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Truss.pptx dbjbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
1. Truss
(a) A truss may be defined as a system of uniform members joined together at their ends by
riveting etc. The truss is formed from two-force members, i.e., members of truss are
straight members
with end point connections, And loads are applied only at joints. Simplest truss is
triangular truss. The individual part of the structure is called Member. The members are
joined either by welding or riveting / nut & bolts.
2. Types of Trusses: Trusses may be of following types:
a) Plane Truss or Space Truss: In plane truss all the members lie in the same plane and the forces act
along the plane of the truss, e.g. Bridge Trusses and roof trusses. In Space truss all the members do not
lie in the same plane, e.g. suspension tower, Tripod etc.
b) Statically Determinate and Statically Indeterminate Truss: The force analysis can be done by
equation of static in the case of S.D.F. Only static equations are not sufficient there isneed of considering
their deformation also in case of SIF.
c) Perfect or Rigid Truss: This is non-collapsible when external supports are removed. A perfect truss is
the one, which contains such number of members as are just sufficient toprevent distortion of its shape
when loaded externally. A perfect truss should satisfy theequation, m = 2j – 3, where m = no. of
members, j = no. of joints.
BasicAssumptions of Truss Analysis:
1. All members of truss are pin joined. The forces are transmitted from one member to anotherthrough smooth pins (no friction).
2. The truss is a perfect one and statically determinate.
3. All the members are straight, rigid, slender, and uniform in cross section and lie in same plane.
4. The external loads and reactions are acting at Joints only.
5. The self-weight of members is neglected.
6. Every joint is treated separately as a free body in equilibrium, i.e., the sum of all the verticalforces as well as the horizontal
forces acting on the joint is equated to zero.
ΣFx = 0 andΣFY = 0
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18. Friction
Friction is defined as the resistance offered by the surfaces that are in
contact when they move past each other.
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20. Two Rectangular blocks of weight W1= 150N and W2= 100N are
connected by a string and rest on an inclined Plane and on a horizontal
surface as shown in figure. The co-efficient of friction for all contiguous
surfaces is Find the magnitude and direction of the least
force P at which the motion of the blocks will impend.
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24. Block A weighing 1000N is to be raised by means of a 15 wedge B weighing 500N
Assuming the coefficient of friction between all contact surfaces to be 0.2,Find what
minimum horizontal Force P should be applied to raise the block.
