Multi-story light steel structure floor design and economic comparison (2)

3. Comparison of the economics of commonly used floors in light steel structures

The following is a comparison of the economics of different forms of flooring based on the design of a certain project.

(1) Basic conditions for design

A furniture exhibition city in Chengdu, Sichuan. The project is a four-story frame structure with a total construction area of ??12668.8㎡ and a horizontal column spacing of 4×7200mm. 3×9000mm 4×7200mm. The longitudinal column spacing is 6×6000mm. For example, the height of one floor is 4.5m, and the height of other floors is 3.9m. The floor dead load of the structure shown is 4.5kN/㎡, and the live load is 5.0kN/㎡. The roof is a roof garden with a roof, the dead load is 5.0 kN/㎡, and the live load is 3.5 kN/㎡. The project is located in 7 It is a seismic zone, Category III site, and the seismic resistance level of the frame is Level 3. An ordinary steel frame structure system is adopted, the main beam adopts welded I-shaped section; the column adopts welded box section. The transverse and longitudinal beams and columns of the frame are designed as rigid connections, and the secondary beams are single-span simply supported beams with an I-shaped section; the foundation adopts independent foundations under the columns.

(2) Design results

(1) Comparison of the amount of steel used in four types of floors.

In the scheme design stage, four different floor types were compared in order to find a design scheme with better steel consumption and better overall performance. In order to quantitatively compare the steel consumption of different floors, only the weight of steel columns and steel beams is considered in the steel consumption statistics, and the weight of profiled steel plates, studs, and cast-in-place steel bars is not considered. The stress ratio of the steel beam is controlled at 0.7~0.9, the deflection is controlled according to L/400, and the stress ratio of the steel column is controlled at 0.6~0.8, and meets the stability requirements.

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column 1 welding box steel section 350x350x10x10 107.61 518.46 40.9 kg/㎡

Pillar 1 welding box steel section 350x350x12x12x12x12x12

Main beam H450X200X8X12 152 152 152 .76 <<

Secondary beam welded H-shaped steel H350X200X6X10 131.18

Main beam 2 welded H-shaped steel H550X200X8X12 86.55

Cast-in-place concrete composite floor profiled steel plate composite floor column 1 welded Box -type steel section 350x350x10x10 107.61 440.75 34.7 kg/㎡

Pillar 1 Welding box steel section 350x350x12x12 40.36

Main beam H450X200X6X10 120.87

Second beam Welding H-shaped steel H350X200X6X8 85.36

Main beam 2 Welded H-shaped steel H550X200X8X12 86.55

SP prestressed hollow slab non-combined floor column 1 Welded box steel section 350X350X10X10 107.61 394.46 31.1kg/㎡

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Column 1 Welded box steel section 350X350X12X12 40.36

Main beam 1 Welded H-shaped steel H350X200X6X10 102.75

Main beam 2 Welded H-shaped steel H750X200X8X12 47.00

Main beam 3 Welded H-shaped steel H550X200X8X12 96.75

SP prestressed hollow plate combined floor column 1 Welded box steel section 350X350X10X10 107.61 344.28 27.2kg/㎡

Column 1 Welded box steel section 350X350X12X12 40.36

Main beam 1 Welded H-shaped steel H350X200X6X10 102.75

Main beam 2 Welded H-shaped steel H650X200X8X10 30.25

Main beam 3 Welded H-shaped steel H450X200X8X10 63.31

Concrete composite slab floor and cast-in-place concrete non-composite floor (combined) 518.46440.75 40.9kg/㎡34.7 kg/㎡

(2) Comparison of comprehensive performance: (see Table 3)

Table 3 Comprehensive indicator analogy

Amount of steel used in floor type kg/㎡ Construction schedule Construction cost Fire protection cost Floor opening Waterproof performance Floor cost Yuan/㎡ Floor cost

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Contoured steel plate non-combined floor (combined) 40.9 (34.7) Fast, small and difficult to achieve 180 1.0

Cast-in-situ concrete non-combined floor (combined) 40.9 (34.7) Slow, small and easy 110 0.61

SP hollow non-combined floor (combined) 31.1(27.2) Fastest, small and difficult 150 0.83

Concrete superimposed non-combined floor (combined) 40.9( 34.7) Kuai Xiao Yi General 130 0.72

Note: 1. The floor cost ratio is based on the floor cost of profiled steel plate composite floor slabs as the reference base price.

2. The thickness of the cast-in-place concrete composite floor slab is calculated as 120mm, and the cost of formwork is taken into consideration.

3. Transportation and hoisting costs are considered for SP hollow slabs and concrete composite slabs; the span of SP hollow slabs is considered to be within 9m.

IV. Conclusion

Through the comparison and analysis of the composite floor used in the multi-layer light steel system through this project example, we can draw the following conclusions:

(1) Although the cost per square meter of non-combined floors with profiled steel plates is the same as that of composite floors, it does not take into account the combination effect with steel beams, resulting in a larger amount of steel used in the middle beams of the structure, which increases the cost. It is rare in engineering applications.

(2) Profiled steel plate composite floor takes into account the combined effect of concrete and steel beams, which can significantly improve the strength and stiffness of the structure, reduce the deflection of the beam by 1/3, and reduce the amount of steel used 15%, the comprehensive benefit is good, and it is widely used in engineering applications.

(3) The amount of steel used in the cast-in-place concrete floor is equivalent to that of the profiled steel plate floor, but its cost is only 61% of the cost of the profiled steel plate floor, and the construction technology is simple and the floor is open. The holes are convenient and suitable for projects with many holes in the floor and long construction period.

(4) The SP hollow slab floor has a larger span and can save secondary beams, which is the most steel-saving; compared with the profiled steel plate floor, the amount of steel is reduced by 22%, and the cost is It saves 17%, does not require formwork, and has fast construction speed. It will have broad application prospects in multi-story light steel structures (including light steel residences).

(5) The concrete composite slab floor has the advantages of cast-in-place concrete and the characteristics of rapid assembly of prefabricated panels. The amount of steel used is the same as that of the cast-in-place slab, and the cost is 72% of that of the profiled steel plate floor. , is the development trend of multi-high-rise buildings.