Durham School of Architectural Engineering and Construction


First Advisor

Jay Puckett

Second Advisor

Terry Stentz

Date of this Version



Habibnezhad, M. (2019). The Impact of Extreme Virtual Elevation above Grade on Construction Workers' Physiological Responses, Physical responses, and Task Performance (Doctoral dissertation).


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Engineering (Construction Engineering and Management), Under the Supervision of Professors Jay A. Puckett and Terry L. Stentz. Lincoln, Nebraska: August, 2019

Copyright 2019 Mahmoud Habibnezhad


On average, in every two work hours, one person dies from work-related injuries at construction sites. Most incidents are due to falling from elevated surfaces. Slips, trips, and loss of balance are the main causes. Studies suggest that instigating visual mismatch and physiological changes are among the most important reasons behind falling from narrow elevated surfaces. By using advanced virtual reality models, this dissertation aims to highlight some of the possible effects of a destabilizing environment (i.e., elevation above grade) on workers’ physiological responses and task performance. More specifically, this dissertation strives to find potential effects of elevation above grade and a moving structural beam as destabilizing environments on construction workers’ postural sway, gait pattern, and task performance accuracy. To that end, a series of virtual reality experiments was conducted on thirty volunteers, all students from the University of Nebraska - Lincoln. There were three required VR tasks asked from the subjects once on the ground and again on the 20th floor of an unfinished building: walking on virtual structural beams, standing still on the virtual platform (force plate in reality), and performing hand-steadiness and pursuit tests (physiological battery tests). In addition, to study the plausible relationship between self-perceived fear (and acrophobia) and physiological responses, all subjects were instructed to complete the electronic James Geer’s fear and Cohen’s acrophobia questionnaires. The result of this study showed that elevation above grade has a substantial effect on the gait pattern. More specifically, exposure to elevation increases gait stride height variability and decreases gait stride length. As a result, subjects spend more time on gait tasks executed on narrow elevated surfaces. Also, the findings indicated that the presence of the virtual avatar significantly affects gait parameters. The presence of synchronized virtual legs caused subjects to increase their stride height and spend more time on similar virtual tasks on the ground. However, the subjects did not exhibit similar differences once exposed to virtual elevation. Furthermore, the moving structural beam significantly increased the heart rate of the subjects. As part of the steel erection simulation, the experimental results implied that construction workers could show noticeable physiological responses in the vicinity of large moving objects. In terms of task performance, working at height affects the result of the posturography and battery tests. This finding suggests that dual-tasks performed in a static position, and in the presence of elevation-related visual stimuli, can cause a reduction in the postural sway. In contrast, in the absence of visual depth, fear of height can positively influence the outcome of the construction tasks performed on elevated platforms.

Advisors: Jay Puckett and Terry Stentz