UNIT II
ANALYSIS OF PLANE TRUSS, THIN CYLINDERS / SHELL
1. What is mean by perfect frame?
If a frame is composed of such members, which are just sufficient to keep the
frame in equilibrium, when the frame is supporting the external load, then the frame
is know as perfect frame.
2. What are the different types of frames?
The different types of frame are:
• Perfect frame and
• Imperfect frame.
3. What is mean by Imperfect frame?
A frame in which number of members and number of joints are not given by
n = 2j – 3 is know as imperfect frame. This means that number of members in an
imperfect frame will be either more or less than (2j – 3).
4. What is mean by deficient frame?
If the number of member in a frame are less than (2j -3), then the frame is
know as deficient frame
5. What is mean by redundant frame?
If the number of member in a frame are more than (2j -3), then the frame is
know as deficient frame
6. What are the assumptions made in finding out the forces in a frame?
The assumptions made in finding out the forces in a frame are:
The frame is a perfect frame
The frame carries load at the joints
All the members are pin-joined.
7. What are the reactions of supports of a frame?
The frame are generally supported
(i) on a roller support or
(ii) On a hinged support.
8. How will you Analysis of a frame?
Analysis of a frame consists of
Determinations of the reactions at the supports and
Determination of the forces in the members of the frame
9. What are the methods for Analysis the frame?
Methods of joints,
Methods of sections, and
Graphical method.
10. How method of joints applied to Trusses carrying Horizontal loads.
If a truss carries horizontal loads (with or without vertical loads) hinged at one
end supported on roller at the other end, the support reaction at the roller support end
will be normal. Whereas the support reaction at the hinged end will consist of (i)
horizontal reaction and (ii) vertical reaction
11. How method of joints applied to Trusses carrying inclined loads.
If a truss carries inclined loads hinged at one end supported on roller at the
other end, the support reaction at the roller support end will be normal. Whereas the
support reaction at the hinged end will consist of (i) horizontal reaction and (ii)
vertical reaction
12. What is mean by compressive and tensile force?
The forces in the member will be compressive if the member pushes the joint
to which it is connected whereas the force in the member will be tensile if the
member pulls the joint to which it is connected.
13. How will you determine the forces in a member by method of joints?
While determining forces in a member by methods of joints, the joint should
be selected in such a way that at any time there are only two members, in which the
forces are unknown.
14. Define thin cylinder?
If the thickness of the wall of the cylinder vessel is less than 1/15 to 1/20 of its
internal diameter, the cylinder vessel is known as thin cylinder.
15. What are types of stress in a thin cylindrical vessel subjected to internal
pressure?
These stresses are tensile and are know as
Circumferential stress (or hoop stress ) and
Longitudinal stress.
16. What is mean by Circumferential stress (or hoop stress) and Longitudinal
stress?
The stress acting along the circumference of the cylinder is called
circumferential stress (or hoop stress) whereas the stress acting along the length of
the cylinder is known as longitudinal stress.
17. What are the formula for finding circumferential stress and longitudinal
stress?
Circumferential stress (f1) is given by as f1 = p x d / 2t x l and the
longitudinal stress (f2) is given by f2 = p x d / 2t x c
.
18. What are maximum shear stresses at any point in a cylinder?
Maximum shear stresses at any point in a cylinder, subjected to internal
fluid pressure is given by f1 –f2 / 2 = pd / 8t
19. What are the formula for finding circumferential strain and longitudinal
strain?
The circumferential strain (e1) and longitudinal strain (e2) are given by
e1 = pd / 2tE (1- 1/2m), e2 pd / 2tE (1/2 – 1/m).
20. What are the formula for finding change in diameter, change in length and
change volume of a cylindrical shell subjected to internal fluid pressure p?
d = pd2 /2tE (1 – 1/2m),
L = pdL /2tE (1/2 – 1/m),
V = pd /2tE (5/2 – 2/m) x volume,
21. What are the formula for finding principal stresses of a thin cylindrical shell
subjected to internal fluid pressure p and a torque?
Major Principal Stress = f1 + f2 / 2 + {(f1 - f2 /2)2 + fs
2}
Minor Principal Stress = f1 + f2 / 2 - {(f1 - f2 /2)2 + fs
2}
Maximum shear stress = ½ [Major Principal Stress - Minor Principal
Stress]
Where f1 = Circumferential stress,
f2 =Longitudinal stress,
fs =shear stress due to torque.
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