How do engineeers test a building to make sure it’s structurally sound many years after its built?
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analyze with software. sometimes do coring samples of concrete or timber. d-meter and other advanced methods to see if thickness of steel is retained. my experience is with bridges but i assume buildings can’t be too different
In the past a lot of ( mostly smaller) samples of structures were made and tested. The results where then calculated to the right scale and used for construction. This is still done today when new materials are developed, but most times computer simulations are used, because there is enough data available about common materials.
During the life span of a construction also a lot of inspection is done and sometimes further tests are necessary ( like ultrasonic testing, x-ray testing, camera inspections etc – it’s called Non Destructive Testing) to check the structual integrity of a construction. Sometimes this leads to further action or improvement.
I bet you have encountered this unconsciously when on a bridge a speed limit “suddenly appeared without a reason”. Then probably damages have been found and by reducing the speed of traffic less stress is applied to the construction and it can still be used and won’t collapse until necessary repairs can be done or a new bridge is built.
I’m not a civil engineer but i work in a field that somehow related to construction. So, the is just my observation & understanding:-
Every parts of the structure (beam, column etc.) are designed to use specific grades of concreate and specific size and number of steel bar. They will be be simulated using professional structure software like STAAD.Pro.
N20 grade are supposed to withstand 20MPA of compressive force per milimeter square (sqmm) and N45 supposed to withstand 45MPA of force per sqmm. The grade requirement are depend on design by structural engineer.
During the construction, each batch of concreate delivery from concreate factory will sampled and tested using Concreate Slump Test to ensure the consistency of the concreate mix. If the slump test failed it will be rejected and will be sent back to factory. The steel bar also will be tested by pulling it apart until break.
Before the concrete was poured, they will take a sample and make few 150×150×150mm cube from the sample. Normally, each of the cubes sample will be tested on 7th day, 14th day & 28th day. The cube are expected to achieve at least 65% strength of 7th day, 90% on 14th day. The cube also expected to achieve 99% of the strength on 28th day. If the cube passed the test on 28th day, the structure of the particular parts of structure will be deemed as safe.
If you have existing construction documents from when it was built you dig those out, look up the code year and material properties specified (these were listed on drawings, going back 100+ years). The. You do a condition survey – depending on how thorough the new owner wants to be this could be a walk through or it could be a gut-job where they remove all interior finishes and you can see the underlying structure.
If no modifications are planned and no change in use (Eg it was built as an office building and will continue to be an office building, and you’re not cutting new openings, and it all looks in OK condition) you stop there and write a report basically saying as much.
If they’re making major modifications or changing loading then you need to analyze the structure to current code, you might do material testing on the existing steel, concrete, etc – mostly if you’re pushing the limits of the originally specified materials as sometimes it’s stronger than they asked for, then you design any strengthening required.
If no original drawings exist the survey involves the engineering team to go out and physically measure beams, columns, etc to determine their accurate size and properties, along with material testing (a testing company will remove samples and take them to a lab to test).
There are steel and concrete buildings that use archaic, and since abandoned, construction methods. If you find these you look them up and see what limits/precautions come with them and include that in design of any strengthening.
For older buildings- eg stone construction- a similar process applies, but is fairly rare as these buildings are often of historic importance and you won’t often see them go through major renovation as the need for historic preservation often outweighs the need to change the use of any particular space.
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