CORRELATION OF INTERNAL AND AREA-AVERAGED EXTERNAL WIND PRESSURES ON LOW-RISE BUILDINGS

This investigation C13 was primarily concerned with the statistics of internal and area-averaged (pneumatic average) external wind pressures on low-rise buildings. The combined effects of internal and external pressure fluctuations are likely to lead to significant peak loads on building components such as cladding. The dependence of the two signal s was studied by simultaneously processing sampled time series of the internal and external pressures and the approaching flow velocity to q uantify their spectral and correlation properties. Considered, in some depth, were the cases of the model with a large windward opening (doo r opening of 5.3 %) and a low background porosity (uniformly distribut ed of 0.025 %). It was found that the internal, as well as the externa l pressure, is highly correlated with the approaching flow (Rxy-int(0) congruent to 0.65, Rxy-ext(0)congruent to -0.6) if the flow approaches perpendicular to the windward wall. This high coefficient exists only for large gusts or low-frequency events (normalized frequency nh/(u) over bar < 0.05 or an eddy wavelength larger than about six times the building length --> Coherence eta(2) greater than or equal to 0.5). Fo r this flow angle-of-attack, as well as for the flow approaching paral lel to the building corner bisector, the combined internal and externa l pressure loads on the building areas considered in this investigatio n are more often additive than canceling in nature. The highest correl ations between internal and external pressures were found for building areas located close to the windward roof edge and building corner. Co rrelations for other areas were less, or, as in the case of the flow d irection parallel to the building bisector, were not correlated with t he internal pressure.