4. fiber cloth installation process
4.1 Surface treatment:
(1) first with coarse sandpaper grinding components of the bonding area, clean up the surface layer, with acetone or alcohol solution to scrub the surface, remove contaminants, dry dry, impregnated with a binder surface.
(2) in the design requirements of the location of drilling, should be away from the site to be reinforced in order to avoid secondary damage;
(3) in the fiber cloth surface of the plastic, the gap between the fiber bundle initially closed, slightly dry and then filling;
(4) glue a little dry after the second application of prestressed to the design of the control stress (the use of extrusion effect, improve the quality of paste), with plastic fiber bundles fully saturated, improve common performance.
(5) After 48 hours at room temperature (when the temperature is low should be appropriate to extend the time), glue fully hardened, cut off the excess screw, according to the actual requirements of the structure of surface protection. This article origin steel alliance
4.2 Prestressed reinforcement design and calculation principles Prestressed reinforced steel structure in addition to compliance with the general steel structure reinforcement guidelines and regulations, but also has the following characteristics:
(1) the static calculation must first determine some of the parameters related to the adjustment of stress, such as auxiliary balance force size, prestressed strength, prestressed unloading moment value, the bearing elevation of the displacement value;
(2) to determine the reasonable load stress or stress level, in other words, to determine whether to determine the reinforcement structure of the need to uninstall, or unload to a certain level.
4.3 The following principles shall be observed in the design calculation of the reinforcement structure:
(1) the reinforcement and the reinforcement are within the elastic range of the material force, both at the same time under the load to achieve the strength of the material design value;
(2) give full play to the potential strength of the material, the pre-erection of the reinforcement can be added to the stress of the reinforcement to the extreme value of its reverse stress;
(3) Prestressed reinforcement design should also consider the prestressing load factor, prestress loss coefficient, working condition coefficient, load factor and so on.
5.Construction Technology and Steps of Prestressed Reinforced Steel Structure
Prestressed reinforced steel structure can be divided into two kinds,
First, the direct paste method, the two ends of the anchor and the application of prestressed, through the adhesive paste on the surface of the steel structure; generally applicable to the surface of the workpiece more flat rod, the components or their local reinforcement;
Second, the beam as a prestressed cable to adjust the stress, generally applicable to the overall structure of the overall reinforcement.
5.1 Selection: Carbon fiber for structural reinforcement is mainly selected PAN-based carbon fiber, the ultimate strength of up to 3500MPa, elastic modulus of about 2.35 ×109MPa. Resin system using epoxy materials.
5.2 Design: According to the force characteristics of the structure to be patched, force transmission path and stress - strain field, determine the amount of cloth, size and laying direction. The direction of the fiber should be consistent with the direction of maximum force in the damaged component. If the injured site is in a complex stress state, the fiber orientation and laying sequence should be consistent with the direction of the control principal stress.
5.3 Embedded prestressed tensioning technology: the special nature of steel structure reinforcement, the need for a simple pre-stress application mode, the traditional pre-stress application is often the first post-tensioning anchor, the need for relatively complex tensioning machine, and the corresponding Of the reaction device. In the anchor when the prestress loss is also relatively large. Embedded prestressed tensioning technology, which is characterized by the first anchor after the tension to the component itself and the previous anchor as a tension force device, without the need for complex tensioning machine. The embedded prestressing tensioning technique can apply prestressing force to produce the extrusion effect on the adhesive layer and improve the reliability of the paste. At the same time, due to the use of the first anchor after the tensioning technology, the prestress loss is small, the method is simple and effective.