A Two-Level Comparative Assessment of Concrete Building Systems and Member Typologies

Concrete building systems require decisions at both the member and the building level, because locally efficient cross sections do not necessarily lead to a favorable whole-building response. This study presents a two-level comparative framework comprising (i) a member-level parametric assessment of nine reinforced-concrete and composite cross-section families across six concrete grades (54 scenarios) and (ii) a building-level ETABS assessment of seven structural configurations (Models A–G) derived from a residential reinforced-concrete frame benchmark. At the member level, the alternatives were evaluated based on axial resistance, along with simplified screening-level CO2 and cost proxies. At the member level, axial resistance increased with concrete grade, although the marginal benefit diminished at higher grades for steel-dominant layouts. Balanced composite sections showed the most favorable normalized strength-to-material-proxy trends, whereas steel-heavy alternatives provided high absolute resistance but lower overall efficiency. The comparison between the member-level hybrid-section screening and the building-level composite configuration further showed that promising local section behavior does not automatically translate into superior whole-building performance. At the building level, the compared configurations were assessed through vertical base reactions, modal properties, and top-level lateral displacement response. Replacing solid beams and columns with hollow members of identical outer dimensions reduced the self-weight-related base reaction from 9591 to 8832 kN (7.9%) but slightly increased the top-level displacement response, indicating a mass–stiffness trade-off. Larger improvements were obtained when the global lateral-force-resisting mechanism was modified directly: the braced configuration produced the shortest fundamental period (T1=0.433 s) and the lowest displacement response, while the core-wall configuration also reduced both period and displacement substantially. By contrast, the height-extended configuration produced the most flexible response among Models A–F. An additional exploratory variant with semi-rigid beam-to-column connections (Model G) confirmed that connection-level flexibility produces a measurable but moderate increase in period and displacement relative to the reference frame, without altering the global load-resisting mechanism. Overall, the results confirm that member-level and building-level assessments should be treated as complementary decision levels in early-stage structural design.