plain and space trusses
TRANSCRIPT
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PLAIN AND SPACETRUSSES
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TRUSS
It is an assemblage of straightmembers connected at their ends
by flexible connections to form a
rigid configration!
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Plane Truss
It is a trss "here all members of atrss and the a##lied loads lie in the
same #lane!
Space TrussThese are three$dimensional bodies
sb%ected to three$dimensional force
system!
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Plane Trusses Common BridgeTrusses
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Types of Plane Trusses
A! Sim#le Trss
These are formed connecting its member from
ti# to tail in a trianglar form and enlarging by
adding a ne" %oint that connects from the othert"o #re&ios %oint!
'! Com#ond trss
These are formed by connecting t"o or more
sim#le trss to form a single rigid body!
Connections mst be ca#able of transmitting at
least three force com#onents!
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C! Com#lex trss
These are trsses "hich is neither a
sim#le trss nor com#ond trss!
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Determining Internal Stability of
Plane Truss
Conditions are(
If m ) *+% , -./ the Trss is Internally
Unstable
If m 0 *+% , -./ the Trss is Internally
Stable
m 1 total nmber of members
% 1 total nmber of %oints
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Example of Internally Stable andUnstable Truss
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Static Determinacy, Indeterminacy
and Instability of Plane Truss
The Conditions of Static Instability/
determinacy/ and Indeterminacy of Plane Trss
are as follo"s(If/
*m 2 r. ) +%/ statically Unstable Truss
*m 2 r. 1 +%/ statically Determinate Truss
*m 2 r. 3 +%/ statically Indeterminate Truss
degree of static indeterminacy
i = (m + r) 2j
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Analysis of Member Forces on Plane Truss
by Method of oints and Method of
Section
A! "y Method of oints
Using this method/ the forces *member/
reactions/ and a##lied loads. shold be in formof co#lanar concrrent force system/ "hich
mst satisfy t"o e4ation of e4ilibrim 5671
8 and 5691 8!
'y this method/ there shold be selectingof %oint "ith no more than t"o n:no"n
forces *"hich mst not be collinear. acting on
it *%oint.!
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SPA#% TRUSS
S#ace Trssis analysed by as three$dimensionalstrctre sb%ected to three$dimensional force
system!
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Reactions on Space Truss
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The Conditions for determinacy externally of s#ace
strctre are as follo"s(
If r ) ?/ the s#ace strctre is statically unstable
e'ternally
If r 1 ?/ the s#ace strctre is statically determinate
e'ternally
If r 3 ?/ the s#ace strctre is statically indeterminate
e'ternally
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Static Determinacy, Indeterminacy
and Instability of Space Truss
StructureConditions are as follo"s(
If *m 2 r. ) -%/ statically unstable space
truss
If *m 2 r. 1 -%/ statically determinate
space truss
If *m 2 r. 3 -%/ statically indeterminate
space truss
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Analysis of Member ForcesA! Determining forces 'y ;ethod of @oint
LA' 1
67A' 16A'*.
67A' 16A'*.
67A' 16A'*.
6A' 1
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C! Identification of ! If all bt one of the members connected to a
%oint lie in a single #lane and no external loads
or reactions are a##lied to the %oint/ then the
force in the member that is not co#lanar is
=ero!
+! If all bt t"o of the members connected to a
%oint ha&e =ero force and no external loads or
reactions are a##lied to the %oint/ then nless
the t"o remaining members are collinear/ the
force in each of them is also =ero!
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End of Re#ort!