1. Which of following statement is correct?
a) elastic buckling stress may be decreased by using longitudinal stiffeners
b) elastic buckling stress may be decreased by using intermediate stiffeners
c) elastic buckling stress may be increased by using intermediate transverse stiffeners
d) elastic buckling stress is not affected by intermediate or longitudinal stiffeners
Explanation: The elastic buckling stress may be increased by using intermediate transverse stiffeners (which will decrease the aspect ratio L/d, thus increasing the value of buckling coefficient), or by using longitudinal stiffeners to decrease the depth-thickness ratio.
2. What is the fundamental path in graph?
a) line along load axis up to P > Pcr
b) line along load axis up to P < Pcr
c) line along load axis up to P = Pcr
d) line along load axis up to P ≥ Pcr
Explanation: If axial load verses lateral displacement is plotted, we get a line along the load axis up to P=Pcr, this is called fundamental path.
3. Which of the following is true about secondary path?
a) lateral displacement increases indefinitely at constant load
b) lateral displacement decreases indefinitely at constant load
c) lateral displacement remains same at constant load
d) lateral displacement increases indefinitely and decreases at constant load
Explanation: When the axial load reaches the Euler bucking load, the lateral displacement increases indefinitely at constant load. This is called secondary path, which bifurcates from fundamental path at the buckling load.
4. Which of the following statement is true?
a) plate cannot carry loads higher than elastic critical load
b) plate cannot carry loads lesser than elastic critical load
c) secondary path for a plate is unstable
d) secondary path for a plate is stable
Explanation: The secondary path shows that plate can carry loads higher than elastic critical load. The secondary path for a plate is stable.
5. What is apparent modulus of elasticity?
a) ratio of average strain carried by plate to average stress
b) ratio of average stress carried by plate to average strain
c) product of average strain carried by plate to average stress
d) product of average stress carried by plate to average strain
Explanation: Elastic post-buckling stiffness is measured in terms of apparent modulus of elasticity, E*. It is the ratio of average stress carried by plate to average strain. In most of the cases, the value of E* is in the range 0.408 – 0.5 E and may be approximately taken as 0.5E.
6.The effective width of hot-rolled and welded plates is given by
a) be/b = α √(fy/fcr)
b) be/b = α √(fcr x fy)
c) be/b = α √(fcr +fy)
d) be/b = α √(fcr/fy)
Explanation: The effective width of hot-rolled and welded plates is given by be/b = α √(fcr/fy), where α is the parameter that indicates the inclusions of influence of initial curvatures and residual stress. Generally α=0.65
7. The effective width of cold-formed steel sections is given by
a) be/b = (fcr/fy)[1-0.22√(fcr/fy)].
b) be/b = (fcr/fy)[1+0.22√(fcr/fy)].
c) be/b = (fy/fcr)[1-0.22√(fcr/fy)].
d) be/b = (fcr/fy)[1+0.22√(fy/fcr)].
Explanation: The effective width based on tests on cold-formed steel sections is given by be/b = (fcr/fy)[1-0.22√(fcr/fy)]. This formula was first adopted in AISC specification for light gauge cold-formed sections.
8. Which of the following is true about local buckling?
a) failure occurs by twisting of one or more individual elements of member
b) failure occurs by buckling of one or more individual elements of member
c) failure occurs by both buckling and twisting of one or more individual elements of member
d) cannot be prevented by selecting suitable width-to-thickness ratio of elements
Explanation: Local buckling is failure which occurs by buckling of one or more individual elements of member. It can be prevented by selecting suitable width-to-thickness ratio of elements.
9. What is squash load?
a) yield stress + area of cross section
b) yield stress – area of cross section
c) yield stress / area of cross section
d) yield stress x area of cross section
Explanation: When length of column is relatively small and its component elements are prevented from local buckling, then column will be able to attain its full strength or squash load (squash load = yield stress x area of cross section).
10. What is overall flexural buckling?
a) failure occurs by excessive deflection in plane of weaker principal axis
b) failure occurs by excessive deflection in plane of stronger principal axis
c) failure occurs by twisting of member
d) failure caused by seismic load
Explanation: Overall flexural buckling is failure which occurs by excessive deflection caused by bending or flexure, about axis corresponding to weaker principal axis(minor) – one with smallest radius of gyration, largest slenderness ratio.