• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.313-322
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• 2007

The PCS system, which consists of precast concrete column and steel beam, is a kind of composite structural systems. In this paper, experimental study has been conducted to analyze seismic performance of bolted beam-to-column connections for the PCS system. Based on experimental results from the seismic testing of eight interior PCS specimens, it shows that behavior of PCS system is satisfactory to seismic performance criteria of ACI such as strength deterioration, stiffness degradation and energy dissipation capacity except initial stiffness. All of the specimens maintain their strength at large levels of story drift without significant loss of stiffness and show high ductility level for inelastic behavior. The energy dissipation capacity is two times greater than requirement of ACI criterion. But the initial stiffness of all specimens does not satisfy ACI criterion, and this phenomenon is similar to the other composite structural systems such as RCS, CFT system.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.3
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• pp.9-21
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• 2012

Concrete filled steel tube (CFT) columns have been widely used in moment resisting frame structures both in seismic zones. This paper discusses the design of such members based on the advanced methods introduced in the 2005 AISC Specification and the 2005 Seismic Provisions. This study focuses particularly on design following both linear and nonlinear methods utilizing equivalent static and dynamic loads for low-rise moment frames. The paper begins with an examination of the significance of pseudo-elastic design interaction equations and the plastic ductility demand ratios due to combined axial compressive force and bending moment in CFT members. Based on advanced computational simulations for a series of five-story composite moment frames, this paper then investigates both building performance and new techniques to evaluate building damage during a strong earthquake. It is shown that 2D equivalent static analyses can provide good design approximations to the force distributions in moment frames subjected to large inelastic lateral loads. Dynamic analyses utilizing strong ground motions generally produce higher strength ratios than those from equivalent static analyses, but on more localized basis. In addition, ductility ratios obtained from the nonlinear dynamic analysis are sufficient to detect which CFT columns undergo significant deformations.

• Journal of Construction Engineering and Project Management
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• v.3 no.4
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• pp.12-19
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• 2013

Green Frame is an environmentally friendly column-beam system composed of composite PC members that can increase buildings' life spans while reducing resource consumption. Typically, connections of PC and RC columns occur at the boundaries of each floor, which is at the upper section of slabs, causing the boundary of each floor to generate the maximum moment. Although it is not optimal in terms of structural safety to connect members at a location where the moment is high, this approach is highly adopted due to its constructability. We propose that a superior approach that employs the concept of connecting columns at the low bending moment zone can be applied to quickly and safely install green columns, the main structural members of Green Frame. Connection of green columns at the low bending moment zone can be classified into three techniques, depending on the method of reinforcing the joints, which have different connection characteristics and construction methods. Research is needed to compare the features of each method of reinforcing the joints so that the most appropriate column connection method can be chosen for the site conditions. This study aims to confirm the structural safety of the connection component at the low bending moment zone and to compare and analyze the construction duration, unit price, quality and safety performance of each column connection method. The study results are anticipated to activate the use of composite precast concrete and to be used as development data in the future.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.6
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• pp.63-68
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• 2007

The purpose of this study was to develop a new connection method between steel beams and PC columns known as SL connectors. Composite moment frames consisting of PC columns (or composite columns) and steel beams make the best use of advantages of both concrete and steel materials. However, the connection between two members of different materials can be complex and/or increase the fabrication costs significantly. The concept of SL connectors is based on using wedges and the emphasis is on a self-locking (SL) feature. SL connectors are easy to install and provide better seismic performance compared to conventional connections. To evaluate the seismic performance of the steel beam-to-PC column joints with SL connectors, cyclic load tests were conducted. Test result showed that steel beam-to-concrete column joint with SL connectors was able to provide sufficient performance for use in seismic resistant moment frames.

• Steel and Composite Structures
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• v.44 no.6
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• pp.845-865
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• 2022

In this study, the performance of shear deficient reinforced concrete (RC) beams with rectangular cross-sections, which were externally bonded reinforced (EBR) with high strength CFRP and GFRP strips composite along shear spans, has been experimentally and analytically investigated under vertical load. In the study, the minimum CFRP and GFRP strips width over spacing were considered. The shear beam with turned end to a bending beam was investigated by applying different composite strips. Therefore various arising in each of strength, ductility, rigidity, and energy dissipation capacity were obtained. A total of 12 small-scaled experimental programs have been performed. Beam dimensions have been taken as 100×150×1000 mm. Four beams have been tested as unstrengthened samples. This paper focuses on the effect of minimum CFRP and GFRP strip width on behaviours of RC beams shear-strengthened with full-wrapping, U-wrapping, and U-wrapping+longitudinal bonding strips. Strengthened beams showed significant increments for flexural ductility, energy dissipation, and inelastic performance. The full wrapping strips applied against shear failure have increased the load-carrying capacity of samples 53%-63% interval rate. Although full wrapping is the best strengthening choice, the U-wrapping and U-wrapping+longitudinal strips of both CFRP and GFRP bonding increased the shear capacity by 53%~75% compared to the S2 sample. In terms of ductility, the best result has been obtained by the type of strengthening where the S5 beam was completely GFRP wrapped. The experimental results were also compared with the analytically given by ACI440.2R-17, TBEC-2019 and FIB-2001. Especially in U-wrapped beams, the estimation of FIB was determined to be 81%. The estimates of the other codes are far from meeting the experimental results; therefore, essential improvements should be applied to the codes, especially regarding CFRP and GFRP deformation and approaches for longitudinal strip connections. According to the test results, it is suggested that GFRP, which is at least as effective but cheaper than CFRP, may be preferred for strengthening applications.

• Steel and Composite Structures
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• v.14 no.1
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• pp.57-71
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• 2013

The prediction of the low cycle fatigue (LCF) life of beam-column connections requires an LCF model that is developed using specific geometric information. The beam-column connection has several geometric variables, and changes in these variables must be taken into account to ensure sufficient robustness of the design. Previous research has verified that the finite element model (FEM) can be used to simulate LCF behavior at the end plate moment connection (EPMC). Three critical parameters, i.e., end plate thickness, beam flange thickness, and bolt distance, have been selected for this study to determine the geometric effects on LCF behavior. Seven FEMs for different geometries have been developed using these three critical parameters. The finite element analysis results have led to the development of a modified LCF model for the critical parameter groups.

• Steel and Composite Structures
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• v.3 no.6
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• pp.451-474
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• 2003

Details are given of a cold-formed steel portal framing system that uses simple bolted moment-connections for both the eaves and apex joints. However, such joints function as semi-rigid and, as a result, the design of the proposed system will be dominated by serviceability requirements. While serviceability is a mandatory design requirement, actual deflection limits for portal frames are not prescribed in many of the national standards. In this paper, a review of the design constraints that have an effect on deflection limits is discussed, and rational values appropriate for use with cold-formed steel portal frames are recommended. Adopting these deflection limits, it is shown through a design example how a cold-formed steel portal frame having semi-rigid eaves and apex joints can be a feasible alternative to rigid-jointed frames in appropriate circumstances.

• Steel and Composite Structures
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• v.10 no.6
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• pp.489-500
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• 2010

The rigid connections of I-beams to Rectangular Hollow Sections (RHS) in steel structures usually behave as semi-rigid connection. This behavior is directly related to the column face deformation. The deformation in the wall of RHS column in the connection zone causes a relative rotation between beam end and column axis, which consequently reduces the rigidity of beam-column connection. In the present paper, the percentages of connection rigidity reduction for serviceability conditions are evaluated by using the finite element analysis. Such percentages for RHS columns without internal stiffeners are considerable, and can be calculated from presented graphs.

• Steel and Composite Structures
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• v.13 no.1
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• pp.35-46
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• 2012

Implementation of openings in beams web has been introduced as an innovative method for improving seismic performance of steel moment frames. In this paper, several steel moment frames have been studied in order to evaluate the effect of openings in beams web. The beam sections with web opening have been modeled as a simplified super-element to be used in designing frames and to determine opening configurations. Finite element models of designed frames were generated and nonlinear static pushover analysis was conducted. The efficient location for openings along the beam length was discovered and the effects of beams with web openings on local and global behavioral characteristics of frames were discussed. Base on the results, seismic performance of steel moment frames was improved by creating openings in beams web, in terms of reduction in stress level of frame sensitive areas such as beam to column connections and panel zones.

• Steel and Composite Structures
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• v.6 no.2
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• pp.103-122
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• 2006

The capacity of tubular truss chords subjected to concentrated reaction forces in the vicinity of the open end (i.e., the bearing region) is not directly treated by existing design specifications; although capacity equations are promulgated for related tubular joint configurations. The lack of direct treatment of bearing capacity in existing design specifications seems to represent an unsatisfactory situation given the fact that connections very often control the design of long-span tubular structures comprised of members with slender cross-sections. The case of the simple-span overhead highway sign truss is studied, in which the bearing reaction is applied near the chord end. The present research is aimed at assessing the validity of adapting existing specifications' capacity equations from related cases so as to be applicable in determining design capacity in tubular truss bearing regions. These modified capacity equations are subsequently used in comparisons with full-scale experimental results obtained from testing carried out at the University of Pittsburgh.