how do architects calculate if a structure like a bridge is stable?
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Usually its the enginerrs more than the architects, but there are many equations regarding this. Much easier for certain types of structure but you can break every structure down to “moments” and build it up from there based on material properties
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Architects don’t calculate that, engineers do. With modern engineering they can model everything in a computer simulation to get a pretty high confidence of stability. Even then things aren’t engineered to be just strong enough, they have safety factors of 3 or 4 times the required strength so even if the calculations are off there is still a lot of leeway. You have to cut a lot of corners in construction, missed some fundamental force in your simulations or use the structure for something it completely wasn’t designed for for it to fail.
If the structure is being designed you calculate the loads the structure is going to be subject to in two situations, intense use and extreme circumstances, based on that you matematically model the stresses and deformations in the different elements and materials. Then you check with a certain safety margin that the deformations and vibrations during intense use are not going to damage the material or scare the people using the structure, also that under extreme circumstances the structure doesn’t just completely fall apart but people can escape even though you’re just going to demolish it later.
If the structure is already being built, you load it with a weight close to the intense use limit (in a home you might use sand bags and on a bridge a column of trucks) and you check the deformations are not over the limit you imposed, in case concrete was used on location you have to collect some simples the same day, one month later check the resistance is at least the one you asked to be provided to you by the production company.
They send the drawings over to the engineer and have them do the calculations. And then they complain when the engineer say it would be unstable and that there is no way to make it stable without adding pillars or beams which would ruin the clean open design of the structure. Sometimes they do not listen to the engineer.
The engineer will do a lot of calculations on the forces and stress involved. I am sorry this post is so short but this is literally an entire collage degree to learn the basics of structural engineering. You calculate what kind of forces the structure will potentially be exposed to such as wind forces, weight from rain and snow, movements to the foundation, people and equipment moving in the structure, and of course the weight of the structure itself. You then calculate how these forces will be distributed down the structure into the foundations. To complicate matters the structure moves and twists depending on the forces applied which changes the forces. Then you multiply all the forces by a safety factor depending on the type of structure. If any structural member have more forces going through them then they are designed for the structure will have to be redesigned.
Usually its the enginerrs more than the architects, but there are many equations regarding this. Much easier for certain types of structure but you can break every structure down to “moments” and build it up from there based on material properties
Usually its the enginerrs more than the architects, but there are many equations regarding this. Much easier for certain types of structure but you can break every structure down to “moments” and build it up from there based on material properties
Architects don’t calculate that, engineers do. With modern engineering they can model everything in a computer simulation to get a pretty high confidence of stability. Even then things aren’t engineered to be just strong enough, they have safety factors of 3 or 4 times the required strength so even if the calculations are off there is still a lot of leeway. You have to cut a lot of corners in construction, missed some fundamental force in your simulations or use the structure for something it completely wasn’t designed for for it to fail.
Architects don’t calculate that, engineers do. With modern engineering they can model everything in a computer simulation to get a pretty high confidence of stability. Even then things aren’t engineered to be just strong enough, they have safety factors of 3 or 4 times the required strength so even if the calculations are off there is still a lot of leeway. You have to cut a lot of corners in construction, missed some fundamental force in your simulations or use the structure for something it completely wasn’t designed for for it to fail.
Computer modeling is a valuable tool. However, this isn’t even necessary for the vast vast majority of bridges. The standards and knowledge are so well developed at this point that it’s mostly a “copy and paste” of previous designs. The safety factors in these are huge was well.
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