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Joists are closely spaced beams, which are used to support
the floor sheathing. Ceiling joist or floor joist spacing
of 12" to 16" is usually provided while designing joists for
residential structures. They are designed for bending, shear,
deflection and bearing. Joist design is governed by joist
span. The load on the joist is usually UDL or a Point Load.
Based upon the nature and magnitude of the load on the joist,
shape of the joist can be rectangular or I-section. The joist
design is governed by the floor joist span / ceiling joist
span
Based on the support system provided joist can be classified
into following types:
i) Simply Supported Joist: Joists having only two supports,
one at each end.
ii) Cantilever Joist: Joist whose one end is resting on the
support and other end is free.
Consulting Engineers, Corp. uses allowable stress design
method to develop framing joist design solutions. This method
is based on the principle that actual stress in the material
should not exceed the permissible stress permitted in the
material. The joist is designed for working load condition.
Floor joist system can be designed for various combinations
of loads and joists shapes using the following joist design
modules:
Special attention is given to the following factors while
designing floor joist of wood:
1. Bending (including lateral stability)
2. Shear
3. Deflection
4. Bearing
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