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Standard codes of practice do not establish clear or rigid criteria for limiting the deflection of structural members, this decision is left to the judgment of the professional design engineer.

DeflectionStructural MemberDeflection LimitationLoad Combination
Vertical DeflectionMain frame raftersSpan/ 180Dead + Live
Roof purlinsSpan/ 180Dead + Live
3 Mezzanine beams and joistsSpan/ 240Dead + Live
Top running crane (TRC) beamsSpan/ 600Dead + Crane
Underhung crane (UHC) beamsSpan/ 500Dead + Crane
Monorail crane (MR) beamsSpan/ 500Dead + Crane
Relative deflection of adjacent frames at point of support of UHC or MR beam.Bay/225Crane only
Relative deflection of UHC beams supported by the same frame.Crane span/ 500Crane only
Rigid frame rafters supporting UHC or MR beams running laterally in the building.Bldg. span/ 500Crane only
Lateral DeflectionMain frame columns with eave height (EH) up to 9.0 mEave height/45Dead + Wind
Main frames supporting top running cranes (TRC) or underhung cranes (UHC)Eave height/60All
Wall girtsSpan/ 120Wind only
Endwall wind columnsSpan/ 120Wind only
Portal framesEave height/45Wind only

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