Research On Evaluation Method Of Wind-induced Fatigue Of Metal Roofs Under Long-term Wind Load

Metal roofing is widely used in China,but wind uplift accidents have occurred frequently in recent years.And there is an urgent need to carry out research on wind resistance of metal roofing systems.The static performance evaluation methods and corresponding test standards of metal roof panels are relatively mature,but there are still many shortcomings in the dynamic performance evaluation methods.The fatigue effect of metal roof is often the main reason for wind-induced damage.The accumulation of fatigue damage of the metal roof will reduce the wind resistance bearing capacity and accelerate the destruction.At present,the domestic metal roof performance testing standards mainly refer to foreign standards,and mainly focus on static performance testing.A reasonable assessment of the fatigue damage of the metal roof of a building is of great significance to the formulation of the testing standards for the dynamic performance of the metal roof.Combining with the long-term statistical law of commen wind and typhoon,this paper studies the wind-induced fatigue damage calculation method of metal roof under the commen wind and typhoon environment,and improves and expands the methods.The main content and conclusions are as follows:（1）Based on the systematic review of structural fatigue damage assessment methods,the frequency domain method based on the GMM model is extended.And the problem of structural fatigue damage under broadband non-Gaussian random loads is proposed,which can be transformed into the calculation problem under two broadband Gaussian random loads.Taking a metal roof under broadband non-Gaussian wind load as an example in this paper.The TB method and the frequency domain method based on the GMM model are used to predict the wind-induced fatigue of the metal roof respectively.The prediction accuracy and stability of the two frequency domain methods are compared.The results show that the frequency domain method based on the GMM model can be used to predict the wind-induced fatigue damage of the metal roof under the action of a broadband non-Gaussian wind load with zero skewness.The prediction accuracy is higher than the TB method.The calculation accuracy of the GMMDirlik method can be controlled within 15%.The prediction accuracy of both methods has nothing to do with the mean square error and kurtosis of random loads.（2）The wind-induced fatigue assessment method of metal roof panels under the commen wind is studied.The double-slope roof panel in Xiamen is taken as an example to study the fatigue damage distribution of the roof in 50 years.First,combined with the wind pressure time history data obtained from the rigid model pressure test,the law of roof fatigue damage with wind speed is studied in the fixed wind direction angle.Then fatigue calculation formula of metal roof panel considering continuous wind speed and discrete wind direction angle is proposed to study fatigue damage distribution law of metal roof panel under long-term good wind load.The results show that the fatigue damage of a certain area of the roof under the fixed wind has an exponential relationship with the wind speed;the windward eaves,corners and other airflow separation positions located in the dominant wind direction is damaged more greatly than other areas of the roof,with the maximum value being about 0.765;the roof slabs at the windward corners and eaves of the double-slope roof may be fatigued under the commen wind,and 5～15 m/s is the main wind speed range.（3）The wind-induced fatigue assessment method of metal roof panels under the influence of typhoons is studied.The double-slope roof building in Xiamen is still taken as an example.Based on typhoon statistics,the accumulation law of fatigue damage of the metal panels of the double-slope roof is studied.The dynamic loading method in the "Technical Regulations for Metal Roofing in Areas Prone to Strong Winds" is evaluated by extracting the cyclic load matrix of the roof dangerous area.The results show that the prediction accuracy and stability of extreme wind speeds in the return period of 50 years can be used as the judgment index to determine the number of typhoon simulations;considering the cumulative effect of typhoons,the probability of fatigue damage on the whole roof increases,and the maximum fatigue damage reaches 2.188;metal roofs meeting the requirements of the "Regulations" can meet the wind-proof performance requirements of double-slope roof buildings in Xiamen.