Two-way spanning structural systems are very efficient. Basic one-way spanning structures, such as beams and plane trusses, must transmit any load applied to...See more »
Two-way spanning structural systems are very efficient. Basic one-way spanning structures, such as beams and plane trusses, must transmit any load applied to them directly to their supports. If, however, a grid of connected intersecting beams is formed in the horizontal plane, a load applied to one beam will be distributed to all other beams in the grid and thus to all of the supports. An efficient load sharing system has been produced - a single-layer grid. A common example of this type of structure in buildings is the coffered reinforced concrete slab where the orthogonal ribs produced by the coffering effectively form a grid of intersecting beams supporting a thin floor slab. When spans exceed 10 to 15 m the use of beam elements in the grid becomes uneconomical and trusses are used to form a double-layer grid (space grid or space frame). The double-layer grid usually consists of two parallel horizontal grids connected with a pattern of vertical and/or inclined (web) elements between the two plane grids. This three-dimensional structural form is commonly known as a space frame or space grid and is one of the most efficient and lightweight structural systems. There are many examples of similar structures in nature, the internal structure of some bones, for instance, where considerable strength is required whilst weight is at a premium. The generic term 'space frame' is often used to describe two structural types, namely space trusses (with inclined 'web' elements) and space frames - with no inclined 'web' elements, although the more general term 'space grid' is more appropriate and will be used here when discussing aspects not limited to one structural type. These two types of space grid carry loads by different structural actions and in strict engineering terminology the majority of 'space frame' structures are in fact space trusses. Space trusses rely primarily on truss action achieved through full triangulation of the structure and the individual bars or members primarily carry axial tension or compression forces as long as the loads are applied directly to the node joints. On the other hand space frames that are not triangulated resist the applied loads by rigid frame action which develops bending, shear and axial forces in all elements even when loads are only applied to the joints. Space grids are generally of modular construction. Most space grids are of modular construction either composed of individual bar elements connected at proprietary node joints or of pre-fabricated, three dimensional modules with a variety of connection methods.See less »
one sec please...
