The Function Of Steel Wire Mesh In Different Concrete Bridges
The Function of Steel Wire Mesh in Different Concrete Bridges
Steel mesh cement or steel mesh fine coagulation due to easy molding, according to the need to make any shape of the prefabricated plate, the thickness can be thin to 1cm, its strength with the increase in the number of reinforcement and network layer increases, Strength and the thickness of the protective layer is directly related to the general thickness of the protective layer should not be greater than 5mm, the concrete should not be lower than the number 40, so as to effectively play the mechanical properties of steel Wire Mesh in the component design theory should also be improved, Concrete composite action to be taken into account, to reduce the weight of the structure, reduce the cost will have a very important significance.
3 steel mesh concrete bridge development prospects - '
Steel mesh concrete is used in the beam of steel bridge is fine steel concrete, and used in the plate is the steel wire dry hard mortar (usually called steel mesh cement). Steel mesh concrete is a high strength composite material, but not As long as the steel containing steel mesh can be called steel Wire Mesh concrete. The division of the boundary is in the form of a layer of concrete per cubic meter of concrete, the amount of fine steel is greater than one 400kg or the area ratio (steel mesh surface area and concrete volume ratio) K, which is in the range of 2K2.5, and the cement label must More than 40. Can not meet these requirements, its structure can not reach the mechanical properties of steel Wire Mesh.There are some steel wire cement ship's hull can not meet this requirement is easy to crack or be destroyed.Wechnology of fine-grained concrete Layer thickness of not more than 10mm, according to the requirements of the mechanical requirements of steel mesh fine concrete sheet thickness of the protective layer is best 3mm, Wire Mesh but the thickness of the protective layer will quickly reduce the bending element 'or sheet of the initial crack strength. In order to overcome this Adverse factors, if the short steel fiber and steel mesh and then composite steel fiber reinforced steel mesh coagulation (referred to as FC), the protective layer of its components have a high anti-cracking ability, under working conditions, can be part of the pre- Stress is the use of the effect.Therefore, FC is a new high-strength composite materials, the bridge can be light so that the bridge to a greater span of development
The Where is the feasibility of building a large span F.C. bridge Wire Mesh ?
(1) the construction of large span bridges, Wire Mesh must make the components can be high strength, thin and light. Which are FC than Rq reinforced concrete) or P. C (prestressed concrete) structure is easy to do, with the material unit weight Y and allowable stress [a] ratio (Y / ') as a measure, The structure ratio is 1.0, in the bending component, RC is 3 to 10, PC is 2 ~ 3, if the FC component bending crack to the width of 0.05mm (which is the steel pipe cement under the hull to allow cracks) The allowable bending stress is 10 ~ 12MPa, the ratio is 3 to 4, if the role of reinforced steel is close to the ratio of the PC, Wire Mesh the allowable fracture width of 0.1mm, bending stress up to 20MPa, the ratio of 2.2, It is quite the ratio with the PC. When the components are prefabricated to form PF C (prestressed steel fiber-steel mesh concrete, the index is superior to that of PC. It is compared with the suspension bridge with length of 200m. The steel and the cost of FC suspension bridge are steel Of the 1/2 and 1 / 2. In terms of the weight per square meter, the steel suspension bridge is 1, FC suspension bridge is 2.5-3, but the PC oblique bridge or continuous bridge is 13 to 14, and thus take FC or PFC , In the development of large span of the bridge, will be better than the PC bridge.
(2) the structural form of the bridge should be changed. Contemporary engineering to aircraft and ship structure as the lightest, its main feature is the thin-walled multi-rib structure. Wire Mesh The cross section of the box girder (see Figure 7) is a typical ship structure with a wall thickness of 1/4 of the thickness of ordinary concrete, and can be adjusted in the box section at the same time The position of the longitudinal stiffener and the neutral axis of the equivalent beam are shifted downward to increase the resistance moment of the cross section. If the reinforced concrete bridge is to be made of a multi-ribbed structure, it is very difficult to construct with many templates, but the FC structure , Because you can prefabricated components, can greatly improve the construction speed.
Bridge ribs in the flat prefabricated, in the platform to install the skeleton, and then covered with steel Wire Mesh, constitute sub-box girder and then hoisting together. Concrete tamping system with high-frequency vibration grouting process molding and can not template, can achieve very dense effect. People talk about some shortcomings of steel wire cement boat, easily lead to illusion. In fact the bridge F.C. thin-walled structure is generally used 4 layers of 3 layers of ribs above the thickness of more than 4cm, if the manual mortar simply can not achieve dense. Therefore, F.C. Construction of the bridge must be prohibited with handmade mortar molding.