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Unsafe behavior is a leading factor in accidents, and the working environment significantly affects behaviors. However, few studies have focused on detailed mechanisms for addressing unsafe behaviors resulting from environmental constraints. This study aims to delineate these mechanisms using cognitive work analysis (CWA) for an elevator installation case study. Elevator installation was selected for study because it involves operations at heights: falls from heights remain a major cause of construction worker mortality. This study adopts a mixed research approach based on three research methodology stages. This research deconstructs the details of the working environment, the workers' decision-making processes, the strategies chosen given environmental conditions and the conceptual model for workers' behaviors, which jointly depict environment-behavior mechanisms at length. By applying CWA to the construction industry, environmental constraints can easily be identified, and targeted engineering suggestions can be generated.

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The aerodynamic drag for speed skating helmets with surface structures was investigated in this work by using numerical and experimental methods. Computational fluid dynamic (CFD) research was performed to analyze the detail of the flow field around the helmets. The simplified helmet models, with riblet and bump surface structures, were analyzed using the CFD simulations. The pressure distribution and velocity field around the helmets were obtained through the CFD analysis. The CFD results showed that the boundary layer separation position was obviously delayed, and the pressure changed to a higher value at the back area for structured helmets. Therefore, the aerodynamic drag for the structured helmet was lower than that of the original model. According to the CFD results, three types of helmets, with the of riblet and bump surface structure printed on the helmets by using flexible film, were tested in a wind tunnel. A full-scaled skater mannequin of half a body was used in the experiment to simulate the actual skating process. Compared with the original helmet, a drag reduction rate of 7% was achieved for the helmet with the bump at the middle region in the wind tunnel experiment, at the average speed in competitions for skaters.

The aerodynamic drag of speed skaters was analyzed numerically at different posture angles of head, back and arm as well as team formation. Computational Fluid Dynamics (CFD) method was used to investigate the optimized posture of the skater and the drag law of the team formation. Detached Eddy Simulation (DES) was used as the numerical technique. CFD results showed that the drag area of the skater increased with the increasing angle of the head, back, and arms due to the increased high-pressure areas on the windward side and the increased low-pressure areas on the leeward side of the skater. CFD results also showed that all three skaters had lower drag area in the team pursuit competition compared with an isolated skater. The drag area of the latter two skaters was significantly smaller than that of the first skater, and the drag area of the foremost skater increased sharply when the axial spacing was more than 0.6 m. The drag area for all three skaters increased as the lateral offset increased. Moreover, the research in this paper presented an important reference for the drag reducing optimization of speed suits and helmets, and the method could be expanded to other sports.