Environmental and circularity assessment of optimized long‐span steel structures

Abstract

This study integrates structural optimisation, cradle‐to‐cradle life cycle assessment (LCA), and circularity evaluation to examine how span configuration, material choice, and steel production routes affect the whole‐life environmental performance of multi‐storey office buildings. A seven‐storey steel‐concrete composite office building (40.5 m × 16.5 m plan, 3.5 m storey height) is optimised using a genetic algorithm‐based Virtual Design Platform to define grid layout, slab orientation, and member sizing. Three scenarios are assessed: (1) low‐carbon steel with low‐carbon concrete, (2) low‐carbon steel with standard concrete, and (3) conventional steel with standard concrete. LCA follows EN 15978 (modules A1–A3, A4, C2–C4, D) using EPD and GaBi data, while circularity is evaluated with One Click LCA. Results show the product stage dominates GWP, with slabs as the main hotspot. The low‐carbon scenario achieves the lowest GWP (3.44× 105 kgCO2e). Circularity scores are similar across variants due to concrete's mass share, despite >90% circularity for steel. Limited disassembly potential (6.78%) restricts reuse. Integrating low‐carbon materials with circular design is therefore essential to reduce embodied impacts and enhance reuse potential.