When to use these column strengthening techniques?

• Original concrete of very low resistance.

• Insufficient amount of armor.

• Change of structural use.

1. Enlarged cross-section

It is one of the most recurring solutions , in which both the concrete area and the available steel area will be increased. 

The adherence of the new armors with the obsolete ones becomes very important if their state allows them to resist still some traction. For this reason, it is sometimes correct to recess the section in order to access said reinforcements, as shown in the image, where some joint forks will be located .

Advantages  of enlarged cross-section

• It is a very recurrent solution in different uses, besides being the most radical and effective in the most complex cases .

• It offers the possibility of correcting possible calculation errors in the strength of the concrete or in the amount of steel.

• Economic.

Disadvantages of enlarged cross-section

• A technical training is necessary to calculate the screed in detail.

• If the original pillar is badly damaged , the screed must be calculated to support all the loads on its own, which includes a more detailed study. In addition, in this case, the structure must be removed to download the element in question, since otherwise, the reinforcement will only act against excess surcharges.

• The modification of the section will generate a change in the structural rigidity, which will lead to a new distribution of tensions in the structure that should be taken into account.

2. CFRP wraped column

With this technique an effective increase of the resistant capacity of the old concrete is obtained, considering itself a complement. It is evident that if the element is confined it will improve its compression behavior in an extraordinary way, but it will also be stiffened in a remarkable way. 

Advantages of CFRP wraped column

• It is one of the most used solutions, given its simplicity .

• Very effective , given the high elastic limit of the material.

• It presents a very fast placement .

• It reinforces remarkably to cutting.

Disadvantages of CFRP wraped column

• The price is the highest , since it is carbon fiber.

• It does not act on primitive armor if necessary.