Benefits from evaluation of condition and strength of the structure

Evaluation of condition and strength of the structure is done in order to know about condition of the structure as well as deterioration, defects, damages, and load carrying capacities (safety limit in carrying loads) of the structure. However, it might be done to collect data for making decision on repair, improvement or retrofit of the structure as well as to gather information for structural analysis, engineering calculation, and designing of structural repair or improvement.

Schemes for evaluation of condition and strength of the structure
Schemes for evaluation of condition and strength of the structure might be categorized roughly as follows.

- Searching for sign of deterioration and damages that occur with the material itself and different members of the structure such as cracks, porosity, defects, inclination, settlement, and movement.
- Define tendency of having damages in the future such as measuring acidity and alkalinity inside the material, measuring electrical potential difference of different parts of the structure, measuring density of the material, inspecting connection pattern of members of the structure.
- Examine responses of different parts of the structure to different patterns of applied forces or different types of stimulation. This will give a broad view on condition and status of the structure. This might be done by measuring forces and movements when carrying some specific load or under normal service condition.
- Comparing key parameters of the structure at different times to observe change in general condition of the structure (which will cause change in values of key parameters). Key parameters must be selected carefully so that they can really reflect deterioration of the structure.

Cause of structural deterioration and damages

Generally, structure of a building, bridge, dam, etc. will be designed to have the maximum capacity in carrying loads at a certain level for some certain service period. That period can be taken as life of the structure. In the case of buildings, that period can be called life of the building. Likewise, it will be called life of the bridge in the case of bridges. Limited service life of a structure is mainly caused by deterioration and damage of construction materials. Deterioration and damage may come from corrosion, fatigue (when load was sustained for a long time or repeated for many cycles), overloading, loading pattern unaccounted for in the design, or chemical degradation. Many factors from surrounding environment like acidity, salt, humidity, and change of ambient temperature also cause deterioration. Earthquake, fire, storm or other kinds of hazardous event that causes damage to the structure may seriously reduce life of the structure.

If analysis, calculation, and design were carried out correctly and properly together with good construction by means of good material, workmanship, equipment and regular maintenance of the structure, the structure will be able to carry the specified maximum load throughout its entire life. Maximum level for a load pattern may be different from those allowed for other load patterns; such as maximum level for a force applied in one direction may not be the same as that allowed for a force applied in another direction.

In conclusion, deterioration of the structure begins since it was constructed and this results in continuous reduction of strength and load carrying capacity of the structure until it is unsafe to use the structure. Repair, retrofit, or strengthening of the structure when there is a sign of deterioration or damage in some part of the structure will help to prevent spreading of the damage to other parts and will considerably prolong life of the structure. Repair, retrofit or strengthening of the structure in the early stage when deterioration and damage is still small will cost much less than doing it when damage already spreads.

Bond test of concrete

Measure deflection of structural members when carrying the load

Measure forces in members of the bridge loaded by using the test locomotive

Force occouring inside the member from measurement