# Design of Steel Structures Questions and Answers – Elastic Buckling of Slender & Built-up Compression Members

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This set of Design of Steel Structures Questions and Answers for Aptitude test focuses on “Elastic Buckling of Slender & Built-up Compression Members”.

1. Which of the following is the attribute of ideal column according to Euler?
a) material is non homogenous
b) material is isotropic
c) load does not act along centroidal axis
d) column ends are fixed

Explanation: According to Euler, the following are the attributes of ideal column: (i) Material is isotropic, homogenous and is assumed to be perfectly elastic, (ii) column is initially straight and load acts along centroidal axis (no eccetricity of loads), (iii) column has no imperfections, (iv) column ends are hinged.

2. Euler critical load for column with both the ends hinged is given by
a) Pcr = 2π2EI/L2
b) Pcr= π2EIL2
c) Pcr = 2π2EIL2
d) Pcr = π2EI/L2

Explanation: The Euler critical load for column with both the ends hinged is given by Pcr= π2EI/L2, where E is elastic modulus of material, I is moment of inertia and L is length of column.

3. Which of the following is true?
a) increasing member length causes reduction in stiffness
b) decreasing member length causes reduction in stiffness
c) member with high stiffness will buckle early than that with low stiffness
d) stiffness of member is not influenced by amount and distribution of material in cross section of column

Explanation: Member with low stiffness will buckle early than that the one with high stiffness. Increasing member length causes reduction in stiffness. Stiffness of member is influenced by amount and distribution of material in cross section of column, the value of radius of gyration reflects the way in which material is distributed.

4. Euler critical load for column with both the ends fixed is given by
a) Pcr = 2π2EI/L2
b) Pcr = π2EIL2
c) Pcr = 4π2EI/L2
d) Pcr= π2EI/L2

Explanation: The Euler critical load for column with both the ends hinged is given by Pcr = 4π2EI/L2, where E is elastic modulus of material, I is moment of inertia and L is length of column, effective length of column in this case = 2L.

5. What is the relation between critical stress and slenderness ratio?
a) critical stress is directly proportional to slenderness ratio
b) critical stress is inversely proportional to slenderness ratio
c) critical stress is square of slenderness ratio
d) critical stress is cube of slenderness ratio

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 .

6. Why is built up section used?
a) to sustain seismic loads only
b) for aesthetic appearance
c) used when rolled section do not furnish required sectional area
d) for resisting bending moment

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.

7. The shear in column may not be due to
a) material used in column

Explanation: The shear in column may be due to (i) lateral loads from wind, earthquake, gravity or other loads, (ii)slope of column with respect to line of thrust due to both unintentional and initial curvature and increased curvature during bending, (iii)end of eccentricity of load due to either end connection or fabrication imperfections.

8. Which of the following is not true?
a) function of lacing and battens is to hold main component members
b) tie plates are provided at top and bottom of column
c) lacing bars and batten plates are not designed as load carrying elements
d) lacing bars and batten plates are designed as load carrying elements

Explanation: Lacing bars and batten plates are not designed as load carrying elements. Their function is to hold main component members of built up column in relative position and equalize stress distribution in them. At ends and at intermediate points where it is necessary to interrupt the lacings, open sides are connected with tie plates. Tie plates are also provided at top and bottom of column.

9. Which of the following is true?
a) built up column lacings or battens are uneconomical if load carrying members permit greater reduction in weight than what is added by lacing or batten
b) built up column lacings or battens are economical if load carrying members permit greater reduction in weight than what is added by lacing or batten
c) no related shear stress force in plane of cross section
d) built up column designed as axially loaded column can never be eccentrically loaded

Explanation: Built up column lacings or battens are economical if load carrying members permit greater reduction in weight than what is added by lacing or batten. Built up column designed as axially loaded column may be accidentally loaded eccentrically or may have initial crookedness. Variable bending moment will be induced in such column because of eccentricity between centroidal axis of column and line of action of applied load due to this, there will be related shear stress force in plane of cross section and in connecting system.

10. The buckling strength of latticed column is ___________ that of solid column having ame area and same slenderness ratio
a) smaller than
b) greater than
c) equal to
d) cannot be compared

Explanation: The buckling strength of latticed column is smaller than that of solid column having same area and same slenderness ratio provided that solid column does not buckle locally because of thinness of material. This is because shear component of axial load produces deformation in lattice which tends to reduce overall stiffness of column and therefore reduce buckling strength of column.

11. Which of the following condition is not considered in design of built up column?
a) buckling of column as whole
b) failure of lattice member
c) material to be used for fabrication
d) buckling of component column

Explanation: In design of built up column, following conditions are considered : (i) buckling of column as whole under axial load, (ii) buckling of component column, (iii) failure of lattice member, (iv) distortion of cross section.

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