Environmental-mechanical performance of steel-concrete composite columns under compression-bending loads based on life-cycle assessment

To comprehensively assess the mechanical and environmental performance for steel-concrete composite columns, the moment-axial force-environmental impact interaction curves of concrete-filled steel tube (CFST) and steel tube confined concrete (STCC) with two cross-sections (circular and square) are obtained by OpenSEES and analyzed in detail. The results show that higher mechanical requirements obviously increase higher load on the environment, which could be relieved by a proper structural configuration. By considering the environmental performance in structural design, the CFST column is the preferable choice than STCC and normal reinforced concrete columns in engineering practice. Higher strength of both steel and concrete is rather beneficial to the environmental-mechanical performance of columns. For square CFST columns, the degree of improvement for the same EI increase is on average 5.77% higher for axial resistance and 4.78% lower for moment resistance than for circular CFST columns. The CFST columns with a high demand for moment resistance will have more environmental impact than those with a high demand for axial resistance. It is preferable to use more steel for reinforcement to improve the mechanical performance after the peak lateral restraint force of the steel tube has reached in STCC columns. With high strength concrete, STCC is also a good choice, given the ease of construction and the superior connection features.