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Building Design and Construction Handbook - Merritt - Ventech!

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7.90 SECTION SEVEN<br />

FIGURE 7.39 Steel beams subject to torsion—good <strong>and</strong> bad practice.<br />

purlin may distort the section; the condition should be corrected by staggering, as<br />

indicated in Fig. 7.39c.<br />

Equations for computing torsion stresses are given in Art. 5.4.2. Also, see Bibliography,<br />

Art. 7.55.<br />

7.28 MEMBERS SUBJECT TO CYCLIC LOADING<br />

Relatively few structural members in a building are ever subjected to large, repeated<br />

variations of stress or stress reversals (tension to compression, <strong>and</strong> vice versa) that<br />

could cause fatigue damage to the steel. Members need not be investigated for this<br />

possibility unless the number of cycles of such stresses exceeds 20,000, which is<br />

nearly equivalent to two applications every day for 25 years.<br />

DESIGN OF CONNECTIONS<br />

<strong>Design</strong> of connections <strong>and</strong> splices is a critical aspect of the design process. Because<br />

each fabricator has unique equipment <strong>and</strong> methods, the detailed configuration of

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