Load
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    All structures must be able to support a load.  There are two types of loads. The first is a static load, which is a load that does not move.  It also is anything added to a structure that does not move.  A dynamic load is a load that does move, such as wind or a car passing over a bridge.  A load that only acts on a single point in a structure is called a point or a concentrated load. Loads that spread all over are called distributive loads.  If a structure has equal distributive loads then the loads are called uniformly distributive loads.

    Loads push and pull structures in all directions, which is why they are usually called forces.  The effects of these forces on structures depend on the magnitude (measured in Newton's) and its direction and point of action.  There are several ways to make structures more stable.  One can give a structure high stability, which means that if a force is applied to it, it will go back to its original shape.  The degree of stability depends on the base, height and weight of the structure.  The center of gravity on a structure is the invisible point of mass which gravity pulls on.  When the center of gravity is low and lies in a large base area, the structure is said to be more stable.  If the center is closer to the outside it is less stable and if it is on the outside it is very unstable and extra support is needed to hold the structure up.  Tall objects are unstable because the center is very high and therefore it can move outside of the base area more quickly.

    A structural failure occurs when a structure cannot withstand the load placed upon it. This usually happens as a result of a part break or a change in shape.  To avoid this, a structure needs strength and stiffness.  One defines the strength of a structure by the maximum load that it can support.  A structure is said to be stiff when it can withstand changing shape under a load.

This Page was last edited on Thursday, July 27, 2000 .

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