Wind-induced vibrations of buildings: role of transient events

摘要

The design of tall buildings, in many cases, is governed by habitability limit states, where accelerations predicted from wind tunnel studies emulating stationary, boundary layer flows associated with synoptic winds are compared to accepted standards for occupant comfort. In both the accelerations predicted for these design limit states and the criteria they are evaluated against, tall building design practice has consciously neglected other types of responses that result from more transient wind events, such as thunderstorms, owing to their short duration. In fact, these types of events and the impulse-like responses they induce in dynamically sensitive structures were not even considered in occupant comfort tests on human subjects until very recently. However, full-scale monitoring programmes on tall buildings, and anecdotal reports from their occupants, have verified that these events do occur regularly and are capable of producing accelerations that exceed those generated by their stationary synoptic counterparts at comparable wind speeds, thus generating perceptible motions on more frequent recurrence intervals. Therefore, it becomes important to investigate the dynamic behaviour of tall buildings under transient wind events and to attempt to gain some understanding of the mechanisms causing these large acceleration responses. The present study attempts to do just that, developing analysis frameworks appropriate for non-stationary records and applying them to full-scale data to enable rare insights into the dynamics of tall buildings under transient wind events, particularly those buildings with marked amplitude dependence and coupling between lateral and torsional modes.