The current gust factor approach in the detailed method of the National Building Code of Canada (NBCC) for the estimation of wind loads on buildings was developed from research work that was largely directed towards very tall and flexible buildings for which resonant responses are very significant; however, the dynamic responses of the majority of intermediate height buildings are dominated by quasi-steady gust loading with little resonant response. This study has been carried out to assess the applicability of the detailed approach of the NBCC to that class of fairly common intermediate height buildings, of which apartment buildings are good examples. For the purposes of this study, these buildings have been defined as buildings whose heights are between 20 and 120 m and whose ratio of height to minimum width is not more than 4. The responses estimated from the detailed approach of the NBCC have been compared with those from wind tunnel tests with a view to verifying and simplifying its application to such intermediate height buildings.Since intermediate height buildings are often arranged in groups, an experimental study of the interference effects between adjacent buildings was also undertaken to assess the effect of an upwind building on the wind-induced overall moments on a downwind building of a similar height. The influence of this interference effect on the member stresses or forces was investigated using the concept of joint action factors.General agreement between the test and the code-estimated responses was obtained in the comparisons. The small resonant responses observed provided a basis for deriving a simplified method for estimating the gust factor in the detailed method without the requirement of knowing the structure's dynamic properties.Significant interference effects were found, particularly for the across-wind and torsional moments on buildings in an open exposure; however, the amplification of the overall wind-induced moments does not necessarily translate into a similar amplification of member forces or stresses. For the buildings studied, the results have shown that for the majority of practical situations, interference effects are not likely to result in amplification of member stresses or forces. A set of additional factors of safety have been proposed, based on the limited experimental data set, to cover load amplification by interference effects for those members that are very sensitive to overall wind-induced torsional moments. Key words: codes, wind loads, wind engineering, intermediate height buildings, interference effects.
Dynamic analysis of a concrete chimney considering the aerodynamic damping
