An Activity-Based Costing Framework for Occupational Safety and Health Management Costs in Modular Building Installation

Modular building installation concentrates lifting, landing, stabilization, and connection hazards into short, repeated cycles, whereas Korean occupational safety and health management cost (OSHMC) is administered mainly by statutory resource category. This study develops an activity-based costing (ABC) framework that preserves the legal eligibility boundary and links eligible resources to five installation work packages, fourteen safety activities, measurable drivers, owners, due points, and evidence. The model was constructed from legislation, official guidance, modular-safety studies, and ABC literature, then tested with a normalized 100-unit case. Cost conservation, driver causality, responsibility, timing, traceability, and four controlled change scenarios were examined. Resource, activity, and work-package totals were identical (100.0 = 100.0 = 100.0; error = 0.0), and all activity records contained an owner, due point, and evidence field. Increases in modules, lift-hours, connections, and shifts produced totals of 113.6, 114.5, 108.5, and 102.2, while unaffected activities remained unchanged. The framework therefore supports internally consistent, selective, and traceable allocation. The normalized values demonstrate model behavior rather than observed project costs or recommended spending ratios; actual project records are required for rate calibration and external validation.