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November 2024 #16304 Page #116
Types of Bearings By MiTek Staff
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earing: A structural support, usually a beam or wall, which is designed by the building designer to carry the truss reactions to the foundation.
MiTek’s engineering software uses two common types of bearings, roller and pinned. There is a third type, fixed, which should not be used for truss design. These bearing types are used in the structural analysis to determine the forces in the truss. Please note that real world supports do not behave exactly as the idealized pin or roller, but they are the best way available to achieve accurate results from the software. A typical truss design has a pin-type bearing at one end and a horizontal roller-type bearing at the other end. If the truss has more than two bearings, then only one bearing is a pin-type and the rest are horizontal roller-type bearings. Bearings may be located anywhere along the truss, at the ends or at midpoints of the chords, or at any other intermediate points.
Pinned Bearings A pinned support allows rotation but does not allow movement in vertical or horizontal directions. A single pinned connection is not sufficient to make a structure stable. Another support must be provided, to prevent rotation of the structure. Except for special cases, there should be only one pinned bearing per truss.
Roller Bearings A roller support is free to move along the surface upon which the roller rests. A roller can resist vertical or horizontal forces, but not both. An H-roller cannot resist forces in the horizontal direction. A V-roller cannot resist forces in the vertical direction. Since most trusses are subjected to lateral loads of some kind, a truss must have at least one other type of support in addition to roller supports.
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