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Truss
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<p>A truss is an assembly of <i>members</i> such as <a href="/facts/Beam_(structure)/V9BPDeS8">beams</a>, connected by <i>nodes</i>, that creates a rigid structure. </p><p>In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object". A <i>two-force member</i> is a structural component where force is applied to only two points. Although this rigorous definition allows the members to have any shape connected in any stable configuration, architectural trusses typically comprise five or more triangular units constructed with straight members whose ends are connected at joints referred to as <i><a href="/facts/Vertex_(geometry)/ID3cea9z">nodes</a></i>. </p><p>In this typical context, external forces and reactions to those forces are considered to act only at the nodes and result in forces in the members that are either <a href="/facts/Tension_(physics)/waNGYp3a">tensile</a> or <a href="/facts/Compression_(physics)/2wwcVmM0">compressive</a>. For straight members, moments (<a href="/facts/Torque/KcrcvNtV">torques</a>) are explicitly excluded because, and only because, all the joints in a truss are treated as <a href="/facts/Revolute_joint/GvmPuln9">revolutes</a>, as is necessary for the links to be two-force members. </p><p>A planar truss is one where all members and nodes lie within a two-dimensional plane, while a <a href="/facts/Space_frame/aKwYtCj6">space frame</a> has members and nodes that extend into <a href="/facts/Three-dimensional_space/KAqKWUbS">three dimensions</a>. The top beams in a truss are called <i>top chords</i> and are typically in <a href="/facts/Compression_(physics)/2wwcVmM0">compression</a>, and the bottom beams are called <i>bottom chords</i>, and are typically in <a href="/facts/Tension_(physics)/waNGYp3a">tension</a>. The interior beams are called <i>webs</i>, and the areas inside the webs are called <i>panels</i>, or from <a href="/facts/Graphic_statics/62W0fPwF">graphic statics</a> (see <a href="/facts/Cremona_diagram/xLSMVjWp">Cremona diagram</a>) <i>polygons</i>. </p>