The upper structure of steel arch bridge is mainly composed of arch ring, suspension rod (or arch column), tie rod, bridge beam and other components.

The arch rib of the arch bridge has steel box arch rib, steel truss arch rib, steel pipe arch rib, etc. The bearing capacity of the section should be checked according to the stress properties of the components of the arch rib (axial compression, axial tension, bending, tensile bending, compression bending, etc.). It is also necessary to check the bearing capacity of the joint of the component (welded connection, peg connection); The anti-fatigue checking calculation of the component and the connection of the component is carried out.

• Section form of main arch ring: steel box arch, steel pipe arch, steel truss arch
• Space posture of two arch ribs: parallel arch ribs, basket arch ribs, butterfly arch ribs
• Position of carriageway system: upper bearing type, middle bearing type and lower bearing type arch bridge
• Layout of the boom: parallel vertical boom, inclined boom, mesh boom

Steel arch bridges have both composite system arch bridges and simple system arch bridges. There are several kinds of combined system arch bridges, such as tie arch, loser arch, lange arch and other combined system arch bridges.

• Simple system arch bridge: only the arch ring is the main force component, and the simple system is a thrust arch structure
• Combined system arch bridge: carriageway beam and arch combination, common force

Steel arch can be designed into truss arch, box arch, plate arch. Many truss arch bridges are built in foreign countries, and more than ten steel box arch bridges are built in China. Truss arch bridge is an important form of rigid arch bridge with large span.

The main arch of truss arch bridge along the span direction: equal height, variable height.

1. Arch rib: The main load-bearing members of the structure mainly bear axial pressure, but also bear part of the bending moment. According to the form of section is divided into: box, pipe, truss type. Trussed arch rib has light weight, greater span capacity and good economy.

2. Boom: It is a force transfer component, which transfer the deck load to the arch rib of the bearing member, the boom is mainly an axial tension member. The rigid boom is made of multi-purpose steel pipe or section steel and can withstand pressure. The flexible boom is made of high-strength steel wire bundle or steel strand, which can only be stretched, convenient construction and beautiful appearance.

3. Tie bar (beam): For the non-thrust arch, the thrust of the arch is borne by the tie rod, and the tie rod bears the larger axial tension. Divided into: rigid tie rod, flexible tie rod.

4. Cross brace: To ensure the transverse stiffness and stability of the two arch ribs and withstand the transverse horizontal forces acting on the arch ribs, bridge deck and boom. The cross brace can greatly improve the out-of-plane stiffness and torsional stiffness of the whole bridge.

5. Arch post: Used for the upper bearing part of the upper bearing arch bridge or the middle bearing arch bridge, and is the force transfer structure between the bridge floor system and the main arch rib.

Axis of arch: The ideal arch axis is consistent with the pressure line on the arch. Common forms: arc line, quadratic parabola, catenary.

Rise span ratio: The common range of arch rib span ratio is 1/4~1/7, the span ratio of steel truss arch bridge is usually 1/4~1/5.

Arch rib vault and arch foot height: According to the variation of arch rib height, it can be divided into equal height arch rib and variable height arch rib.

The thrust of tie arch is digested by internal system, which is suitable for long span rigid arch bridge. The Roser arch with rigid arch and rigid beam is suitable for heavy-duty railway bridge; The Rangel arch with rigid beam and flexible arch is suitable for the double-deck arrangement of both roads and railways.

• High strength and durability
• Superior aesthetic appeal
• Versatile for various applications
• Efficient load transfer capability
• Capable of long spans (up to 552m built)
• Relatively quick construction
• Magnificent appearance
• High carrying capacity