Key points of steel structure reinforcement

The method of strengthening steel structure by changing the calculation graph: the method of strengthening the structure by changing the load distribution, force transmission path, joint properties and boundary conditions, adding additional members and supports, exerting prestress, considering the spatial cooperation and other measures. The general method to calculate the graph by changing the structure is:

(1) add support to form a space structure and check according to the space structure, add support to increase the structural stiffness or adjust the natural vibration frequency of the structure, so as to improve the bearing capacity of the structure and improve the dynamic characteristics of the structure;

(2) add support or auxiliary members to reduce the slenderness ratio of the structure to improve its stability;

(3) in the frame structure, focus on strengthening the stiffness of a column, so that it can bear most of the horizontal force, in order to reduce the load of other columns.

Additional fulcrum reinforcement method: beam and plate in the span of the additional fulcrum, reduce the span, so as to greatly improve the bearing capacity, and can reduce and limit the deflection deformation of beam and plate. It is suitable for the reinforcement of horizontal structures such as beams, plates, trusses and grids in large-span structures with unlimited headroom. Its advantage is simple and reliable, drawback is to use a space to be able to get certain influence.

Bonded steel reinforcement method of outsourcing: extension-story reinforcement of reinforced concrete beam with wet method of outsourcing, namely the steel by adopting the method of chemical grouting epoxy resin and the bonding of the strengthened beam into a whole, after reinforcement component, due to the tension and compression steel cross section area is greatly increased, so the bearing capacity of normal section and cross section stiffness is increasing sharply.

Paste fiber reinforced plastic reinforcement method: paste fiber reinforced plastic reinforcement method in addition to outsourcing sticking steel strengthening method advantages, also have corrosion material, resistant to moisture, almost not increase the weight, durable, maintenance costs low advantage, but need special fire prevention, suitable for all kinds of mechanical properties of concrete structural components and structures in general.

After the completion of the reinforcement project, the application of small hammer gently hit the paste steel plate, judging the bonding effect from the sound or using ultrasonic method to detect the paste density. If the adhesive area of anchorage area is less than 90% and that of non-anchorage area is less than 70%, the adhesive is invalid and should be peeled off and pasted again.

For major projects, in order to test the reinforcement effect, sampling load test is required, generally only for the standard load test, the unloaded load is added all again, the deformation and crack development of the structure should meet the design requirements.

Prestressed reinforcement steel structure technology: the bolt connection needs to be opened on the base metal near the damaged part, which weakens the section and forms a new stress concentration area; The common bolt is easy to loosen under dynamic load, while the high strength bolt is easy to relax, which reduces the repair effect of the structure. The reinforcing technology of bonding steel is to stick steel plate on the surface of steel structure with special structural adhesive, and make it work together as a whole by relying on structural adhesive, so as to improve the bearing capacity of structure. The disadvantage is that the weight of the structure increases a lot, the steel plate is not easy to make a variety of complex shapes, transportation and installation is not convenient, and the steel plate is easy to rust, affect the bond strength, high maintenance costs.