior of WFP connections for external joints in steel moment resisting frames (SMRFs). The main parameter in the testing program was the panel zone strength having a wide variation to gain the different levels of panel zone yielding. Results showed that all specimens had a high connection rotation capacity to satisfy the requirements of special moment frame connections. However, specimens with different panel zone strengths could provide the different amount of energy dissipation. Severe beam buckling was followed by tearing along the k-line region of the beam in the plastic hinge location, as well as tearing of the beam at the nose of the bottom flange plates which were both observed as a predominant failure mode in the specimens with a stronger panel zone. However, specimens with weak panel zone could develop a significant plastic rotation without causing any major problem to the beam-to-column connection groove welds. Based on mentioned observations and considering the effect of panel zone yielding because of different panel zone strengths on the hysteresis behavior of specimens, failure modes, plastic rotation capacity, and energy dissipation, some modifications were proposed for design requirements of the panel zone strength.

Cyclic Performance of Welded Unreinforced Flange-Welded Web Moment Connections

The welded unreinforced flange-welded web (WUF-W) moment connection is a prequalified connection for the special moment frame (SMF) specified in AISC 358-10. In this study, inelastic cyclic tests of four WUF-W specimens were conducted to evaluate the seismic performance of WUF-W connections with different beam depths and panel zone strength ratios. The specimens were made to satisfy the design and detailing criteria specified in AISC 341-10 and AISC 358-10. Test results showed that the WUF-W connections with a beam depth of 692 mm passed the acceptance criteria required for SMF connections, whereas the WUF-W connections with a beam depth of 890 mm did not meet the criteria.

Cyclic Behavior and Seismic Design of Bolted Flange Plate Steel Moment Connections

The AISC Connection Prequalification Review Panel (CPRP) is currently reviewing the bolted flange plate moment connection for inclusion in the next edition of the AISC Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications. To expand the experimental database for prequalifying the bolted flange plate (BFP) moment connection for special moment frames, cyclic testing of three full-scale BFP steel moment connection specimens has been conducted. Beam sizes for these specimens (W30x108, W30x148, and W36x50) were larger than previously tested to extend the range of available experimental results. All three specimens performed well and met the Acceptance Criteria of the AISC Seismic Provisions. The specimens achieved an interstory drift angle of 0.06 radians before failure.

철근콘크리트 보-기둥 접합부의 비탄성 회전 능력에 대한 성능 평가

본 논문에서는 철근콘크리트 모멘트 골조의 보-기둥 접합부에 대한 비탄성 회전 능력의 성능을 조사한 연구 결과를 하고 있다. 총 91개의 보-기둥 접합부 실험체에 대해 상세히 조사되었으며, 그 중 28개의 실험체는 ACI 318-02의 상세 요구에 기초하여 특수 모멘트 골조 접합부로서 분류되었다. AISC-97 내진 기준에서 철골 모멘트 골조 접합부를 위해 정의된 허용기준이 분류된 철근콘크리트 모멘트 골조의 접합부에 대해 평가하기 위해서 사용되었다. 특수 모멘트 골조 접합부에 대한 설계 상세를 만족하는 28개의 실험체 중 27개의 특수 모멘트 골조 접합부가 충분한 강도를 가지고 있었으며, 급격한 강도 감소 없이 0.03 rad.의 소성 회전에 대해 연성 거동을 발휘할 수 있음을 보여 주었다. 접합부의 전단 강도, 기둥과 보에 대한 휨 강도 비율, 접합부내에서의 횡방향 철근비 등에 대한 제한이 보-기둥 접합부의 만족스런 내진 성능을 보여주는데 중요한 역할을 하였다. This study summarizes the results of a research project aimed at investigating the inelastic rotation capacity of beam-column connections of reinforced concrete moment frames. A total of 91 test specimens for beam-column joint connections were examined in detail, and 28 specimens were classified as special moment frame connections based on the design and detailing requirements in the ACI 318-02 Provisions. Then the acceptance criteria, originally defined for steel moment frame connections in the AISC-02 Seismic Provisions, were used to evaluate the joint connections of concrete moment frames. Twenty-seven out of 28 test specimens that satisfy the design requirements for special moment frame structures provide sufficient strength and are ductile up to a plastic rotation of 0.03 rad. without any major degradation in strength. Joint shear stress, column-to-beam flexural strength ratio, and transverse reinforcement ratio in a joint all play a key role in good performance of the connections.

Seismic behaviour of composite concrete-filled tube column-to-beam moment connections

This paper describes the results of cyclic loading applied to seven square concrete-filled tube column-to-beam connections. Connections of all seven specimens were reinforced with T-shaped stiffeners attached to the beam flanges. The specimens are divided into three series: the TS series specimens were reinforced with T-shaped stiffeners only; those in the TSD series had RBS beams in addition to the stiffeners; and those in the TSH series had small holes in the stiffeners. The test results presented in terms of the ductility capacity of the test specimens. All the specimens developed plastic rotations in excess of 3% rad, suggesting that the ductility capacity of the specimens exceeds the requirements for special moment frame connections in the AISC seismic provisions. The tapered horizontal stiffener elements, RBS cutouts and the horizontal stiffener holes were effective in reducing the stress concentration at the tip of the horizontal element. However, some of the specimens failed by a premature fracture in the HAZ of vertical element welds, suggesting that in designing the T-stiffeners strain hardening should be considered.

Collapse Behavior of Steel Special Moment Resisting Frame Connections

There is a common perception that seismic detailing can improve the collapse resistance of steel frame buildings. However, the effect on connection performance of the potentially large catenary, i.e., tensile, forces that can develop during collapse has not yet been adequately studied. The objective of this paper is to use computational structural simulation to investigate a number of key design variables that influence formation of catenary action in steel special moment resisting frame subassemblages. The numerical model used in the study employs a calibrated micromechanical fracture model and is validated using existing test data. The simulation results demonstrate the ductility of seismically designed special moment frame connections and their ability to deform in catenary mode. It is shown that connection ductility and strength are adversely influenced by an increase in beam depth and an increase in the yield to ultimate strength ratio and that the beam web-to-column detail plays an influential role in connection response. A number of conclusions with practical implications are drawn from the numerical results.