2.8m Wide, 2.9m Tall: One Single Box Girder Weighs 200 Tons

Steel box girder sections are the closed rectangular tubes that carry bridge loads. Below is cross-section data from an actual 200-ton frame crossbeam box girder.

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Basic Specs

 

Item	Value
Section type	Single box single cell
Width	2,800 mm
Depth	~2,900 mm
Top flange	36 mm thick
Bottom flange	36 mm thick
Webs	28 mm thick, 2 webs
Material	Q370qE bridge steel
Unit weight	200,701 kg (200.7 t)
Shear studs	φ22×150, 6,816 pcs
High-strength bolts	M24×100, 160 sets

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Component Weight Breakdown

 

Part	Section	Weight
Top flange	320×36×33,300	30,768 kg
Bottom flange	314×36×31,000	27,677 kg
Webs (×2)	294×28×33,300	44,695 kg
End diaphragms	3,144×28×2,928	4,127 kg
Intermediate diaphragms	3,144×18/28×2,928	25,237 kg
Stiffeners	Various sizes	~65,000 kg
Shear studs	φ22×150 ML15	3,408 kg
Welds (1.5%)	—	2,966 kg
Total	—	200,701 kg

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Section Details

The box section consists of:

Top flange: 36 mm thick, 2,800 mm wide

Bottom flange: 36 mm thick, 3,144 mm wide

Two webs: 28 mm thick inclined webs

Diaphragms: end diaphragms 28mm, intermediate 18mm

Stiffeners: vertical and longitudinal stiffeners on webs and flanges

Shear studs: φ22×150 on top flange for composite deck

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Advantages

High torsional stiffness — closed box resists torsion on curved and skew bridges

Q370qE toughness — bridge-grade steel with low-temperature toughness

36mm thick flanges — thick flanges handle heavy moment and shear

Diaphragms prevent buckling — internal diaphragms keep box shape

Composite deck ready — shear studs on top flange for concrete deck

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Disadvantages / Limitations

Very heavy per span — 200 tons per box needs heavy lifting equipment

36mm plate welding — thick plates require preheat and special weld procedure

Inside inspection hard — closed box interior difficult to inspect

Q370qE more expensive — bridge steel costs more than structural Q355

Fabrication precision high — 2.8m wide, 2.9m tall box must be dimensionally accurate

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Typical Applications

Bridge superstructures — highway and urban bridges

Long-span crossbeams — frame crossbeams in large structures

Curved and skew bridges — torsion demands box section

Railway bridges — heavy rail load on box girder

Combined bridges — wide box for mixed traffic

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Fabrication Notes

Top and bottom flanges CNC cut from 36mm Q370qE plate

Webs 28mm thick, welded to flanges with full penetration welds

Diaphragms welded inside box at 4–5 m spacing

φ22×150 shear studs welded on top flange by stud gun

All Q370qE welds preheated and tested

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Steel box girder section — single box, 2,800 mm wide × 2,900 mm tall, 36 mm top/bottom flanges, 28 mm webs, Q370qE bridge steel, 200.7 tons per unit, with 6,816 shear studs, built for highway and urban bridge superstructures.

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**Email**: eddie@zdsteels.com, wells@zdsteels.com