Due to the advantages of light weight, good plasticity, toughness and rich shape, steel structure engineering buildings are widely used in building structures with large span, high height, large load and large dynamic effect.But with the wide application of steel structure, its stability is more and more important, so how to reinforce and repair the steel structure engineering building?

 Reinforcement is not blind. Steel structure engineering buildings that need to be reinforced after the inspection of building safety appraisal organization can be divided into local structure reinforcement and overall structure reinforcement according to the damage scope. 

Three dimensional steel structure engineering building

Local structure reinforcement is to reinforce a member or connection node with insufficient bearing capacity. It can be strengthened by increasing the section of member, reducing the free length of member and connecting joint.

 The whole structure reinforcement is to reinforce the whole structure of steel structure engineering building. There are two kinds of reinforcement methods, which are not changing the structure static calculation figure and changing the structure static calculation figure.

 Steel structure engineering construction reinforcement generally involves the following reinforcement technologies:

 　　1.Strengthening method by adding fulcrum

 The span of beams and slabs is reduced by adding fulcrum in the middle of the span, so as to improve the bearing capacity and reduce and limit the deflection deformation of beams and slabs.The method is suitable for the reinforcement of beams, slabs, trusses, grids and other horizontal structures of large-span structures with unrestricted house clearance.Its advantages are simple and reliable, but the disadvantage is that the use space will be affected.

 　　2.Reinforcement method by changing the calculation figure of steel structure

 The reinforcement method is to change the load distribution, force transfer way, joint properties and boundary conditions, add additional members and braces, apply prestressing force, and consider spatial cooperative work to strengthen the structure.Generally speaking, they are: 

Construction reinforcement technology of steel structure engineering

(1) In order to increase the bearing capacity of the structure and improve the dynamic characteristics of the structure, the support is added to increase the structural stiffness or adjust the natural frequency of the structure;

 (2) In order to improve the stability of the structure, support or auxiliary members are added to reduce the slenderness ratio of the structure;

 (3) In the bent structure, the stiffness of a column should be strengthened so that it can bear most of the horizontal force, so as to reduce the load of other columns.

 　　3.Steel structure strengthened by sticking

 The strengthening method is to use the adhesive to stick to the surface of the damaged part of the steel structure, so that a part of the load is transferred to the surface through the adhesive layer, which reduces the stress of the damaged part of the structure.Compared with other reinforcement methods, it has obvious advantages

 (1) The specific strength and stiffness are high, and the weight of the original structure and the size of the original components are not increased after reinforcement;

 (2) The composite has good fatigue resistance and corrosion resistance;

 (3) Flexible composite materials have special advantages for arbitrary closed structures and reinforced structures with complex shapes.Good sealing performance reduces the hidden danger of leakage and even corrosion;

 (4) It is easy to operate, low cost and high efficiency. It can be constructed in a narrow space, especially suitable for on-site repair.

 　　4.Strengthening method of sticking fiber reinforced plastic

 This method is suitable for all kinds of concrete structural members and general structures.Compared with other reinforcement methods, it has the advantages of corrosion resistance, moisture resistance, durability and low maintenance cost, but it needs special fire protection treatment. 

Construction reinforcement technology of steel structure engineering

　　5.Technical method of prestressed strengthening steel structure

 The technical methods of prestressed strengthening steel structure include direct bonding method and integral reinforcement method.The direct bonding method is to bond the surface of steel structure with adhesive after both ends are anchored and prestressed. Generally, the tie rod which is relatively flat with the surface of the component is used to reinforce the component or its part.The integral reinforcement method is to adjust the stress of the tendons as prestressed cables, which is suitable for the integral reinforcement of the whole structure.

 The advantages of prestressed reinforcement technology are as follows

 (1) The reinforcement work can be carried out without unloading and stopping production;

 (2) Prestressing can directly reduce the deformation and quickly eliminate the excess stress and internal force peak;

 (3) It can eliminate the phenomenon of stress lag, make full use of the high strength characteristics and improve the reinforcement efficiency.

 (4) It can reduce the peeling stress of bonding interface, avoid the overall spalling, and improve the reliability of reinforcement;

 (5) It can reduce the cost of strengthening and using.

 The damage of steel structure engineering buildings has the characteristics of local and multiple occurrence. It is impossible for these structures to be decommissioned immediately when the damage occurs.Therefore, to seek economic and efficient steel structure reinforcement technology is not only a technical problem to be solved in the field of civil engineering, but also a problem related to the sustainable development of society.