Conventional spiral-type transverse reinforcement is effective at increasing the ductility and the maximum strength of reinforced concrete (RC) columns because it confines the inner concrete and the longitudinal reinforcement. However, when arranging crossties in a RC column with spirals, problems such as mutual interference with longitudinal reinforcement, overcrowding of reinforcement, and deterioration of constructability occur. Furthermore, the loosening of 90 and 130-degree standard hooks due to the lateral expansion of concrete causes buckling of the longitudinal reinforcement. This paper describes the ability of a newly developed spiral-type transverse reinforcement with various yield strengths to confine RC columns subjected to cyclic lateral load and constant axial load. The ductility capacity, energy dissipation, and effective stiffness of RC columns confined by the developed spiral-type transverse reinforcement were compared with those of RC columns confined by typical rectangular reinforcement. The experimental results showed that RC column specimens with the developed spiral-type transverse reinforcement have better performances in terms of ductility capacity and energy dissipation, even though the amount of reinforcement used for the specimens decreased by about 27% compared with the specimen with typical rectangular reinforcement.
In the present study, pull-out and pull-off tests were conducted to examine the bond strength between an inorganic cement adhesive (hereinafter referred to as the “matrix”) and a textile, which composed a fabric-reinforced cementitious matrix (FRCM). The matrix was developed by mixing slag and short fibers in an attempt to improve the alkali resistance and compressive strength. The developed matrix was examined with regard to its alkali resistance, water resistance, and void distribution. Bond tests were conducted in two parts: a pull-out series and pull-off series. The type of textile (carbon or basalt) and the weaving methods were selected as test parameters. These tests were performed in accordance with the methods described in ISO10406-1 (pull-out) and ASTM C1583 (pull-off). The test results showed that the developed matrix was superior to existing mortar methods in terms of alkali resistance, water resistance, and compressive strength. Additionally, the FRCM in which carbon textiles were used exhibited excellent bond performance.
This study was conducted to evaluate the flexural performance of hollow core slabs (HCS) incorporating the effect of surface roughness. The HCSs are suitable for long span structures due to reduced self-weight. The specimens were HCS with topping concrete and the variables were cross sectional height and surface roughness. The tests were conducted on simply supported beams under four-point loads. The results showed that specimens with interface roughness applied in the lengthwise direction of members exhibited ductile flexural behavior up to peak load than those with interface roughness applied in the member width direction. Their flexural strength was also higher by 1–7% on average, indicating that they are advantageous in improving structural performance.
In general, the lateral confinement capacity of RC columns is influenced by the strength and configuration of transverse reinforcement. In this study, performed antisymmetric flexural moment experiments that simulated seismic loads, with the configuration and yield strength of the transverse reinforcement of RC square columns as main variables. The eight specimens were square cross-sections measuring 250 × 250 mm, and the lateral confinement effect in relation to main variables was examined by inducing flexural failure in the plastic hinge zone under a shear span-to-depth ratio (a/D) of 3.0. Transverse reinforcements comprised a square and octagonal S-series and tie-based H-series. The yield strengths of the transverse reinforcements were 453 MPa and 1053 MPa, respectively. Compared to the H-series, the S-series, whose configuration of transverse reinforcement is closer to a circular form, exhibited more prominent ductile behavior after flexural yield with increasing yield strength of transverse reinforcement, which indicates greater lateral confinement.
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