Hyun Do Yun

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.

Structural Health Monitoring Systems for a Steel Structure Using an Ambient Vibration

This study aims at identifying the structural dynamic characteristics using an ambient vibration, and developing a health monitoring system which adopts damage detecting algorithms. One of the main problems for this system design is to measure long-time dynamic response signals and simultaneously estimate the structural dynamic properties. In order to be suitable for a long-time monitoring, we conduct an ambient dynamic testing for a 3-floor moment resistance steel structure and analyze structural dynamic characteristics using time domain estimation techniques. Also, a damage detecting test is performed to evaluate damage state by various detecting algorithms (modal correlation method (MAC & COMAC), eigen-parameter change method). Finally, this paper suggests the optimal algorithms for the identification of the structural damage locations and damage quantities with all such comparisons. The algorithms presented in this paper prove to be applicable in structural health monitoring of structures.

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.

Using Acoustic Emission to Quantify Damage in High-Performance Fiber-Reinforced Cement Composites under Cyclically Compressive Loading

High performance fiber-reinforced cement composites (HPFRCCs) show multiple cracks and a limited damage tolerance capability due to the debonding of the fibers of the cement matrix. For practical applications, it is necessary to investigate the fractural behavior of HPFRCCs to understand the mechanism of the microbehavior of a cement matrix containing reinforcing fibers. We have investigated the acoustic emission (AE) signals in HPFRCCs under monotonic and cyclic uniaxial compressive loads. Four types of specimen were tested. The experimental parameters studied were: the type of fiber (polyethylene or polyvinyl alcohol), the hybrid type (with steel cord), and the loading pattern. The data shows that the progress of the damage in HPFRCCs in the compressive mode is characteristic of the type of hybrid fiber and its volume fraction. From the AE data, the second and third compressive load cycles resulted in a successive decrease in the amplitude compared to the first compressive load cycle. In addition, an AE Kaiser effect was observed in HPFRCCs specimens up to 80% of their ultimate strength. These observations suggest that the AE Kaiser effect has potential for use as a new tool to monitor the loading history of HPFRCCs.

Influence of Casting Temperature on the Heat of Hydration in Mass Concrete Foundation with Ternary Cements

This study is conducted to evaluate analytically the effect of casting temperature on the heat of hydration in mass concrete foundation with ternary cements and Type IV low heat cement. The mat foundation has the dimension of 15m length, 20m width and 3m depth. Casting temperatures considered for mat foundation consist of 10, 20 and 30C ̊. A commercial software MIDAS/Gen was used to analyze the hydration heat of mass concrete foundation. The maximum adiabatic temperature rise (K), and the coefficient of temperature rise˰˸α˹˰for thermal analysis were drawn from adiabatic temperature rise test. Analytical results show that blended cement PSLB_352 is the most effective to control the heat of hydration in mass concrete foundation and external temperature increases the maximum heat of hydration and crack probability of mat foundation with mass concrete.

Seismic Performance of Steel Fiber Reinforced Concrete (SFRC) Infill Wall Element with Vertical Slits for Strengthening of Non-Ductile Frame

This paper provides experimental results on the seismic performance of four concrete infill wall elements with test variables of vertical slits and hooked end steel fiber reinforcing. 1/3-scale infill wall elements with height-to-length ratio of 0.55 were manufactured and tested up to failure. Four walls (CIW-N and-S, SCIW-N and-S) are similar to each other except presence of steel fiber reinforcement and vertical slits with the width of 40 mm. All specimens had the same rectangular cross-section of 1,100 mm x 50 mm, with wall panel height of 600 mm. The experimental results showed that concrete infill wall element with vertical slits exhibited more stable hysteretic behavior than solid infill wall element. This phenomenon is remarkable for steel fiber reinforced concrete infill wall element. Inclusion of vertical slits on the normal concrete and steel fiber reinforced concrete infill wall element improve the ductility and energy dissipation capacity but decrease the load-carrying capacity and stiffness of infill walls.

Shear Behavior of Squat Steel Fiber Reinforced Concrete (SFRC) Shear Walls with Vertical Slits

Three 1/3-scale squat steel fiber reinforced concrete (SFRC) shear walls with height-to-length ratio of 0.55 were manufactured and tested up to failure. Two walls (SFRC-SS and-LS) are similar to each other except the height (230 and 460mm) of vertical slits with the width of 40mm. For comparison, solid wall (SFRC-NS) was made. All specimens had the same rectangular cross-section of 1,100mm x 50mm, with wall panel height of 600mm. The experimental results showed that squat SFRC shear walls with vertical slits exhibited more stable hysteretic behavior than a solid SFRC shear wall. Vertical slits on the squat SFRC shear walls improve the ductility and energy dissipation capacity but decrease the load-carrying capacity and stiffness of squat SFRC walls.