Strength Evaluation of Concrete Columns with Cross-Sectional Holes

Abstract

Today, concealing a longitudinal circular rainwater pipe in the center of a column cross section is common practice in the construction of skeleton RC frames. This research studies the strength reduction caused in short braced columns and the effect of factors that will increase or reduce the strength change. Sixteen columns (1 × 1 × 5 mm) were tested to investigate the effects of the hole:cross section ratio (i.e., the ratio of the hole to the cross section), concrete compressive strength, main reinforcement ratio, and ties spacing on the axial load capacity of the columns. The longitudinal and lateral deformations of the columns were measured to determine the first crack appearance and elastic work of the columns. The test results show that changing the hole diameter within the cross-sectional area has a major significant effect on load carrying capacity, in which a 5 and 1.8% reduction in the cross-sectional area caused a decrease of 2 and 1% in bearing strength capacity, respectively. However, increasing the concrete compressive strength and the reinforcement ratio does not show a considerable effect, whereas the spacing of the ties has a minor effect on the results.