JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III Year DESIGN OF STEEL STRUCTURES Previous Question Paper (July - 2023 - R16)
i) Question paper consists of Part A, Part B.
ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions.
iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
iv) IS 800-2007, IS875 (part 3):2015 and Steel tables are allowed.
Part A
Discuss about strength criteria in the design of steel structures.
Answer
The strength criteria in the design of steel structures ensure that the structural members can safely resist the applied loads without failure. This requires that the design strength of a member, calculated based on material properties and cross-sectional characteristics, must be greater than or equal to the factored design loads. Specifically, the structure must be checked for limit states such as yielding, rupture, buckling, and plastic collapse to ensure the internal forces do not exceed the ultimate capacity of the steel sections.
Classify the section ISMB 450 @ 710 N/m assuming Fe 410 steel.
Answer
To classify the ISMB 450 section, we determine the width-to-thickness ratios of its elements and compare them with the limiting values defined in IS 800:2007 for Fe 410 steel. For Fe 410, the yield stress fy is 250 N/mm2, resulting in a constant ε = √(250/fy) = 1.0.
For an ISMB 450 section:
- Web classification: The ratio of depth of web to thickness of web (d/tw) is compared against the limit for a rolled section under compression. For ISMB 450, d/tw is approximately 42.0, which is well below the limit of 84ε for a plastic section.
- Flange classification: The ratio of outstand of flange to thickness of flange (b/tf) is compared against the limit of 9.4ε. For ISMB 450, b/tf is approximately 7.5, which is less than 9.4ε.
Since both the flange and web satisfy the criteria for a plastic section, the ISMB 450 section is classified as a Plastic Section.
Explain the purpose of a splice in column design.
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Explain the design strength due to yielding of gross section in tension members.
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Name the different types of mechanisms in plastic analysis.
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Distinguish between static and kinematic theorem in plastic analysis.
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Explain the importance of economical depth in plate girder design.
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What are the key considerations for designing intermediate stiffeners in plate girders?
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Discuss the design considerations for end bearings in roof trusses.
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Why should channel section purlins be oriented with flanges towards the truss apex?
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Part B
Two plates of thickness 20 mm and 12 mm are to be joined by a butt joint. The joint is required to transmit a factored load of 625 kN. Design the joint using 8 mm thick cover plates provided on both sides of the plates. Use steel of grade Fe410 and 20 mm diameter of grade 4.6.
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A double angle section ISA 90 × 60 × 8 mm is welded on opposite sides of a 12 mm thick gusset plate. If the member is required to carry a factored load of 280 kN with long side of the angle welded to gusset, design the site welded fillet weld. Use steel of grade Fe410.
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A tension member 1 m long is required to resist a service dead load of 15 kN and a service live load of 55 kN. Design a rectangular bar of steel grade Fe410 assuming that the member is connected by one line of 16 mm diameter bolts of grade 4.6.
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Design a built-up column with four angles, the column length being 10 m which supports an axial compressive load of 440 kN under working conditions. The column ends are held in position and restrained against rotation. Also design a suitable connecting system for the angles. Use steel of grade Fe410.
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What are plastic hinges in structural engineering, and how do they form in structures with prismatic members/materials? Discuss their implications on structural behavior, provide examples, and explain the design considerations associated with plastic hinge formation.
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A propped cantilever carries a uniformly distributed load w per m over a span L. Determine the ultimate collapse load Wu, if the plastic moment capacity of the beam is Mp.
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A simply supported beam of span 4 m (effective) is laterally supported throughout. It carries a total uniformly distributed load of 30 kN including its self-weight. Design the beam and perform the checks for shear, deflection, and web bearing.
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Design a welded plate girder 24 m in span and laterally restrained throughout. It has to support a uniform load of 100 kN/m throughout the span inclusive of self-weight. Design the girder without intermediate transverse stiffeners. Use steel of grade Fe410.
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Explain the design considerations for the connections between the web and flange in plate girders. Discuss the importance and implications of these connections in ensuring structural integrity.
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Explain the design considerations for roof trusses, including the selection of appropriate types of trusses and their load-bearing capacities. Discuss the importance of purlin design in ensuring efficient load distribution and structural stability.
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Discuss the key design considerations for joints in roof trusses, including joint selection factors and the importance of strength, stiffness, and durability. Illustrate the significance of well-designed joints in ensuring optimal performance and longevity of roof truss systems through examples.
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