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In the Engineering Design Process, Engineers know what they are building and how it is planned to be used

How do engineers design the things they build? Designing and building things are not the only engineering activities. However, engineering design is often what people think about when they think about engineering.

Engineers design things before they build them. They start with what they know about what it needs to do, as well as how it is planned be used. A good example of an engineering design problem is building a bridge. When the engineers think about how to design a bridge, they know where the bridge is supposed to go, such as across a wide river, or a narrow creek or a deep canyon. And, they know what it is supposed to carry, for example, cars and trucks, or trains, or people. As you might imagine, a walking bridge would be designed differently than a train bridge.

You can imagine what might happen if a bridge is built incorrectly for its planned use. For example, what might happen if you build a walking bridge over a deep canyon and then drive a cement truck over it? The truck could be far too heavy for the bridge, and it could end up at the bottom of a ravine. Or if you build a very short bridge over a very wide river, your bridge users might end up in the river. Sometimes, however, engineers make assumptions about how something will be used, and then it ends up being used somewhat differently. That's a topic we'll cover another day.


Engineers incorporate goals and constraints in their design

Using the bridge example, we might start with the following goals and constraints:

We need a bridge to connect San Francisco to Oakland over the San Francisco Bay (goal). It needs to be able to handle the weight of cars with bumper to bumper traffic, at or above 2500 cars at a time (constraint). It needs to be able to handle the weight of people occupying the full span of the bridge for festivals (constraint). It needs to be able to withstand winds of up to 60 miles per hour (constraint). It needs to be able to withstand an earthquake of up to 7.5 magnitude on the Richter scale (constraint).

If a bridge is needed in an area where there are earthquakes or hurricanes or tornadoes, then the engineers have to think about how to design the bridge to be able to withstand those types of expected events. They might spend a great amount of time thinking about designing for earthquake safety for bridges in California. But, in Florida, they’d think hurricanes. And, in Oklahoma, they would have anticipate tornados.

By the way, engineers think not only about whether a particular event may occur in an area, but also how strong an event of that type is likely to be. For example, Japan's Fukishima nuclear power plant was designed to withstand an 8.6 earthquake. Engineers had predicted that a larger earthquake was not likely to happen. The March 11, 2011 magnitude 9.1 earthquake showed that their prediction was wrong. Sometimes designs are flawed, because perfect knowledge is never available. However, engineers have to do the best job they can with the information they have.


Engineers may use computers to simulate what they plan to build

Engineers may try out different materials and design options to see what works better. They may simulate the different options using a computer. Simulate means that to try out a design on a computer, so that they can see how it might perform without having to build it.


Unlike innovation or invention, Engineers know what they are building when using the Design Process

Engineering Design involves figuring out the best way to build something for a particular use. When you're starting the design, you know what you're building at the end, and how it is planned to be used. You're just figuring out the best way to do it. This is very different from inventing something, like figuring out how to invent a vehicle that can fly. People tried lots of different designs for aircraft and gliders before they found anything that worked. Invention often takes a long time like that. Engineering design is also different from research which is exploring what something does, or is capable of, or could be used for. Inventing, or innovation, is another Engineering Process.


Design process Innovation process Failure analysis Reverse engineering