In general, bending is the most critical criterion for medium-span beams, deflection and vibration for long-span beams, and shear for heavily loaded short-span beams, but in practice, however, design checks have to be carried out for all of the design and displacement conditions.

For strength-related conditions, the design value of each stress (i.e. the design stress) is calculated and compared with the design value of its equivalent strength (i.e. the design strength modified where appropriate by strength factors) and, to meet the code

(a) Solid section joists with skewed blocking (b) Solid section trimmer beam and joists
(c) Deep long-span LVL joists exposed (d) Purlins

Fig. 4.1. Examples of flexural members.

reliability requirements, when using the partial factor method the following condition must be met:

Design stress < (Strength factors) x Design strength

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