Combination Of Wind Load Effect On Low-Rise Building With Portal Frame Structure

When calculating the wind load of the main structure of a low-rise building,only the average component of the wind load is considered,and the effect of the actual wind load on the structural is obviously underestimated.In structural design,the structural response extreme under dynamic wind loads should be considered.That is to say,the extreme values should be calculated by both the average wind pressure and the fluctuating wind pressure.In order to accurately estimate the peak value of the structural response,the corresponding maximum response values of each surface are calculated by taking the maximum wind load distribution on the roof and the wall,respectively.Since the response at each surface does not reach the peak value at the same time,it is significant to consider the correlation and peak value combination of the responses.This article takes the portal frame structure as an example and contains the following research work and essential conclusions:(1)According to the data from the wind tunnel test of the University of Western Ontario,the time history of the wind load effect of the gable-roofed and low-rise buildings with the portal frame structural system is calculated on the premise that the structure is rigid.According to comparing the different probability models by PPCC test,the most suitable probability distribution of wind load effect time history is Gaussian distribution.(2)After selecting the complete quadratic combination method and eliminating the influence of peak factor ratio,the combination process is divided into three steps:the combination of the windward wall and leeward wall components,the combination of the windward roof and leeward roof components,and the combination of the total wall and roof components.Then the applicability of the combination method is verified according to the comparison of the peak value of this method and the peak values of other combination methods and the real extremum under different building shapes and wind angle conditions.The results show that the error between the real extreme value and extreme value calculated by the complete quadratic combination method is negligible,the extreme value calculated by the Asami method is always conservation,and the error is relatively large,the error between the real extreme value and extreme value calculated by the Turkstra rule is also significant.(3)It can be concluded that the correlation coefficient has the most important influence on the combination factor.Qualitatively study the relationship between the correlation of each component and the building shape and wind direction angle in a phase-plan expression.Then distinguish the difference in the correlation of wind load and wind load response by the correlation coefficient graph,and the correlation coefficients significantly vary with the changes in building shape and wind direction angle.Based on the correlation coefficients of wind load and wind load response,considering the influence of root-mean-square ratio,a further research is finished that the variation law of combination factor in different building shapes and different wind direction angles.And the suggested values of combination factor are given under the different conditions.