The main damage factors of steel structure are as follows:
(1) Due to the change of load, overdue service, code and regulation, the bearing capacity of the structure is insufficient;
(2) Due to all kinds of accidents, the members are deformed, distorted, disabled and sunken, resulting in the weakening of the cross section of the members, warping of the members, cracking of the connection, etc;
(3) Deformation, cracking and warping of components or connections caused by temperature difference;
(4) Corrosion and electrochemical corrosion caused by chemical corrosion weaken the section of steel structure;
(5) Others include mistakes in design, production and construction as well as illegal use and operation during the service period.
There are three kinds of strengthening technical measures for steel structure:
(1) Section reinforcement method: steel is used to reinforce the part or along the whole length of the component, and the whole part is connected to bear the common force;
(2) Change the calculation diagram: add additional support, adjust the load distribution, reduce the internal force level, carry out forced displacement on the bearing of statically indeterminate structure and reduce the peak stress;
(3) Prestressed cable method: use high-strength cable to strengthen the weak link of the structure or improve the overall bearing capacity, stiffness and stability of the structure.