Structures

Structures

1. All physical bodies or objects have a structure. Its purpose is to maintain the object's shape and not to break when a force acts on them. An elephant's skeleton on the grooves on a plastic cup are examples of estructures.

   • Sometimes the structure is easily identified in the body or object, like the bones of vertebrates, the frame of a boat or the columns and beams in a building. For other objects the strutures are not easy to distinguish because the whole object forms the structure.
   • A structure is the set of elements in a body that are made to resist the effects of the forces that on it. A structure prevents a body from breaking or deforming.

2. Natural and man-made structures

   • Natural structures:
     • Are not made by man. They are living beings, in their composition ,or the result of a geological process, for example, the shell of a crab, a bird's nest or a cave.
   • Man-made structures:
     • Are made by people to satisfy a need. Some examples are the legs of a table or the case of a camera.

3. Forces and loads

   • Physical bodies and objects need a structure to support the different forces that act on them, like gravity which attacks objects to Earth and cause them to have weight
     • A force is anything that can deform a body (static effect) or make it move or stop (dynamic effect). Two main types of loads: 
     • Fixed or permanent loads: Are constant they don't vary over time. An example would be the weight of the structure of a bridge and its component parts (columns, road, surface, etc.)
     • Variable loads: Vary over time, like the trafic going across a bridge or the wind hitting it. Load: Force that acts on a structure. It can be fixed or variable. Loads produces stress.