The basic element of a plane truss is the triangle.Three bars
joined by pins at their ends, constitute arigid frame. The term
rigid is used to meannoncollapsible and also to mean that
deformation ofthe members due to induced internal strains
isnegligible.
Main Philosophy
On the other hand, four or more bars pin-jointed to form a
polygon constitute anonrigid frame. By adding a diagonal bar
joining A and D or B and C formingtwo triangles nonrigid frame
becomes rigid.
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If three members are pin connected at their ends they forma
triangular truss that will be rigid. Attaching two moremembers and
connecting these members to a new joint Dforms a larger truss. This
procedure can be repeated asmany times as desired to form an even
larger truss. If atruss can be constructed by expanding the basic
triangulartruss in this way, it is called a simple truss.
Simple truss
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Simple truss
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Space truss
Although a great majority of trusses can be analyzed as plane
trusses, there aresome truss systems, such as transmission towers
and latticed domes, that cannotbe treated as plane trusses because
of their shape, arrangement of members, orapplied loading. Such
trusses, which are called space trusses, are analyzed
asthree-dimensional bodies subjected to three-dimensional force
systems.
