Why, if arch’s are the best for bearing loads are the majority of modern structures made with using 90 degree angles?

Question

Seems like they would be better for areas with earthquakes, hurricanes, and high wind while also being more durable in general.

In: Engineering

Answer 1

Aches have a huge advantage if you build in a material that has high compression strength but low tensile strength. That means strong if you compress them but week if you try to pull them apart. An example is concrete, bricks, stones you put together with or without mortar

The advantage is a lot lower if you have material that can have high compressive and tensile strength. Examples are steel, reinforced concrete.

You have a lot of arches in old stone building because that was the only way you could build it and support the load. Today you can do the same with horizontal steel or reinforced concrete beams.

There is a relatively well know the quote

>Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands.

The general meaning is that building something strong is not hard the problem is if you what to build is at a reasonable cost. For a building, there is also the amount of usable space, windows sizer etc.

There is a lot of prefabrication today where you move the part to the building site and assemble there both steel and reinforced concrete. The flat part is simple to make and simpler to transport

It is not hard to build stuff that survives earthquakes, hurricanes, and high winds. It is hard to do that at a reasonable cost and having a large internal volume.

So arches are a lot less needed today than in the past because we can build strong enough without it at a lower cost. If you see a short arch it is likely for the visual, not the strength.

But they are still used when it is the best option like if you build a [concrete bridge with a ](https://en.wikipedia.org/wiki/List_of_longest_arch_bridge_spans#/media/File:Qinglong_Railway_Bridge.jpg)[445-meter](https://en.wikipedia.org/wiki/List_of_longest_arch_bridge_spans#/media/File:Qinglong_Railway_Bridge.jpg)[ span](https://en.wikipedia.org/wiki/List_of_longest_arch_bridge_spans#/media/File:Qinglong_Railway_Bridge.jpg)