|Modeling rebar labor productivity in hot weather
|Construction industry -- Health aspects.
Construction industry -- Safety measures.
Construction industry -- Labor productivity.
Hong Kong Polytechnic University -- Dissertations
|Department of Building and Real Estate
|xx, 236 p. : ill. ; 30 cm.
|Heat stress, having physiological and psychological effects on workers, can lead to reduction of work enthusiasm and productivity, increased incident rate, heat illness, and death. The construction industry is found to be more susceptible to heat stress than other industries because construction workers are subjected to heat stress not only from outdoor strenuous physical work but also in confined working spaces which could be even worse. The Hong Kong government and the industry have expressed concerns of working in hot weather and promulgated a series of fundamental practice notes and guidelines on working in hot weather. However, their recommendations are by and large some "dos and don'ts" and are not based on scientific measurements. The continuing high frequency of heat related incidents in the Hong Kong construction industry calls for better approaches in deriving scientific algorithm to detect impending attacks of heat stress. The present study aims to develop a set of good practices and indices to ensure the health and safety of site personnel working in hot weather. Its objectives are to assess the current health and safety precautionary measures for working in hot weather; determine heat tolerance time and optimal recovery time for construction workers to prevent the occurrence of heat related disorders; optimize work-rest schedule for construction workers in hot and humid environment; and formulate recommendations for working in hot weather to safeguard workers' health and safety. Experimentation, facilitating the creation and discovery of knowledge and leading to the improvement and development of a real setting, is adopted in this study. Data are collected through clinical experimental studies, field studies, and focus group meetings.
In the current study, the major factors affecting heat strain and constriction labor productivity were identified. Findings of research indicate that (1) drinking habit, age, and work duration are the top three predictors to determine rebar workers’ physiological responses; (2) wet bulb globe temperature (WBGT) is the best model to predict the effects of heat stress on construction workers; (3) the heat stress model could be further developed to determine the heat tolerance time (HTT) of construction workers by keeping certain parameters constant. For example, the maximum heat tolerance time for a 45-year old rebar worker who smokes and consumes alcohol occasionally and works continuously at WBGT of 30°C and API of 30 with moderate workload is 72 minutes, (4) on average a rebar worker could achieve 94% recovery in 40 min; 93% in 35 min; 92% in 30 min; 88% in 25 min; 84% in 20 min; 78% in 15 min; 68% in 10 min; and 58% in 5 min; and (5) an optimized schedule between 8:00 am and 12:00 pm with a 15 min break at 10:00 am in the morning; and between 1:00 pm and 5:30 pm with a 30 min break at 3:00 pm in the afternoon could maximize the labor productivity and minimize the occurrence of heat stress on construction site. The current study sheds light on how to further enhance occupational health and safety in construction. It contributes to filling the research gap arising from limited studies in heat stress, an issue of rising importance. Experimentation adopted in this study indicates it is a rigorous, structured, and reliable research approach that is viable for conducting CM research. It fosters better collaboration between industry practitioners and the academia in the quest for excellence in the industry. The findings and recommendations have been adopted in the latest CIC Guidelines on "Site Safety Measures for Working in Hot Weather" released in April 2013. An additional 15-minute rest period would be introduced for workers during hot summer months (from May to September every year).
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