• Journal of Korean Society of Steel Construction
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• v.30 no.2
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• pp.77-85
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• 2018

A through diaphragm is often used to ensure their stiffness for moment-resisting connections using rectangular steel-tube column and H-shaped beam. The through-diaphragm connections, however, have some difficulties for their applicabilities to the field due to the complexity of the fabrication and construction processes. This study thus proposes a new modular system of steel structures assembled only using bolts without welding, by bringing a connection module composed of rectangular steel-tube column, H-shaped beam and oneway bolt onto the site. An experimental study to evaluate the seismic performance of the proposed connection details based on the new modular system is then conducted. The length and type of the inner reinforcement plate are considered as the primary design parameters, and the strength, stiffness, ductility and energy dissipation capability of the new connections are experimentally analyzed by comparison to those of conventional through diaphragm connections.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.611-623
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• 1997

This paper provides the results of an experimental and analytical study performed on the beam to Concrete Filled Circular Steel Column connections with the external stiffener rings under the gravity loads. Specimens are modeled as a 1/4 scale of the beam-columns as gravity loads are applied to a multi-story frame. Important parameters in this study are the width of the external rings, the diameter-thickness ratios of column and whether or not the external rings are welded to the circular column. A total of 20 specimens are tested to clarify the structural behavior of the CFT column connections with the external stiffener rings. The test results are summarized for the yield and maximum strength and stiffness. The existing design equations for the allowable and yield load capacities are referred to verify the structural characteristics for the connections.

• Steel and Composite Structures
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• v.19 no.4
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• pp.1035-1053
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• 2015

A genetic algorithm-based minimum weight design method is presented for steel frames containing composite beams, semi-rigid connections and column bases. Genetic Algorithms carry out optimum steel frames by selecting suitable profile sections from a specified list including 128 W sections taken from American Institute of Steel Construction (AISC). The displacement and stress constraints obeying AISC Allowable Stress Design (ASD) specification and geometric (size) constraints are incorporated in the optimization process. Optimum designs of three different plane frames with semi-rigid beam-to-column and column-to-base plate connections are carried out first without considering concrete slab effects on floor beams in finite element analyses. The same optimization procedures are then repeated for the case of frames with composite beams. A program is coded in MATLAB for all optimization procedures. Results obtained from the examples show the applicability and robustness of the method. Moreover, it is proved that consideration of the contribution of concrete on the behavior of the floor beams enables a lighter and more economical design for steel frames with semi-rigid connections and column bases.

• Coupled systems mechanics
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• v.3 no.2
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• pp.195-211
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• 2014

When strong seismic forces act on reinforced concrete structures, their beam-column connections are very susceptible to damage during the earthquake event. The aim of this numerical work is to evaluate the influence of the internal steel reinforcement array on the nonlinear response of a RC beam-column connection when it is subjected to strong cyclic loading -as a seismic load. For this, two specimens (extracted from an experimental test of 12 RC beam-column connections reported in literature) were modeled in the Finite Element code FEAP considering different stirrup's arrays. In order to evaluate the nonlinear response of the RC beam-column connection, the 2D model takes into account the nonlinear thermodynamic behavior of each component: for concrete, a damage model is used; for steel reinforcement, it is adopted a classical plasticity model; in the case of the steel-concrete bonding, this one is considered perfect without degradation. At the end, we show a comparison between the experimental test's responses and the numerical results, which includes the distribution of shear stresses and damage inside the concrete core of the beam-column connection; in the other hand, the effects on the connection of a low and high state of confinement are analyzed for all cases.

• Structural Engineering and Mechanics
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• v.68 no.5
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• pp.591-601
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• 2018

Non-moment beam-to-column connections, which are usually referred to as simple or shear connections, are typically designed to carry only gravity loads in the form of vertical shears. Although in the analysis of structures these connections are usually assumed to be pinned, they may provide a small amount of rotational stiffness due to the typical connection details. This paper investigates the effects of this small rotational restraint of simple beam-to-column connections on the behavior and seismic response of steel braced non-moment resisting frames. Two types of commonly used simple connections with bolted angles, i.e., the Double Web angle Connection (DWC) and Unstiffened Seat angle Connection (USC) are considered for this purpose. In addition to the pinned condition - as a simplified representation of these connections - more accurate semi-rigid models are established and then applied to some frame models subjected to nonlinear pushover and nonlinear time history analyses. Although the use of bracing elements generally reduces the sensitivity of the global structural response to the behavior of connections, the obtained results indicate considerable effects on the local responses. Namely, our results show that consideration of the real behavior of connections is essential in designing the column elements where the pin-connection assumption significantly underestimates design of outer columns of upper stories.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.711-722
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• 2008

Existing tube for concrete filled tubular structure is made through welding of four plates irrespective of tube thickness, so production performance is poor and special welding technique is needed to weld the internal diaphragm and through the diaphragm. Therefore, through manufacturing by cold forming development of beam to column connections that is no welding in position of stress concentration is needed. In this study the proposal of beam to column connections details and to making tube specimens by method of bending steel plates, we want to know the compositeeffect between internal anchor and concrete by processing on stress distribution and internal force evaluation of concrete filled tube beam to column connections with a variable of flange welding existence between column and beam, welding quantity between column and diaphragm, existence of concrete in tube, column with diaphragm and general column.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.200-207
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• 2003

The seismic behaviors of steel moment connections are investigated based on the numerical analysis of the connections with US and Japanese typical details. The rupture index, representing the fracture potential, is used to evaluate the ductility of the connections at the critical location. The results show that the presence of a slab increases the beam strength, imposes constraint near the beam top flange, and consequently, induces concentrated deformation near the beam access hall, which reduces the ductility of the connection. The total deformation capacity of the connection depends not only on a beam but also on a column and panel zone.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.385-395
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• 1999

Square hollow section columns and H-section beams have recently been increasing1y used. Rigid column-beam connections cannot be made for the structural system and thus some measures to improve the rotational stiffness of connections should be developed. For this purpose, several types of connections. such as H-section beams connected to concrete-filled square hollow section columns, have been contrived and put to experiment. Since the experimental works are usually difficult and expensive. Particularly test of all the types of connections with similar behavior may not be feasible. Instead, the numerical analysis will be adopted predict the flexural stiffness of connections. In this work, FEM modeling techniques are examined and parametric analysis study has been carried out. The major parameters considered are concrete strength, thickness of steel column, magnitude and eccentricity of axial forces.

• Steel and Composite Structures
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• v.50 no.5
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• pp.515-529
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• 2024

Cold-formed steel (CFS) is a popular choice for construction due to its low cost, durability, sustainability, resistance to high environmental and seismic pressures, and ease of installation. The beam-column connections in residential and medium-rise structures are formed using self-drilling screws that connect two CFS channel sections and a gusset plate. In order to increase the moment capacity of these CFS screwed beam-column connections, stiffeners are often placed on the web area of each single channel. However, there is limited literature on studying the effects of stiffeners on the moment capacity of CFS screwed beam-column connections. Hence, this paper proposes a new test approach for determining the moment capacity of CFS screwed beam-column couplings. This study describes an experimental test programme consisting of eight novel experimental tests. The effect of stiffeners, beam thickness, and gusset plate thickness on the structural behaviour of CFS screwed beam-column connections is investigated. Besides, nonlinear elasto-plastic finite element (FE) models were developed and validated against experimental test data. It found that there was reasonable agreement in terms of moment capacity and failure mode prediction. From the experimental and numerical investigation, it found that the increase in gusset plate or beam thickness and the use of stiffeners have no significant effect on the structural behaviour, moment capacity, or rotational capacity of joints exhibiting the same collapse behaviour; however, the capacity or energy absorption capacities have increased in joints whose failure behaviour varies with increasing thickness or using stiffeners. Besides, the thickness change has little impact on the initial stiffness.

• Steel and Composite Structures
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• v.14 no.5
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• pp.431-451
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• 2013

The Big Bang-Big Crunch (BB-BC) optimization algorithm is developed for optimal design of non-linear steel frames with semi-rigid beam-to-column connections. The design algorithm obtains the minimum total cost which comprises total member plus connection costs by selecting suitable sections. Displacement and stress constraints together with the geometry constraints are imposed on the frame in the optimum design procedure. In addition, non-linear analyses considering the P-${\Delta}$ effects of beam-column members are performed during the optimization process. Three design examples with various types of connections are presented and the results show the efficiency of using semi-rigid connection models in comparing to rigid connections. The obtained optimum semi-rigid frames are more economical solutions and lead to more realistic predictions of response and strength of the structure.