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ECIV 320 Structural Analysis I

Infuence Lines

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ANALYSIS OF FORCES DUE TO

LIVE LOADS

Live or Moving Loads Variable point of Application Temporary Loads

Common Structures Bridges Industrial Crane Rails Conveyors

Floor Girders any other structure where

loads move across its

span

INFLUENCE LINES

Variation of

Reaction, Shear, Moment or

Deflection

at a !"CIFIC !#I$T

due to aconcentratedforce

movingon member

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Prc!"ur!s

Tabulate Values

!lace %$IT L#A& at a number of fixedlocations!erform a seriesof static analysesto determine t'e value

of reaction(s'ear(moment(deflection at t'e specific point)Tabulate Values

Influence Line Equations

!lace %$IT L#A& at a variablelocationx!erform a static analysisto determine t'e function

of reaction(s'ear(moment(deflection at t'e specific

point as a function ofx)

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HINTS

Be*are of !oints of &iscontinuities

Influence lines of statically determinate beams consist of straight line

segments

!lace unit load at points representing t'e end points of t'ese segments

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#ualitati$! In%lu!nc! Lin!s

Muller!"reslau #rinci$leInfluence Line for a function is to t'e same scale as t'e

deflected s'ape of t'e beam *'en t'e beam is acted upon

by t'e function

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#ualitati$! In%lu!nc! Lin!s

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#ualitati$! In%lu!nc! Lin!s

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In%lu!nc! Lin!s %r &!a's

Concentrated Loads &istributed Loads

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Li$! La"s %r (i)*+ay &RID,ES

Caused by Traffic+eaviest, eries of Truc-s

S$ecifications %%SHT&American Association of tate and

+ig'*ay Transportation #fficials

Load 'esigantions

+ ./011 + 23011

2 A4le Truc-

./ Tons 5.30236

7ear of

pecifications

23 Tons

2 A4le Truc- 8

. A4le emitrailer

7ear of

pecifications

Sim$lification%niform Load plus a Concnetrated force placed at critical

locations

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Li$! La"s %r Railra" &RID,ES

S$ecifications %(E%American Railroad "ngineers

Associations

Load 'esigantions

"092

&evised by

T'eodore Cooper

.:;1

Loading on &riving

A4le

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I'-act La"s

Impact Loads

Calculated as ? of Live Loads 0 Impact Factor I

.2/

/3

+=L

I

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Ma.i'u' In%lu!nc! "u! t a S!ri!s % Cnc!ntrat!"

La"s / S*!ar

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Ma.i'u' In%lu!nc! "u! t a S!ri!s % Cnc!ntrat!"

La"s / S*!ar

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Ma.i'u' In%lu!nc! "u! t a S!ri!s % Cnc!ntrat!"

La"s / S*!ar

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Ma.i'u' In%lu!nc! "u! t a S!ri!s % Cnc!ntrat!"

La"s / S*!ar

.2/)32/)/@9/)/2. == V

:9/)2@9/)//)2@2 == V

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Ma.i'u' In%lu!nc! "u! t a S!ri!s % Cnc!ntrat!"

La"s / S*!ar

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Ma.i'u' In%lu!nc! "u! t a S!ri!s % Cnc!ntrat!"

La"s / S*!ar

To compute c'ange

( ).2 xxPsV =

loping Line

( ).2 yyPV =

ump

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Ma.i'u' In%lu!nc! "u! t a S!ri!s % Cnc!ntrat!"

La"s / M'!nt

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Ma.i'u' In%lu!nc! "u! t a S!ri!s % Cnc!ntrat!"

La"s / M'!nt

( ).2 xxPsM =

loping Line