Category: Design of Steel Structures Objective Questions

Design of Steel Structures Multiple Choice Questions on “Stiffeners”.

1. The function of bearing stiffener is to
a) improve buckling strength of web
b) preclude any crushing of web
c) restrain against torsional effects
d) increase buckling resistance of web
Answer: b
Clarification: The function of bearing stiffener is to preclude any crushing of web at locations of heavy concentrated loads. Thus, they transfer heavy reactions or concentrated loads to the full depth of web. They are placed in pairs on the web of plate girders at unframed girder ends and where required for concentrated loads.

2. Match the following

	Stiffeners				Function
A) Load carrying stiffener		(i) increases buckling resistance of web
B) Torsional stiffener			(ii) local strengthening of web
C) Diagonal stiffener			(iii) prevent local buckling of web
D) Tension stiffener			(iv) restrain against torsional effects
E) Longitudinal stiffener		(v) transmit tensile forces

a) A-i, B-ii, C-iii, D-iv, E-v
b) A-v, B-iv, C-iii, D-ii, E-i
c) A-iv, B-v, C-i, D-ii, E-iii
d) A-iii, B-iv, C-ii, D-v, E-i
Answer: d
Clarification: Load carrying stiffener prevents local buckling of web due to any concentrated load. Torsional stiffener are provided at supports to restrain girders against torsional effects. Local strengthening of web under the combination of shear and bending is provided by diagonal stiffeners. The tensile forces from the flange are transmitted to the web through the tension stiffener. A longitudinal stiffener increases the buckling resistance of web.

3. The outstand of stiffener from face of web is restricted to
a) 20t_q/ε
b) 120t_qε
c) 20t_qε
d) 50t_qε
Answer: c
Clarification: Unless the outer edge is continuously stiffened, the outstand of stiffener from face of web should not exceed 20t_qε,where t_q is thickness of stiffener. When the outstands of web is between 14t_qε and 20t_qε, then the stiffener design should be on the basis of a core section with an outstand of 14t_qε.

4. What is the stiff bearing length?
a) length which cannot deform appreciably in bending
b) length which deform appreciably in bending
c) length of outer end of flange
d) length of web
Answer: a
Clarification: The stiff bearing length of any element b₁ is that length which cannot deform appreciably in bending. To determine b₁, the dispersion of load through a steel bearing element should be taken as 45˚ through solid material, such as bearing plates, flange plates, etc.

5. The effective length of web on each side of centreline of stiffeners for interior stiffeners is limited to
a) 10 t_w
b) 50 t_w
c) 40 t_w
d) 15 t_w
Answer: c
Clarification: The effective length of web on each side of centreline of stiffeners is limited to 20 times the web thickness, i.e. 40t_w for interior stiffeners and 20t_w for end stiffeners . The effective section is the full area or core area of stiffener together with effective length of web on each side of centreline of stiffeners.

6. The effective length of intermediate transverse stiffener is taken as
a) 2 times the length of stiffener
b) 0.7 times the length of stiffener
c) 1.4 times the length of stiffener
d) 0.5 times the length of stiffener
Answer: d
Clarification: The effective length of intermediate transverse stiffener is taken as 0.7 times the length of stiffener. The intermediate transverse stiffener is provided mainly to improve shear buckling resistance of the web.

7. The second moment of area of transverse web stiffeners not subjected to external loads or moments is given by
a) I_s ≤ 0.75dt_w²
b) I_s ≥ 0.75dt_w²
c) I_s ≤ 1.5dt_w²
d) I_s ≥ 12.5dt_w
Answer: b
Clarification: Transverse stiffeners not subjected to external loads or moments should have second moment of area Is about centreline of the web, if stiffeners are on both sides of the web and about face of the web, if stiffener is on only one side of the web such that Is ≥ 0.75dt_w² for c/d ≥ √2 and Is ≥ 1.5dt_w²/c² for c/d < √2.

8. Which of the following buckling check is applied to stiffeners?
a) [(V+V_c)/γ_m0] ≤ F_qd
b) [(V+V_c)γ_m0] ≥ F_qd
c) [(V-V_c)/γ_m0] ≤ F_qd
d) [(V-V_c)γ_m0] ≥ F_qd
Answer: c
Clarification: Stiffeners not subjected to external loads or moments should be checked for buckling for a force F_d = [(V-V_c)/γ_m0] ≤ F_qd, where F_qd is design resistance of intermediate stiffeners, V is factored shear force adjacent to the stiffener, V_cr is shear buckling resistance of the web panel designed without using tension field action. This check is required for intermediate stiffeners only when tension field action is utilized in webs.

9. The interaction expression for stiffeners subjected to external loads or moments is given by
a) [(F_q-F_s)/F_qd]+(F_s/F_sd)+(M_q/M_yq) < 1
b) [(F_q-F_s)/F_qd]+(F_s/F_sd)+(M_q/M_yq) > 1
c) [(F_q-F_s)/F_qd]-(F_s/F_sd)-(M_q/M_yq) < 1
d) [(F_q+F_s)/F_qd]-(F_s/F_sd)-(M_q/M_yq) > 1
Answer: a
Clarification: Stiffeners subjected to external loads and moments should meet the conditions of load carrying stiffeners. In addition, they should satisfy the following interaction equation: [(F_q-F_s)/F_qd]+(F_s/F_sd)+(M_q/M_yq) q is stiffener force, F_qd is design resistance of intermediate stiffeners corresponding to buckling about axis parallel to the web, F_s is external load or reaction at stiffener, F_sd is design resistance of load carrying stiffener corresponding to buckling about axis parallel to the web, Md is moment on the stiffener due to eccentrically applied load and transverse load, M_yq is yield moment capacity of stiffener based on its elastic modulus about its centroidal axis parallel to the web.

10. Which of the following is not true regarding longitudinal stiffeners?
a) longitudinal stiffeners increase buckling resistance considerably as compared to transverse stiffeners
b) they consist of plane section for welded plate girder
c) first horizontal stiffener is provide at one-fifth of distance from compression flange
d) first horizontal stiffener is provide at neutral axis
Answer: d
Clarification: Longitudinal stiffeners are also called horizontal stiffeners. They increase buckling resistance considerably as compared to transverse stiffeners when the web is subjected to buckling. They consist of angle section for riveted/bolted plate girder and plane section for welded plate girder and are provided in the compression zone of the web. The first horizontal stiffener is provide at one-fifth of distance from compression flange to tension flange. If required another stiffener is provided at the neutral axis.

11. The connection of intermediate transverse stiffeners are designed for shear of
a) t_wb_s
b) t_w²/5b_s
c) t_w²5b_s
d) t_w5b_s
Answer: b
Clarification: Intermediate transverse stiffeners not subjected to external loading should be connected to the web so as to withstand a shear between each component of the stiffener and the web not less than t_w²/5b_s, where t_w is thickness of web, b_s is outstand width of stiffener.

12. The second moment of area of torsional stiffeners about center line of the web is given as
a) I_s ≤ αs_sD³
b) I_s ≤ 0.34α_sD³T_cf
c) I_s ≥ 0.34α_sD³T_cf
d) I_s ≥ α_sD³
Answer: c
Clarification: When bearing stiffeners are required to provide torsional restraint at the support of the beams, the second moment of area of the stiffener section about center line of the web should be such that I_s ≥ 0.34α_sD³T_cf , where αs = 0.006 for L_LT/r_y ≤50, 0.3/( L_LT/r_y) for 50LT/r_y≤100, 30/( L_LT/r_y)² for L_LT/r_y ≥100, D = overall depth of beam at the support, T_cf = maximum thickness of compression flange in the span under consideration, KL = laterally unsupported effective length of compression flange of beam, r_y = radius of gyration of the beam about minor axis.

Design of Steel Structures Multiple Choice Questions on “Types of Steel”.

1. Which of the following is the property of high carbon steel?
a) high toughness
b) reduced ductility
c) high strength
d) reduced strength
Answer: b
Clarification: High carbon steel contains high carbon content. Hence it has reduced ductility, toughness and weldability.

2. High carbon steel is used in ______________
a) transmission lines and microwave towers
b) structural buildings
c) fire resistant buildings
d) for waterproofing
Answer: a
Clarification: High carbon steel is used in transmission lines and microwave towers where relatively light members are joint by bolting.

3. What is the permissible percentage of micro-alloys in medium and high strength micro-alloyed steel?
a) 0.1%
b) 0.5%
c) 0.25%
d) 1.0%
Answer: c
Clarification: Medium and High strength micro-alloyed steel have low carbon content, but alloys such as niobium, vanadium, titanium or boron are added to achieve high strength.

4. Fire resistant steels are also called as ____________
a) Stainless steel
b) Weathering steel
c) High strength steel
d) Thermomechanically treated steel
Answer: d
Clarification: Fire resistant steels are also called as thermomechanically treated steel. They perform better than ordinary steel under fire.

5. What is the minimum percentage of chromium and nickel added to stainless steel?
a) 0.5%, 10.5%
b) 2%, 20%
c) 10.5%, 0.5%
d) 30%, 50%
Answer: c
Clarification: Stainless steel are low carbon steels to which a minimum of 10.5% chromium (maximum 20%) and 0.5% nickel is added.

6. Match the pair of Type of steel with its ultimate tensile strength :

	TYPE OF STEEL					ULTIMATE TENSILE CAPACITY
(A) Carbon Steel 					(i) 700-950 MPa
(B) High Strength Carbon Steel				(ii) 440-590 MPa
(C) Weathering Steel					(iii) 410-440 MPa
(D) High Strength quenched & tempered steel		(iv) 480 MPa
(E) Medium and High strength microalloyed steel	        (v) 480-550 MPa

a) A-i, B-ii, C-iii, D-iv, E-v
b) A-v, B-iv, C-iii, D-ii, E-i
c) A-iii, B-v, C-iv, D-i, E-ii
d) A-ii, B-iii, C-v, D-i, E-iv
Answer: c
Clarification: Ultimate tensile strength is the capacity of material to withstand loads tending to elongate. It is the maximum stress that a material can withstand while being stretched or pulled. The ultimate tensile strength for Carbon Steel is 410-440 MPa, 480-550 MPa for High Strength Carbon Steel, 480 MPa for Weathering Steel, 700-950 MPa for High Strength quenched & tempered steel, 440-590 MPa for Medium and High strength microalloyed steel.

7. What is weathering steel?
a) low-alloy atmospheric corrosion-resistant steel
b) low-carbon steel
c) high strength quenched and tempered steel
d) fire resistant steel
Answer: a
Clarification: Weathering steel are low-alloy atmospheric corrosion-resistant steel. They are often left unpainted. They have an ultimate tensile strength of 480 MPa.

8. Match the pair of Type of steel with its yield strength:

	TYPE OF STEEL					YIELD STRENGTH
(A) Carbon Steel 					(i) 300-450 MPa
(B) High Strength Carbon Steel				(ii) 350 MPa
(C) Weathering Steel					(iii) 350-400 MPa
(D) High Strength quenched & tempered steel		(iv) 230-300MPa
(E) Medium and High strength microalloyed steel	        (v) 550-700 MPa

a) A-i, B-ii, C-iii, D-iv, E-v
b) A-i, B-iii, C-v, D-iv, E-ii
c) A-v, B-iv, C-iii, D-ii, E-i
d) A-iv, B-iii, C-ii, D-v, E-i
Answer: d
Clarification: Yield Strength is the stress that a material can withstand without any permanent deformation i.e. the point of stress at which any material starts to deform plastically. The yield strength of carbon steel is 230-300MPa, 350-400 MPa for High Strength Carbon Steel, 350 MPa for Weathering Steel, 550-700 MPa for High Strength quenched & tempered steel, 300-450 MPa for Medium and High strength microalloyed steel.

Design of Steel Structures Multiple Choice Questions on “Types and Properties of Welding”.

1. Arrange the following welds in ascending order as per their usage in structural engineering applications.
a) fillet weld, groove weld, slot and plug weld
b) slot and plug weld, groove weld, fillet weld
c) groove weld, fillet weld, slot and plug weld
d) fillet weld, slot and plug weld, groove weld
Answer: b
Clarification: Fillet welds are used extensively (about 80%) followed by groove welds (15%). Slot and plug welds are rarely used (less than 5%) in structural engineering applications.

2. Which of the following type of weld is most suitable for lap and T-joints?
a) Fillet weld
b) Groove weld
c) Slot weld
d) Plug weld
Answer: a
Clarification: Fillet welds are suitable for lap and T-joints and groove welds are suitable for butt, corner, and edge joints.

3. Which of the following is true about back-up strip provided at bottom of single-V grooves?
a) Back-up strips are commonly used when welding is done from both the sides
b) Back-up strips are commonly used when root opening is sufficient
c) It creates a problem of burn-through
d) It introduces a crevice into the weld geometry
Answer: d
Clarification: Back-up strip is provided at the bottom of single-V/bevel/J or U grooves. It is commonly provided when welding is done from one side or when the root opening is excessive. It introduces a crevice into the weld geometry and prevents the problem of burn-through.

4. The size of root gap and root face for groove weld does not depend on :
a) type of welding process
b) welding position
c) type of metal plate
d) volume of deposited material
Answer: c
Clarification: For groove weld, the root opening or gap is provided for the electrode to access the base of the joint. The size of root gap and root face depends on the following : (i) type of welding process, (ii) welding position, (iii) volume of deposited material, (iv)cost of preparing edges, (v)access for arc and electrode, (vi)shrinkage and distortion.

5. Which of the following groove weld is used for plates of thickness more than 40mm?
a) Double-bevel
b) Single-J
c) Single-U
d) Double-U
Answer: d
Clarification: The groove is made of double-bevel or double-V for plates of thickness more than 12mm, and made of double-U or double-J for plates of thickness more than 40mm. For plates of thickness between 12-40mm, single-J and single-U grooves may be used.

6. Groove welds should have ________ strength as member they join.
a) same
b) less
c) greater
d) half
Answer: a
Clarification: Groove welds will transmit full load of the members they join, so they should have the same strength as the members they join.

7. Which of the following is not true regarding fillet welds?
a) They require less precision in fitting up two sections
b) They are adopted in field as well as shop welding
c) They are assumed to fail in tension
d) They are cheaper than groove welds
Answer: c
Clarification: Fillet welds require less precision in fitting up two sections. They are adopted in field as well as shop welding. They are assumed to fail in shear and are cheaper than groove welds.

8. Which of the following is true about slot and plug welds?
a) They are extensively used in steel construction
b) They are assumed to fail in shear
c) The inspection of these welds is easy
d) They are normally used to connect members carrying tensile loads
Answer: b
Clarification: Slot and plug welds are not extensively used in steel construction. They are used to fill up holes in connections. They are assumed to fail in shear. The inspection of these welds is difficult. They are useful in preventing overlapping parts from buckling.

9. Choose the correct option regarding weld metal.
a) Weld metal is same as parent metal
b) Weld metal is same as steel
c) It has higher yield to ultimate ratio
d) It has higher ductility compared to structural steel
Answer: c
Clarification: Weld metal is a mixture of parent metal and steel melted from electrode. The solidified weld metal has properties characteristic of cast steel. It has higher yield to ultimate ratio but lower ductility compared to structural steel.

10. Which of the following is not true regarding pre-heating of heat affected zone ?
a) Pre-heating does not help to reduce heat affected zone cracks
b) Pre-heating increases the cost of welding
c) It is done to remove surface moisture in highly humid conditions
d) It is done to disperse hydrogen away from weld pool and heat affected zone
Answer: a
Clarification: Pre-heating of joints help to reduce heat affected zone cracks but increases the cost of welding. It is done to remove surface moisture in highly humid conditions, to disperse hydrogen away from weld pool and heat affected zone, to bring steel to ambient temperature in cold climates.

Design of Steel Structures Multiple Choice Questions on “Local Buckling of Plates”.

1. Buckling occurs to members or elements mainly subjected to ________
a) seismic forces
b) tensile forces
c) compressive forces
d) shear forces
Answer: c
Clarification: Buckling may be defined as structural behavior in which mode of deformation develops in direction or plane perpendicular to that of bending which produces it. Such deformation changes rapidly with increase in magnitude of applied loading. It occurs mainly members or elements that are subjected to compressive forces.

2. The critical stress of infinite plate having width b and thickness t loaded by compressive forces acting on simply supported sides is given by
a) (kπ²E)/ [12(1-μ²)(b/t)].
b) (kπ²E)/ [12(1-μ²)(b/t)²].
c) (kπ²E)/ [12(1+μ²)(b/t)].
d) (kπ²E)/ [12(1+μ²)(b/t)²].
Answer: b
Clarification: The critical stress of infinite plate having width b and thickness t loaded by compressive forces acting on simply supported sides is given by
f_cr = (kπ²E)/ [12(1-μ²)(b/t)²],
where μ is Poisson’s ratio of material, b/t is width-to-thickness ratio of plate, k is buckling coefficient and E is Young’s modulus of rigidity of material. The value of coefficient k depends on constraints along non-loaded edges of plate.

3. Which of the following statement is correct?
a) stiffened elements are supported along one edge perpendicular to axial stress
b) un-stiffened elements are supported along one edge perpendicular to axial stress
c) stiffened elements are supported along one edge parallel to axial stress
d) un-stiffened elements are supported along one edge parallel to axial stress
Answer: d
Clarification: Unstiffened elements are supported along one edge parallel to axial stress (eg : legs of single angles, flanges of beams, and stems of T-section). Stiffened elements are supported along both the edges parallel to axial stress (eg: flanges of square and rectangular hollow sections, perforated cover plates, and webs of I-sections and channel sections).

4. Lowest value of buckling coefficient for simply supported plates is _____
a) 4.0
b) 2.0
c) 5.0
d) 3.0
Answer: a
Clarification: The lowest value of buckling coefficient for simply supported plates is 4.0. The buckilng stress depends upon buckling coefficient.

5. The buckling stress f_cr varies _____
a) inversely as plate slenderness or width-to-thickness ratio
b) directly as plate slenderness or width-to-thickness ratio
c) inversely as square of plate slenderness or width-to-thickness ratio
d) directly as square of plate slenderness or width-to-thickness ratio
Answer: c
Clarification: The buckling stress f_cr varies inversely as square of plate slenderness or width-to-thickness ratio, √(f_y /f_cr) = (b/t)√{(f_y / E)[12(1-μ²)/(π²k)]} .

6. The buckling coefficient for thin flat plate free along one longitudinal edge is given by
a) k = 0.425 + (b/a)
b) k = 0.425 + (b/a)²
c) k = 0.425 + (a/b)²
d) k = 0.425 – (b/a)²
Answer: b
Clarification: For a thin plate simply supported along both transverse edged and one longitudinal edge and free along the other longitudinal edge, the buckling coefficient can be approximated by k = 0.425 + (b/a)².

7. The elastic buckling stress of thin flat plate of length L, depth d and thickness t simply supported along four edges and loaded by shear stresses distributed uniformly along its edges is given by
a) f_cr = kπ²E / [12(1-μ²)(d/t)²].
b) f_cr = kπ²E / [12(1+μ²)(d/t)²].
c) f_cr = kπ²E / [12(1-μ²)(d/t)].
d) f_cr = kπ²E / [12(1+μ²)(d/t)].
Answer: a
Clarification: The elastic buckling stress f_cr of thin flat plate of length L, depth d and thickness t simply supported along all four edges and loaded by shear stresses distributed uniformly along its edges is given by f_cr = kπ2E / [12(1-μ²)(d/t)²], where buckling coefficient can be approximated by k=5.35 + 4(d/L)², when L ≥ d and k = 5.35(d/L)2 + 4, when L ≤ d.

8. The elastic buckling stress for thin flat plate of length L, depth d and thickness t simply supported along four edges and loaded by bending stress distribution is given by
a) f_cr = π²E/k[12(1-μ²)(d/t)²].
b) f_cr = π²E/k[12(1+μ²)(d/t)²].
c) f_cr = kπ²E/[12(1+μ²)(d/t)²].
d) f_cr = kπ²E/[12(1-μ²)(d/t)²].
Answer: d
Clarification: The elastic buckling stress for thin flat plate of length L, depth d and thickness t simply supported along all four edges and loaded by bending stress distribution, which varies linearly across its width is given by f_cr = kπ²E/[12(1-μ²)(d/t)²], where buckling coefficient k depends on aspect ratio L/d and the number of buckles along the plate.

9. 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
Answer: c
Clarification: 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.

10. Match the following values of limiting b/t or d/t ratio for various cases

	Plates			                 (b/t))√(fy /250) or (d/t)√(fy /250)
 
i. Simply supported plates					A) 17.5
ii. Long plate elements in shear				B) 131.4
iii. Long plate elements free along one longitudinal edge	C) 81.9
iv. Long plate elements in bending				D) 53.8

a) i-A, ii-B, iii-C, iv-D
b) i-D, ii-C, iii-A, iv-B
c) i-C, ii-D, iii-B, iv-A
d) i-D, ii-C, iii-B, iv-A
Answer: b
Clarification: i) For simply supported plates, if material ceases to be linearly elastic at yield stress f_y, the width-to-thickness ratio b/t is given by (b/t)√(f_y /250) = 53.8
ii) For long plate elements simply supported along both transverse edges and one longitudinal edge and free along other longitudinal edge, elastic buckling stress is equal to yield stress if (b/t)√(f_y/250) = 17.5
iii) The elastic buckling stress is equal to yield stress in shear τy = f_y/√3 when (d/t)√(f_y/250) = 81.9
iv) For long plates elements simply supported along four edges and loaded by bending stress distribution, limiting ratio d/t may be given as (d/t)√(f_y/250) = 131.4.

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.

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