CE-801 Design of Steel Structures - May 2022 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aExplain block shear failure.
   How to answer

   • Define block shear as combined shear and tension rupture along perimeter of bolt group.
   • Sketch typical failure paths in gusset/plate and angle tension member.
   • Give IS 800 block shear strength formula with shear and tension areas.
   • Distinguish gross vs net areas and role of end/edge distance.
2. 7 Marks
   bDesign a double cover joint between the two plates of width 300 mm, if the thickness of one plate is 18 mm and the other is 10 mm. The joint has to transfer a working load of 260 kN. The plates are of Fe 410 grade. Use bolt of grade 4.6.
   How to answer

   • Determine design strengths of Fe 410 plate and grade 4.6 bolt in shear and bearing.
   • Calculate required number of bolts for 260 kN working load with factor of safety.
   • Fix pitch, gauge, edge distances per IS 800 and check block shear.
   • Give final joint layout with cover plate sizes.
3. 7 Marks
   aThe plates of a tank 8 mm thick are connected by a single bolted lap joint with 20 mm diameter bolts at 50 mm pitch. Calculate the efficiency of the joint. Assume Fe 410 plate and grade 4.6 bolts.
   How to answer

   • Compute bolt hole diameter, pitch and shear/bearing strengths per IS 800.
   • Calculate tearing strength of plate per pitch length.
   • Take minimum of bolt strength and plate strength as joint strength.
   • Efficiency = joint strength / solid plate strength x 100.
4. 7 Marks
   bWhy is steel considered superior for structural applications compared to the cast iron and wrought iron?
   How to answer

   • Compare carbon content, ductility and tensile strength of steel vs cast/wrought iron.
   • Explain weldability, homogeneity and formability of steel.
   • Note brittle nature of cast iron and low strength of wrought iron.
   • Conclude suitability for structural members and connections.
5. 7 Marks
   aWhat are the advantages of bolted connections over riveted or welded connections?
   How to answer

   • List speed of erection, no skilled labour for bolting, and dismantling.
   • Explain quality control, noise, and fire risk vs riveting/welding.
   • Compare fatigue, inspection and prestressing in HSFG bolts.
   • Conclude economy and suitability for field connections.
6. 7 Marks
   bDesign a base plate for an ISHB 200 column to carry a factored load of 600 kN. Assuming Fe 410 grade of steel and M25 concrete.
   How to answer

   • Calculate required base plate area from factored load and M25 bearing strength.
   • Fix plate dimensions beyond ISHB 200 column size for projections.
   • Check bending of plate for cantilever moment and find thickness.
   • Detail holding-down bolts and weld/connection.
7. 7 Marks
   aState the possible failure modes of an axially loaded column. Why is it better to choose plastic or compact sections for columns?
   How to answer

   • List crushing, overall buckling, and local buckling failures.
   • Explain effective length, slenderness ratio and section classification.
   • Give reason: plastic/compact prevents local buckling before yielding.
   • Note higher design compressive strength and ductility.
8. 7 Marks
   bThe strut of a space frame member having a length of 3.5 m has to carry a factored load of 300 kN. Assuming yield stress of steel 250 Mpa. design a circular tube to carry the load. Assume that ends are simply supported.
   How to answer

   • Compute factored load and effective length for simply supported ends.
   • Assume suitable circular hollow section and check slenderness.
   • Verify design compressive strength per IS 800 for yield 250 MPa.
   • Select lightest tube satisfying strength and revise if needed.
9. 7 Marks
   aWhat is difference between laterally restrained and un-restrained sections?
   How to answer

   • Define lateral restraint to compression flange preventing LTB.
   • Contrast bending strength: full plastic moment vs reduced LTB moment.
   • Give examples of restrained beams vs unrestrained purlins/beams.
   • Note IS 800 clauses for effective length and $M_{cr}$.
10. 7 Marks
    bA flat roof building of 18 m span has 1.5 m deep trusses at 5 m centres. The total dead load is $0.7\text{ kN/m}^2$ and the imposed load is $0.75\text{ kN/m}^2$. Design the truss using angle sections with welded internal joints and bolted field splices.
    How to answer

    • Estimate dead, live and wind loads per IS 875 for 18 m span at 5 m spacing.
    • Compute panel loads and member forces by method of joints/sections.
    • Select angle sections for chord and web members and check slenderness.
    • Detail welded internal joints and bolted field splices.
11. 7 Marks
    aWhat is a pin connection? List some of the pinned connection used in steel structures?
    How to answer

    • Define pin as hinge transmitting axial/shear but no moment.
    • List examples: truss joints, base hinges, beam-column brackets, bridges.
    • Explain components: pin, plates, and rotation capacity.
    • Note IS 800 checks for bearing and bending of pin.
12. 7 Marks
    bDesign a bridge truss diagonal carrying a pull of 200kN using double angle section. The centre to centre distance of inter sections is 3m. The member is subjected to reversal of stresses.
    How to answer

    • Consider 200 kN tension plus compression due to stress reversal.
    • Select back-to-back double angles with gusset and check slenderness.
    • Check design tensile and compressive strengths per IS 800.
    • Provide tacking, end connections and detailing.
13. 14 Marks
    A tie member used as a diagonal in a roof truss consists of two angles $75 \times 50 \times 8$ mm ($f_y = 280$ MPa) placed back to back on the each side of gusset plate. The rivets of 18 mm diameter are provided in one row and the angles are tack riveted. Determine the tensile strength of the member.
    How to answer

    • Compute gross area of two $75 \times 50 \times 8$ mm angles and hole deduction.
    • Calculate design strength due to gross yielding $T_{dg}$.
    • Calculate design strength due to net rupture $T_{dn}$ including shear lag.
    • Check block shear $T_{db}$ and report minimum as tensile strength.
14. 14 Marks
    Answer the following questions.

    1. i)State the advantages of using wide flange beams over narrow ISMB beams.
    2. ii)What is difference between lacing and battens?
    3. iii)What are the types of base plates used in practice?
    4. iv)What are various types of groove welds? What is difference between groove weld and fillet weld?
    How to answer

    • Wide flange: higher $I_x$, lateral stability, economy and connection ease.
    • Lacing vs battens: truss action vs frame action and shear transfer.
    • Base plates: slab, gusseted, and moment bases with uses.
    • Groove vs fillet welds: types, strength and application difference.