Hyun-Su Seo

Performance Evaluation and Analysis Model for the Post-Installed Anchor

The post-installed anchors were installed in non-cracked concrete. And then pullout and shear strength of the anchor were investigated. The test of pullout and shear was conducted torque, diameter and insertion depth of the anchor. If it subjected to pullout load, the performance of it was affected by torque, diameter and insertion of anchor. It it subjected to shear load, the performance of it was affected by diameter and insertion of anchor, but torque was less affected. In failure mode of pull-out test, steel failure of the anchor and concrete cone failure occur. And shear failure mode, most of the tests showed shear failure of the anchor. A commercially available finite element program, ABAQUS, is used in this study, and then the behavior of pull-out of anchor were analyzed. When the interpretation of the available anchor system are derived for finite element modeling of concrete structure, interpreted the resulted with the installation of a target anchor for a relatively accurate prediction was possible.

The Properties of Durability and Strength of Fiber-Reinforced Polymer-Modified Mortars Using Eco-Friendly UM Resin

ABSTRACT In this study, performance of fiber-reinforced polymer-modified mortar was studied for the development of eco-friendly materials for high performance repair and reinforcement. The general cement mortar and eco-friendly UM resin was mixed with a certain percentage for increased durability. To increase the strength of the polymer-modified mortar, PVA fiber, steel fiber and hybrid fiber were added at a constant rate. Hybrid fiber is contains the same percentage of PVA fiber and steel fiber . In order to determine the strength properties of fiber-reinforced polymer-modified mortar, the compressive strength test, the splitting tensile strength test and the flexural strength test were performed. And, in order to determine the durability properties of fiber-reinforced polymer-modified mortar, water absorption test and chemical resistance test were performed. From the experimental results, polymer-modified mortar using UM resin was improved durability. And the tensile strength and flexural strength increased, which were the vulnerability of fiber reinforced polymer-modified mort ar. From this study, fiber-reinforced polymer-modified mortar u sing eco-friendly UM resin can be used to repair and reinforcement for the external exposure of concrete structures to improve the durability.

Evaluation of Damaged RC Columns with GFRP-Strip Device

AbstractDamage 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...

Experimental Study on Torsional Behavior of RC Beam with High Strength Stirrup

In this study, the behavior of the reinforced concrete beams according to the strength of the stirrups and the spacing of the stirrups was evaluated through experiments. From the experiment results, the torsional strength was almost the same even if the strength of stirrup was as large as 20 %. When the spacing of the stirrups doubled, the maximum torsional moment was reduced by about 16 %. However, the twist angle at the occurrence of the maximum torsional moment increases by about 50 % as the spacing of the stirrup decreases. It is considered that the spacing of the stirrup increases the ductility behavior of the RC beam by increasing the number of effective stirrup in the torsional behavior of the RC beam.

Long-term performance of mechanically post-installed anchor systems:

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.

Analysis of Nonlinear Torsional Behavior for High Strength Reinforced Concrete Structure Using 3-Dimensional Lattice Model

Because of earthquakes that have recently struck, seismic design criteria that considered performance of structure were included in the design concepts. Thus, a simple analysis tool is needed to predict the strength and ductility of RC structures. In this study, three-dimensional lattice model was developed to expand the two-dimensional lattice model. Torsional analysis of the structure was done to evaluate the developed three-dimensional lattice model. Lattice model was evaluated by comparing analytical results with experimental results. Lattice element size was evaluated using the results of analysis. Torsional analysis results, using three-dimensional lattice model, show that the results are relatively consistent with the experimental values.