The effect of wind-induced tall building motion on occupant comfort, wellbeing, and work performance

Abstract

Tall buildings vibrate at low frequencies in response to wind excitation that can be perceptible to building occupants, may cause fear and alarm and can induce motion sickness. The majority of previous research has attempted to determine the thresholds of perception for motion to minimise perceptible motion and therefore reduce the likelihood of occupant complaint. There is insufficient research conducted on actual tall building occupants to investigate whether wind-induced building motion significantly affects occupant comfort, wellbeing and work performance. This thesis investigates the effect of wind-induced building motion on occupant comfort, wellbeing, and work performance, particularly with regard to the effects of typically neglected low-dose symptoms of motion sickness. Study 1 investigates the occupant response to wind-induced building motion in a sample of 1014 office workers in Wellington, New Zealand, known for its consistent high-wind climate. A survey administered at street level, measured detailed information about reported building motion to investigate the role of individual differences, particularly susceptibility to motion sickness, occupant comfort, and compensatory (adaptive) behaviours. Respondents who were highly susceptible to motion sickness reported avoidance of many nauseogenic environments, such as ships and roller coasters, and reported a preference to work on the lower floors of tall buildings. Despite their preferences, highly susceptible individuals were equally likely to work on high floors as the least susceptible individuals. These highly susceptible individuals were subsequently more likely to experience symptoms of motion sickness, and were therefore more likely to engage in compensatory behaviours in an attempt to manage their discomfort. Building motion caused 42% of respondents to report difficulty concentrating, indicating low-dose motion sickness. Despite reported discomfort, respondents directed almost all complaint informally to co-workers and family. Less than 1% (N = 2) of those who reported building motion complained to their "landlord / property manager", and no respondents complained directly to the building owner, contradicting the belief that complaint is a valid indicator of building performance. Study 2 compares the results from Study 1 to an identical survey administered in Sydney, Australia. Respondents returned 733 surveys, showing that wind-induced building motion was four times more likely to occur in Wellington than Sydney. Wind-induced building motion was on average felt on significantly higher floors and in taller buildings in Sydney than in Wellington. As in Wellington, highly susceptible Sydney respondents indicated a preference to work on low floors, but were equally likely to work on high floors as the least susceptible individuals. Reports of motion sickness were significantly more frequent in Wellington than Sydney. No Sydney respondents formally complained about building motion. Study 3 examines the effects of wind-induced building motion on the comfort, wellbeing, and work performance of a sample of 47 office workers on high floors of wind-sensitive buildings, compared with a control sample of 53 office workers located near the ground floor. Short 5-minute CAPI (Computer Aided Personal Interviewing) surveys repeatedly measured comfort, wellbeing, and work performance under no-motion conditions and during high winds. Participants completed 2,261 surveys over 8 months. Participant reports of building motion were supported by objectively measured wind speeds and building accelerations (predicted and actual). Clusters of both low-dose (tiredness and distractibility) and high-dose symptoms of motion sickness (nausea and dizziness) were 2-3 times more likely during building motion than under no-motion conditions. Reported motion sickness mediated self-reported work performance; higher levels of motion sickness were associated with a greater degradation of work performance. Building occupants affected by moderate to high levels of motion sickness reported work performance 0.76 to 0.90 standard deviations below their normal performance. Building occupants attempted to manage their discomfort with a 28% increase in the use of analgesic medication and the most susceptible individuals took 31% longer breaks outside of their building. Wind excitation can induce low frequency building motion, which can have significant adverse effects on occupant comfort, wellbeing, and work performance. Occupants almost universally judge building motion as unpleasant, and can experience symptoms of motion sickness, which adversely affects occupant comfort and wellbeing. Motion sickness degrades work performance, therefore also affecting the efficiency of organisations located in tall buildings. Despite these effects, occupants rarely complain, therefore complaint is a misleading measure of building performance. Robust and comprehensive future serviceability criteria should incorporate, not only the perception of motion, but the 'dose' (acceleration and duration) of motion that can potentially compromise the comfort and performance of office workers.

Date of Award	2013
Original language	English