Composite Bridge Steel Cable Suspension Bridges Big Loading Capacity

Composite Bridge Steel Cable Suspension Bridges Big Loading Capacity

Description:

Steel Cable Suspension Bridge is iconic bridge structures that utilize steel cables under tension to support the bridge deck. They are known for their long spans and graceful appearance.

It consists of bridge tower, main cable, sling, stiffening beam, anchor, saddle and other main parts.

At present, most of the bridges with a span greater than 1000m are suspension bridge structures.

Load characteristics: the load is transmitted from the sling to the cable, and then the cable is transmitted to the anchor, to the pier and to the tower.

Under the external load, the main cable and stiffened beam bear the same force.

The main cable is the main load-bearing component, which deforms under load.

It directly affects the internal force and deformation of the bridge.

The main cable is the main load-bearing component in the structural system, which is mainly strained.

The bridge tower is the main load-bearing component of suspension bridge to resist vertical load.

The stiffening beam is a secondary structure of suspension bridge to ensure vehicle running and provide structural stiffness, and it mainly bears bending internal force.

The sling is a force transmission component that transmits the self-weight and external load of the stiffened beam to the main cable, and is the link connecting the stiffened beam and the main cable.

An anchor is a structure that anchors the main cable, which transmits the tension in the main cable to the foundation.

Main cable: The load is borne by the clamps and boom, and it is passed directly to the top of the tower.

The main cable is divided into two types: wire rope main cable and parallel wire bundle main cable.

1.Wire rope main cable: wire rope main cable is twisted into strands by wire, and then twisted into rope by strands. Generally, it adopts 7 strands and used for small span suspension bridges.

2.Parallel wire bundle main cable.

Prefabricated parallel steel wire strand method (PPWS method): the use of parallel steel wire to speed up the construction progress of the main cable, the section shape is divided into pointed and flat top shape.

Bridge tower:

1. Bridge to form

According to the mechanical properties, it can be divided into three structural forms: rigid tower, flexible tower and rocking column tower.

A rigid tower refers to a bridge tower with relatively small horizontal displacement at the top. The flexible tower. It refers to the bridge tower with relatively large horizontal displacement at the top. Rocking column tower, it is only used for suspension bridges with small span, and the lower end is hinged single-column structure.

2. Cross bridge form

The bridge tower of transverse bridge adopts three forms: truss type, rigid frame type and mixed type structure.

Main parameters involved:

The main parameters that affect the design of bridge tower are: material parameters, environmental parameters and structural size parameters.

Stiffening beam:

The types of stiffened beams mainly include steel truss beams, steel box beams, concrete beams, steel-mixed composite beams and other structural forms, as shown in the figure:

Sling:

(1) The material of the sling:

It can be made of steel wire rope, parallel steel wire bundle or steel strand.

(2) Connection mode with cable clamp

Straddle type, pin type

(3) Vertical sling and diagonal sling

Traditional slings are vertical, starting with the Severn Bridge in the United Kingdom.

Anchorage:

The anchorage of ground anchored suspension bridge is divided into two structural forms: gravity anchorage and tunnel anchorage, as shown in the figure: Gravity anchorage is composed of anchor body, bollard, anchor chamber and foundation. Tunnel anchorage is composed of anchor plug body, loose saddle support pier and anchor chamber.

Compared with gravity anchorage, tunnel anchorage has much less concrete consumption and more significant economic performance. In terms of applicability only, gravity anchorage is suitable for almost all occasions. When the comprehensive geological condition of the anchor site is good, the terrain is conducive to the overall layout of the whole bridge, and the construction conditions can meet the tunnel excavation and slag discharge. From the economic point of view, the possibility of building tunnel anchors should be considered first. 

Saddle:

The saddle sits between the main cable and the top of the tower. The saddle is an important member that supports the main cable and gives the main cable a turning angle here. Through it, the pull force in the main cable can be evenly transmitted to the top of the tower and the anchor in the form of vertical force and unbalanced horizontal force.

The saddle is divided into the main rope saddle at the top of the tower and the loose rope saddle at the anchor.

Classification of steel cable suspension bridges:

1.According to the number of suspension span are divided into: single-span suspension bridge, three-span suspension bridge, four-span suspension bridge, five-span suspension bridge.

2.According to the main cable anchoring form are divided into: ground anchor and self-anchoring.

Ground anchorage: The tension of the main cable is transferred to the foundation by the gravity anchorage or tunnel anchorage at the end of the bridge.

Self-anchoring: The main cable tension is transmitted directly to its stiffening beam.

Steel cable suspension bridge construction method:

The construction process of suspension bridge is: anchor foundation construction, anchor construction, bridge tower foundation construction, bridge tower construction, main cable construction, stiffened beam construction, bridge deck construction, etc.

Construction features of Steel Cable Suspension Bridge :

Construction of the foundation of the bridge tower and anchor, and processing and manufacturing of the components required for the construction of the superstructure to prepare for the upper construction.

Construction of bridge tower and anchor body, including saddle and anchor steel frame installation.

Installation and erection of the cable system, including installation of the main saddle, loose saddle, pilot cable crossing the river, erection of the traction system, erection of the catwalk, main cable strand prefabrication, erection, tightening cable, cable clamp, sling installation, etc.

Hoisting and erection of stiffened beam segments, including integral welding or bolted, etc.

Protection design of Steel Cable Suspension Bridge

(1) Concrete structure

Concrete structure protection design mainly adopts the following measures:

• Improve the thickness of concrete protective layer.
• Adopting high performance concrete, with durability.
• The sound concrete coating or sealing layer has the characteristics of preventing the contact between the corrosive medium and the concrete, thus extending the life of concrete and reinforced concrete.
• Improve the steel bar material and steel bar coating.
• Add reinforcement corrosion inhibitor (rust inhibitor) to concrete.
• The concrete structure uses cathodic protection (protection) system.

(2) Steel structure

The protection design of suspension bridge steel structure mainly adopts the following measures:

• Paint coating.
• Metal zinc, aluminum or their alloys are thermally sprayed on the surface of steel structures and then coated with high-performance fluorocarbon resin topcoat to form a high-efficiency protection system.
• Weathering steel is used in steel structure.
• Improve the environment of steel structure members.

Application of Steel cable suspension bridges

Highway Bridges: Steel cable suspension bridges are frequently used to span large bodies of water or deep valleys where conventional bridge designs are not feasible. They provide efficient and cost-effective solutions for highway crossings, allowing for uninterrupted traffic flow over significant distances.

Pedestrian Bridges: Steel cable suspension bridges are popular choices for pedestrian and cyclist crossings, especially in scenic locations or urban environments. They offer safe and visually appealing pathways, enhancing connectivity and accessibility for pedestrians and non-motorized transportation.

Advantages of Steel cable suspension bridge: steel cable suspension bridge has become more and more the preferred type of bridge with large span (over 1000m) because of its large span capacity, good seismic performance and light appearance.

Evercross Steel Bridges Overview :