ABSTRACT

The shear strength of reinforced concrete (RC) columns are generally known to be affected by the strength and quantity of shear reinforcements. However, the bond strength of RC members is greatly affected by the amount of shear reinforcements, whereas it is insensitive to the yield strength of the shear reinforcement. Therefore, using high-strength shear reinforcements can lead to the bond failure of RC columns.
This study estimates the bond behavior of RC columns with various axial force ratio and the detailing of transverse reinforcement under cyclic loading to investigate the effective application of high-strength transverse reinforcing bars. The experimental results showed that the specimens with the same transverse reinforcement ratio exhibited similar bond behavior, regardless of the yield strength of shear reinforcements. The test results also confirmed that confining the longitudinal re-bars bars by the proposed U-shape unclosed reinforcements greatly improved the bond performance of RC columns.

This study consists of four chapters, and the contents of each chapter are as follows:

▣ Chapter Ⅰ: Introduction

▣ Chapter Ⅱ: Investigation of previous study

▣ Chapter Ⅲ: Evaluation of bond performance of RC
columns according to detailing of
transverse reinforcement

▣ Chapter Ⅳ: Discussion of test results

▣ Chapter Ⅴ: Conclusions

Based on the cyclic load tests of nine RC columns with various axial force ratio and the detailing of transverse reinforcement, the following conclusions were derived:

1. The B-type specimens with the internal and external longitudinal reinforcements confined by closed hoops had an enhancement of 60% in bond capacity compared to the A-type specimens confined by only the external longitudinal reinforcements.


2. The C-type specimens with internal longitudinal reinforcements effectively confined by the proposed unclosed U-shape reinforcement had superior bond capacity than the A-type specimens by 48%.

3. When the axial force ratio increased from 0% to 15%, the strength enhancement of the specimens was not significantly affected by the detailing of transverse reinforcement. On the other hand, the maximum bond stress increased when the internal longitudinal reinforcements were confined by transverse reinforcements.