Problem statement
In an industrial building, the existing 40-year-old concrete columns showed extensive damage. The damage was due to a combination of corrosion and overloading. In addition, it was not possible to shut down operations for more than 2-3 days at a time. In total, about 35-40 columns will be reinforced over a 20-year period.
Outcome
About 20 columns with the dimension 600x600x5000 mm have been reinforced with surrounding carbon fiber fabric. In total, between 5-10 layers of fabric were applied. The reinforcement of the first pillars was done around 2010 and continues annually according to plan. Approximately 4-5 pillars are reinforced each year and the project is planned to be completed around 2027-2028. The result is successful and instructive where, among other things, early shortcomings in the execution of the reinforcement have led to improvements over time. The environment is very aggressive with temperatures of 50-60 C and humidity above 90% RH.
Solution
After carrying out a standard condition assessment and performing load-bearing calculations of the columns, carbon fiber fabric reinforcement was designed. The work was carried out in the following steps:
Preparatory work
- Installations are disconnected/removed and then retrofitted.
- Loose concrete is mechanically removed.
- Injection of cracks.
- Corrosion protection of reinforcement.
- Concrete piling.
- Grinding of concrete before reinforcement.
Reinforcement work
- Priming of sanded and cleaned concrete surface.
- Application of adhesives.
- Installation of carbon fiber fabric.
- New layer of glue to wet the fiber and then new carbon fiber fabric. The procedure is repeated until the prescribed number of layers are applied.
Finishing work
- Bomb disposal.
- In some cases, the reinforcement is fireproofed or painted.
- Reassembly of installations.
Standard
EN1504-9 and SS-ISO 13822.
Commentary
To obtain a good strengthening effect of rough columns, one needs to be careful with the underwork and stretch the carbon fiber fabric in connection with the reinforcement, avoiding folds and bends. Furthermore, more layers of carbon fiber were applied in the sections where there were attachments in the columns. The reinforcement method is used by the client on an ongoing basis to ensure the safety of their building.
