(1)Structural steel defects caused by design or construction, such as insufficient weld length, overcutting of rebars, and excessive section weakening.
(2) After long-term use, the structure experiences varying degrees of corrosion, wear, and abnormal operation. This leads to structural defects, severely weakening the cross-section of the structural components.
(3) Changes in the process production conditions have increased the load on the structure, rendering the existing structure infeasible to adapt to.
(4) The quality of the steel used does not meet the requirements.
(5) Accidents and natural disasters have severely damaged the structure.
(6) The deformation and destruction of the structure are caused by the settlement of the foundation.
Principles of Reinforcement for Structures or Components
Rebars should be produced as little as possible, or not at all, as the losses from shutdown often multiply the cost of rebars by several or even dozens of times. Whether to halt production and reinforce under load depends on the stress-strain state of the structure. When the internal stress of general components is less than 80% of the steel's design strength, and the damage and deformation are not too severe, non-stop production reinforcement methods can be employed.
(2) The structural reinforcement plan should be easy to manufacture, construct, and inspect.
(3) Structural manufacturing and assembly should be conducted as far as possible outside of the production area.
(4) Preferably use high-tensile bolts or welding for connecting rebar. When reinforcing with high-tensile bolts, check the bearing capacity of the reduced-diameter drilled section; for welded rebar, the actual load-induced stress on the original rebar should be greater than 60% of the rebar's design strength, with no more than 80% of the ultimate stress. Otherwise, appropriate measures should be taken prior to welding.
