Structural strengthening can not only improve the bearing capacity and durability of the structure, but also improve the seismic capacity. So can it be considered that conventional structural strengthening can simultaneously enhance the bearing capacity and seismic capacity, the two can be treated the same?

With the increasing number of existing concrete structure diseases and the continuous improvement of people’s seismic awareness, more and more building structures have been unable to meet the use needs. Structural strengthening can not only improve the bearing capacity and durability of the structure, but also improve the seismic capacity. So can it be considered that conventional structural strengthening can simultaneously enhance the bearing capacity and seismic capacity, the two can be treated the same?

In fact, although bearing capacity strengthening and seismic strengthening belong to structural strengthening, there are still some differences between them. If seismic resistance is not considered, only the bearing capacity of members is raised, it will often have adverse effects on the seismic resistance of the structure. For example, strengthening the members in the seismic fortification area may not be beneficial to seismic resistance. Therefore, in the reinforcement, we should make clear the difference between the two and prevent the reinforcement from having the opposite effect.

Design life difference

The design service life in reinforcement refers to a period of continuous use of a building. During this period, the structure does not need large-scale maintenance, but only needs normal maintenance to achieve the intended use function. The design service life should consider the durability, safety, economy, rationality and so on. There are different requirements in seismic appraisal standards and reinforcement design specifications.

In the seismic appraisal standard, the design service life is mainly based on the construction time of the existing buildings and the seismic design code series adopted to distinguish. In reinforcement design, the design life is affected by the owner, reinforcement materials, and the remaining design life of the original building. Therefore, when there is a need for seismic strengthening of buildings, the design service life should be coordinated between the two to prevent the structure after strengthening does not meet the seismic requirements.

The difference between reinforcement methods

In the bearing capacity reinforcement, each reinforcement method pays more attention to the improvement of the bearing capacity of individual members. For example, in the flexural members, the flexural and shear bearing capacity can be improved by sticking carbon fiber fabric and U-shaped stirrups. When the structure is strengthened, attention should be paid to the improvement of seismic performance from individual members to the whole members, so as to avoid the reinforcement of individual members or parts, and cause other members or parts to become weak links.

On the other hand, seismic strengthening can be carried out from two aspects, one of which is to improve the bearing capacity of the structure, and the other is to enhance the seismic performance of the structure by improving the deformation capacity of the structure. This may lead to the same method in bearing capacity reinforcement and seismic reinforcement performance is different, such as the concrete wall bonded with carbon fiber cloth, the bearing capacity of the reinforcement is basically not effective, but can improve the ductility of the wall to improve seismic performance. That is to say, we should pay attention to the difference between the two methods in the choice of methods.

The similarities between bearing capacity and seismic reinforcement

From the point of view of reinforcement technology, all kinds of reinforcement methods for bearing capacity reinforcement can be used in seismic reinforcement, and the reinforcement process is basically similar. The identification of the original structure is an important reference for both bearing capacity strengthening and seismic strengthening of the structure, and it should be strictly carried out according to the code requirements. The selection of construction technology should be combined with the actual situation of the site, select the appropriate method, and select the professional construction team for reinforcement.

To sum up, bearing capacity reinforcement and seismic strengthening cannot be treated the same way.