When a structure is designed, it is created with a specific purpose in mind. However, when it becomes damaged, it is important to restore its original strength so that it can continue to fulfill its intended use. This is especially true for unreinforced load bearing masonry works, where even small cracks can significantly reduce its strength. Therefore, it is crucial to locate any damages and carry out repairs to restore the structure’s original strength.
Fortunately, there are various techniques that can be employed to carry out the necessary repair works. These techniques aim to restore the structure’s original strength and ensure that it can continue to function as intended. The repair works can be done in many ways, depending on the nature and extent of the damage.
Restoring the original strength of a structure is essential to ensure its longevity and safety. Failure to address damages can result in further deterioration and eventual collapse, which can be catastrophic. Therefore, it is crucial to carry out repair works promptly and effectively to restore the structure’s original strength and ensure that it can continue to serve its intended purpose.
Techniques to Repair and Restore Strength of Structural Members
1. Repair of Small cracks:
The process of repairing small cracks with a width of 0.075mm involves using pressure injection of epoxy. To begin the procedure, the external surface must be cleaned thoroughly to ensure that there are no dust particles present. Plastic ports are then placed along the crack surface on both sides of the structural member and secured in place with an epoxy sealant. The spacing between these ports should be approximately equal to the thickness of the element. Once the sealant has cured, the injection of the epoxy resin can begin.
If the structural member is vertical, the injection of the resin should start at the lowest part of the crack, while if it is horizontal, the injection should begin at one end of the crack. The resin should be injected one part at a time. The injection of the resin should continue until it starts to flow from the opposite side of the structural member at the corresponding port, or from the adjacent port on the same side of the member. At this stage, the injection port should be closed, and the injection of the epoxy resin can continue at the next port. The same procedure should be repeated as discussed above. It is important to note that the distance between the ports should be more closely spaced as the cracks get smaller and the pressure of injection should be higher. This ensures that the epoxy is injected throughout the length of the crack.
This technique can be used for all types of structural elements, including beams, columns, walls, and floor units in masonry as well as concrete structures. Its purpose is to restore the original strength of the structural member.
2. Repair of Large cracks and crushed concrete
When repairing large cracks that are over 6mm and crushed concrete or masonry structural elements, it is recommended to follow a specific procedure. First, it is necessary to remove any loose material and clean the surface of the concrete cracks. Then, the crushed concrete or masonry should be replaced with either expansive cement mortar, quick-setting cement, or gypsum cement mortar. This will ensure that the repaired structure is strong and durable.
Shear reinforcements should be provided in areas where they are necessary, and these should be covered with mortar. This will not only provide added strength to the structure but will also protect the reinforcement from external factors.
In cases where the concrete or masonry members are severely damaged, it may be necessary to remove the complete damaged portion and replace it with shear reinforcement and masonry as explained above. This will ensure that the repaired structure is stable and secure.
If walls and floor diaphragms are damaged, Ferro-cement can be used for repairs. Steel mesh should be provided on the outside surface and fixed on the damaged surface by means of nailing or bolting. The mesh should then be covered with plaster or micro-concrete. This will ensure that the repaired walls and floor diaphragms are strong and durable.
3. Repair of Fractured, excessively yielded, and buckled structural member
When a structural member undergoes excessive yielding or buckling, it can result in damage to its reinforcement. To repair such a structural member, the first step is to remove the damaged portion of the concrete and cut the yielded section of the reinforcement. After this, new reinforcement bars can be used as a replacement and welded to the old section of the reinforcement steel. Fresh concrete is then used to replace the damaged concrete. It is important to note that providing temporary supports may be necessary during the repair process to avoid potential collapse of the structure, as splicing reinforcement without supports can be hazardous. Additionally, if needed, it is recommended to install additional reinforcement steels and shear reinforcements to prevent future buckling of the structural member.
4. Repair of Fractured wooden members and joints
Structural members made of wood, such as beams, columns, struts, and ties, can be easily repaired by splicing additional material to restore their original strength. Before splicing, any weathered or rotten wood must be removed. Connectors such as nails, wood screws, or steel bolts are convenient for splicing. To ensure that splices and joints remain tight and stiff, it is advisable to use straps to cover them.