Steel structure is often used in various engineering structures with large span, high height, large load and large dynamic action, and has a wide range of applications. With the development of steel structure, its stability becomes more and more important.

Adding fulcrum reinforcement method

After adding the fulcrum in the middle of the span, the span is reduced, which can greatly improve the bearing capacity and reduce and limit the flexural deformation of the beam and slab. It is suitable for the reinforcement of horizontal structures such as beams, plates, trusses and space grids in large-span structures with unrestricted clearance. Its advantage is simple and reliable, the disadvantage is that the use of space will be affected.

Strengthening method with bonded steel encased

Generally, the reinforced concrete beams strengthened with steel encasement adopt the wet encasement method, that is, the epoxy resin grouting method is used to bond the section steel and the strengthened members as a whole. After reinforcement, the bearing capacity and stiffness of the normal section are greatly improved due to the large increase of the cross-sectional area of the tension and compression steel.

Strengthening method with fiber reinforced plastics

In addition to the similar advantages of the bonded steel encased reinforcement method, the bonded fiber reinforced plastic reinforcement method also has the advantages of corrosion resistance, moisture resistance, almost no increase in the weight of the structure, durability and low maintenance cost. However, it needs special fire prevention treatment, and is suitable for all kinds of stressed concrete structural members and general structures.

After the reinforcement project is completed, the small hammer is used to tap and paste the steel plate gently to judge the bonding effect from the sound or to detect the bonding density by ultrasonic method.

If the bonding area of anchorage zone is less than 90% and that of non anchorage zone is less than 70%, the bonding is invalid and should be peeled off and pasted again.

For major projects, in order to check the reinforcement effect, the load test must be carried out by sampling. Generally, only the standard service load test is carried out, that is, to add all the removed load again. The deformation and crack development of the structure should meet the design requirements.