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This paper presents results from experimental studies on the seismic performance of RC-frame structures strengthened with glass-fiber-reinforced polymer (GFRP) infill panels. Three RC specimens were fabricated and then tested to evaluate the efficiency of the GFRP infill panels. The performance of GFRP infill panels installed in RC-frame structures was evaluated based on the results from measures of strength, failure mode, initial lateral displacement, displacement ductility and hysteretic dissipated energy. Both the strength and the initial lateral stiffness of the RC-frame structures strengthened with GFRP infill panels was greater than that of the un-strengthened specimen; however, the displacement ductility and energy-dissipation capacity of specimens strengthened only with GFRP infill panels decreased. This decreased-ductility issue was resolved by adding GFRP column reinforcement at the tops and bottoms of the columns. The strength, initial lateral stiffness, displacement ductility and energy dissipation capacity of the specimens strengthened with both GFRP infill panels and GFRP column reinforcement increased over the un-strengthened specimen. Finally, it is important that GFRP infill panels, if used together with GFRP column reinforcements, be considered in seismic-strengthening design in order to increase the seismic performance of existing RC-frame structures.

A mechanically post-installed anchor, which is one of the most widely used post-installed anchors in South Korea, was selected to evaluate long-term usage through a pullout test. Two types of specimens were constructed: the original specimens and freeze and thaw specimens. Mechanically post-installed anchors were installed in both of them. A freeze and thaw test method was utilized to consider the long-term usage. The compressive strength of concrete during the freeze and thaw test method is reduced by about 20% compared to that of the original concrete. From the pullout test results, the pullout strength of the freeze and thaw specimen was smaller by about 50% than that of the original specimens. Furthermore, the failure mode of the freeze and thaw specimens was changed. Cone shape destruction of anchors and anchor pullout destruction occurred in the original specimens; concrete pullout destruction occurred dominantly in the freeze and thaw specimens. Based on the comparison results, the reduction factor ( λ) for long-term usage of the mechanically post-installed anchor was derived using a probability function and was proposed to modify the concrete capacity design equation.

A seismic strengthening method using Velcro is proposed to improve the seismic performance of columns in RC frame structures. The proposed method was evaluated experimentally using three fabricated RC specimens. Velcro was wrapped around the columns of the RC-frame specimen to prevent concrete spall falling. The reinforcing performance of the Velcro was determined from comparison of results on seismic performance (i.e., strength, displacement, failure mode, displacement ductility capacity and amount of dissipated energy). As the displacement of the reinforced specimens was increased, the amount of dissipated energy increased drastically, and the displacement-ductility-capacity of the reinforced specimens also increased. The final failure mode of RC frame structure was changed. As a result, it was concluded that the proposed seismic strengthening method using Velcro could be used to increase the displacement ductility of RC columns, and could be used to change the final failure mode of RC-frame structures.

The acrylic pressure-sensitive adhesive (acrylic PSA) shows satisfactory adhesion to high-surface-energy substrates, such as glass, metal, and SUS, but it shows very low adhesion to low-surface-energy substrates, such as polyethylene, polypropylene, and polydimethylsiloxane (PDMS). To increase the adhesion strength of PSA to the low-surface-energy substrates, silicone dimethacrylate (SiDMA) was added to decrease the surface energy of the PSA, but it induced degraded peel strength due to plasticization and miscibility problems. In this study, various types of silicone urethane dimethacrylates (SiUDMAs) were synthesized by controlling the ratio of diisocyanate to PDMS to overcome the miscibility problem. As the ratio increased, their molecular weight and viscosity decreased, but their surface energy increased due to the reduced PDMS content. With the addition of SiUDMA2.0, which has a similar molecular weight to SiDMA, PSA showed 4- and 6-times higher loop tack and peel strength, respectively, on the PDMS substrate without UV curing. All types of SiUDMAs lowered the surface energy of the PSA and significantly increased the loop tack and peel strength on the PE, PP, and PDMS substrates. On the PDMS substrate, PSA that was modified with 20 wt% of SiUDMA2.0 and cured at 200 mJ/cm2 showed a peel strength of 520 gf/25 mm, which was more than 3 times higher than that of the control PSA (138 gf/25 mm). The shear adhesion failure test showed that SiUDMA2.0-modified PSA endured a temperature of 70 °C, which is higher than the 46.5 °C of the control PSA.

Damage of reinforced-concrete (RC) structures commonly occurs during major earthquakes, and becomes worse because of aftershocks. For these reasons, repair technology for seismic damage is needed to prevent possible collapse of damaged RC structures before aftershocks. In this paper, a seismic retrofitting device is proposed to improve the seismic performance of damaged RC columns using glass fiber–reinforced polymer (GFRP), which can be easy to install and quick to repair. The proposed GFRP-strip device consists of a GFRP-composite strip and aluminum clip connectors, used to increase the shear strength of the damaged column. Three RC specimens were constructed with reference to existing RC structures. Two of the specimens were damaged before installing the GFRP-strip devices. After the pretest damage was done, the GFRP-strip devices were installed along the plastic-hinge regions on both ends of the test columns. A comparison of the experimental results indicates that the seismic performance of th...