The gable frame light steel structure building possesses the advantages of small steel consumption, low cost and short installation period. It is widely used in industrial plants, warehouses, farmer's markets, poultry houses, stadiums and etc. However, many accidents have been happened such as structure’s partial damages and even collapse due to the structure's use time has increased and various extreme weather conditions have gradually been experienced. The gable frame steel structures generally use lightweight roof and wall materials, which have lighter weight and are more sensitive to external loads. Therefore, serious consequences may occur if the design is not considered properly. The designer should pay enough attention to the calculation of wind load.
Different regulations have different requirements for wind load calculation. Building Structure Load Regulation GE50009-2012 (hereinafter referred to as Load Regulation) and Gable Frame Lightweight Building Steel Structure Technical Regulation CECS102:2002 (hereinafter referred to as Gable Steel Regulation) have calculation requirements for wind loads. However, the calculation formula and parameter values are different. The following calculation and analysis are carried out through examples to compare how to value a more safe and reliable wind load.
Example 1: Single Span Workshop Without Crane
a. Basic Parameters
The steel column spacing is 6m, the eave height is 9m, the span is 24m, single-span double-slope roof, the roof slope is 5%, closed building, articulated column bottom, the roof dead load is 0.3kN/m², the roof live load is 0.5kN/m², the basic wind pressure will be set as 0.35kN/m² and 0.7kN/m² respectively, and the ground roughness category is B.
b. Calculation Model & Main Result
According to the Load Regulation and Gable Steel Regulation, when the basic wind pressure is set to 0.35kN/m², the calculated bending moment envelope diagram is shown in picture 2.1a and 2.1b, when the basic wind pressure is set to 0.7kN/m², the calculated bending moment envelope diagram is shown as picture 2.1c and 2.1d in turn.
c. Result Analysis
For the column top bending moment: when the wind pressure is small, the moment calculated based on Gable Steel Regulation is only less than 5% smaller than Load Regulation, and the calculations of the two regulations will not be much different. However, as the wind pressure increases, the difference will gradually increase. When the wind pressure reaches 0.75, the calculation result based on Gable Steel Regulation is more than 8% smaller than Load Regulation, which may affect the safety reserve of the structure.
For the beam and column bending moment: as the combination of roof’s constant load and live load is always a control combination, the wind load has no control effect on the upward bending of the beam. The design requirements can be well met after the angle support is set according to the requirements of Gable Steel Regulation.
Example 2: Single Span Workshop With 5T Crane
a. Basic Parameters
The steel column spacing is 6m, the eave height is 9m, the span is 24m, single-span double-slope roof, the roof slope is 5%, closed building, rigid column bottom, two single 5t crane beams, the roof dead load is 0.3kN/m², the roof live load is 0.5kN/m², the basic wind pressure will be set as 0.35kN/m² and 0.7kN/m² respectively, and the ground roughness category is B.
b. Calculation Model & Main Result
According to the Load Regulation and Gable Steel Regulation, when the basic wind pressure is set to 0.35kN/m², the calculated bending moment envelope diagram is shown in picture 3.1a and 3.1b, when the basic wind pressure is set to 0.7kN/m², the calculated bending moment envelope diagram is shown as picture 3.1c and 3.1d in turn.
c. Result Analysis
For the column foot bending moment: when the wind pressure is small, the moment calculated based on Gable Steel Regulation is only less than 5% smaller than Load Regulation, and the calculations of the two regulations will not be much different. However, as the wind pressure increases, the difference will gradually increase. When the wind pressure reaches 0.75, the calculation result based on Gable Steel Regulation is more than 11% smaller than Load Regulation, which may affect the safety reserve of the structure.
For the beam and column bending moment: as the combination of roof’s constant load and live load is always a control combination, the wind load has no control effect on the upward bending of the beam. The design requirements can be well met after the angle support is set according to the requirements of Gable Steel Regulation.
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