The Robustness Design Of Bidirectional Variable Cross-section Portal Frame Under Extreme Snow Load

Tapered portal frame structure has been widely used in our country for its light weight, quick installation and wide range of application. But in recent years the global extreme climate occurred frequently, especially in the case of the heavy snowstorm, causing a lot of damage to the global portal frame structure, pose a threat to human life and property. With the development of China’s economic, lightweight construction materials become the development trend of modern architecture. This paper cuts by changing the portal frame flange section value, and considering the plate thickness variation and yield strength of the material deviation and other factors, analysis the robust of the portal frame that under the extreme snow.According to the internal force distribution of the lightweight steel portal frame under vertical static load, In this paper, the traditional tapered portal steel structure designed for bidirectional variable cross-section structure, namely on the basis of the wedge-shaped section of the web change the column and beam flange section, using finite element analysis software MARC established the portal frame model that satisfy the necessary calculation accuracy and constraint, carries on the stress analysis of the model. Explore the portal rigid structure’s yield load and ultimate load change rule under different flange cut value, find out the flange cut value that steel consumption is less and the bearing capacity is improved or does not significantly changed.In the vicinity of the calculated values of the flange cut portal frame make the robust optimization design. There are a lot of factors that affect the portal frame’s carrying capacity, including the reduction of the value of the flange, the flange of beams and column and the web’s thickness, yield strength of steel, etc., in order to simulate the actual stress state of the rigid frame, the comprehensive influence of the subject is considered on the rigid frame structure. Using the Design Expert software for different levels of the various factors combination, the finite element model is established for various combinations of different factors and stress analysis, draw the frame structure of the ultimate bearing capacity value. Build response surface function value of the carrying capacity of each factor through the analysis of response surface function get the significance of the function and the significance of the various factors. Using mathematical statistics method find the response surface function of the stable point, determine the nature of the stable point. If the point is not within the stable experimental area, the use of the purpose of SNR method to identify a stable position to meet the experimental area, calculation the bearing capacity, compared with the design bearing capacity of the rigid frame, to ensure that the structure designed meet the security requirements of the reserve value.