Category: Design of Steel Structures Objective Questions

Design of Steel Structures Multiple Choice Questions on “Factors affecting Lateral Stability”.

1. Which of the following does not affect lateral stability?
a) cross sectional shape
b) support conditions
c) type of loading
d) height of building
Answer: d
Clarification: The factors affecting lateral stability are cross sectional shape, support conditions, effective length, level of application of transverse loads.

2. Which of the following statement is correct?
a) I-section has high torsional stiffness
b) Closed section has high torsional stiffness
c) Closed section has less stiffness
d) Hollow circular tube has more efficiency as flexural member
Answer: b
Clarification: I-section with the larger in-plane bending stiffness does not have matching stability. in contrast, closed sections such as tubes, boxes and solid shafts have high torsional stiffness, often high as 100 times that of an open section.

3. Which of the following statement is not correct?
a) Hollow circular tube has more efficiency as flexural member
b) Hollow circular tube has lesser efficiency as flexural member
c) It is the most efficient shape for torsional resistance
d) It us rarely used as a beam element
Answer: a
Clarification: Hollow circular tube is the most efficient shape for torsional resistance, but is rarely employed as beam element because of difficulties encountered in connecting it to other members and lesser efficiency as a flexural member.

4. Open cross sections have major part of material distributed
a) is not distributed
b) on the centroid
c) towards centroid
d) away from centroid
Answer: d
Clarification: In open cross sections ( I and channel sections), major part of material is distributed at the flanges, i.e. away from their centroids, to improve their resistance to in-plane bending stresses.

5. The effective length factor is _____ for beams flanges fully restrained
a) 1
b) 0.5
c) 0.75
d) 1.5
Answer: b
Clarification: The effective length factor K is 0.5 theoretically for flanges fully restrained. But for design purpose, it may be taken as 0.7.

6. The effective length of compression flange of simply supported beam not restrained against torsion at ends is
a) 1.2 L
b) 1.0 L
c) 0.8 L
d) 0.5 L
Answer: a
Clarification: The effective length of compression flange of simply supported beam not restrained against torsion at ends is 1.2 L, where L is span length.

7. Effective length of compression flanges at the ends unrestrained against lateral buckling is
a) 1.5 L
b) 0.85 L
c) 0.5 L
d) L
Answer: d
Clarification: Effective length of compression flanges at the ends unrestrained against lateral buckling (i.e. free to rotate in plan) is L, where L is length of span.

8. Effective length of compression flanges at the ends partially restrained against lateral buckling is
a) 1.75 L
b) 1.0 L
c) 0.85 L
d) 0.5 L
Answer: c
Clarification: Effective length of compression flanges at the ends partially restrained against lateral buckling (i.e. free to rotate in plane in the bearings) is 0.85 L, where L is length of span.

9. Restraint against torsion can be provided by
(i) web cleats, (ii) bearing stiffeners acting together with bearing of beam, (iii)lateral end frames to ends of compression flanges
a) i only
b) i and ii
c) ii and iii
d) i, ii and iii
Answer: d
Clarification: Restraint against torsion can be provided by (i) web or flange cleats, (ii) bearing stiffeners acting together with the bearing of beam, (iii) lateral end frames or external supports to ends of compression flanges, (iv)the beam built into the supporting walls.

10. The most severe loading condition for cantilever is
a) point load acting at centre
b) point load acting at tip
c) point load acting between centre and fixed end
d) point load acting at L/4 distance
Answer: b
Clarification: For cantilevers, the most severe loading condition is point load acting at the tip because the tip is unsupported.

11. Provision of intermediate lateral supports ______ lateral stability of beam
a) increases
b) decreases
c) does not change
d) cannot say
Answer: a
Clarification: Provision of intermediate lateral supports increases the lateral stability of beam. For bracings to be effective, the braces should be prevented from moving in axial direction.

12. The requirement of effective bracing is
a) it should not have sufficient strength not to withstand forces transferred to it by beam
b) it should not have sufficient strength to withstand forces transferred to it by beam
c) it should have sufficient stiffness so that buckling of beam occurs in between braces
d) it should not have sufficient stiffness so that buckling of beam occurs in between braces
Answer: c
Clarification: The requirements of effective bracing are (i) it should have sufficient strength to withstand forces transferred to it by beam, (ii) it should have sufficient stiffness so that buckling of beam occurs in between braces.

13. Which of the following is correct?
a) torsional bracing attached near bottom flange should bend in single curvature
b) torsional bracing attached near bottom flange should not bend in single curvature
c) its flexural stiffness should be 4EI_b/S
d) its flexural stiffness should be 6EI_b/S
Answer: a
Clarification: Torsional bracing attached near bottom flange should bend in single curvature and its flexural stiffness should be 2EI/S, where I_b is moment of inertia of brace, S is spacing between girders.

14. The lateral stability of tranversely loaded beam is dependent on
a) arrangement of load only
b) level of application of load only
c) both arrangement and level of application of load
d) is not dependent on any of these
Answer: c
Clarification: The lateral stability of tranversely loaded beam is dependent on the arrangement of load as well as level of application of loads with respect to centroid of cross section.

Tough Design of Steel Structures Questions and Answers on “Gantry Girders & Design of Industrial Buildings”.

1. Which of the following is correct regarding gantry girders?
a) It is laterally supported except at the columns
b) It is subjected to impact load
c) It should not be analysed for unsymmetrical bending
d) It is not subjected to longitudinal load
Answer: b
Clarification: Gantry girder are different from beams in buildings. It is generally laterally unsupported except at the columns. It is subjected to impact load. It must be analysed for unsymmetrical bending because of lateral thrust from the starting and stopping of the crab. It is subjected to longitudinal load due to starting and stopping of crane bridge itself. They are always simply supported.

2. Which of the following loads are not considered in the design of gantry girders?
a) longitudinal loads
b) gravity loads
c) lateral loads
d) wind loads
Answer: d
Clarification: The loads considered in the design of gantry girders are vertical loads or gravity loads, longitudinal loads, lateral loads and impact loads. The vertical force is the reaction from crane girder, acting vertically downward. The longitudinal thrust is due to starting and stopping of crane acting in longitudinal direction. The lateral thrust is due to starting and stopping of the crab acting horizontally normal to the gantry girder.

3. The wheel load transferred from trolley to gantry girder is given by
a) W₁ = [W_t(L_c+L₁)]/(2L_c)
b) W₁ = [W_t(L_c-L₁)](2L_c)
c) W₁ = [W_t(L_c-L₁)]/(2L_c)
d) W₁ = [W_t(L_c+L₁)]/( L_c)
Answer: c
Clarification: Since trolley moves on the crane girder along the span of truss, its weight is transferred to the crane wheels as the axle load and finally to gantry girder. The wheel load transferred from trolley to gantry girder is given by W₁ = [W_t(L_c-L₁)]/(2L_c), where W₁ is load of each wheel on gantry girder, W_t is weight of trolley or crab car, L_c is distance between gantry giders, L₁ is distance between centre of gravity of trolley and gantry.

4. For gantry girders carrying electrically operated overhead travelling cranes, the lateral forces are increased by ____ for impact allowance.
a) 10% of weight of crab and weight lifted on the crane
b) 20% of weight of crab and weight lifted on the crane
c) 25% of maximum static wheel load
d) 50% of maximum static wheel load
Answer: a
Clarification: For gantry girders carrying electrically operated overhead travelling cranes, the lateral forces are increased by 10% of weight of crab for impact allowance and weight lifted on the crane. The vertical forces can be increased by 25% of maximum static wheel load.

5. For gantry girders carrying hand operated cranes, the vertical forces are increased by____ for impact allowance
a) 10% of maximum static wheel load
b) 25% of maximum static wheel load
c) 10% of weight of crab and weight lifted on the crane
d) 20% of weight of crab and weight lifted on the crane
Answer: c
Clarification: For gantry girders carrying hand operated cranes, the vertical forces are increased by 10% of maximum static wheel load for impact allowance. The lateral forces can be increased by 5% of weight of crab and weight lifted on the crane.

6. Fatigue effect for light and medium duty cranes need not be checked if
a) N_sc > 10×10⁶ [(27/γ_mft)/γ_mt].
b) N_sc < 5×10⁶ [(27/γ_mft)/γ_mt]³
c) N_sc > 5×10⁶ [(27/γ_mft)/γ_mt]²
d) N_sc < 5×10⁶ [(27/γ_mft)γ_mt].
Answer: b
Clarification: Fatigue effect for light and medium duty cranes need not be checked if normal and shear design stress ranges f ≤ (27/γ_mft) or if actual number of stress cycles, N_sc < 5×10⁶ [(27/γ_mft)/γ_mt]³, where f = actual fatigue stress range, γ_mft = partial safety factor for strength, γ_mf = partial safety factor for material = 1.10.

7. The maximum wheel load is obtained when
a) crane crab is farthest to gantry girder
b) crane crab is closest to gantry girder
c) crane crab is not attached
d) crane crab is at mid span
Answer: b
Clarification: The maximum wheel load is obtained when crane crab is closest to gantry girder. The crab in such position on the crane girder gives maximum reaction on the gantry girder. The vertical reaction of crane girder is transferred through its two wheels on to the gantry girder. Therefore, the maximum wheel load is half of this reaction. This maximum wheel load is then increased for impact and used for design of gantry girder.

8. The bending moment due to dead load of girder is maximum at
a) one-third distance at span
b) two-third distance at span
c) end of span
d) centre of span
Answer: d
Clarification: The bending moment considered in the design of gantry girder are the bending moment due to maximum wheel loads (with impact) and the bending moment due to dead load of the girder and rails. The bending moment due to dead loads is maximum at the centre of span.

9. What is the maximum vertical deflection allowed for a gantry girder where the cranes are manually operated?
a) L/500
b) L/700
c) L/600
d) L/800
Answer: a
Clarification: The vertical deflection of gantry girder where the cranes are manually operated should not exceed L/500, where L is the span of gantry girder. The maximum vertical deflection allowed for a gantry girder where the cranes are travelling overhead and operated electrically upto 500kN is L/750 and operated electrically over 500kN is L/1000. When gantry girders carry moving loads such as charging cars, the deflection should not exceed L/600.

10. The minimum recommended rise of trusses with Galvanised Iron sheets is
a) 1 in 12
b) 1 in 6
c) 1 in 10
d) 1 in 18
Answer: b
Clarification: The pitch of truss depends upon the roofing material. The minimum recommended rise of trusses with galvanised iron sheets is 1 in 6 and with asbestos cement sheets is 1 in 12.

11. The economic spacing of roof truss depends on
a) cost of purlins only
b) cost of purlins and cost of roof covering
c) dead loads
d) cost of roof covering and dead loads
Answer: b
Clarification: The economic spacing of the truss is the spacing that makes the overall cost of trusses, purlins, roof coverings, columns, etc. the minimum. It depends upon the relative cost of trusses, purlins, roof coverings, spacing of columns, etc. If the spacing is large, the cost of these trusses per unit area decreases but the cost of purlin increases. But if the spacing of trusses is small, the cost of trusses per unit area increases. Roof coverings cost more if the spacing of trusses is large.

12. Which of the following is true for economic spacing?
a) cost of trusses should be equal to twice the cost of purlins
b) cost of trusses should be equal to twice the cost of purlins minus cost of roof coverings
c) cost of trusses should be equal to the cost of purlins plus cost of roof coverings
d) cost of trusses should be equal to twice the cost of purlins plus cost of roof coverings
Answer: d
Clarification: For economic spacing of roof trusses, the cost of trusses should be equal to twice the cost of purlins plus cost of roof coverings. This equation is used for checking the spacing of trusses and not for design of trusses.

13. Which of the following load combination is not considered for design of roof trusses?
a) Dead load + crane load
b) Dead load + wind load
c) Dead load + earthquake load
d) Dead load + live load + wind load
Answer: c
Clarification: Earthquake loads are not significant for roof trusses because of the small self weights. The following load combinations can be considered : (i) Dead load + snow load, (ii) Dead load + partial/full live load, (iii) dead load + live load + internal positive air pressure, (iv) dead load + live load + internal suction air pressure, (v) dead load + live load + wind load.

14. Live load for roof truss should not be less than
a) 0.4kN/m²
b) 0.2kN/m²
c) 0.75kN/m²
d) 0.8kN/m²
Answer: a
Clarification: The live load for roof truss should not be less than 0.4kN/m². For roof slopes ≤ 10^o and access provided, the live load to be taken is 1.5kN/m² of plan area. For roof slopes > 10^o and access is not provided , the live load to be taken is 0.75kN/m² of plan area.

To practice Tough questions and answers on all areas of Design of Steel Structures,

Design of Steel Structures Multiple Choice Questions on “Design Considerations, Analysis & Methods”.

1. Which of the following is correct criteria to be considered while designing?
a) Structure should be aesthetically pleasing but structurally unsafe
b) Structure should be cheap in cost even though it may be structurally unsafe
c) Structure should be structurally safe but less durable
d) Structure should be adequately safe, should have adequate serviceability
Answer: d
Clarification: Structure should be designed such that it fulfils it intended purpose during its lifetime and be adequately safe in terms of strength, stability and structural integrity and have adequate serviceability. Structure should also be economically viable, aesthetically pleasing and environment friendly.

2. What is serviceability?
a) It refers to condition when structure is not usable
b) It refers to services offered in the structure
c) It means that the structure should perform satisfactorily under different loads, without discomfort to user
d) It means that structure should be economically viable
Answer: c
Clarification: Serviceability is related to utility of structure. The structure should perform satisfactorily under service loads, without discomfort to user due to excessive deflection, cracking, vibration, etc. Other considerations of serviceability are durability, impermeability, acoustic and thermal insulation etc.

3. Analysis is referred to _____________
a) determination of cost of structure
b) determination of axial forces, bending moment, shear force etc.
c) determination of factor of safety
d) drafting architectural plans and drawings
Answer: b
Clarification: Analysis refers to determination of axial forces, bending moment, shear force, torsional moments etc. acting on different members of structure due to applied loads and their combinations.

4. The structure is statically indeterminate when________________
a) static equilibrium equations are insufficient for determining internal forces and reactions on that structure
b) static equilibrium equations are sufficient for determining internal forces and reactions on that structure
c) structure is economically viable
d) structure is environment friendly
Answer: a
Clarification: When the static equilibrium equations are insufficient for determining internal forces and reactions on that structure, the structure is said to be statically indeterminate. Analysis of these structures is complex and cannot be analysed only by using laws of statics, various analytical methods like slope deflection method, moment distribution method, etc.

5. Which of the following is one of the methods of analysis prescribed in the code for steel structures?
a) Hinge Analysis
b) Limit Analysis
c) Roller Analysis
d) Dynamic Analysis
Answer: d
Clarification: Code suggests the use of any of the following methods for steel structures : (i) elastic analysis, (ii) plastic analysis, (iii) advanced analysis, (iv) dynamic analysis.

6. Which method is mainly adopted for design of steel structures as per IS code?
a) Limit State Method
b) Working Stress Method
c) Ultimate Load Method
d) Earthquake Load Method
Answer: a
Clarification: Steel structures and their elements are normally designed by limit state method. When limit state method cannot be conveniently adopted, working stress method may be used.

7. Which IS code is used for general construction of steel?
a) IS 456
b) IS 256
c) IS 800
d) IS 100
Answer: c
Clarification: IS 800:2007 is the code of practice for general construction in steel. It is issued by Bureau of Indian Standards.

8. Which of the following relation is correct?
a) Permissible Stress = Yield Stress x Factor of Safety
b) Permissible Stress = Yield Stress / Factor of Safety
c) Yield Stress = Permissible Stress / Factor of Safety
d) Permissible Stress = Yield Stress – Factor of Safety
Answer: b
Clarification: Permissible Stress = Yield Stress / Factor of Safety. Permissible Stress is the amount of stress that will not cause failure. It is a fraction of yield stress. It takes care of overload or other unknown factors.

9. In Working Stress Method, which of the following relation is correct?
a) Working Stress ≤ Permissible Stress
b) Working Stress ≥ Permissible Stress
c) Working Stress = Permissible Stress
d) Working Stress > Permissible Stress
Answer: a
Clarification: In Working Stress Method, Working Stress ≤ Permissible Stress. Each member is checked for number of different combinations of loadings.

10. Arrange the following in ascending order according to their factor of safety in working stress method :
(i) tension members, (ii) long column, (iii) short column, (iv) connections
a) i < ii < iii < iv
b) i < iv < ii < iii
c) i = iii < ii < iv
d) iv = i < iii < ii
Answer: c
Clarification: In working stress method, the factor of safety for the above are as follows : (i) for tension members = 1.67, (ii) for long column = 1.92, (iii) for short columns = 1.67, (iv) for connections = 2.5-3.

11. What is Load Factor?
a) ratio of working load to ultimate load
b) product of working load and ultimate load
c) product of working load and factor of safety
d) ratio of ultimate load to working load
Answer: d
Clarification: Load Factor = working load / ultimate load. In ultimate load design, different types of loads and load combinations have different load factors assigned.

12. Which of the following is not a main element of framed structure?
a) Beam
b) Column
c) Shear connector
d) Lattice member
Answer: c
Clarification: For framed structure, the main elements are beam, column, beam-column, tie and lattice members.

13. Which of the following are subjected to both axial loads and bending moments?
a) Beam-Column
b) Column
c) Lattice member
d) Beam
Answer: a
Clarification: Beams are those elements which are subjected to bending moments and shear force only. Columns are subjected to axial loads. Beam-Column is subjected to axial load and bending moment. In special cases, beams are subjected to torsional moments.

14. How much percentage increase of permissible stress is allowed when dead load, live load and wind load are considered together in working stress method?
a) 50%
b) 33%
c) 40%
d) 60%
Answer: b
Clarification: In working stress method, working stress ≤ permissible stress.
Stress due to dead load + live load ≤ permissible stress
Stress due to dead load + wind load ≤ permissible stress
Stress due to dead load + live load + wind load ≤ 1.33 permissible stress.

Design of Steel Structures Multiple Choice Questions on “Weld Defects & Types of Joints”.

1. The production of sound welds is not governed by ______
a) type of joint
b) choice of electrode
c) type of metal plate
d) arc length
Answer: c
Clarification: The production of sound welds is governed by type of joint, its preparation, root opening, etc. The choice of electrode, welding position, welding current and voltage, arc length, rate of travel also affect the quality of weld.

2. Which of the following is not a reason for incomplete fusion?
a) surfaces to be jointed are coated with oxides
b) insufficient current supplied by welding equipment
c) high rate of welding
d) use of large electrode
Answer: d
Clarification: Incomplete fusion may result if surfaces to be jointed have not been cleaned properly and are coated with oxides and other foreign materials. Insufficient current supplied by welding equipment and high rate of welding will result in incomplete fusion.

3. Which of the following is true?
a) incomplete penetration is found in fillet welds
b) it is due to use of large size of electrodes
c) it is due to excessive welding current
d) it is due to insufficient welding rates
Answer: b
Clarification: Incomplete penetration is due to failure of weld metal to penetrate the complete depth of joint where full penetration has been specified. This defect is found in groove welds sue to unsuitable groove design for selected welding process, use of large size of electrodes, insufficient welding current, excessive welding rates.

4. Which of the following is not true?
a) Porosity is caused due to insufficient current
b) It is caused due to longer arc length
c) It may be due to poor welding procedure
d) It results in stress concentration
Answer: a
Clarification: Porosity is formed when gas pockets or voids are draped during cooling process. It may be due to excessively high current or longer arc length or due to poor welding procedure. Porosity results in stress concentration and reduced ductility of metal.

5. Which of the following is true regarding undercutting defect?
a) Undercutting is due to local increase of thickness of parent metal at weld toe
b) It is due to insufficient current
c) It can be corrected by depositing additional weld material
d) It is not easy to detect
Answer: c
Clarification: Undercutting is due to local decrease of thickness of parent metal at weld toe. This results in groove in base metal adjacent to toe of weld and left unfilled by weld metal during welding process. Undercutting may result in loss of gross section and will act as stress riser. This defect may be due to excessive current or longer arc length. It can be easily detected visually and can be corrected by depositing additional weld material.

6. Hot cracks can be prevented by __________
a) faster cooling
b) non uniform heating
c) pre-heating
d) slower cooling
Answer: d
Clarification: Hot cracks form as weld begin to solidify and are caused by brittle constituents (presence of sulphur, carbon, silicon and hydrogen). They can be prevented by more uniform heating and slower cooling.

7. Cold cracks can be prevented by __________
a) uniform heating
b) by use of low hydrogen electrode
c) faster cooling
d) slower cooling
Answer: b
Clarification: Cold cracks occur under room temperature run parallel to but under the weld in base metal. Use of low hydrogen electrodes along with proper pre-heating and post-heating may reduce possibility of cold cracks.

8. The types of welded joints does not depend on _________
a) size of members connected at joint
b) type of loading
c) area available for welding
d) size of weld
Answer: d
Clarification: The types of welded joints depends on (i) size and shape of members connected at joint, (ii) type of loading, (iii) area available for welding at the joint, (iv) relative cost of various types of weld.

9. Which of the following are correct regarding butt joints over lap joints?
a) Lap joints eliminates eccentricity whereas butt joints develops eccentricity
b) Butt joints minimizes the size of connection
c) Lap joints are aesthetically pleasing over butt joints
d) Butt joint obtained from full penetration groove weld has 50% efficiency
Answer: b
Clarification: Butt joints eliminates eccentricity developed using lap joints. Butt joints minimizes the size of connection and are aesthetically pleasing over lap joints. Butt joint obtained from full penetration groove weld has 100% efficiency.

10. What is face reinforcement used in butt joint?
a) It is extra weld metal that makes throat dimensions greater than the thickness of the welded material
b) It is extra weld metal that makes the throat dimensions smaller than the thickness of the welded material
c) It is extra weld metal that makes the throat dimensions equal to the thickness of the welded material
d) It is parent metal makes that the throat dimensions smaller than the thickness of the welded material
Answer: a
Clarification: Face reinforcement is extra weld metal that makes the throat dimensions greater than the thickness of the welded material. The provision of reinforcement increases the efficiency of joint and ensures that depth of weld is at least equal to thickness of the plate.

11. When plates of two different thicknesses and/or widths are joined, the wider or thicker part should be reduced at the butt joint to make __________
a) thickness less than smaller part, the slope being steeper than one in five
b) thickness greater than smaller part, the slope being steeper than one in five
c) thickness equal to smaller part, the slope not being steeper than one in five
d) thickness equal to smaller part, the slope being steeper than one in five
Answer: c
Clarification: When plates of two different thicknesses and/or widths are joined, the wider or thicker part should be reduced at the butt joint to make thickness equal to smaller part, the slope not being steeper than one in five. When reduction is not possible, the weld metal shall be built up at the junction with thicker part to dimensions at least 25% greater than those of thinner part, or alternatively to the dimensions of thicker member.

12. Which of the following is not true regarding lap joint?
a) Connection using lap joint requires large number of erection bolts
b) It can accommodate minor errors in fabrication
c) Lap joints are well suited for shop as well as field welding
d) It introduces some eccentricity of loads
Answer: a
Clarification: Lap joints offer ease of fitting and ease of jointing. It can accommodate minor errors in fabrication or minor adjustment in length. They are well suited for shop as well as field welding. Connection using lap joint requires a small number of erection bolts. The main drawback of lap joint is that it introduces some eccentricity of loads, unless a double lap joint is used.

13. T-joints are not used to fabricate _________
a) I-shapes
b) T-shapes
c) Brackets
d) Plates joined at straight angles
Answer: d
Clarification: T-joints are used to fabricate built up sections such as T-shapes, I-shapes, plate girders, brackets and stiffeners where two plates are joined at right angles.

14. Match the pair

	Types of joints					Use / Application
	A) Butt joint			i) used to keep two or more plats in given plane
	B) Lap joint			ii) used to join ends of flat plates of nearly equal thickness
	C) Tee joint			iii) used to form built-up rectangular box sections
	D) Corner joint		        iv) used to fabricate built-up sections  
	E) Edge joint		        v) plates with different thickness can be joined without any difficulty

a) A-i, B-ii, C-iii, D-iv, E-v
b) A-ii, B-v, C-iv, D-iii, E-i
c) A-ii, B-iii, C-iv, D-v, E-i
d) A-v, B-iv, C-iii, D-ii, E-i
Answer: b
Clarification: Butt joint is used to join of flat plates of nearly equal thickness. Plates with different thickness can be joined without any difficulty using lap joints. Tee joint is used to fabricate built-up sections, where two plates are joined at right angles. Corner joint is used to form built-up rectangular box sections, which may be used as columns or beams to resist high torsional forces. Edge joints are not used in structural engineering applications, they are used to keep two or more plats in given plane.

Design of Steel Structures Multiple Choice Questions on “Cross Sectional classification”.

1. Which of the following factor is considered for classification of cross section?
a) location where member is used
b) width-to-thickness ratio
c) length of member
d) seismic force
Answer: b
Clarification: Cross section are classified into four behavioural groups depending upon the material yield strength, width-to-thickness ratio of individual components (e.g. webs and flanges) within the cross section, and the loading arrangement.

2. What is a plastic section?
a) cross section which can develop plastic moment
b) cross section which can resist seismic force
c) cross section in which buckling can occur
d) cross section which can develop plastic hinges
Answer: d
Clarification: Plastic or class I sections are cross sections which can develop plastic hinges and have a rotation capacity required for failure of structure by formation of plastic mechanism.

3. What is a compact section?
a) cross section which can develop plastic moment resistance
b) cross section which can resist seismic force
c) cross section in which buckling can occur
d) cross section which can develop plastic hinges
Answer: a
Clarification: Compact or class II sections are cross sections which can develop plastic moment resistance, but have inadequate plastic hinge rotation capacity because of local buckling.

4. What is a semi-compact section?
a) cross section which can develop plastic moment resistance
b) cross section which can resist seismic force
c) cross section in which elastically calculated stress in extreme compression fibre can reach yield strength
d) cross section which can develop plastic hinges
Answer: c
Clarification: Semi-compact or class III sections are cross sections in which elastically calculated stress in extreme compression fibre of steel can reach yield strength.

5. What is a slender section?
a) cross section which can develop plastic moment resistance
b) cross section which can resist seismic force
c) cross section in which elastically calculated stress in extreme compression fibre can reach yield strength
d) cross section in which local buckling will occur before yield stress
Answer: d
Clarification: Slender or class IV sections are cross section in which local buckling occurs even before the yield stress is attained in one or more parts of the cross section.

6. Which of the following is correct regarding class I section?
a) They are not fully effective under pure compression
b) They are capable of reaching and maintaining full plastic moment in bending
c) They are not capable of reaching and maintaining full plastic moment in bending
d) They does not exhibit sufficient ductility
Answer: b
Clarification: Class I sections are fully effective under pure compression, and capable of reaching and maintaining full plastic moment in bending and hence used in plastic design. These sections will exhibit sufficient ductility.

7. Match the following design moment capacity with the classes of cross section

                    Cross section			Design moment capacity
                       i) Compact			A) Md = Zpfy
                      ii) Semi-Compact			B) Md < Zefy
                     iii) Plastic			C) Md = Zefy
                     iv) Slender

a) i – B, ii – C, iii – A, iv – B
b) i – A, ii – B, iii – C, iv – B
c) i – A, ii – C, iii – A, iv – B
d) i – C, ii – C, iii – A, iv – B
Answer: c
Clarification: The design moment capacity M_d of each of the four classes of cross sectioncan be calculated as i) Plastic – M_d = Z_pf_y, ii) Compact – M_d = Z_pf_y, iii) Semi-Compact – M_d = Z_ef_y, iv) Slender – Md < Z_ef_y, where Z_p = plastic modulus, Z_e = elastic modulus.

8. Which of the following statement is correct?
a) Internal elements are elements attached along both longitudinal edges to other elements
b) Outstanding elements are elements attached along both longitudinal edges to other elements
c) Outstanding elements are elements which are free along both the edges
d) Internal elements are elements which are free along both the edges
Answer: a
Clarification: Internal elements are elements attached along both longitudinal edges to other elements or to longitudinal stiffeners connected at suitable intervals to transverse stiffeners connected at suitable intervals to transverse stiffeners (e.g. web of I-sections and flange and web of box sections). Outstanding elements are attached along only one of the longitudinal edges to an adjacent element, the other edge being free to displace out of plan (e.g. flange overhang of an I-section, stem of T-section, leg of angle section).

Design of Steel Structures Multiple Choice Questions on “Behaviour of Real Beam”.

1. As the beam undergoes bending under applied loads, axial strain distribution at a point in beam
a) axial strain is not produced
b) remains constant
c) varies along depth of beam
d) varies along length of beam
Answer: c
Clarification: As the beam undergoes bending under applied loads, axial strain distribution at a point in beam varies along the depth of beam.

2. The beam buckles elastically if
a) M_cr < M_y
b) M_cr > M_y
c) M_cr = M_y
d) M_cr = 2M_y
Answer: a
Clarification: If M_cr critical moment of a section is less than yield moment M_y , then beam buckles elastically.

3. If M_cr > M_y of a beam section, then
a) beam does not buckle
b) beam buckles fully elastically
c) beam buckles completely plastically
d) some amount of plasticity is experienced
Answer: d
Clarification: When critical moment of a section M_cr is greater than M_y , some amount of plasticity is experienced at the outer edges before buckling is initiated.

4. Beams with intermediate slenderness fail by
a) elastic buckling
b) inelastic lateral buckling
c) attains M_p without buckling
d) do not fail
Answer: b
Clarification: Beams with intermediate slenderness (0.4 < √M_p/M_cr < 1.2) fail by inelastic lateral buckling at loads below M_p and above M_cr .

5. What are residual stresses?
a) stresses developed during construction
b) stresses developed due to seismic load
c) stresses developed due to vibration
d) stresses developed during manufacturing
Answer: d
Clarification: During the process of manufacture, steel sections are subjected to large thermal expansions resulting in yield level strains in sections. As subsequent cooling is not uniform throughout the section, self-equilibrating patterns of stresses are formed. These stresses are called residual stresses.

6. Which of the following is correct?
a) yielding of section starts at lower moments
b) yielding of section starts at higher moments
c) yielding of section does not start at lower moments
d) yielding of section does not occur
Answer: a
Clarification: Due to presence of residual stresses, yielding of section starts at lower moments. Then with increase in moment, yielding spreads through the cross section.

7. Match the pair

(i) high slender beams		 	   (A) attain Mp without buckling
(ii) stocky beams			   (B) fail by inelastic buckling
(iii) intermediate slender beams           (C) fail by elastic buckling

a) i-A, ii-B, iii-C
b) i-C, ii-B, iii-A
c) i-C, ii-A, iii-B
d) i-A, ii-C, iii-B
Answer: c
Clarification: Beams with high slenderness fail by elastic lateral buckling at M_cr. Beams of intermediate slenderness fail by inelastic lateral buckling at loads below M_p and above M_cr. Stocky beams attains M_p without buckling with negligible lateral deformations.

8. Which of the following is correct?
a) torsional bracing attached to top flange should bend in single curvature
b) torsional bracing attached to top flange should not bend in reverse curvature
c) its flexural stiffness should be 6EI_b/S
d) its flexural stiffness should be 4EI_b/S
Answer: c
Clarification: Torsional bracing attached to top flange should bend in reverse curvature and its flexural stiffness should be 6EI_b/S, where S is spacing between girders.