One of the primary objectives of engineers who design buildings is to create structures that protect people from the outside environment while providing comfortable and efficient spaces in which to live or work. Houses, apartments, and office buildings need to withstand powerful winds and rainstorms, and possibly the weight of heavy snow, depending on where they are built. First, however, a building must be able to support its own weight.
Engineers refer to the internal and external forces that structures such as buildings or bridges must counteract as "loads." They identify two major types of loads: A structure's dead load includes its own weight and the weight of anything permanently attached to it. Live loads include the temporary forces a structure withstands during normal use, such as the weight of cars, trucks, and office equipment, for example, and normal weather conditions, such as wind and precipitation.
The design process helps engineers find ways to meet the needs of a building's future residents as well as the challenges posed by the various loads the structure will encounter. These considerations influence the shape and dimensions of a building, as well as the materials from which it will be constructed.
Cardboard and tape may be sufficient to construct a temporary home for a teddy bear. However, homes and office buildings intended for humans are generally made of materials such as wood, concrete, stone, and steel that are strong enough to resist heavy loads and durable enough to maintain their shape and strength for decades or centuries.
One of the most important aspects of a structure's strength is the stability of its foundation. Regardless of the size and strength of a building's columns and beams, if these structural elements are not attached to a stable foundation, they will not be able to resist the force of even very light loads. Therefore, the design process must consider not only the structure itself, but also the ground on which the structure will sit. Only then can a structure be strong enough to meet its intended uses for years to come.
Apart from some of the obvious differences between a real house and a teddy bear house, the techniques the children use in this video segment mirror many of those used by professional engineers. First, the children identify a problem that needs to be solved: Their bear needs shelter. Next, they determine what materials they have available to solve the problem, and then they find ways to shape and connect these materials to create a stable structure. Along the way, they consider what they already know about how houses and other structures are built and use this knowledge to shape the design of their teddy bear house. As a final step, they test their design with the garden hose to see how well the house protects its occupant from the elements. Surely, finding a damp bear at the end of such a test will lead to design modifications and further testing.
