The variation of peak loads with tributary area near corners on flat low building roofs

Abstract

Abstract This paper discusses the effect of spatial averaging of roof pressures on peak loads over various tributary areas near the corner of flat-top low-rise buildings. Simultaneous time series of pressures measured at locations within the corner region were used for analysis to form new time series of up-lift loads by instantaneous spatial averaging, for various building heights and plan dimensions. The variations of effective peak loads with location, shape and area, as well as with building dimensions, are presented and compared with those currently recommended for the corner zone by building codes, such as NBCC 1995 and ASCE 7-93. For areas including the corner point, the load reduces rapidly with increasing tributary area from the very high local peak value at the corner. The results demonstrate that the relationship between the effective load and tributary area is insensitive to the building dimensions if area is normalized by H2 where H is the building height, and is only slightly dependent on the shape of the areas that include the corner point. From an aerodynamic point of view, for buildings with plan dimensions larger than the height, the roof zoning by building codes should be based on H, and the specified load should be related to tributary areas normalized by H2.