Several thoughts on the mechanism of concrete structural strengthening

In the middle and late 20th century, with the rapid development of reinforcement technology, RC beams reinforced by the outsourcing bonding steel method became representative. The use of external steel plates or polymers to strengthen reinforced concrete structures has been successfully applied to civil engineering. Recently, high-strength polymer materials such as carbon fiber and glass fiber have been developed as substitutes for steel plates. This is the so-called fiber-reinforced polymer series, which has many advantages, such as light weight, corrosion resistance, and ease of use. In the reinforcement of structures damaged by natural disasters, the commonly used reinforcement method is to quickly reinforce with polymer sheets. The sheet material can be attached to a specific position of the structure for construction, and the operation is simple, and the maximum reinforcement effect is achieved.

In the process of construction and use, the fiber fabric may be exposed to complex environments, such as fire, ultraviolet radiation, etc., which will weaken the adhesion of the material. Therefore, the bond between the organic binder and concrete becomes a weak link. However, the inorganic adhesive has excellent high temperature resistance, low shrinkage, and strong aging resistance. It is a new type of adhesive with great development prospects. It is better to use a thicker carbon fiber sheet to strengthen the system.

The calculation results show that the stiffness increases with the increase of the plate area, but the increase is limited. In order to improve the ultimate bending capacity, the reinforcement effect on both sides of the beam is not obvious. The sheets on both sides of the beam have a great inhibitory effect on crack development. Due to the destruction of the carbon fiber material, the beam completely failed in the inorganic glue reinforcement system. When organic bonding is used for reinforcement, the beam fails due to carbon fiber peeling damage. This mechanism can reduce the tensile deformation of the concrete interface.

General procedures for structural reinforcement

1) The best way to strengthen the structure

In the entire structural reinforcement project, it is very important to choose a reasonable reinforcement plan. The construction period is short, the investment is small, the environmental impact is small, the construction difficulty is small, the technology is mature, the appearance effect is good, and it can be used for a long time after reinforcement. To consider the above characteristics and determine the ideal reinforcement plan.

2) Design improvement plan

Based on the above analysis, according to the actual situation of the building structure and the requirements for reconstruction and reinforcement, a reinforcement plan is proposed. The design of the steel bar mainly includes three aspects: calculation of the bearing capacity of the steel bar, calculation of the conditions of use, structural treatment and construction drawings. When designing, it is necessary to pay attention to the adjustment of existing and new parts of the reinforcement structure. And take corresponding technical means and structural measures to minimize the hysteresis of stress.

3) Organizational structure design

After determining the reinforcement design plan, design the construction organization according to the actual situation of the construction site. In order to minimize the stress lag and adjust the stress between the new and old structures as much as possible, some steps can be taken during the construction process, such as unloading materials or part of materials or adding supports. After preparing and approving the design plan of the construction organization, in order to ensure the safety of the construction site, relevant technical personnel should be organized to carry out the construction in time, and the construction situation should be dynamically fed back to the construction site on a regular basis. After the completion of the project, the owner will organize relevant personnel, such as the construction party, the supervision party and the design institute, for acceptance.