• Steel and Composite Structures
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• v.7 no.6
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• pp.457-468
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• 2007

Analytical and experimental investigation on dynamic properties of extra lightweight concrete sandwich beams reinforced with various lay ups of carbon reinforced epoxy polymer composites (CFRP) are discussed. The lightweight concrete used in the core of the sandwich beams was made up of extra lightweight aggregate, Lica. The density of concrete was half of that of the ordinary concrete and its compressive strength was about $100Kg/cm^2$. Two extra lightweight unreinforced (control) beams and six extra lightweight sandwich beams with various lay ups of CFRP were clamped in one end and tested under an impact load. The dimension of the beams without considering any reinforcement was 20 cm ${\times}$ 10 cm ${\times}$ 1.4 m. These were selected to ensure that the effect of shear during the bending test would be minimized. Three other beams, made up of ordinary concrete reinforced with steel bars, were tested in the same conditions. For measuring the damping capacity of sandwich beams three methods, Logarithmic Decrement Analysis (LDA), Hilbert Transform Analysis (HTA) and Moving Block Analysis (MBA) were applied. The first two methods are in time domain and the last one is in frequency domain. A comparison between the damping capacity of the beams obtained from all three methods, shows that the damping capacity of the extra lightweight concrete decreases by adding the composite reinforced layers to the upper and lower sides of the beams, and becomes most similar to the damping of the ordinary beams. Also the results show that the stiffness of the extra lightweight concrete beams increases by adding the composite reinforced layer to their both sides and become similar to the ordinary beams.

• Journal of Korean Society of Steel Construction
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• v.8 no.4 s.29
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• pp.85-94
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• 1996

This paper investigated structural behaviors of joint of concrete filled steel tube column and P.C reinforced concrete beam through a series of hysteretic behavior experiment. The results are summarised as follows: (1) The joint stiffness of concrete filled square steel tube column and P.C reinforecd beam was higher than that of concrete filled circular steel tube column and P.C reinforecd beam, and it was decreased as the increase of the number of hysteretic cycle. (2) The aspects of the hysteretic behavior in the joint was stable as the increase of the number of hysteretic cycle, and rotation resisting capacity of joint of concrete filled square steel tube column and P.C reinforced concrete beam was higher than those of the concrete filled circular steel tube column and P.C reinforced concrete beam. (3) Some restriction must be put upon the ratio of axial force in this joint model because the load carrying capacity was decreased by flexural and flexural-torsional buckling in case of the ratio of axial force 0.6. (4) The emprical formula to predict the ultimate capacity of joint model to superimpose shearing strength of steel web(H section) and bending strength of reinforced concrete beam was expected.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.197-204
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• 2005

Multipurpose Floor Level Joint(MFLJ) is a new construction technology system which was developed in domestic. By using this system, it is possible not only to absorb the deformation at expansion joint due to shrinkages of concrete but also to make ease the floor leveling during the concrete casting at floor. The system consists of two elements, supporting devices and rails. Their structural capacities were verified through several experimental programs, such as compressive strength test of support and bending test of rail. The purpose of this paper is to evaluate the deformation absorbing capacity of the floor level joint. An experimental work was carried out to simulate the deformation condition at the joint and the test result was analyzed and evaluated. In addition, FEM analysis for expansion joint of typical building was also performed to predict the real behavior of MFLJ. The test results showed that MFLJ has sufficient deformation capacity required to act as expansion joint.

• Magazine of the Korea Concrete Institute
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• v.7 no.5
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• pp.133-144
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• 1995

This study investigated to the properties of structural behaviors through a series of experiment with the key parameter, such as diameter-to-thickness(D/t) ratio, selenderness ratio of steel t~ube and strength of concrete under loading condition simple confined concrete by steel tube as a fundmental study on adaptability with structural members in high-rise building. The obtained results are sumnarised as follow. (1) The fracture mode of confined concrete was presented digonal tension fracture in the direction of $45^{\circ}$ with compression failure at the end of specimen in stub column, but the fracture mode of long column was assumed an aspect of bending fracture transversely. (2) The deformation capacity and ductility effect was increased by confine steel tube for concrete. (3) 'The emprical formula to predict the ultimate capacity of confined concrete by steel tube and concrete filled steel tube column using restraint of concrete considered D / t ratio, selenderness ratio of steel tube anti strength of' concrete were proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.1
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• pp.95-102
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• 2002

The flexural behavior of the reinforced concrete (RC) structure upgraded by external reinforcements was examined in this study. It is well known that the incorporation of carbon fiber sheet (CFS) with concrete is one of the most effective ways to strengthen the RC structure. Complete bonding is required between CFS and concrete in order to make the RC structure provide its full function until the time the Re structures serve. Many studies have reported that construction deficiencies have caused the debonding of the CFS from concrete before the RC structure with CFS reaches its ultimate capacity. This research took a systematic look at the failure mechanism, macroscopic load-deformation characteristics, the maximum load applied, and maximum bending moment when construction deficiencies exist. The results of the experiment conducted were compared with theoretically derived values. In the future, the results of this investigation will help minimize the factors of construction deficiencies, which may occur when CFS is used to reinforce a RC structure. The experiment was manipulated with steel reinforcement ratio and piles of CFS on a total of 14 beams ($20cm{\times}30cm{\times}240cm$). The results showed that internal moment capacity increased even when construction deficiencies existed. However, RC structures with CFS in the field still contain a considerable level of potential risks.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.67-79
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• 2008

In this study, a bending test with three encased composite beams were carried out and analyzed using FEM in order to find how chemical adhesion, interface interlock, friction and composite action by shear studs contribute to stiffness, strength and composite action in the interface of encased compo site beams. The test and results of the FEM analysis showed that the difference in the ultimate moment capacity of the composite beams with and without studs is under 10%. The reason is that the effect of chemical adhesion, interface interlock, and friction in the interface on the composite action is so high that the encased beams have a moment capacity above some defined magnitude. Also, the increment of moment capacity up to plastic moment is not large and the increase of linearly proportioned.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.961-970
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• 2012

The behavior of the load bearing capacity of a pipeline with unequal wall thickness was evaluated using finite element analyses. Pipelines with a wall thickness ratio of 1.22-1.89 were adopted to investigate plastic collapse under tensile, internal pressure, or bending stress. A parametric study showed that the tensile strength and moment of a pipeline with a wall thickness ratio less than 1.5 were not influenced by the wall thickness ratio and taper angle; however, those of a pipeline with a wall thickness ratio more than 1.5 decreased considerably at a low taper angle. The failure pressure of a pipeline with unequal wall thickness was not influenced by the wall thickness ratio and taper angle.

• Steel and Composite Structures
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• v.29 no.4
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• pp.451-464
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• 2018

This paper presents some quasi-static tests for 4 mixed columns composed of CFST column and RC column. The seismic performance and failure mode were studied under low-cyclic revised loading. The failure mode was observed under different axial compression ratios. The hysteretic curve and skeleton curve were obtained. The effects of axial compression ratio on yield mechanism, displacement ductility, energy dissipation, stiffness and strength attenuation were analyzed. The results indicate that the failure behavior of CFST-RC mixed column with archaized style is mainly caused by bending failure and accompanied by some shear failure. The axial compression ratio performs a control function on the yielding order of the upper and lower columns. The yielding mechanism has a great influence on the ductility and energy dissipation capacity of specimens. Based on the experiment, finite element analysis was made to further research the seismic performance by ABAQUS software. The variable parameters were stiffness ratio of upper and lower columns, axial compression ratio, yielding strength of steel tube, concrete strength and rebar ratio. The simulation results show that with the increase of stiffness ratio of the upper and lower columns, the bearing capacity and ductility of specimens can correspondingly increase. As the axial compression ratio increases, the ductility of the specimen decreases gradually. The other three parameters both have positive effect on the bearing capacity but have negative effect on the ductility. The results can provide reference for the design and engineering application of mixed column consisted of CFST-RC in Chinese archaized buildings.

• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.55-64
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• 2009

One of the important use of piles is to furnish lateral support and nowadays it is getting highlighted due to the increase of skyscrapers, transmission towers, wind turbines, and other lateral action dependent structures. After Broms (1964), many researchers have suggested methods for estimating lateral capacity of pile. But each method assumes different earth pressure distribution and lateral earth pressure coefficient causing confusion on the part of pile designers. Lateral earth pressure, essential in lateral capacity estimation, is influenced by pile's rotational behavior under lateral load. Prasad and Chari (1999) assumed the rotation point of pile and suggested an equation of ultimate lateral load capacity. In this study, we investigate the depth of rotation point in both homogeneous soil and multi layered soil, and compare with the estimation value by previous research. Test results show that measured rotation point and estimated value by Prasad and Chari's equation show good agreement and multi layered condition affects the location of rotation point to be changed.

• 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.