• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.147-153
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• 2019

The prestressing steel wire, which is applied a tension to reinforce the structure, is applied flexure simultaneously by the duct and the deviator. In order to evaluate the deflected tensile performance of the prestressing steel wire subjected to both tensile and flexural stresses, the numerical analysis for 600 cases with variables of wire diameters, mandrel diameters, and friction coefficient between mandrel and steel wire was performed. As the result of analysis, the larger the diameter of the steel wire was, the lower the deflected tensile performance was, and the effect decreased with the increase of the wire elongation. The effect of mandrel diameter and friction coefficient between mandrel and wire on the deflected tensile performance of the wire was very small. But the deflected tensile performance and the friction coefficient between mandrel and strand showed a relatively high correlation. Therefore, it is necessary to make enough large elongation to secure the deflected tensile performance. If there is a restriction on the elongation, it is necessary to reduce the diameter of the steel wire to an appropriate value, and to increase the friction between steel wires by adjusting the surface condition of the steel wire.

• Journal of Korean Association for Spatial Structures
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• v.20 no.2
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• pp.39-49
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• 2020

In this study, we will develop a hybrid cross-sectional shape of steel inserted type glued-laminated timber that can improve the strength of structural glued-laminated timber and maximize the ductility by using steel plate with excellent tensile and deformation ability. A total of three specimens were fabricated and the flexural performance test was carried out to evaluate the structural performance of the steel inserted type glued-laminated timber. In order to compare the effect of steel inserted glued-laminated timber, one structural glued-laminated timber test specimen composed of pure wood was manufactured. In addition, in order to evaluate the adhesion performance of the steel inserted, one each of a screw joint test specimen and a polyurethane joint test specimen was prepared. As a result, all the specimens showed the initial crack in the finger joint near the force point. This has been shown to be a cause of crack diffusion and strength degradation. The use of finger joints in the maximum moment section is considered to affect the strength and ductility of the glued-laminated timber beam. Polyurethane-adhesive steel inserted glued-laminated timber showed fully-composite behavior with little horizontal separation between the steel plate and glued-laminated timber until the maximum load was reached. This method has been shown to exhibit sufficient retention bending performance.

• Land and Housing Review
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• v.6 no.3
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• pp.129-138
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• 2015

The building structure in Korea is planned to maximize the use of space in recent. The hybrid OCB(Optimized Composite Beam) beam is developed to take advantage of using the space. The OCB beam is composed of the steel H-beam section reinforced by open strands in negative moment zone and the pretensioned PSC concrete section in positive zone. Flexural behavior of typical architectural hybrid OCB beam section was investigated by F.E.M. The 15m, 20m, 30m OCB models were tested on nonlinear material and geometry under static loading system. Following results are obtained from the analysis; 1)The OCB beam develop initial flexural cracking over full service loading. 2)Overall deflections of OCB beam under the service loads are less than those of the allowable limits in KCI Code(2012). 3)The ultimate load capacity get over the nominal strength of the OCB main section. The OCB beam is verified of structural reliability from the finite element analysis.

• Journal of the Korea Institute of Building Construction
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• v.20 no.4
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• pp.305-311
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• 2020

Polymer modified cement mortar (PCM) can improve the performance of adhesion strength, flexural strength, chemical resistance, etc., compared with cement mortar, and is widely used when repairing RC structures. However, PCM causes a burst in an environment with high temperature and fire rate, which causes problems in the stability of the structure. In this study, for the purpose of developing explosive reduction PCM, the polymer mixing ratio is 2%, 4%, 6%, the fiber length is 6mm, 12mm, 6+12mm, and the PP fiber mixing rate is 0.05 Vol% and 0.1 Vol%. Furnace heating experiment (600℃, 800℃) was carried out. As a result of comparative analysis of the explosive properties, it was confirmed that the explosive reduction effect due to the fiber incorporation was insufficient when the polymer mixing amount was 6% or more.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.95-103
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• 2012

In order to improve the dimensional stability and mechanical performance of cement-based composites, the effect of an expansive admixture based on calcium sulphoaluminate (CSA) on the shrinkage and mechanical properties of strain-hardening cement-based composite (SHCC), which exhibits multiple cracks and pseudo strain-hardening behavior in the direct tension, is investigated. Polyethylene fibers reinforced SHCC mixtures with three levels (30, 70, and 100MPa) of compressive strength were compared through free shrinkage, compressive strength, flexural strength, and direct tensile strength measurements. The SHCC mixtures were cast with and without replacing 10% of Portland cement content with CSA admixture. According to test results, CSA admixture is effective in reducing shrinkage of SHCC material. SHCC mixture with CSA admixture exhibited a little higher strength than companion mixture without CSA admixture.

• Journal of Korean Society of Steel Construction
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• v.29 no.3
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• pp.249-260
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• 2017

In order to investigate the structural performance of a novel prefabricated-SRC column using bolt-connected steel angles(PSRC column), eccentric axial loading tests were performed for six PSRC column specimens and two conventional SRC column specimens. The test parameters were the spacing and sectional configurations of lateral reinforcement, and eccentricity ratio of axial load. The test results showed that, due to high axial-stiffness of the angles located at the corners of the cross section, the compressive load-carrying capacity and deformation capacity of the PSRC specimens were greater than those of the SRC specimens in the large eccentricity ratio of axial load. Closely spaced lateral steel plates and Z-shaped lateral steel plates improved lateral confinement, which increased the load-carrying capacity of the PSRC specimens. The combined flexural and axial load-carrying capacity of the specimens by tests and nonlinear numerical analysis were greater than the predictions by current design codes. The numerical analysis agreed well with the test results including the initial stiffness, peak strength, and post-peak strength degradation.

• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.85-94
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• 2005

Post-tensioned Precast concrete System(PPS) consists of U-shaped precast wide beams and concrete column. The continuity of beam-column joint is provided with floor concrete cast on the PC shell beam and post-tensioning. The purpose of this paper is to evaluate the response of PPS interior beam-column joint subjected to cyclic lateral loading. To this end, an experimental investigation was performed with three half-scale specimens of interior connection. The design parameters are the amount of beam reinforcement placed inside the joint core. The test results showed that cracks were distributed well without my significant degradation of strength and ductility. Also, it was found that the prestressing may affect to alter the torsional crack angle. And the specimens sufficiently resist up to limiting drift ratio of 0.035 in accordance with the provisional by ACl of acceptance criteria for concrete special moment frames.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.438-444
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• 2019

In this study, the effect of polypropylene fiber on the freeze-thaw damage of mortar was evaluated experimentally. The effects of the reinforcing of polypropylene fiber on the compressive and bending performance of mortar after 300 cycles of freeze-thaw test were evaluated by comparing the normal mortar and the mortar with polyvinyl alcohol fiber. In addition, the mass loss, relative dynamic elastic modulus, and cumulated pore volume of mortar were measured by each cycle of freeze-thaw test. As a result, it was confirmed that the fiber reinforced mortar, regardless of the fiber type, was effective not only in maintaining the performance of the compressive strength and the bending strength but also suppressing the mass loss after the freeze-thaw test of 300 cycles. Meanwhile, it was confirmed that not only polyvinyl alcohol fibers but also polypropylene fibers can effectively act to suppress the damage of the mortar by freeze-thaw. However, in order to improve the freeze-thaw resistance of mortar mixed with polypropylene fiber, it is necessary to increase the bonding performance with the cement matrix which can be expected from polyvinyl alcohol fiber.

• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.271-282
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• 2008

Specific joint devices composed of end-plates and through bolts are under development to assemble steel beams to PC columns efficiently by dry construction method for the PCS structural system, of which major structural components are precast concrete columns and steel beams. Seismic performance of the joint devices had been evaluated by experimental tests in the previous studies and it was showed that all the performance requirements regarding to strength deterioration, stiffness degradation and energy dissipation capacity were satisfied to the criteria of ACI requirements, but the initial stiffness was not. In order to find out possible causes of the insufficient rigidity of the joint devices and provide the proper measures to improve the performance of the joint accordingly, numerical analyses were carried out by using ABAQUS. Parameters, such as thickness of neoprene pad, conditions of surface between PC column and end-plate, magnitude of pretension forces of through bolts, stiffness of end-plate were taken into consideration. As the result, it was found that the rigidity of the PCS system was negatively affected by the magnitude of initial gaps between PC columns and end-plates, and insufficient stiffness of neoprene fillers and end plates. In order to improve the initial stiffness performance of the joints, measures such as increase of the magnitude of pretension forces on through bolts and increase of the stiffness of end-plate by reducing the bolt pitch and providing adequate stiffeners are recommended.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.9-14
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• 2017

In the present work, a mechanical performances under cyclic loading in RC (Reinforced Concrete) beams with normal steel and FRPH (Fiber Reinforced Plastic Hybrid) bar are investigated. For the work, RC beam members with $200{\times}200{\times}2175mm$ of geometry and 24 Mpa of design strength are prepared, and 4-point-bending tests are performed for evaluation of cracking, yielding, and ultimate loads. Through static loading test, 48.9kN and 36.0 kN of yielding loads are measured for normal RC and FRPH beam, respectively. They have almost same ultimate load of 50.0 kN. Typical tension hardening behavior is observed in FRPH beam, which is caused by the behavior of FRPH bar with tension hardening. In cyclic loading conditions, FRPH beam has more smaller crack width and scattered crack pattern, and it shows more elastic recovery than normal RC beam. The energy dissipation ratio in FRPH beam is 0.83, which is greater than 0.62 in normal RC beam and it shows more effective resistance to cyclic loadings.