Portal Frame

Portal Frame

The main methods of steel structure reinforcement are:

Reduce the load, change the calculation graphics, increase the cross-section and connection strength of the original structural members, and prevent crack propagation.

When mature experience is available, other reinforcement methods can also be used. Steel structures that need to be reinforced are generally divided into partial reinforcement and comprehensive reinforcement according to the scope of damage.

Local reinforcement is the reinforcement of a rod or connection node with insufficient load-bearing capacity. There are methods of increasing the section of the member, reducing the free length of the member, and the method of reinforcing the connection node.

Comprehensive reinforcement is the reinforcement of the overall structure. There are two types of reinforcement methods that do not change the static calculation of the structure and the reinforcement method that changes the static calculation of the structure.

Adding or strengthening the supporting system is also an effective method to strengthen the structural system.

The reinforcement method of increasing the cross-section of the original member is the most costly and labor-intensive method (but it is often a feasible method); the method of changing the calculation diagram is the most effective and diverse, and its cost is greatly reduced.

1. Before determining the reinforcement plan, the following information should be collected:

(1) As-built drawings (including modified drawings) and acceptance records of the original structure.

(2) Copy of original steel material material report or on-site material inspection report.

(3) The acceptance record of the original structural component production and installation.

(4) Original structural design calculation book.

(5) Inspection report on damage of structure or component.

(6) The data of the existing actual load and the newly added load after reinforcement.

2. Main factors of steel structure damage and reinforcement technical measures

2.1 The main factors of steel structure damage are:

(1) The structural bearing capacity is insufficient due to load changes, overdue service, and changes in codes and regulations;

(2) Due to various accidental deformations, distortions, disability, dents, etc. of the components, the cross-section of the components is weakened, the rods are warped, and the connection is cracked;

(3) Deformation, cracking and warping of components or connections caused by temperature difference;

(4) Corrosion caused by chemical substance corrosion and electrochemical corrosion cause the weakening of the section of steel structure;

(5) Others include errors in design, production, construction, and illegal use and operation during the service period. The source of this article

2.2 There are mainly three types of reinforcement technical measures for steel structures:

(1) Sectional reinforcement method: Reinforce with steel locally or along the entire length of the member, and connect them as a whole to make them bear the force together;

(2) Change the calculation diagram: add additional supports, adjust the load distribution, reduce the level of internal force, force the displacement of the statically indeterminate structure support, and reduce the peak stress;

(3) Prestressed cable method: Use high-strength cables to reinforce the weak links of the structure or improve the overall bearing capacity, rigidity and stability of the structure.

2.3 Characteristics of traditional steel structure reinforcement methods

Welded steel structure reinforcement

During welding reinforcement, the local rapid heating and cooling process, the welding zone can not expand and contract freely due to the constraints of the surrounding workpiece body. After cooling, welding stress and deformation will be generated in the weldment. The high temperature effect makes the structure and performance of the welded part. Deterioration; and there must be defects in the weld, which will produce new cracks; there are residual stresses in the welded structure, which may cause cracks in combination with other effects. Welding makes the structure form a continuous whole. Once the cracks become unstable and expand, they may break to the end and cause major accidents.