Subject :- Design of Steel Structures / DOS-I(Steel)LSM / SE-I (Steel)
Unit-IV :- COMPRESSION MEMBERS
1. What is compression member?
a)
structural member subjected to torsion
b) structural member subjected to tensile force
c) structural member subjected to compressive force
d) structural member subjected to bending moment
Answer: c
Explanation:
Structural member which is subjected to compressive forces along its axis is
called compression member. Compression members are subjected to loads that tend
to decrease their lengths.
2. For very short compression member________
a) failure stress will be twice the yield stress
b) failure stress will be greater than yield stress
c) failure stress will be less than yield stress
d) failure stress will equal yield stress
Answer: d
Explanation:
For very short compression members, the failure stress will the equal yield
stress and no buckling will occur.
3. The length of member should be _________ for a
short column
a)
L ≤ 88.5r
b) L ≥ 88.5r
c) L ≥ 180r
d) L > 150r
Answer: a
Explanation:
For a member to be classified as short column, length of member should be L ≤
88.5r , where r is radius of gyration. The slenderness ratio of column defines
the column as short or long column.
4. Long compression members will ______
a)
buckle inelastically
b) buckle plastically
c) buckle elastically
d) not buckle
Answer: c
Explanation:
Long compression members will buckle elastically where axial buckling stress
remains below proportional limit.
5. Which of the following is not a parameter for
decrease in strength of slender member?
a)
seismic load
b) variation of material properties
c) initial lack of straightness
d) residual stress
Answer: a
Explanation:
The decrease in strength of slender member is due to following parameter:
imperfections- initial lack of straightness, accidental eccentricities of
loading, residual stress, and variation of material properties over the cross
section.
6. ________________ is the property of compression
member?
a)
elements of member need not prevent local buckling
b) member must be sufficiently rigid to prevent general buckling
c) member must not be sufficiently rigid to prevent local buckling
d) elements of member should be thin to prevent local buckling
Answer: b
Explanation:
Member must be sufficiently rigid to prevent general buckling in any possible
direction, and each element of member must be thick enough to prevent local
buckling.
7. How can moment of inertia be increased?
a)
by spreading material of section at its axis
b) by increasing load
c) by spreading material of section towards its axis
d) by spreading material of section away from its axis
Answer: d
Explanation:
Most important property of section in compression member is radius of gyration
and thus moment of inertia. it can be increased by spreading material of
section away from its axis.
8. ____________ is an ideal section for
compression member?
a)
one made up of costly material
b) one having same moment of inertia about any axis through its centre of
gravity
c) one having larger length
d) one having different moment of inertia about any axis through its centre of
gravity
Answer: b
Explanation:
Ideal section is the one which has same moment of inertia about any axis
through its centre of gravity.
9. Rods and bars are recommended when length is
___________
a)
greater than 3m
b) greater than 4m
c) greater than 5m
d) less than 3m
Answer: d
Explanation:
Rods and bars withstand very little compression when length is more. Hence
these are recommended for lengths less than 3m only.
10. Which of the following is true about tubular
section?
a)
tubes do not have torsional resistance
b) tubes have same radius of gyration in all direction
c) weight of tubular section is more than the weight required for open profile
sections
d) tubes have low buckling strength
Answer: b
Explanation:
Tubes have same radius of gyration in all direction. They have high buckling
strength and have excellent torsional resistance. Weight of tubular section is
less than one half the weight required for open profile sections.
11. Which of the following statement is true?
a)
single angle sections are suitable for long lengths
b) unequal angles are desirable over equal angles
c) least radius of gyration of equal angle is less than that of unequal angle
for same area of steel
d) least radius of gyration of single angle section is small compared to
channel and I-sections
Answer: d
Explanation:
Equal angle are desirable and economical over unequal angles because least
radius of gyration of equal angle is greater than that of unequal angle for
same area of steel. Single angle sections are not suitable for long lengths.
Least radius of gyration of single angle section is small compared to channel
and I-sections.
12. Effective length of compression member is
________
a)
distance between end point and centroid of member
b) distance between points of contraflexure
c) distance between ends of members
d) distance between end point and midpoint of member
Answer: d
Explanation:
Effective length of compression member is distance between points of
contraflexure. It should be derived from actual length and end conditions.
13. Magnitude of effective length depends upon
a)
load applied on member
b) material of member
c) rotational restraint supplied at end of compression member
d) location where member is used
Answer: c
Explanation:
Magnitude of effective length depends upon rotational restraint supplied at end
of compression member and upon resistance to lateral movement provided.
14. Which of the following is true regarding
compression member?
a)
greater the effective length, greater the load carrying capacity
b) smaller the effective length, smaller the danger of lateral buckling
c) smaller the effective length, smaller the load carrying capacity
d) smaller the effective length, more the danger of lateral buckling
Answer: b
Explanation:
Smaller the effective length of particular compression member, smaller is the
danger of lateral buckling and greater is the load carrying capacity.
15. What is the effective length when both ends of
compression member are fixed?
a)
0.65L
b) 0.8L
c) 1.2L
d) 2.0L
Answer: a
Explanation:
The effective length of compression member when both ends of compression member
are fixed is 0.65L (i.e. L/√2), where L is the length of the member.
16. What is the effective length when both ends of
compression member are hinged?
a)
0.65L
b) 0.80L
c) 1.0L
d) 2.0L
Answer: c
Explanation:
The effective length of compression member when both ends of compression member
are hinged is L, where L is the length of the member.
17. What is the effective length when one end of
compression member is fixed and other end is free?
a)
0.65L
b) 2.0L
c) 0.8L
d) L
Answer: b
Explanation:
The effective length of compression member when one end is fixed and other end
is free is 2L, where L is the length of the member.
18. What is the effective length when one end of
compression member is fixed and other end is hinged?
a)
0.8L
b) 0.65L
c) 2L
d) L
Answer: a
Explanation:
The effective length of compression member when one end is fixed and other end
is hinged is 0.8L, where L is the length of the member.
19. Slenderness ratio of compression member is
__________________
a)
product of radius of gyration and effective length
b) ratio of effective length to radius of gyration
c) ratio of radius of gyration to effective length
d) difference of radius of gyration and effective length
Answer: b
Explanation:
The tendency of member to buckle is usually measured by its slenderness ratio.
Slenderness ratio of member is ratio of effective length to appropriate radius
of gyration (λ = kL/r). This is valid only when column has equal unbraced
heights for both axes and end condition is same for particular section.
20. Minimum slenderness ratio (Maximum radius of
gyration) can be obtained by
a)
by increasing load
b) by spreading material of section at its axis
c) by spreading material of section away from its axis
d) by spreading material of section towards its axis
Answer: c
Explanation:
Maximum radius of gyration is obtained when material of section is farthest
from centroid i.e. away from its axis.
21. What is the relation between critical stress
and slenderness ratio?
a)
critical stress is cube of slenderness ratio
b) critical stress is directly proportional to slenderness ratio
c) critical stress is inversely proportional to slenderness ratio
d) critical stress is square of slenderness ratio
Answer: c
Explanation:
fcr = Pcr/Ag = π2E/λ2, critical stress
is inversely proportional to slenderness ratio of column and very large values
can be obtained by using L/r → 0.
22. Why built up section are used?
a)
for resisting bending moment
b) to sustain seismic loads only
c) for aesthetic appearance
d) used when rolled section do not furnish required sectional area
Answer: d
Explanation:
Size and shape of rolled sections are limited because of limitation of rolling
mills. When rolled section do not furnish required sectional area or when
special shape or large radius of gyration is required in two different
direction, a built up section is used.
23. Which of the following is correct?
a)
single laced system on opposite of main component shall be in opposite
direction view from either side
b) lacings and battens should not be provided on opposite sides of same member
c) lacing system should not be uniform throughout length of column
d) single and double laced systems should be provided on opposite sides of same
member
Answer: b
Explanation:
Lacing system should be uniform throughout length of column. Single and double
laced systems should not be provided on opposite sides of same member. Lacings
and battens should not be provided on opposite sides of same member. Single
laced system can be in same direction view from either side on opposite of main
component so that one is shadow of other.
24. Lacing shall be designed to resist a total
transverse shear equal to ____ of axial force in member
a)
4.3%
b) 5.2%
c) 1.5%
d) 2.5%
Answer: d
Explanation:
Lacing can be designed to resist a total transverse shear at any point in the
member equal to 2.5% of axial force in member. This shear shall be divided
among lacing systems in parallel planes. Lacings should also be designed to
resist any shear due to bending moment or lateral load on member.
25. Slenderness ratio of lacing is limited to
a)
200
b) 145
c) 400
d) 350
Answer: b
Explanation:
Slenderness ratio is the ratio of effective length by radius of gyration.
Slenderness ratio of lacing shall not exceed 145.
26. Which of the following is true about effective
length?
a)
effective length shall be taken as length between inner end bolts/rivets of
bars for double lacings
b) for welded bars, effective length shall be taken as 0.9 times distance
between inner end welds connecting single bars to members
c) effective length shall be taken as 1.5 times length between inner end
bolts/rivets of bars for double lacings
d) effective length shall be taken as length between inner end bolts/rivets of
bars for single lacings
Answer: d
Explanation:
Effective length shall be taken as length between inner end bolts/rivets of
bars for single lacings and 0.7 times length between inner end bolts/rivets of
bars for double lacings. For welded bars, effective length shall be taken as
0.7 times distance between inner end welds connecting single bars to members.
27. Minimum width of lacing bars shall _______
a)
be less than 2 times diameter of connecting bolt/rivet
b) not be less than 3 times diameter of connecting bolt/rivet
c) be less than 3 times diameter of connecting bolt/rivet
d) be less than 5 times diameter of connecting bolt/rivet
Answer: b
Explanation:
Minimum width of lacing bars shall not be less than approximately 3 times the
diameter of connecting bolt/rivet.
28. Thickness of lacing member should be
a)
less than 1/60thof the effective length for
double lacing
b) less than 1/40th of the effective length
for single lacing
c) less than 1/60th of the effective length
for single lacing
d) not less than 1/60th of the effective length
for double lacing
Answer: d
Explanation:
Thickness of lacing member should not be less than 1/40th of the effective length for single lacing and
not less than 1/60th of the effective length
for double lacing.
29. Which of the following condition should be
satisfied for spacing of lacings?
a)
maximum slenderness ratio of component of main members between two consecutive
lacing connection should not be more than 0.9 x most unfavourable slenderness
ratio of combined column
b) maximum slenderness ratio of component of main members between two
consecutive lacing connection should be greater than 50
c) maximum slenderness ratio of component of main members between two
consecutive lacing connection should be not greater than 50
d) maximum slenderness ratio of component of main members between two
consecutive lacing connection should be more than 0.7 x most unfavourable
slenderness ratio of combined column
Answer: c
Explanation:
The spacing of lacing bars should be such that maximum slenderness ratio of
component of main members between two consecutive lacing connection is not
greater than 50. It should not be greater than 0.7 times most unfavourable
slenderness ratio of combined column.
30. Lacing bars shall be inclined at an angle of
___ to axis of built up member.
a)
25o
b) 35o
c) 50o
d) 90o
Answer: c
Explanation:
Lacing bars shall be inclined at an angle of 40o to 70o to axis of built up member.
31. Minimum radius of gyration for lacing flats is
a)
t/√12
b) t/24
c) t/12
d) t/√24
Answer: a
Explanation:
Minimum radius of gyration for lacing flats is t/√12 , where t is thickness of
flat.
32. Minimum number of bolts for connecting end of
strut is
a)
0
b) 2
c) 1
d) 3
Answer: b
Explanation:
Ends of strut should be connected with minimum of 2 bolts/rivets or equivalent
length of weld length (length must not be less than maximum width of member).
33. Which of the following is true?
a)
when leg of angles greater than 125mm wide or web of channel is mm wide,
minimum bolt is sufficient for connection
b) when there is small spacing between the two sections placed back-to-back,
washers and packing should not be provided
c) when there is small spacing between the two sections placed back-to-back,
washers and packing should be provided
d) there should be additional connection in between along the length of member
Answer: c
Explanation:
There should be minimum of two additional connection in between, spaced
equidistant along the length of member. When there is small spacing between the
two sections placed back-to-back, washers(in case of bolts) and packing(in case
of welding) should be provided to make connection. When leg of angles greater
than 125mm wide or web of channel is mm wide, minimum two bolts/rivets should
be for connection.
34. Which of the following is not true?
a)
spacing of tack bolt should be greater than 600mm
b) spacing of tack bolt should be less than 600mm
c) connection should extend at least 1.5 times the width of the member
d) if bolts are used, they should be spaced longitudinally at less than 4 times
the bolt diameter
Answer: a
Explanation:
Spacing of tack bolt should be less than 600mm. If bolts are used, they should
be spaced longitudinally at less than 4 times the bolt diameter. Connection
should extend at least 1.5 times the width of the member.
35. Members connected back-to-back connected by
bolts should be
a)
not be used
b) subjected to twice the transverse loading in plane perpendicular to bolted
surface
c) subjected to transverse loading in plane perpendicular to bolted surface
d) not subjected to transverse loading in plane perpendicular to bolted surface
Answer: d
Explanation:
Members connected back-to-back connected by bolts should not be subjected to
transverse loading in plane perpendicular to riveted/bolted/welded surface.
36. Longitudinal spacing between intermittent
welds used for connection should be
a)
greater than 18t
b) not greater than 16t
c) greater than 16t
d) equal to 18t
Answer: b
Explanation:
Longitudinal spacing between intermittent welds used for connection should not
be greater than 16t, where t is thickness of thinner connection.
37. The strength of compression members subjected
to axial compression is defined by curves corresponding to _______ classes
a)
a, d
b) b, e, f
c) e, f, g
d) a, b, c and d
Answer: d
Explanation:
The strength of compression members subjected to axial compression is defined
by curves corresponding to a, b, c and d classes. The value of imperfection
factor depends on type of buckling curve.
38. ___________of the following is not a
compression member?
a)
boom
b) strut
c) tie
d) rafter
Answer: c
Explanation:
Strut, boom and rafter are compression members, whereas tie is a tension
member.
39. The best compression member section generally
used is_____________
a)
channel section
b) single angle section
c) I-section
d) double angle section
Answer: c
Explanation:
Generally, ISHB sections are used as compression members.
40. The best double-angle compression member
section is_____________
a)
unequal angles on same side of gusset plate
b) unequal angles with short leg connected
c) unequal angles with long leg connected
d) unequal angles on opposite side of gusset plate
Answer: b
Explanation:
Unequal angles with short leg connected are preferred as compression member
section.
41. The flange is classified as semi-compact if
outstand element of compression flange of rolled section is less than
a)
8.4ε
b) 9.4ε
c) 10.5ε
d) 15.7ε
Answer: d
Explanation:
The flange is classified as semi-compact if outstand element of compression
flange of rolled section is less than 15.7ε and for a welded section, less than
13.6ε.
42. The flange is classified as plastic if
outstand element of compression flange of rolled section is less than
a)
15.7ε
b) 9.4ε
c) 8.4ε
d) 10.5ε
Answer: b
Explanation:
The flange is classified as plastic if outstand element of compression flange
of rolled section is less than 9.4ε and for a welded section, less than 8.4ε.
43. The outstand element of compression flange of
a rolled section is 10.2 (ε=1). The flange will be classified as
a)
slender
b) compact
c) plastic
d) semi-compact
Answer: b
Explanation:
The flange is classified as compact if outstand element of compression flange
of rolled section is less than 10.5ε and for a welded section, less than 9.4ε.
44. The design compressive strength of member is
given by
a)
Ae /fcd
b) fcd
c) 0.5Aefcd
d) Aefcd
Answer: d
Explanation:
The design compressive strength of member is given by Pd = Aefcd, where Ae is
effective sectional area, fcd is design
compressive stress.
45. The design compressive stress, fcd of column is given by
a)
[fy / γm0] / [φ + (φ2-λ2)].
b) [fy / γm0] / [φ – (φ2-λ2)0.5].
c) [fy / γm0] / [φ + (φ2-λ2)0.5].
d) [fy / γm0] / [φ – (φ2-λ2)2].
Answer: c
Explanation:
The design compressive stress, fcd of column
is given by fcd = [fy / γm0] / [φ + (φ2-λ2)0.5], where fy is yield
stress of material, φ is dependent on imperfection factor, λ is non dimensional
effective slenderness ratio.
46.
The value of imperfection factor for buckling class a is __________
a)
0.75
b) 0.5
c) 0.34
d) 0.21
Answer: d
Explanation:
The value of imperfection factor, α for buckling class a is 0.21. The
imperfection factor considers all the relevant defects in real structure when
considering buckling, geometric imperfections, eccentricity of applied loads
and residual stresses.
47. If imperfection factor α = 0.49, then as per
IS:800-2007 the buckling class will be_______
a)
a
b) c
c) b
d) g
Answer: b
Explanation:
For buckling class c, the value of imperfection factor is 0.49. The
imperfection factor takes into account all the relevant defects in real
structure when considering buckling, geometric imperfections, eccentricity of
applied loads and residual stresses.
48. The value of φ in the equation of design
compressive strength is given by
a)
φ = 0.5[1+α(λ-0.2)+λ2].
b) φ = 0.5[1-α(λ-0.2)+λ2].
c) φ = 0.5[1-α(λ-0.2)-+λ2].
d) φ = 0.5[1+α(λ+0.2)-λ2].
Answer: a
Explanation:
The value of φ in the equation of design compressive strength is given by φ =
0.5[1+α(λ-0.2)+λ2], where α is imperfection
factor(depends on buckling class) and λ is non-dimensional effective
slenderness ratio.
49. Euler buckling stress fcc is given by____________
a) (π2E KL/r)2
b) (π2E)/(KL/r)
c) (π2E)/(KL/r)2
d) (π2E)/(KLr)2
Answer: c
Explanation:
Euler buckling stress fcc is given
by fcc = (π2E)/(KL/r)2, where E is modulus of elasticity of material and
KL/r is effective slenderness ratio i.e. ratio of effective length, KL to
appropriate radius of gyration, r.
50. What is the value of non dimensional
slenderness ratio λ in the equation of design compressive strength?
a)
(fy /fcc)
b) √(fy fcc)
c) (fy fcc)
d) √(fy /fcc)
Answer: d
Explanation:
The value of non dimensional slenderness ratio λ in the equation of design
compressive strength is given by λ = √(fy /fcc) , where fy is yield
stress of material and fcc = (π2E)/(KL/r)2, where E is
modulus of elasticity of material and KL/r is effective slenderness ratio i.e.
ratio of effective length.
51. The design compressive strength in terms of
stress reduction factor is given by
a)
X / fy
b) Xfy / γm0
c) X /fy γm0
d) X γm0 /fy
Answer: b
Explanation:
The design compressive strength in terms of stress reduction factor is given by
fcd = Xfy / γm0 , where X = stress reduction factor for
different buckling class, slenderness ratio and yield stress = 1/ [φ + (φ2-λ2)0.5], fy is yield
stress of material and γm0 is partial
safety factor for material strength.
52. The value of design compressive strength is
limited to
a)
fy / γm0
b) fy
c) fy + γm0
d) fy γm0
Answer: a
Explanation:
The value of design compressive strength is given by fcd = [fy / γm0] / [φ + (φ2-λ2)0.5] ≤ fy / γm0 i.e. fcd should be less than or equal to fy / γm0.
53. The compressive strength for ISMB 400 used as
a column for length 5m with both ends hinged is
a)
382 kN
b) 275 kN
c) 375.4 kN
d) 453 kN
Answer: c
Explanation:
K = 1 for both ends hinged, KL = 1×5000 = 5000, r = 28.2mm (from steel table),
Ae = 7846 mm2(from steel
table)
KL/r = 5000/28.2 = 177.3
h/bf = 400/140 = 2.82, t = 16mm Therefore, buckling class = b
From table in IS code, fcd = 47.85MPa
Pd = Ae fcd = 7846 x 47.85 = 375.43 kN
54. Compression member in a
roof truss is called as __________
a) Stanchion
b) Post
c) Strut
d) Column
Answer:
c
Explanation: A compression member in a roof truss is called strut and tension members are termed as tie member.
ADE(22607) ke mcq dalo
ReplyDeleteRefere Tension member for Unit I of ADE 22607 and Compression members mcqs for Unit II of ADE 22607.
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