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How to choose the steel structure plan to reduce the amount of steel used?


1. The choice of building length and width

At least, the principle of length greater than width should be when arranging the column net, which can reduce the amount of steel used for the rigid frame, and also reduce the wind direction of the support between the columns, thereby reducing the amount of steel used for the support system.

Example 1: When the size of the building is 60×50m, when arranging the factory building, 60m should be taken as the length direction and 50m as the span direction, that is: 60(L)×50(W) instead of 50(L)×60(W) ) ).

2.Selection of column spacing in steel building

The comparison of technical standards shows that the most economic pillar under the effect of the standard is 8-9m. When it exceeds 9m, the steel consumption of the roof purlin and wall frame system will increase too much, and the comprehensive cost will not be economical. The standard here refers to: roof live load is 0.3KN/m2, basic wind pressure is 0.5KN/m2, and the economic column distance should be reduced correspondingly for a long time. For workshops with cranes of more than 10 tons, the economic operation distance should be 6~7m.

When arranging the column spacing, if unequal column spacing is required, the end span should be arranged as small as possible than the middle span. This is because the end span wind is larger than the middle span. In addition, when the continuous purlin design is used, the end span The deflection of the span and the mid-span bending distance are always larger than other spans. Using more end spans makes roof purlin design more convenient and economical.

3. Determination of reasonable span of steel construction

Different production processes and use functions are deciding whether to implement plant spans. Some owners even require light steel manufacturers to determine their economic spans based on their own use functions. To meet the production process and use functions, a reasonable span should be determined according to the height of the house. Under normal circumstances, when the column height is at least certain, the span is appropriately increased. The increase in steel consumption of the rigid frame is not obvious, but the space is saved, the basic cost is low, and the overall benefits are considerable. Through a large number of calculations, it is found that when the eaves height is 6m and the column distance is 7.5m, when the situation is exactly the same, the unit steel consumption (Q345-B) of the rigid frame with a span between 18-30m is 10-15kg/m2. For rigid frames with a span between 21-48m, the steel consumption per unit is 12-24kg/m2. When the eaves height is 12m and the span exceeds 48m, a multi-span rigid frame (swinging column designed in the middle) should be used. The rigid frame can save more than 40%, so when designing the portal frame, select multiple economic spans according to the specific requirements, and it is not advisable to blindly pursue a large span.

4. Choice of roof slope in steel structure

The roof slope needs to be determined according to the comprehensive factors such as the structure of the roof panel, the length of the drainage slope and the height of the column structure, and it is generally 1/10~1/30. Studies have shown that different roof slopes have a cohesive effect on the amount of steel used in the rigid frame.

The following results are obtained by calculating and analyzing the steel consumption of a single span of 42m and a cornice height of 6m under different roof failures:

When the roof breaking degree is 0.5:10, the weight of the frame is 3682 Kg

When the roof breakage is 1.0: 10, the weight of the frame is 3466 Kg

When the roof breakage is 1.5:10, the weight of the frame is 3328 Kg

When the roof breakage is 2.0: 10, the weight of the frame is 3240 Kg

It can be polished. For a single-span rigid frame, a better way to reduce the weight of the rigid frame is to increase the slope of the roof. The smaller the slope, the more saving the amount of steel.

However, the situation is different for multi-span frames. A large slope will increase the amount of steel used in the frame. This is because a large fracture will increase the length of the inner column. When the span of the building penetrates, the increase in damage can reduce the deflection of the roof steel.

Through research and calculation, the more economical slope is:

Multi-span building: 1:20

Single span, span less than 45m: ́0.5: 10

Single span, span less than 60m: 1.5: 10

Single span, with a span greater than 60m: 2.0: 10

In fact, the pick-up of the roof slope is also related to whether the building has a parapet, and the slope gradually increases, leading to an increase in the cost of the parapet.

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