Structural strengthening

Issues you may face

BS EN 1504 Principle 4 is concerned with structural strengthening by increasing or restoring the structural load bearing capacity of an element of the concrete structure. It is essential when using this Principle that all stresses associated with a repair and the original or deteriorated structure are considered. Certain systems may impose additional stresses on the repaired structure, resulting in changes in the function of the original structure.

1. Deflections

Deflections due to increases in loads applied to the original structure, forming cracks to reinforced concrete slabs.

2. Voids or insufficient reinforcement

Voids in the concrete or insufficient rebar found in the structure.

3. Seismic damage

Damage due to earthquakes or sudden impact (explosions), causing structural failure and cracking.

4. Structural bonding

Hardened precast concrete to hardened precast concrete for repair.

5. Overloading

Overloading to structural elements due to extra loads applied to columns, forming structural cracks to columns and beams.

6. Cracking

Cracking to structural concrete due to insufficient reinforcement, flexural cracks, shear loading or overloading.

Solutions

Methods of protection based upon the BS EN 1504 Principle 4 is the use of the following:

• 4.1 Adding or replacing embedded or external reinforcing steel bars
• 4.2 Installing bonded rebars
• 4.3 Plate bonding
• 4.4 Adding mortar or concrete
• 4.5 Injecting cracks or voids
• 4.6 Filling cracks or voids
• 4.7 Prestressing

1. Plate bonding to floor slabs

Using FRP carbon-fibre plates bonded as external reinforcement to strengthen reinforced concrete. Bonded FRP to tension face. Use webertec force carbon plate (S&P 150kN/m² modulus or S&P 200kN/m² modulus).

2. Grouting in rebar

For grouting in rebar, use webertec anchor grout.

3A. Filling cracks or voids: crack injection

Using epoxy resin.

3B. Strengthening to walls

Use FRP sheet wrap and FRP plates:

• webertec force carbon plate
• webertec force aramid sheet
• webertec force glass sheet
• webertec force carbon sheet

4. Structural bonding

Using epoxy structural adhesive webertec EP structural adhesive.

5. Strengthening columns

Using near surface mounted, NSM, reinforcement and sheet wrap:

• webertec force carbon plate (10mm or 20mm)
• webertec force carbon sheet
• webertec force aramid sheet

6A. Shear strengthening

Using ultra-high modulus, UHM, carbon-fibre sheet, webertec force carbon sheet C640.

6B. Filling cracks

Using epoxy resin.