Seok Joon Jang

Insulation Type Effect on the Direct Shear Behavior of Concrete Sandwich Panel (CSP) with Non-Shear Connectors

Precast concrete sandwich panels (PCSP) are often used as exterior cladding of residential buildings due to thermal efficiency. PCSP systems consist of two precast reinforced concrete walls separated by a layer of insulation and connected with connectors which penetrate the insulation layer and are anchored at two precast walls. This paper provides the pull-out test results of concrete sandwich panel (CSP) with non-shear connectors. The variables in this study were the casting direction of reinforced concrete walls and types of insulation. Test results indicated that the types of insulations and casting direction have a significant effect on the bond strength between concrete wall and insulation. The effect of insulation type is notable for CSP cast horizontally concrete walls.

Effect of Fiber Volume Fraction on Compressive and Flexural Properties of High-Strength Steel Fiber Reinforced Concrete

The purpose of this study is to investigate the compressive and flexural properties of high-strength steel fiber reinforced concrete (SFRC). For this purpose, a total of 5 mixture whose variable is fiber volume fraction, were made and tested in a range of high strength with 70MPa. In case of normal and ultra-high strength, experimental results were collected from existing literatures on the tests conducted in South Korea. Flexural behavior of SFRC is enhanced according to the fiber volume fraction and compressive strength. Experimental and collected data were applied to existing equations, so it was found that the distinctions occurred between experimental or collected data and calculated values. Thus, more efforts are required to predict the flexural behavior of SFRC manufactured in South Korea with respect to the fiber volume fraction.

Effect of GFRP Shear Ties on Shear Behavior of Interfaces between Precast Concrete Panel and Extruded Polystyrene Special Insulation

This paper describes the test results on the direct shear behavior of glass-fiber reinforced polymer (GFRP) shear tie reinforced interfaces between precast concrete sandwich panels (PCSP) and extruded polystyrene (XPS) insulations. The insulated PCSP consists of two concrete panels with 100mm or 80mm thick insulation between inner/outer concrete panel layers. In order to achieve composite action concrete panels are connected by corrugated GFRP shear connector. In this study, three types of couple replicate insulated PCSP with different embedment length of GFRP shear connector were made and loaded in push-out. The test results indicated that the reinforcement of GFRP shear ties for interface between PCSP and XPS insulation improves initial and post-peak shear performance of insulated PCSPs. These phenomena are remarkable for XPS insulated PCSPs with larger embedment length of GFRP shear connectors.

Shear Reinforcing Influence of GFRP Shear Connectors in the Concrete Sandwich Wall Panel (CSWP) for Exterior Envelopes of Buildings

This paper summarizes the experimental results of concrete sandwich wall panels (CSWP)specimens under pull-out loading conducted to investigate the effect of insulation type and reinforcing area of shear connector made with glass fiber-reinforced polymer (GFRP) on the shear behavior of CSWP used as exterior cladding walls.In this study, two types of thermal insulations;expanded polystyrene(EPS)and extruded polystyrene with special slots(XPSS) and wave-shaped GFRP shear connectors with different reinforcing area; 6mm x 2mm and 12mm x 2mm were used for CSWP specimens.Test results indicated that the types of insulations and reinforcing area of GFRP shear connectors have a significant effect on the direct shear behavior between concrete wall and insulation. As reinforcing area of GFRP shear connector increase, increase in shear strength of CSWP with EPS insulation is less than CSWP specimens with XPSS insulation due to relatively lower strength of EPS compared to XPSS strength.

Direct Shear Responses of Insulated Concrete Sandwich Panels with GFRP Shear Connectors

This paper investigates shear flow strength of insulated concrete sandwich panels with glass fiber reinforced polymer (GFRP) shear connectors based on push-out test. The precast insulated concrete panels consist of 60mm concrete wall, 100mm insulation, and 130mm concrete wall. Two concrete walls were connected with GFRP corrugated shear connector. Four specimens with variables such as the insulation type and the width of GFRP corrugated shear connector were made. Failure modes, shear flow-deflection relationships and post-peak strength were investigated. Test results indicate that the specimens with EPS insulation show higher shear flow strength than those with XPSS insulation due to the relatively high surface roughness of EPS insulation, and the shear flow strength increased with increasing shear connector width.

Influence of Fiber Volume Fraction and Aggregate Size on Flexural Behavior of High Strength Steel Fiber-Reinforced Concrete (SFRC)

The effects of aggregate size and fiber volume fraction on the flexural behavior of 70MPa high strength steel fiber-reinforced concrete (SFRC) were investigated in this work. Test variables consist of fiber volume fraction (0, 1 and 2 %) and maximum aggregate size (8, 13 and 20 mm). The prism for flexural test was 100 x 100 x 400 mm and was tested under four points loading. Flexural toughness index was measured using ASTM C 1018 procedure. Test results indicated that the addition of steel fiber to 70MPa high strength concrete improves flexural and post-cracking behaviors. This phenomenon is remarkable for SFRC mixture with higher fiber content and smaller aggregate size. Also, the flexural toughness of high strength SFRC depends primarily on fiber content. The maximum aggregate sizes were secondary in importance.

Compressive Strength Effects on Flexural Behavior of Steel Fiber Reinforced Concrete

This paper presents results of experimental investigation to evaluation the effects of compressive strength on flexural behavior of steel fiber-reinforced concrete (SFRC). For this purpose, normal and high strength SFRCs with two different fiber volume fractions of 0.5 and 1.0% were prepared. Compressive strength, modulus of elasticity, flexural strength and toughness were measured with tests on SFRC cylinders and prisms. Test results indicated that steel fiber volume fraction significantly affects the flexural strength and toughness of SFRC. However, the high strength SFRC showed reduction in flexural toughness compared with the normal strength SFRC. It can be concluded that flexural behavior of SFRC depends on both compressive strength and fiber volume fraction.

Seismic Performance of Strain-Hardening Cement Composite (SHCC) Squat Shear Walls with vertical slits

This study investigates experimentally the applicability of selectively weakening retrofit for existing and non-ductile squat shear walls. To evaluate the effect of vertical seams on the wall panel on the hysteretic behavior and failure mode of Strain-Hardening Cement Composite (SHCC) squat shear walls, two 1/3 scale shear walls with vertical seams as a variable were made and tested under reversed cyclic loadings. All specimens had same rectangular cross-section 1,100mm¡¿50mm, with panel height 600mm. The vertical seam is 40mm wide and 260mm high and 460 high. SHCC for wall specimens was supplied by a local ready mix company with specified strength of 50MPa. The test results of this study; length of the slit is increased in squat shear wall, which the specimen became load-carrying capacity and stiffness. But have vertical silt, the squat shear wall shows aspects of ductility destruction.

Tensile and Cracking Behaviors of Strain-Hardening Cement Composite (SHCC) with Fluosilicate Based Shrinkage-Reducing Agent (SRA)

This paper provides the results of direct tensile tests for strain-hardening cement composite (SHCC) to investigate the influence of fluosilicate based shrinkage-reducing agent (SRA) on the tensile and cracking behaviors of SHCC material under direct tension. The specified compressive strength of the SHCC material is 50MPa. The adding ratio of fluosilicate based SRA for SHCC material is 2.5 and 5.0%. Two mixitures of SHCC with 2.2% polyvinyl alcohol (PVA) fibers at the volume fraction were mixed; two mixtures with SRA and one mixture of conventional SHCC material. To evaluate the tensile and cracking behaviors of SHCC materials, two dumbbell-shaped tensile specimens for each mixture were manufactured and tested in direct tension. Test results show that the addition of fluosilicate based SRA improved direct tensile and cracking behaviors of SHCC materials with rich mixture. This phenomenon is noticeable for SHCC with higher volume of SRA.

Flexural Behaviors of Double Reinforced Beam with High-Performance Cement Composite and Steel Bar

This paper describes the flexural behaviors of double reinforced beams with strain hardening cement-based composite (SHCC) materials and high-performance steel bar (HPSB). To evaluate the effects of cement composite type and strength on flexural response of reinforced beam, three specimens made and tested under monotonic flexural loading. Test results indicated that superior flexural and uniaxial performance with multiple fine cracking are observed for SHCC materials compared to those of conventional high strength concrete (HSC). Specifically, HPSB reinforced beam with SHCC materials exhibits more effectively crack-damage mitigation and flexural performance than that with HSC.