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Design of Steel Structures Multiple Choice Questions | MCQs | Quiz

Design of Steel Structures Interview Questions and Answers
Practice Design of Steel Structures questions and answers for interviews, campus placements, online tests, aptitude tests, quizzes and competitive exams.

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•   Steel Properties
•   Steel Types
•   Design Considerations
•   Limit State Method
•   Characteristic Loads
•   Earthquake Loads
•   Load Combinations
•   Analysis Assumptions
•   Riveted Connections
•   Bolted Connections - 1
•   Bolted Connections - 2
•   Bolted Connections - 3
•   Pin Connections
•   Simple Connections
•   Beam - Beam Connections
•   Beam & Column Splices
•   Welding Process
•   Welding Types & Properties
•   Weld Defects & Joint Types
•   Design Specifications
•   Welds Design
•   Tension Members & Types
•   Slenderness Ratio
•   Tension Members Behavior
•   Angles Under Tension
•   Lug Angles & Gusset Plate
•   Tension Members Design
•   Plastic Theory
•   Plastic Hinge
•   Plastic Collapse Load
•   Plastic Analysis Conditions
•   Plastic Collapse Theorem
•   Portal Frame Plastic Design
•   Plates Local Buckling
•   Sectional Classification
•   Possible Failure Modes
•   Compression Members
•   Sections Types
•   ↓ Compression Members ↓
•   Effective Length & Ratio
•   Slender Elastic Buckling
•   Lacings
•   Battens
•   Back - Back Connection
•   Members Design - 1
•   Members Design - 2
•   Beams Basics
•   Beam Types & Sections
•   Beams Lateral Stability
•   Lateral Torsional Buckling
•   Lateral Stability Factors
•   Real Beam Behavior
•   ↓ Design Strength ↓
•   Supported Beams - 1
•   Supported Beams - 2
•   Supported Beams - 3
•   Unsupported Beams - 1
•   Unsupported Beams - 2
•   Beams Shear Strength
•   Web Buckling & Crippling
•   Beams Deflection & Holes
•   Castellated Beams & Lintel
•   Purlins
•   Plate Girders
•   Flanges Proportioning
•   Shear Web Panel
•   Stiffeners
•   Gantry Girders

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Design of Steel Structures Books
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Design of Steel Structures Questions and Answers – Purlins

Posted on January 3, 2018 by Manish

This set of Design of Steel Structures Multiple Choice Questions & Answers (MCQs) focuses on “Purlins”.

1. What are purlins?
a) beams provided in foundation
b) beams provided above openings
c) beams provided over trusses to support roofing
d) beams provided on plinth level
View Answer

Answer: c
Explanation: Purlins are beams provided over trusses to support sloping roof system between adjacent trusses. Channels, angle sections, and old formed Z-sections are widely used as purlins.
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2. Theoretically, purlins are generally placed at
a) only at panel points
b) only at edges
c) only at mid span
d) only at corners of roof
View Answer

Answer: a
Explanation: Theoretically, it is desirable to place purlins only at panel points. They are placed at panel points to avoid bending in the top chords of roof trusses. For large trusses, it is more economical to space purlins at closer intervals.

3. Purlin section is subjected to
a) not subjected to bending or twisting
b) twisting only
c) symmetrical bending
d) unsymmetrical bending
View Answer

Answer: d
Explanation: The wind force is assumed to act normal to roof truss and gravity load pass through centre of gravity of purlin section. Hence, the purlin section is subjected to twisting in addition to bending. Such bending is called unsymmetrical bending.

4. If purlins are assumed to be simply supported, the moments will be
a) wl2/10
b) wl/8
c) wl/10
d) wl2/8
View Answer

Answer: d
Explanation: Purlins can be designed simple, continuous or cantilever beams. If purlins are assumed to be simply supported, the moments will be wl2/8. If they are assumed to be continuous, the moments will be slightly less and taken as wl2/10. IS 800 recommends the purlins to be designed as continuous beams.

5. While erecting channel section purlins, it is desirable that they are erected over rafter with their flange
a) facing down slope
b) facing up slope
c) does not depend whether up slope or down slope
d) flanges are placed randomly
View Answer

Answer: b
Explanation: While erecting angle, channel or I- section purlins, it is desirable that they are erected over rafter with their flange facing up slope. In this position, the twisting moment does not cause any instability. The twisting moment will cause instability if the purlins are kept in such a way that the flanges face the downward slope.

6. Sag rods are provided at
a) one-third points between roof trusses
b) end of span
c) two-third points between roof trusses
d) are never provided
View Answer

Answer: a
Explanation: Purlin sections have tendency to sag in the direction of sloping roof . So, sag rods are provided midway or at one-third points between roof trusses to take up the sag.
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7. Which of the following is not true about sag rods?
a) sag rods are provided at midway or at one-third points between roof trusses
b) these rods reduce the moment Myy
c) these rods increase the moment Myy
d) these rods result in smaller purlin sections
View Answer

Answer: c
Explanation: Sag rods are provided midway or at one-third points between roof trusses to take up the sag in the direction of sloping roof by purlins. These rods provide lateral support with resprct to y-axis bending. Consequently, moment Myy is reduced and thereby result in smaller purlin section. they are useful in keeping the purlins in proper alignment during erection until roofing is installed and connected to purlins.

8. When one sag rod is used, the moment about web axis
a) reduces by 50%
b) increases by 50%
c) increases by 75%
d) reduces by 75%
View Answer

Answer: d
Explanation: If sag rods are not used, the maximum moment about web axis would be wl2/8. When one sag rod is used, the moments are reduced by 75% and when two sag rods are used at one-third points, the moments are reduced by 91%.

9. The maximum bending moment for design of channel/I-section purlin is calculated by
a) Wl/10, where W= concentrated load
b) Wl/8, where W= concentrated load
c) W/10, where W= concentrated load
d) W/8, where W= concentrated load
View Answer

Answer: a
Explanation: The gravity load, P1 and load due to wind component, H1 are computed. The loads are multiplied by load factors. Thus, P = γfP1, H = γfH1 . The maximum bending moment are calculated as Mz = Pl/10 and My = Hl/10, where P= factored load along z-axis, H = factored load along y-axis, l= span of purlin (c/c distance between adjacent trusses).

10. The required section modulus of the channel/I-section purlin can be determined by
a) Zpz = Myγm0/fy + (b/d)(Mzγm0/fy)
b) Zpz = Mzγm0/fy + (b/d)(Myγm0/fy)
c) Zpz = Mzγm0/fy + 2.5(b/d)(Myγm0/fy)
d) Zpz = Myγm0/fy + 2.5(b/d)(Mzγm0/fy)
View Answer

Answer: c
Explanation: The required section modulus of the purlin section can be determined by Zpz = Mzγm0/fy + 2.5(b/d)(Myγm0/fy ), where γm0 is partial safety factor for material = 1.1, d is depth of trial section, b is the breadth of the trial section, Mz and My are factored bending moments about Z and Y axes, respectively, and fy is yield stress of steel. Since the above equation involves b and d of a section, trial section must be used and from the above equation , it is checked whether chosen section is adequate or not.

11. The design capacity of channel/I-section purlin is given by
a) M = Zp/fy
b) M = Zpγm0fy
c) M = Zpγm0/fy
d) M = γm0/fy
View Answer

Answer: b
Explanation: The design capacity of channel/I-section purlin is given by Mdz = Zpzγm0/fy and Mdy = Zpyγm0/fy , Mdz and Mdy are design moment capacity about Z and Y axes, respectively, Zpz and Zpy are plastic section modulus about Z and Y axes, respectively and fy is yield stress of steel. For safety, design moment capacity should be always greater than or equal to factored bending moments.

12. The check for design capacity of channel/I-section purlin is given by
a) Mdz ≤ 1.2Zeyfy/γm0, Mdy ≤ 2.4Zezfy/γm0
b) Mdz ≤ Zezfy/γm0, Mdy ≤ 1.2Zeyfy/γm0
c) Mdz ≤ γfZeyfy/γm0, Mdy ≤ 1.2Zezfy/γm0
d) Mdz ≤ 1.2Zezfy/γm0, Mdy ≤ γfZeyfy/γm0
View Answer

Answer: d
Explanation: The check for design capacity of channel/I-section purlin is given by Mdz ≤ 1.2Zezfy/γm0 , Mdy ≤ γyZeyfy/γm0 , where Mdz and Mdy are design moment capacity about Z and Y axes, respectively, Zez and Zey are elastic section modulus about Z and Y axes, respectively and fy is yield stress of steel. Since in y-direction, the shape factor Zp/Ze will be greater than 1.2, γf is used instead of 1.2. If 1.2 is used the onset of yielding under unfactored loads cannot be prevented.
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13. Which of the following relation is correct for design of channel/I-section purlin?
a) (Mz/Mdz) + (My/Mdy) ≥ 1
b) (Mz/Mdz) + (My/Mdy) ≤ 1
c) (Mdz/Mz) + (My/Mdy) ≤ 1
d) (Mdz/Mz) + (Mdy/My) ≥ 1
View Answer

Answer: b
Explanation: The local capacity of the section is checked by interaction equation. It is given by (Mz/Mdz) + (My/Mdy) ≤ 1 , where Mdz and Mdy are design moment capacity about Z and Y axes, respectively, and Mz and My are factored bending moments about Z and Y axes, respectively.

14. For which of the following slope of roof truss, angle section purlin can be used?
a) 25˚
b) 50˚
c) 75˚
d) 60˚
View Answer

Answer: a
Explanation: Angle sections are unsymmetrical about both the axes. Angle sections can be used as purlin section. provided slope of the roof truss is less than 30˚.

15. The modulus of section required for angle section purlin is given by
a) Z = M/(0.66xfy)
b) Z = M/(1.33×0.66xfy)
c) Z = M/(1.33×0.66xfy)
d) Z = M/(1.33xfy)
View Answer

Answer: c
Explanation: The modulus of section required for angle section purlin is given by Z = M/(1.33×0.66xfy), M = maximum bending moment = wl2/10, w = unfactored uniformly distributed load, l = span of purlin, fy is yield stress. The gravity and wind loads are determined to calculate bending moment and both loads are assumed to be normal to roof truss.

Sanfoundry Global Education & Learning Series – Design of Steel Structures.

To practice all areas of Design of Steel Structures, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Facebook | Twitter

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