• Steel and Composite Structures
• /
• 제47권4호
• /
• pp.489-502
• /
• 2023

The strong column-weak beam (SCWB) moment ratio is specified in AISC 341 to prevent an abrupt column sway in steel special moment frames (SMFs) during earthquakes. Even when the SCWB requirement is satisfied for an SMF, a column-sway can develop in the SMF. This is because the contribution of the composite beam action developed in the concrete floor slab and its supporting beams was not included while calculating the SCWB moment ratio. In this study, we developed a new method for calculating the SCWB moment ratio that included the contribution of composite beam action. We evaluated the seismic collapse performance of the SMFs considering various risk categories and building heights. We demonstrated that the collapse performance of the SMFs was significantly improved by using the proposed SCWB equation that also satisfied the target performance specified in ASCE 7.

• Structural Engineering and Mechanics
• /
• 제85권1호
• /
• pp.65-80
• /
• 2023

To explore the effect of Engineered Cementitious Composite (ECC) on improving the progressive collapse resistance of reinforced concrete frames under a middle column removal scenario, six beam-column substructures were tested by quasistatic vertical loading. Among the six specimens, four were ECC-concrete composite specimens consisting of different depth of ECC at the bottom or top of the beam and concrete in the rest of the beam, while the other two are ordinary reinforced concrete specimens with different concrete strength grades for comparison. The experimental results demonstrated that ECC-concrete composite specimens can improve the bearing capacity of a beam-column substructure at the stages of compressive arch action (CAA) and catenary action in comparison with ordinary concrete specimen. Under the same depth of ECC, the progressive collapse resistance of a specimen with ECC at the beam bottom was superior to that at the beam top. With the increase of the proportion of ECC arranged at the beam bottom, the bearing capacity of a composite substructure was increased, but the increase rate slows down with the proportion. Meanwhile, the nonlinear numerical analysis software MSC Marc was used to simulate the whole loading process of the six specimens. Theoretical formulas to calculate the capacities of ECC-concrete composite specimens at the stages of flexural action, CAA and catenary action are proposed. Based on the research results, this study suggests that ECC should be laid out at the beam bottom and the layout depth should be within 25% of the total beam depth.

• Steel and Composite Structures
• /
• 제22권1호
• /
• pp.141-159
• /
• 2016

Commonly in steel frames, steel beam and concrete slab are connected together by shear keys to work as a unit member which is called composite beam. When a composite beam is subjected to positive bending, flexural strength and stiffness of the beam can be increased due to "composite action". At the same time despite these advantages, composite action increases the strain at the beam bottom flange and it might affect beam plastic rotation capacity. This paper presents results of study on the rotation capacity of composite beam connected to Rectangular Hollow Section (RHS) column in the steel moment resisting frame buildings. Due to out-of-plane deformation of column flange, moment transfer efficiency of web connection is reduced and this results in reduction of beam plastic rotation capacity. In order to investigate the effects of width-to-thickness ratio (B/t) of RHS column on the rotation capacity of composite beam, cyclic loading tests were conducted on three full scale beam-to-column subassemblies. Detailed study on the different steel beam damages and concrete slab damages are presented. Experimental data showed the importance of this parameter of RHS column on the seismic behavior of composite beams. It is found that occurrence of severe concrete bearing crush at the face of RHS column of specimen with smaller width-to-thickness ratio resulted in considerable reduction on the rate of strain increase in the bottom flange. This behavior resulted in considerable improvement of rotation capacity of this specimen compared with composite and even bare steel beam connected to the RHS column with larger width-to-thickness ratio.

• Steel and Composite Structures
• /
• 제47권2호
• /
• pp.203-216
• /
• 2023

The composite beam connections often encountered fracture failure in the welded bottom flange joint, and a bottom flange bolted connection has been proposed to increase the deformation ability of the bottom flange joint. The seismic performance of the bottom flange bolted composite beam connection was suffered from both the composite action of concrete slab and the asymmetric load transfer mechanisms between top and bottom beam flange joints. Thus, this paper presents a comprehensive numerical study on the working mechanism of the bottom flange bolted composite beam connections. Three available modelling methods and a new modelling method on the flange-stud-slab interactions were compared. The efficient numerical modeling method was selected and then applied to the parametric study. The influence of the composite slab, the bottom flange bolts, the shear composite ratio and the web hole shape on the seismic performance of the bottom flange bolted composite beam connections were investigated. A hogging strength calculation method was then proposed based on numerical results.

• 한국산학기술학회논문지
• /
• 제14권8호
• /
• pp.4048-4057
• /
• 2013

부모멘트를 받는 합성보 슬래브에서 인장균열 발생과 균열의 진행에 따른 슬래브의 강성저하가 전단연결부의 합성거동에 미치는 영향을 실험적으로 분석하기는 매우 어렵다. 본 논문에서는 부모멘트를 받는 합성보에서 콘크리트 슬래브 및 강재 보, 스터드를 포함한 전단연결부 등의 형상과 물성을 최대한 실제와 유사하게 모델링하는 기법을 이용함으로써, 부재 간 합성작용을 해석할 수 있는 3차원 유한요소모델을 개발하였다. 개발된 3차원 유한요소모델을 이용하여 부모멘트 구간에 설치되는 합성보의 전체 휨거동 및 기존의 1차원 또는 2차원 모델로는 해석이 어려운 전단합성작용을 분석할 수 있었다. 해석결과에 따르면 부모멘트를 받는 합성보에서의 전단연결부 거동은 철근콘크리트 슬래브의 철근비 및 인장 균열거동에 지배를 받게 됨을 알 수 있었다. 전단연결부의 하중-슬립 관계를 검토해 본 결과, 전단연결부의 슬립강성은 슬래브의 초기균열 및 철근의 항복이 발생한 시점을 기준으로 변화됨을 알 수 있었다. 또한, 구간별로 합성율이 100% 미만으로 설계되는 부분합성 설계가 합성설계의 효율성 측면에서 더 유리할 수 있다는 기존의 실험적 연구결과를 간접적으로 확인할 수 있었다.

• Steel and Composite Structures
• /
• 제45권6호
• /
• pp.895-905
• /
• 2022

Composite flooring systems consisting of cold-formed steel joists and reinforced concrete slabs offer an efficient, lightweight solution. However, utilisation of composite action to achieve enhanced strength and economical design has been limited. In this study, finite element modelling was utilised to create a three-dimensional model which was then validated against experimental results for a composite flooring system consisting of cold-formed steel joists, reinforced concrete slab and steel bolt shear connectors. This validated numerical model was then utilised to perform parametric studies on the performance of the structural system. The results from the parametric study demonstrate that increased thickness of the concrete slab and increased thickness of the cold formed steel beam resulted in higher moment capacity and stiffness of the composite flooring system. In addition, reducing the spacing of bolts and spacing of the cold formed steel beams both resulted in enhanced load capacity of the composite system. Increasing the concrete grade was also found to increase the moment capacity of the composite flooring system. Overall, the results show that an efficient, lightweight composite flooring system can be achieved and optimised by selecting suitable concrete slab thickness, cold formed beam thickness, bolt spacing, cold formed beam spacing and concrete grade.

• 한국강구조학회 논문집
• /
• 제15권4호통권65호
• /
• pp.467-474
• /
• 2003

일반적인 합성보는 콘크리트 슬래브와 H형강 철골보 사이에 작용하는 수평전단력을 쉬어코넥터로 긴결하여 휨내력 및 강성을 증가시킨 구조다. H형강대신 U형 철골을 사용하고 그 속에 콘크리트를 채운 새로운 형태의 합성보 시스템이라 할 수 있는 T형 합성보의 구조 특성을 실험에 의해 분석하고, 기존의 합성보 설계이론을 토대로 내력평가를 하는 데 그 목적이 있다. 또한 T형 합성보의 구조설계 및 시공에 필요한 기초자료를 제시하고자 한다.

• Steel and Composite Structures
• /
• 제34권1호
• /
• pp.91-105
• /
• 2020

Steel-concrete composite beam with profiled steel sheet has gained its popularity in the last two decades. Due to the ageing of these structures, retrofitting in terms of flexural strength is necessary to ensure that the aged structures can carry the increased traffic load throughout their design life. The steel ribs, which presented in the profiled steel deck, limit the use of shear connectors. This leads to a poor degree of composite action between the concrete slab and steel beam compared to the solid slab situation. As a result, the shear connectors that connects the slab and beam will be subjected to higher shear stress which may also require strengthening to increase the load carrying capacity of an existing composite structure. While most of the available studies focus on the strengthening of longitudinal shear and flexural strength separately, the present work investigates the effect of both flexural and longitudinal shear strengthening of steel-concrete composite beam with composite slab in terms of failure modes, ultimate load carrying capacity, ductility, end-slip, strain profile and interface differential strain. The flexural strengthening was conducted using carbon fibre reinforced polymer (CFRP) or steel plate on the soffit of the steel I-beam, while longitudinal shear capacity was enhanced using post-installed high strength bolts. Moreover, a combination of both the longitudinal shear and flexural strengthening techniques was also implemented (hybrid strengthening). It is concluded that hybrid strengthening improved the ultimate load carrying capacity and reduce slip and interface differential strain that lead to improved composite action. However, hybrid strengthening resulted in brittle failure mode that decreased ductility of the beam.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.421-426
• /
• 2003

For the replacement of deteriorated concrete decks or wider-span slab, composite slab could be very attactive due to higher stiffness and strength. Based on the previous research, a modified I-beam composite hollow slab was suggested. In order to investigate the static flexural behavior of the proposed composite slab and to suggest its flexural design method, experiments were performed. Judging from the tests, a composite slab with I-beam having a semi-circle hole showed better structural performance. The effect of web details on the flexural stiffness was negligible. Flexural stiffness, ultimate strength, and ductility of the composite slabs were significantly greater than the RC slab due to composite action. While the failure of the RC slab was punching shear failure, the composite hollow slab showed flexural cracking and failure by yielding of the I-beams and crushing of concrete. Therefore, the current one-way design concept is appropriate for the design of I-beam composite hollow slab.

• Steel and Composite Structures
• /
• 제4권3호
• /
• pp.169-188
• /
• 2004

A mechanics model is developed in this paper for concrete-filled steel CHS (circular hollow section) beam-columns. A unified theory is described where a confinement factor (${\xi}$) is introduced to describe the composite action between the steel tube and the filled concrete. The predicted load versus deformation relationship is in good agreement with test results. The theoretical model was used to investigate the influence of important parameters that determine the ultimate strength of concrete-filled steel CHS beam-columns. The parametric and experimental studies provide information for the development of formulas for the calculation of the ultimate strength of the composite beam-columns. Comparisons are made with predicted beam-columns strengths using the existing codes, such as LRFD-AISC-1999, AIJ-1997, BS5400-1979 and EC4-1994.