NUMERICAL INVESTIGATION ON THE STACK EFFECT OF A GENERAL HIGH-RISE BUILDING MODEL

The stack effect of super high-rise buildings is a phenomenon of uncontrolled indoor and outdoor air infiltrations caused by certain factors such as the indoor and outdoor environmental conditions and the architectural features as well. Strong stack effect may lead to the operation failure of the elevator, the aerodynamic noise in elevator shaft and the energy waste of air conditioning etc. Currently, the research on this issue is far behind the construction of high-rise buildings. Based on the field investigations on the stack effects of more than 10 super high-rise buildings, their common architectural features were summarized and a general high-rise building model for the analysis of stack effect was designed, which was based on the standard high-rise building model usually used in structural wind engineering field. A multi-zone network model method was employed to analyze the influences of several important factors on the pressure distributions of the elevators, i.e., the airtightness level of building envelope, the design of the entrance door, the indoor space division and the outdoor meteorological condition etc. The following conclusions were finally obtained:comparatively, doors of the shuttle elevators were most likely affected by strong stack effect; in addition to the outdoor meteorological conditions and the height of the elevator shaft, other factors such as the airtightness of the curtain wall and the indoor space divisions would affect the pressure distributions of the elevator doors as well, improving the airtightness of the curtain wall could effectively reduce the strength of the stack effect and the pressure difference on the elevator doors; the design and the status of the entrance door on the first floor would play an important role for the whole stack effect performance, and the opening and closing process of the sliding door would have a great influence on the pressure differences acting on the elevator doors on the first floor; when the elevator lobby door was either installed in the first or the top floor, the pressure difference acting on the elevator doors would significantly decrease; the stack effect would be affected by the outdoor wind conditions as well, and the influences of the wind speed and the wind direction on the stack effect were relatively more complex than those of the thermal pressure. Different wind conditions would bring different results, thereby, it was necessary to perform individual investigation combined with the local meteorological conditions. Results obtained from the detail parameter analyses based on the general high-rise building model in this paper could provide a useful reference for investigating the stack effect phenomena of real super high-rise buildings, as well as the mitigation measures for strong stack effects.