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| '''Span''' is the distance between two intermediate supports for a structure, e.g. a [[beam (structure)|beam]] or a [[bridge]].
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| A span can be closed by a solid beam or by a rope. The first kind is used for bridges, the second one for [[electric power transmission|power line]]s, overhead telecommunication lines, some type of [[Antenna (radio)|antennas]] or for [[aerial tramway]]s.
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| [[Image:Bending.svg|frame|right|Side view of a [[Simply supported#Beams|simply supported]] beam (top) bending under an evenly distributed load (bottom).]]
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| The span is a significant factor in finding the strength and size of a beam as it determines the maximum [[bending moment]] and [[Deflection (engineering)|deflection]]. The maximum bending moment <math>M_{max}</math> and deflection <math>\delta_{max}</math>in the pictured beam is found using:<ref name='gere'>{{Cite book|title=Mechanics of Materials |edition=Eighth| isbn = 978-1-111-57773-5|last1=Gere|first1= James M.|last2=Goodno|first2=Barry J.|page=1086}}</ref>
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| :<math>M_{max} = \frac {q L^2} {8}</math> | |
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| :<math>\delta_{max} = \frac {5 M_{max} L^2} {48 E I} = \frac {5 q L^4} {384 E I}</math>
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| where
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| :<math>q</math> = Uniformly distributed load
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| :<math>L</math> = Length of the beam
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| :<math>E</math> = [[Modulus of elasticity]]
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| :<math>I</math> = [[Area moment of inertia]]
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| Note that the maximum bending moment and deflection occur midway between the two supports. From this it follows that if the span is doubled, the maximum moment (and with it the [[tensile stress|stress]]) will quadruple, and deflection will increase by a factor of sixteen.
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| For long-distance rope spans, used as power line, antenna or for aerial tramways, see [[list of spans]].
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| ==References==
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| {{Reflist}}
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| {{DEFAULTSORT:Span (Architecture)}}
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| [[Category:Architectural elements]]
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| [[Category:Structural engineering]]
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