Steps in diagnosing a structure for rehabilitation

Diagnosing the problem of a structure before rehabilitation follows a systematic sequence:

1. Collect background information: age, drawings, design and construction records, use and loading history, earlier repairs, exposure conditions, and any damaging events (earthquake, fire, flood).
2. Preliminary (visual) inspection: record cracks (width, pattern, location), deflection, tilting, leakage, spalling, rust stains, efflorescence, settlement and signs of distress with sketches and photographs.
3. Plan the detailed investigation: select the points and the tests required.
4. Non-destructive testing (NDT): rebound hammer, ultrasonic pulse velocity, cover meter, half-cell potential for corrosion.
5. Partial destructive tests and sampling: concrete cores, steel samples, mortar and soil samples; carbonation depth, chloride and sulphate tests, compression tests.
6. Structural analysis: reassess the load capacity of the damaged structure with actual material strengths and the geometry.
7. Find the causes of distress: design or construction errors, overloading, poor material, corrosion, chemical attack, settlement, thermal movement, seismic damage.
8. Evaluate extent and severity; classify the damage (minor, moderate, severe), and check safety and need for temporary support.
9. Decide the remedial measures: repair, strengthening, protection or demolition, and prepare a rehabilitation plan with materials, methods, cost and schedule.
10. Report and monitoring: prepare a report and install monitoring (crack gauges, tell-tales) to check the effect of the repair.