A discrete-event scheduling framework for structural system selection under crane and crew constraints: application to discuss a hybrid precast building

Abstract

Abstract Rapid urbanisation and population growth mean that, for multi-storey projects, construction time under realistic crane and crew constraints can be as decisive as material quantities in structural system selection. This paper presents a discrete-event, optimisation-supported formulation of the Resource-Constrained Project Scheduling Problem (RCPSP) to compare alternative structural systems under explicit limits on labour, technicians, cranes, and hoists. A digital building model is mapped to a precedence- and resource-constrained task network, simulated in a discrete-event engine, and coupled with Particle Swarm Optimisation (PSO) to search for schedules with reduced project makespan, denoted by $$C_{\max }$$ , while tracking resource utilisation and direct site resource-cost indicators. A Hybrid Precast Concrete–Steel Frame (HPCSF), designed to support high prefabrication, early enclosure, and task-level concurrency, is evaluated against three alternatives: cast-in-situ reinforced concrete (RC), a steel frame with in-situ floors, and a commercial precast skeletal frame in a six-storey residential case. Under a common baseline set-up, optimised on-site construction durations are 367, 285, and 271 days for the conventional systems, compared with 200 days for HPCSF. Within the on-site construction and assembly boundary of the model, the corresponding direct site resource-cost indicator is about 22–39% lower for HPCSF relative to the three reference systems, and resource use is more even. This indicator does not include off-site fabrication, transportation, storage, quality control, or supply-chain costs. Parametric variations in crew and lifting/hoisting capacities reveal saturation plateaux and indicate that, under the assumed on-site resource-rich scenarios, HPCSF can translate additional lifting/hoisting capacity into larger reductions in $$C_{\max }$$ than the reference systems, reaching about 82–100 days only when high crew, hoist, and crane capacities are simultaneously available. Overall, the results demonstrate how schedulability under explicit resource constraints can be incorporated into early structural-system selection.