There are many factors that cause the insufficient bearing capacity of the beam. The following are common construction defects, design errors, improper usage, beyond the original carrying capacity and safety, durability failure, or end of life.

In addition, some other factors are also the reasons for the reinforcement of structural beams, such as:

1. the non – uniform settlement of the foundation makes the beam produce additional force.

2. using improper material or beam itself has inherent defects lead to the lack of durability, such as material or surface crack or internal micro cracks, promote commercial carbonization of the concrete cover, to a certain extent so that the lower beam tension reinforcement erosion, reduce the yield strength steel itself even brittle fracture accident;

3. the adverse effects of the unreasonable beam structure, such as 60% to 80% of the design load on the thin abdominal beam, there are serious oblique cracks near the middle of the center of the web.

4. others, such as insufficient anchorage of steel bar, short length of reinforcing bar, unreliable welding, sudden action of load or instantaneous overload, etc.

Which structural strengthening materials can effectively reinforce various damage of structural beams?

1. Carbon fiber reinforced polymer(CFRP) wrap

   High strength, high efficiency, quick construction, good corrosion resistance, light weight and no cross section, widely applied in practical engineering. In many cases, it has replaced the various reinforcement methods created in the last century, and has achieved remarkable economic and social benefits.

1. Epoxy bonded steel plate

   The steel plate is glued to the surface of the concrete component with high-performance epoxy structural adhesive, which makes the steel plate and concrete form a unified whole. The purpose of strengthening the bearing capacity and stiffness of the steel plate is to make good use of the tensile strength of the steel plate.

1. Anchoring adhesive

   The enlargement section method is to increase the cross section area of the structure or structure of the commercial concrete, which is used to improve its bearing capacity and meet the normal use. It has the characteristics of simple construction technology, strong adaptability and so on. In engineering practice, there are many situations to supplement the commercial concrete layer in the tension area of the beam, which increases the effective height of the beam section, thereby increasing the stiffness and effectively improving the bending and shearing capacity of the beam.

1. Steel jacketing adhesive

   In the structural member or rod angle or four horns package with steel reinforcement method, is also a kind of reinforcement method is widely used in the traditional. It is divided into two forms, the dry outsourced steel method and the wet outsourced steel method. It can increase the bearing capacity and increase the ductility and stiffness without increasing the section size.