• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.142-152
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• 2010

In this study, eleven reinforced concrete beams, without stirrup, using high ductile fiber-reinforced mortar with ground granulated blast furnace slag(SHF Series, SHFSC Series) and standard specimens without or with stirrup(SSS, BSS) were constructed and tested under monotonic loading. Experimental programs were carried out to improve and evaluate the shear performance of such test specimens, such as the load-displacement, the failure mode, the maximum strength, and shear strength. All the specimens were modeled in scale-down size. Test results showed that test specimens(SHF Series, SHFSC Series) was increased respectively the shear strength carrying capacity by 26%, 20% and the ductility capacity by 5.27, 5.75 times in comparison with the standard specimen without stirrup(SSS). And the specimens(SHF Series, SHFSC Series) showed enough ductile behavior and stable flexural failure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.92-98
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• 2014

Spacer is a construction material for maintaining cover depth and steel installation, however several problems like staining, leakage, and cracking are currently issued due to performance degradation and unsatisfactory dimensional stability of spacer. Plastic composite is widely used for prevention of brittle failure in cement based material, which yields improvement of crack resistance and ductile failure. This study is for development and applicability evaluation of high strength spacer with slag cement for environmental load reduction and plastic composite like polypropylene fiber, nylon fiber, and glass fiber. For this work, unit weight of 4 different plastic fibers are evaluated through preliminary tests. Physical tests including compressive, flexural, and tensile strength and durability tests including absorption, permeability, length change, crack resistance, carbonation, and freezing and thawing are performed. Through various tests, optimum plastic fiber is selected and manufacturing system for high strength spacer with the selected fiber is developed. Dimensional stability of the developed spacer is evaluated through field applicability evaluation.

• Computers and Concrete
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• v.30 no.4
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• pp.277-287
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• 2022

Due to the scarcity of extortionate experimental data, fatigue failure of the reinforced concrete (RC) element might be achieved economically adopting nonlinear finite element (FE) analysis as an alternative approach. However, conventional implicit dynamic analysis is expensive, quasi-static method overlooks interaction effects and inertia, direct cyclic analysis computes stabilized responses. Apart from this, explicit dynamic analysis may provide a numerical operating system for factual long-term responses. The study explores the fatigue behavior based on a simplified explicit dynamic solution employing nonlinear time domain analysis. Among fourteen RC beams, one beam is selected to validate under static loading, one under fatigue with the experimental study and other twelve to check the detail fatigue behavior. The SWOT (Strength, Weakness, Opportunities, Threats) analysis has been carried out to pinpoint the detail scenario in the adoption of numerical approach as an alternative to the experimental study. Excellent agreement of FE and experimental results is seen. The 3D nonlinear RC beam model at service fatigue limits is truthful to be used as an expedient contrivance to envisage the precise fatigue behavior. The simplified analysis approach for RC beam under fatigue offers savings in computation to predict responses providing acceptable accuracy rather than the complicated laboratory investigation. At higher frequency, the flexural failure occurs a bit earlier gradually compared to the repeated loading case of lower frequency. The deflection increases by 6%-10% at the end of first cycle for beams with increasing frequency of cyclic loading. However, at the end of fatigue loading, greater deflection occur earlier for higher load range because of more rapid stiffness degradation. For higher frequency, a slight boost in concrete compressive strains at an initial stage of loading has been seen indicating somewhat stepper increment. Stiffness degradation in larger loading cycle at same duration escalates the upsurge of the rate of strain in case of higher frequency.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.1
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• pp.47-57
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• 2024

Recently, in newly constructed apartment buildings, the exterior wall structures have been characterized by thinness, having various openings, and a significantly low reinforcement ratio. In this study, a nonlinear finite element analysis was performed to investigate the crack damage characteristics of the exterior wall structure. The limited analysis models for a 10-story exterior wall were constructed based on the prototype apartment building, and nonlinear static analysis (push-over analysis) was performed. Based on the finite element (FE) analysis model, the parametric study was conducted to investigate the effects of various design parameters on the strength and crack width of the exterior walls. As the parameters, the vertical reinforcement ratio and horizontal reinforcement ratio of the wall, as well as the uniformly distributed longitudinal reinforcement ratio and shear reinforcement ratio of the connection beam, were addressed. The analysis results showed that the strength and deformation capacity of the prototype exterior walls were limited by the failure of the connection beam prior to the flexural yielding of the walls. Thus, the increase of wall reinforcement limitedly affected the failure modes, peak strengths, and crack damages. On the other hand, when the reinforcement ratio of the connection beams was increased, the peak strength was increased due to the increase in the load-carrying capacity of the connection beams. Further, the crack damage index decreased as the reinforcement ratio of the connection beam increased. In particular, it was more effective to increase the uniformly distributed longitudinal reinforcement ratio in the connection beams to decrease the crack damage of the coupling beams, regardless of the type of the prototype exterior walls.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.535-547
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• 2012

PSRC column is a concrete encased steel angle column. In the PSRC column, the steel angles placed at the corner of the cross-section resists bending moment and compression load. The lateral re-bars welded to steel angles resist the column shear and the bond between the steel angle and concrete. In the present study, current design procedures in KBC 2009 were applied to the flexure-compression, shear, and bond design of the PSRC composite column. To verify the validity of the design method and failure mode, simply supported 2/3 scaled PSRC and correlated SRC beams were tested under two point loading. The test parameters were the steel angle ratio and lateral bar spacing. The test results showed that the bending, shear, and bond strengths predicted by KBC 2009 correlated well with the test results. The flexural strength of the PSRC specimens was much greater than that of the SRC specimen with the same steel ratio because the steel angles were placed at the corner of the column section. However, when the bond resistance between the steel angle and concrete was not sufficient, brittle failures such as bond failure of the angle, spalling of cover concrete, and the tensile fracture of lateral re-bar occurred before the development of the yield strength of PSRC composite section. Further, if the weldability and toughness of the steel angle were insufficient, the specimen was failed by the fracture of the steel angle at the weld joint between the angle and lateral bars.

• Journal of the Korean Wood Science and Technology
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• v.49 no.2
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• pp.107-121
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• 2021

The purpose of this study is to optimize the bonding method of the plywood suitable for cross-laminated timber (CLT) with plywood as a core by analyzing the flexural performance and failure mode according to the lamina species, the method of bonding plywood in the longitudinal direction, and whether or not adhesive is applied to the joint. In the case of the Douglas fir lamina layer, the modulus of elasticity decreased by about 11.5% due to longitudinal bonding, and the modulus of rupture increased or decreased according to the adhesive application and bonding method. The optimal conditions were derived as the butt joint without adhesive, half lap joint with adhesive, and butt joint. In the case of the larch lamina layer, the modulus of rupture and the modulus of elasticity decreased by about 15% and 40%, respectively. When using the half lab joint and tongue & groove joint, it is believed that it reduces the load transmitted to the middle layer by primarily preventing the failure on flexure at the joint of the plywood layer. From the results of this study, the larch lamina layer used in the manufacturing process of Ply-lam CLT did not show any difference based on the bonding method. Butt joint and half lap joint bonding method are determined to be suitable when using Douglas fir lamina layer.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.279-288
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• 2008

In this study, the slip behavior of high-tension bolted joints subjected to compression force is investigated through 3D finite element analysis and experiments. The relation with sliding load, bolt deformation, and failure load are studied with the metal thickness affecting the bolted joint. The post-sliding behavior considering bolt stiffness is presented and compared with the results by finite element and experiments. The finite element model is constructed by solid elements in ABAQUS, in consideration of all the friction effects between metal plates and bolts. The stress-strain relations in the literature are used, and the sliding displacements and axial stresses around the bolt connection are investigated. The flexural buckling of species happened when the plate thickness is less than the bolt diameter. However, the shear failures of bolt occurred in the opposite case.

• Steel and Composite Structures
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• v.22 no.5
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• pp.937-974
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• 2016

While extensive efforts have been made in the past to develop finite element models (FEMs) for concrete-filled steel tubular columns (CFSTCs), these models may not be suitable to be used in some cases, especially in view of the utilisation of high strength steel and high strength concrete. A method is presented herein to predict the complete stress-strain curve of concrete subjected to tri-axial compressive stresses caused by axial load coupled with lateral pressure due to the confinement action in square and rectangular CFSTCs with normal and high strength materials. To evaluate the lateral pressure exerted on the concrete in square and rectangular shaped columns, an accurately developed FEM which incorporates the effects of initial local imperfections and residual stresses using the commercial program ABAQUS is adopted. Subsequently, an extensive parametric study is conducted herein to propose an empirical equation for the maximum average lateral pressure, which depends on the material and geometric properties of the columns. The analysis parameters include the concrete compressive strength ($f^{\prime}_c=20-110N/mm^2$), steel yield strength ($f_y=220-850N/mm^2$), width-to-thickness (B/t) ratios in the range of 15-52, as well as the length-to-width (L/B) ratios in the range of 2-4. The predictions of the behaviour, ultimate axial strengths, and failure modes are compared with the available experimental results to verify the accuracy of the models developed. Furthermore, a design model is proposed for short square and rectangular CFSTCs. Additionally, comparisons with the prediction of axial load capacity by using the proposed design model, Australian Standard and Eurocode 4 code provisions for box composite columns are carried out.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.18-25
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• 2012

This paper estimates the ductility of reinforced concrete columns according to configurations of transverse reinforcement. A total of 8 reinforced concrete columns were cast and tested in flexure. The test variables in this study were the configurations, yield strength, and amount of transverse reinforcement. The specimens had a cross-section of $250{\times}250mm$ and had a shear span-to-depth ratio of 4.1 to induce flexural failure. In the test, cyclic lateral load was applied to the specimens with a constant axial load. The experimental result indicated that the specimens with proposed configurations of transverse reinforcement showed higher ductility and energy dissipation capacity than the specimens with rectangular tie.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.97-104
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• 2014

Hollow slab is a floor system which reduces the load of vertical structural members and earthquake load by decreasing self-weight of slab. Although hollow slab can reduce self-weight of slab remarkably, flexural strength and shear strength reduce due to the hollow section inside the slab, so it is very important to predict structural behavior. In spite of plenty of domestic and foreign studies on hollow slab, there is a shortage of research on shear performance according to shear reinforcement of one-way hollow slab. Therefore, this study aims to verify the need for shear reinforcement of one-way hollow slab by analyzing failure modes of one-way hollow slab depending on the state of shear reinforcement and comparing shear strengths of estimation formula and experimental value with one another.