A comparative study of environmental performance between CFST and RC columns under combinations of compression and bending

To better understand the environmental performance of columns and assist construction designers in achieving a balance between structural requirements and environmental protection, this paper assessed and compared the EI of columns constructed with two concrete types (CFST and RC) and three cross-sections (circular, rectangular and square) under different combinations of compression and bending. The BEPAS model categorized the columns' EI into two safeguard areas-ecosystem and natural resources, and then expressed the impacts using the EIV index in unit of “yuan”. Based on the assessment results and M-N interactive curves, M-N-EI interactive curves were developed to present the EI of columns under various combinations of axial force (N value) and bending moment (M value). Thus, structural performance and environmental performance can be shown in a single figure to conveniently contribute decision-making. The M-N-EI interactive curves were also compared to optimize choices of environmentally friendly concrete types and cross-sections to satisfy structural bearing capacity requirements. Moreover, the influences of various parameters, the H/B of rectangular columns, steel ratio of RC columns, steel strength, steel recycling rate and solid waste recycling rate, were analyzed. An engineering scenario was served as a case study to test the application and operation of the assessment methodology and M-N-EI interactive curves. The results indicate that the new curves can effectively express the EI of columns under different combinations of compression and bending and can potentially be used by the construction industry to achieve environmental goals and provide clear implications for practice.