Optimizing work–rest schedule for construction rebar workers in hot and humid environment

Heat stress, having physiological effects on workers, can lead to reduction of work enthusiasm and productivity, increased incident rate, heat illness, and death. This paper aims to optimize the work–rest schedule for construction rebar workers in hot and humid environment. Two objectives are addressed in the optimization process when such schedules are designed. These objectives include maximizing the labor productivity and minimizing the occurrence of heat stress on construction site. Field studies were conducted during the summer time in Hong Kong (July–September 2010–2011). The physiological conditions of rebar workers and environmental parameters of construction sites were measured and collated. Monte Carlo simulation technique was used to account for the uncertainties and variations of meteorological and physiological parameters during summer time in Hong Kong. On the basis of work-to-exhaustion-then-take-a-rest principle, an optimized work–rest schedule that maximizes productive time and at the same time safeguarding the health and safety of rebar workers is developed. An optimized schedule of having a 15 min break after working 120 min continuously in the morning (WBGT = 28.9 ± 1.3 °C), and having a 20 min break after working 115 min continuously in the afternoon (WBGT = 32.1 ± 2.1 °C) is proposed. The current study has contributed in providing an objective and scientific mechanism to optimize work–rest schedule which may benefit the industry to produce solid guidelines for working in hot weather.