• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.155-156
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• 2020

The purpose of this study is to evaluate tensile performance of cementitious composites reinforced with steel fiber. The tensile performance of steel fiber reinforced cementitious composites is related to the tensile performance of reinforced fiber, and depends on the fracture or pull-out of fiber. Therefore, the tensile performance was compared and analyzed by conducting a direct tensile test on the tensile specimens of cementitious composites reinforced with hook-type steel fiber and amorphous steel fiber.

• Journal of Korean Society of Steel Construction
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• v.21 no.1
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• pp.45-53
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• 2009

More than 40% of railway bridges on the conventional lines in Korea consist of track-on-steel plate girder (TOSPG) bridges. This type of bridge is typically designed without considering seismic loadings, as most of them were built before 1970. The seismic performance of this particular type of bridge could be upgraded through various seismic retrofit schemes, and seismic risk assessment could play a key role in decision-making on the level of the seismic retrofit. This study performed a seismic risk assessment of TOSPG bridges in Korea. The seismic damage of several crucial components of TOSPG bridges--fixed bearings, free bearings, and piers--were probabilistically estimated, and their seismic fragility curves were developed. The probability that the components would exceed their predefined limit states was also calculated by combining the fragility curves and the seismic hazard function. The analysis showed that the piers of TOSPG bridges, which are made of plain concrete without rebars, have relatively low risk against seismic loadings in Korea. This is because the mass of the superstructures of TOSPG bridges is relatively small, and hence, the seismic loading being transferred to the piers is minimal. The line-type bearings typically used for TOSPG bridges, however, are exposed to a degree of seismic risk. Among the bearings, the probability of the free-end bearings and the fixed-end bearings exceeding the slight damage state in 50 years was found to be 12.78% and 4.23%, respectively. The gap between these probability values lessened towards more serious damage states. This study could effectively provide an engineering background for decision-making activities on the seismic retrofit of railway bridges.

• Journal of the Korea Institute of Building Construction
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• v.18 no.2
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• pp.99-107
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• 2018

The objective of the present study is to propose a reliable shape of supplementary V-ties in the section jacketing approach for seismic strengthening of reinforced concrete columns. A total of 24 pull-out specimens were prepared. The test parameters selected with regard to bond strength of V-ties were the shape of V-ties, embedment length of V-tie legs, and compressive strength of concrete. The measured bond strength of V-ties with different shapes were compared with that of the conventional V-ties and predictions using CEB-FIP equation. Ultimately, V-ties with pressed end-details at their legs could be recommended for the supplementary lateral reinforcement of strengthening columns with jacketing thickness less than the embedment length [= max (75mm, $6d_b$)] of conventional V-ties, where $d_b$ is the diameter of the reinforcing bar used for V-ties.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.461-469
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• 2011

In this study, the effect of polyvinyl alcohol (PVA) fiber volume fraction on the pullout behavior of structural synthetic fiber in hybrid structural synthetic fiber and PVA fiber cement composites are presented. Pullout behavior of the hybrid fiber cement composites and structural synthetic fiber were determined by dog-bone bond tests. Test results found that the addition of PVA fiber can effectively enhance the structural synthetic fiber cement based composites pullout behavior, especially in fiber interface toughness. Pullout test results of the structural synthetic fiber showed the interface toughness between structural synthetic fiber and PVA fiber reinforced cement composites increases with the volume fraction of PVA fiber. The microstructural observation confirms the incorporation of PVA fiber can effectively enhance the interface toughness mechanism of structural synthetic fiber and PVA fiber reinforced cement composites.

• Composites Research
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• v.15 no.4
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• pp.17-22
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• 2002

Small diameter composite helical springs (CS) are developed using a hot plated mold for reinforcement of common optical fiber jumper cord (OJC). The outer diameters of the springs are about 2 ~ 3mm. These springs are inserted into the OJC to protect the damage of an optical fiber from the sudden lateral load. Two types of CS, Yarn type (Y-type) and Band type (B-type), are manufactured to compare the effectiveness for the damage protection. The experimental works were conducted to check the effect of the CS covered around OJC on the mechanical and optical properties. Experimental observations show a considerable effect on the flexural resistance, hence slowing down the deterioration of the optical power by the internal damage of the fiber. Obtained main results are as follows: (1) Y-type CS has better protection abilities to lateral loading than B-types. (2) Compared with bare OJC, CS-OJC has less power loss under the loading. (3) OJC covered with the composite coil spring has a possibility for a practical usage with full fruits.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.191-198
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• 2010

This study investigated that the stress reduction of single edge cracked plates with patch repairs according to different type of patching such as material, size and thickness of patch and adhesive as well as single sided or double sided patches. As a numerical tool, the p-convergent partial layerwise model has been employed. The proposed model is formulated by assuming piecewise linear variation of in-plane displacement and a constant value of out-of-plane displacements across thickness. The integrals of Legendre polynomials are chosen to define displacement fields and Gauss-Lobatto numerical integration is implemented in order to directly obtain maximum values occurred at the nodal points of each layer without other extrapolation techniques. Also, total strain energy release rate method is adopted to obtain stress intensity factors. Numerical examples are presented not only to demonstrate the stress reduction effect in terms of non-dimensional stress intensity factor and deflection with respect to different type of patch repairs, but also the accuracy of proposed model.

• Journal of Korean Society of Steel Construction
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• v.24 no.2
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• pp.149-161
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• 2012

The use of seismic energy-dissipative devices for passive control is increasing exponentially in the recent years for both new and existing buildings. Use of these devices started in and has been somewhat limited to developed countries. One of the current challenges is to promote the use of seismic dampers in earthquake-prone developing countries by lowering the cost of the devices. This paper proposed a new type of seismic damper based on yielding of a cantilever type metallic element for seismic retrofit of existing and new building structures. The hysteretic behavior and energy dissipation capacity of the proposed damper was investigated using component tests under cyclic loads. The experimental results indicated that the damping device had stable restoring force characteristics and a high energy dissipation capacity. Based on these results, a simple hysteretic model for predicting the load-displacement curve of the seismic damper was proposed.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.71-80
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• 2015

Steel stiffener is required for reinforcing the structure of the window frame made of versatile but weak PVC material. Steel stiffener however becomes a source of greater heat loss and frequently plays a role of thermal bridge due to its high thermal conductivity. To maintain thermal resistance similar to PVC frame, steel stiffener is perforated to reduce the effective heat transfer area. To compensate the structural strength of the steel stiffener which is weakened by the perforation, the thickness is increased. Increase in thickness will also increase the thermal heat resistance. Five samples which are PVC frame, PVC frame + original steel stiffener, PVC frame + 30% perforated steel stiffener, PVC frame + 50% perforated steel stiffener, PVC frame + 65% perforated steel stiffener are modeled and simulated for 2nd moment of area and thermal resistance. Therm/window version 6.3 is used for thermal analysis. The results show that among the five samples analyzed, PVC frame + 65% perforated steel stiffener best satisfies both structural strength and thermal resistance.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.197-208
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• 2000

Choi et al./sup 1)/ presented the total Lagrangian formulation based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors and taking into account the second order rotation terms in the incremental displacement field. Assumed strain concept is adopted in order to overcome the shear locking phenomena and to eliminate the spurious zero energy mode. In this paper, for the ultimate strength analysis of stiffened shell structures considering effects of residual stresses, the return mapping algorithm based on the consistent elasto-plastic tangent modulus is applied to anisotropic shell structures. In addition, the load/displacement incremental scheme is adopted for non-linear F.E. analysis. Based on such methodology, the computer program is developed and numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with the results in literatures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.121-128
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• 2014

In this study, The purpose of this study is to experimentally investigate the shear behavior of reinforced flat plate embedded with GFRP(glass fiber reinforced polymer) plate with openings. The GFRP shear reinforcement is manufactured into a plate shape with several openings to ensure perfect integration with concrete. The test was performed on 7 specimens. the parameters include the type of reinforcement and amount of the shear reinforcement., From the test, we analysed the crack, failure mode, Strain, load-displacement graph. a calculation of the shear strength of reinforced flat plate with GFRP plate based on the ACI 318-11 was compared with the test results. The results of the experiment indicate that GFRP plate is successfully applied as a shear reinforcement in the flat plate under punching shear.