No abstract

A hollow reinforced concrete (RC) column has been used to obtain a more economical design by reduction of the material or the self weight of the column. Although a hollow RC column offers a high effectiveness of section properties, it may show poor ductility owing to brittle failure at its inner face. In order to develop a more economical and safer model for a RC column, an internally confined hollow (ICH) RC column and its non-linear concrete model were proposed with the considerations of confining effects. To determine the relation of stressstrain for the concrete in an ICH RC column, possible failure modes of the column were investigated and the confining pressure was derived from equilibriums for each failure mode. A computer program was developed with respect to the derived equilibrium equations and parametric studies were performed to evaluate the application of the developed program. The ICH RC column significantly improved its strength and ductility by the internal confinement.

No abstract

In this study, coating equipment for the effective underwater repair of submerged structures was developed. The tensile bond characteristics of selected epoxy resin coatings were investigated by coating the surface of a specimen using each of the four types of equipment. Using the experimental results, the tensile bond strength and the coating thickness were analyzed according to the type of equipment, coating, and curing time. The results show that the type of coating equipment used had the greatest effect on the measured bond strength and coating thickness of the selected coatings. However, the effect of coating type and curing time on the bond strength and the thickness was observed to be insignificant. Compared with the developed equipment, the surface treatment of the coating was observed to be more effective when using the pre-existing equipment, and thus the bond performance of the coating was improved compared to using the pre-existing equipment. Based on the experimental results, improvements and needs involving the equipment for further research were discussed.

No abstract