Experimental Tests on High-Strength Concrete Columns Subjected to Combined Medium Axial Load and Flexure

摘要

To resist large deformability demand due to earthquake attack, high strength concrete (HSC) columns of tall buildings in high seismicity regions are designed to be fully ductile by providing heavy confining steel in the plastic hinge region. However, in areas of low to moderate seismic risks, where the columns are subjected to reduced seismic demand, the same provision of confining steel causes unwanted increase in construction cost (i.e. less cost effective) and embodied energy or carbon level of the structures (i.e. less environmentally friendly). Especially for ultra-HSC columns, the required confining steel will be too large to be provided in the plastic hinge region, which adversely affects the concrete placing quality. To alleviate the problem, a series of experimental tests on HSC columns that contain less confining steel than that of fully ductile columns in the plastic hinge region was carried out to investigate their performance under medium axial load and flexure. From the obtained test results, it was found that these columns perform better than the HSC columns without sufficient confining steel. Also, the drift of these columns can reach about 3% and the respective curvature ductility factors of about 10.