influence lines 2 f2008
TRANSCRIPT
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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