Structural strengthening of concrete structures considers when the existing structure damages. And alteration of the structure is to make due to which the structure fail to serve its purpose.
Before strengthening all failure modes should Identify. Strengthening a structure for flexure lead to shear failure instead of giving the desired increased load-bearing capacity. It identifies that not only the failure mode of the strengthening member is important. If a critical member in a structure is strengthening, another member becomes the critical one. Because of change stiffness in an undetermined structural system, the whole structure investigates. This strengthening designs with consideration to minimizing the maintenance and repairs.
THE NEED OF STRUCTURAL STRENGTHENING
- Load increases due to higher live loads, increased wheel loads, installations of heavy machinery, or vibrations.
- Damage to structural parts due to fire damage, corrosion of steel reinforcement, and/or impact of vehicles.
- Improvements in suitability for use due to a limitation of deflections, reduction of stress in steel reinforcement. And the reduction of crack widths.
- Modification of structural system due to an elimination of walls columns and openings cut through slabs.
- Errors in planning or construction due to insufficient design dimensions or insufficient reinforcing steel.
Methods of Strengthening
1. Strengthening a slab by increasing its depth from top
2. Strengthening a slab by increasing its depth from the bottom
Procedure for strengthening
- Remove the concrete cover.
- Clean the reinforcing steel bars using a wire brush or a sand compressor.
- Coat the steel bars with an epoxy material that prevent corrosion
- Install a new steel mesh, designed according to the requirements.
- Install the new reinforcing steel mesh. Fix it vertical to the slab of the roof and horizontally to the surrounding beams, using steel dowels.
- Coat the concrete surface with an appropriate epoxy material that guarantees the bond between the old and new concrete.
- Pour concrete before the epoxy dries to the required thickness. Add materials that lower the shrinkage to the concrete.