structure

Arrangement designed to protect and support the items within it, by withstanding the action of forces that might cause damage.

There are two main types of structure: shell structures and frame structures. Shell structures are made from sheet material, while frame structures are made from pieces called members. Horizontal members are known as beams, vertical members as columns or pillars. The two main forces that act on members are tensile forces and compression forces. Members that are in tension are called ties, while members that are under compression are called struts. Frame structures can be made in many shapes, but the triangle is the strongest and triangulation is therefore a common approach to designing structures.

Examples of shell structures include cardboard boxes, while examples of frame structures include vehicle chassis and scaffolding. Shell structures are often combined with frame structures to make stronger structures. For example, a canvas or plastic shell is attached to a tent frame, concrete is set around steel bars to make reinforced concrete, and a shell structure is attached to girder frames to make buildings.