The Robust Optimization Design Of Portal Frame Structure’s Facade Shape Under Extreme Snow Load

Portal frame structures are widely used in industrial buildings because of itsadvantages of large span and light quality. However, in recent years, the frequency ofextreme events is increasing, the portal rigid frame often suffer several damage or evencollapse under extreme snow load.As for tapered portal frame structure, the facade shape has a great impact on itsbearing capacity. In this paper, robust optimization design is carried by changing thefacade form, at the same time taking into the deviation of the steel plate thickness andsteel strength. So that the portal frame structure will have a higher and more stablesecurity reserves in extreme snow loads.This paper mainly considers the impact of one controllable factor and fiveuncontrollable factors on the ultimate bearing capacity and extreme bearing capacity. Eachfactor has three levels, the experiment is arranged by Box-Behnken experiment designmethod. The stress process of the portal frame structure under extreme snow load and thebearing capacity can be obtained by MSC.MARC. As for the result of the test, we cancollate it with response surface methodology and fit the appropriate response surfacemodel. Then the response surface model should be tested whether is significant andexcellent. The factors which are not significant are identified and removed by analysis ofvariance, then the new response surface model which satisfies the requirement ofsignificance and superiority is formed. Comparing the two response surface models, wecan find that the adjust R square of improved response surface model is bigger, theimproved response model can reflect the relationship between various factors and thebearing capacity of the portal frame structure.Finally, the robust optimization design of the portal frame structure’s facade shape iscarried by using the response surface model of ultimate bearing capacity and the extremebearing capacity. Based on the resort of the robust optimization design, the ultimatebearing capacity and the extreme bearing capacity of portal frame structure are obtainedwhen the portal frame structure has high robustness. Then the security reserves are calculated when the portal frame structure has high robustness, providing a basis forengineering.