how do architects calculate if a structure like a bridge is stable?
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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.
Engineers do it. The bridge is modeled as a number of discrete elements, the stress and strain within each is calculated depending on the material being used etc, how weight is distributed, and a million other things, and a factor of safety is applied.
There’s an old saying, anyone can design something to stand, but only an engineer can design it to*barely* stand.
Engineers do it. The bridge is modeled as a number of discrete elements, the stress and strain within each is calculated depending on the material being used etc, how weight is distributed, and a million other things, and a factor of safety is applied.
There’s an old saying, anyone can design something to stand, but only an engineer can design it to*barely* stand.
Engineer here, we learned how to do this in a class called statics. Basically the study of non moving systems (ie structues like bridges and buildings). The math is surprisingly easy and it was one of my easier classes.
Fluid dynamics on the other hand still gives me nightmares…
That reminds me… what do architects even do? Collecting data for engineers? Design how pretty the structures must be?
That reminds me… what do architects even do? Collecting data for engineers? Design how pretty the structures must be?
The architects don’t do that, that’s for engineers. We have a few friends called equilibrium and superposition.
Safety factor vary by structure type, region, design methodology, etc… Most civil and structural engineers will set the limits at 4 or above for critical structures where loss of life is probable if it fails. This helps to account for conditions that go beyond the maximum loading (which is already generous), but more importantly, it allows for the non homogeneous nature of most of the materials that are used in daily construction. Steel is fairly uniform, but it’s exposure to the elements can and will degrade its section integrity over time. Reinforced concrete can have pocketed aggregate, voids, misplaced rebar, etc… Soil, even select material can vary greatly from load to load. Wood varies by direction of grain, wood type, treatment methods, and knot placement as well.
Additional factors such as historical data for wind, snow, earthquake magnitude, and other natural loads is still being developed and we don’t know the true risk factors. Items such as vehicle weights and maximum loading of trucks and rail cars has also increased greatly over the years. All of these things contribute to the need to apply generous overdesign to these types of structures.
Engineer here. Dm me and I’ll run you through the math of your live and dead loads. You’ll likely need some data for your location like snow loads, wind loads, any seismic or anything else that will be in the building. I need pitch of the roof and the materials you plan to use and any opening or penetrations. I’ll need to know the makeup of your headers and the makeup of your structure ie. Wood studs, metal studs, lvl engineered lumber, steel beam etc.. I’ll also need the risk category and soil test results. Assuming this is residential. You should have a print and that’s where I would take off all of this info. It’s the architects job to track all of this down with the authority having jurisdiction who issues the permits.
Engineer here. Dm me and I’ll run you through the math of your live and dead loads. You’ll likely need some data for your location like snow loads, wind loads, any seismic or anything else that will be in the building. I need pitch of the roof and the materials you plan to use and any opening or penetrations. I’ll need to know the makeup of your headers and the makeup of your structure ie. Wood studs, metal studs, lvl engineered lumber, steel beam etc.. I’ll also need the risk category and soil test results. Assuming this is residential. You should have a print and that’s where I would take off all of this info. It’s the architects job to track all of this down with the authority having jurisdiction who issues the permits.
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