Kil-Hee Kim

Structural performance of spirally confined concrete with EAF oxidising slag aggregate

This study evaluated the behaviour of spirally confined concrete with electric arc furnace (EAF) oxidising slag aggregates. To investigate the structural performance of confined concrete containing EAF oxidising slag aggregates, 12 unconfined and 48 laterally reinforced specimens are casted and tested in this study. The test variables are the type of aggregates, yield strength of reinforcement and steel ratio of spirals. The strength and strain enhancement effects, stress–strain relationships and lateral expansion ratios relative to axial strain of the specimens with EAF oxidising slag aggregates are evaluated based on this experimental result. Furthermore, the experimental results are compared with analytical results obtained using previous formulas. Specimens with EAF oxidising slag aggregate showed similar enhanced strength to specimens with natural aggregate as well as superior enhanced ductility with increasing yield strength and steel ratio of spirals. Due to this trend for enhanced ductility, the accuracy of the previous formulas deteriorates in predicting the peak strain of the specimens with EAF oxidising slag aggregates.

Bond Behavior of RC Beams with Electric Arc Furnace Oxidizing Slag Aggregates

Abstract Electric arc furnace (EAF) slag is a by-product of steel production. Because the amount of slag produced is increasing each year, there is a growing need for effective methods of recycling this material. In this study, simple beam tests proposed by Ichinose were carried out to estimate the bond performance of reinforced concrete beams with EAF oxidizing slag aggregates. The main test variable was the type of aggregate used. A total of four specimens were designed to estimate the bond properties of top and bottom bars for the concrete. The bond test results revealed that the specimens with EAF oxidizing slag aggregates showed better bond performance than the basic specimen with natural aggregates. Furthermore, the experimentally observed bond strength of the specimens was compared with the theoretical results obtained from existing formulas. Consequently, the analytical results considering the effect of transverse reinforcement showed reasonable agreement with the experimental results.

Size Effect in Shear Failure of Reinforced Concrete Beams with Recycled Aggregate

This study evaluates the size effect of shear strength in reinforced concrete (RC) beams with various replacement ratios of recycled coarse aggregate. A total of 15 simply supported specimens with recycled aggregates were cast and tested in shear. The test variables were designed to be the width and effective depth of the beam and the replacement ratio of recycled coarse aggregate. The width of the specimens was varied from 200 mm to 400 mm, and the effective depth was changed from 300 mm to 600 mm. To estimate the size effect of shear strength in recycled aggregate concrete beams, the specimens had no shear reinforcement. The experimental results showed that the shear strength of the specimens made of recycled aggregate decreased with a higher effective depth irrespective of the replacement ratio, whereas the beam width exhibited no size effect. Furthermore, the strength reduction and crack patterns of the specimens with recycled aggregates were similar to those of the specimens with natural aggregates.

Flexural Behavior of Reinforced Concrete Beams with Electric Arc Furnace Slag Aggregates

Abstract This study estimates the flexural performance of reinforced concrete (RC) beams with electric arc furnace (EAF) oxidizing slag aggregates. EAF oxidizing slag is a byproduct of steel production. It is composed mainly of CaO and SiO2, which are similar to the chemical properties of natural aggregates. Simply supported RC beams having various types of aggregates were tested to evaluate the applicability of EAF oxidizing slag as a concrete aggregate. The moment-curvature relationship and crack patterns up to peak load as well as the effective moment of inertia and deflection of the specimens under service load were analyzed and compared with the experimental results of natural aggregate specimens. The experimental results showed that the specimens with EAF oxidizing slag aggregates exhibited similar flexural performance to that of the specimens with natural aggregates.

Flexural Performance of Reinforced High-Strength Concrete Beams with EAF Oxidizing Slag Aggregates

This study evaluates the flexural behavior of reinforced high-strength concrete beams with electric arc furnace (EAF) oxidizing slag aggregates. The main test parameters include the type of aggregates, compressive strength of concrete, and tension reinforcement ratio. A total of eight simply supported beam specimens subjected to four point loads are cast and tested in flexure. Two types of aggregates, natural and EAF oxidizing slag aggregates, are used in this study. The compressive strength of the concrete is designed to have normal- and high-strengths of 24 MPa and 100 MPa, respectively. The tension reinforcement ratios of beam specimens are 0.3 and 0.5 times the balanced reinforcement ratio for flexure. The experimental results indicated that the flexural strength of specimens was not affected by the type of aggregate, whereas the flexural ductility of specimens with EAF oxidizing slag aggregates was superior to that of specimens with natural aggregates, regardless of the compressive strength of concrete and the tension reinforcement ratio.

Bond Action Effect of Longitudinal Cut-Off Bars on Shear Transfer Mechanism of RC Beams

Abstract A method is proposed to estimate the required length of double-layered flexural reinforcing bars for reinforced concrete (RC) beams. This research deals with deep beams in which the shear reaction is dominant and the plastic hinge is not formed. The ACI (American Concrete Institute) and AIJ (Architectural Institute of Japan) guidelines propose several methods to determine the cut-off length of double-layered bars for typical foundation beams. However the theoretical and experimental bases are not yet presented. A series of experimental works was conducted to measure the bond strength of double-layered bars. A method to estimate the double-layered length and the shear strength of beams with small shear span-to-depth ratio is then developed based on the concept of the partial truss mechanism.

A Prediction Model for Bond Deterioration in RC Members. I: Bond Stress-Slip Behavior for Splitting Failure

AbstractThis study proposes a model to predict bond stress-slip behavior by conducting tests on RC members that experience splitting bond failure when subject to cyclic loading such as seismic load...

Evaluation of bond capacity of reinforced concrete columns with U-shaped transverse reinforcement

This paper presents the bond performance of reinforced concrete (RC) columns according to the confinement conditions of the longitudinal reinforcement. This study is carried out to evaluate the bond capacity of RC columns subjected to reversed cyclic antisymmetric moment under seismic load. The main parameters are the confinement conditions of the longitudinal reinforcement and the axial force ratio of the specimens. The overall performance of each specimen is examined in the shear force verse drift angle relationships and the crack patterns of the specimens. An analytical approach which can consider the bond strength of the longitudinal reinforcement is also used to predict the failure mode and the shear strength of the specimens. Experimental results showed that the bond strength of specimens is not affected by the axial force ratio. Furthermore, it can be found that the confinement of inner longitudinal reinforcement effectively increases the bond strength of RC columns by controlling the bond cracks.

Flexural Behavior of Reinforced Concrete Columns Using Electric Arc Furnace Oxidizing Slag Aggregates

This study is performed to evaluate the flexural performance of reinforced concrete columns with electric arc fur- nace oxidizing slag aggregates. Electric arc furnace slag is a by-product obtained from the process of refining scrap steel. The elec- tric arc furnace slag can be used as a concrete aggregate, because it mainly consists of CaO and SiO2, similar to natural rocks and minerals. Three rectangular columns with various types of aggregate were cast to test in flexure. All of the test specimens had a cross-section of 250 × 250 mm and a height of 1,500 mm in test region. The specimens were designed to apply reversed cyclic anti- symmetric moment and constant axial force. The experimental results showed that the specimens with electronic arc furnace oxi- dizing slag aggregates had superior flexural performance than the specimen with natural aggregates.

A Prediction Model for Bond Deterioration in RC Members. II: Bond Failure after Flexural Yielding

AbstractReinforced concrete (RC) structures are designed in such a way that flexural yielding precedes bond failure, in order to ensure the ductile behavior of members. When subject to cyclic loadi...