Question 1

Slenderness ratio basics: The slenderness ratio λ of a column is defined as L_e / r. Under what condition would the slenderness ratio be zero?

Accepted Answer

Introduction / Context: Slenderness ratio λ = L_e / r is a key geometric parameter in column stability. It influences the buckling capacity and the applicability of Euler or inelastic buckling curves. Given Data / Assumptions: L_e is the effective length accounting for end restraints. r is the radius of gyration about the buckling axis. Concept / Approach: By definition, λ approaches zero only if the numerator L_e → 0, since r is positive for any real cross-section. Physically, L_e = 0 is a limiting conceptual case (e.g., an element of zero effective length), not realized in practice but useful to understand the mathematics. Step-by-Step Solution: Recall λ = L_e / r.Set λ = 0 ⇒ L_e must be 0 (r ≠ 0 for a real section).Hence the condition is L_e = 0. Verification / Alternative check: Other conditions (e.g., L_e = r) give λ = 1, not zero; making supports “continuous” reduces L_e but not to zero in real structures. Why Other Options Are Wrong: L_e = r yields λ = 1; “continuously supported” reduces but does not nullify L_e; “between points of zero moment” defines buckling curve but not λ = 0; r = 0 is non-physical for a finite cross-section. Common Pitfalls: Confusing “very small slenderness” with “zero”; neglecting direction-specific r and end-restraint factors in effective length calculation. Final Answer: When the effective length is zero (L_e = 0)

Question 2

Structural terminology (stairs): In building construction, the beams that support the treads and risers along the sides of a staircase are called ________.

Accepted Answer

Introduction / Context: Staircases are assemblies of structural and architectural components. Correct terminology helps in detailing, load estimation, and site communication. The long inclined members that carry the steps (treads and risers) need a precise name in structural drawings. Given Data / Assumptions: A conventional straight flight stair in a framed building. Steps (treads and risers) are supported along their edges by inclined members. We are to identify the correct term used for these supporting members. Concept / Approach: In stair construction, the inclined side members that directly support the steps are known as stringers (also called strings). Other terms such as headers, trimmers, or spandrel beams have different, specific roles in floor and frame construction, not the direct support of stair treads/risers along the slope. Step-by-Step Solution: Identify the inclined members running along the stair flight.Recall standard stair parts: treads, risers, landings, newels, balusters, and stringers.Match function: the members carrying the step edges are called stringers.Therefore, choose “Stringers”. Verification / Alternative check: Typical structural details label these members as “stringers/string courses,” with thickness and connection details to floor beams or landings. Architectural references align with the same naming convention. Why Other Options Are Wrong: Headers: floor framing members running perpendicular to joists near openings, not stair supports. Trimmers: joists or beams that frame openings (e.g., around stair wells), not the inclined stair members. Spandrel beams: edge beams at slab perimeters or façade lines, not for stair step support. Girders: primary beams; not the specific inclined stair members. Common Pitfalls: Confusing trimmer joists at the stair opening with the inclined step-supports. Using generic terms like “beam” instead of the precise term “stringer.” Final Answer: Stringers.

Question 3

Steel design (minimum thickness): For steel members not exposed to weather, the minimum thickness that should be specified to ensure durability and ease of fabrication is ________.

Accepted Answer

Introduction / Context: Minimum plate or component thickness limits in steel design prevent premature corrosion, facilitate welding, and ensure practical fabrication. Codes prescribe larger minimum thicknesses for members exposed to weather and slightly lower values for protected, interior members. Given Data / Assumptions: Steel members located in internal, non-weather-exposed conditions. Standard building occupancy with normal humidity control. Objective is to choose a recognized minimum that balances durability and constructability. Concept / Approach: Design practice and common code guidance adopt 6 mm as a practical minimum for non-weather-exposed steel plates and similar elements. Thicker minimums (often 8 mm or more) are required for weather-exposed components or where corrosion risk is elevated. Thinner plates can be difficult to weld and are more susceptible to local buckling or damage in handling. Step-by-Step Solution: Identify exposure: not exposed to weather.Consult standard practice: 6 mm minimum thickness commonly specified for interior members.Select the appropriate value from options. Verification / Alternative check: Project specifications and many national standards reflect 6 mm as a lower bound for protected plates and flats, with welding procedure qualifications tailored accordingly. Why Other Options Are Wrong: 4.5 mm: generally too thin for structural members; fabrication and durability concerns. 8 mm or 10–12 mm: acceptable but exceed the typical minimum for non-exposed situations; these are more aligned with exposed or robust applications. Common Pitfalls: Copying exterior minimums (≥8 mm) for interior members without need. Overlooking paint/coating systems and service environment in final selection. Final Answer: 6 mm.

Question 4

Advantages of structural steel members: Considering performance and serviceability, which statement best summarises the main advantages of using steel members in building frames and tanks?

Accepted Answer

Introduction / Context: Material selection for structural systems involves strength-to-weight ratios, durability, constructability, and service performance. Steel is a leading choice for frames, bridges, and tanks due to a combination of mechanical and service attributes when properly designed and protected. Given Data / Assumptions: Modern steel with controlled chemistry, appropriate welding, and coatings. Reasonable inspection and maintenance regimes. Applications ranging from building frames to water- or gas-containing shells/tanks. Concept / Approach: Steel offers high yield and tensile strengths, enabling slender members and long spans. With continuous welds and adequate detailing, steel enclosures can be made gas- and water-tight. Protective systems (galvanizing, paint, cathodic protection) extend service life significantly in diverse environments. Step-by-Step Solution: Compare each option against known steel properties.(a) High strength → lighter sections and longer spans.(b) Welded steel shells/liners are commonly used for tanks and pressure parts, achieving tightness.(c) Longevity with coatings and maintenance is well documented.Hence, “All of the above”. Verification / Alternative check: Case histories of steel bridges and tanks show decades of service when protected. Design manuals discuss steel’s high specific strength and proven watertight performance with weld quality assurance. Why Other Options Are Wrong: Option (e) omits (b), which is valid when proper welding and inspection are provided. Common Pitfalls: Assuming “water-tightness” is an inherent property without considering weld quality and details. Ignoring corrosion protection when estimating service life. Final Answer: All of the above.

Question 5

Column splices (different depths): When the depth of the upper column section is smaller than that of the lower column, what should be provided at the splice to ensure proper load transfer and alignment?

Accepted Answer

Introduction / Context: Steel column splices must provide continuity for axial load, moments (if any), and alignment. When mating sections have different depths, detailing must address geometry and bearing to avoid local overstress and eccentricities. Given Data / Assumptions: Upper column is shallower than lower column. Splice is designed primarily for axial load transfer with alignment control. Fabrication tolerances require packings where necessary. Concept / Approach: Filler plates compensate for the difference in depth so that splice plates and flanges align correctly. Bearing plates (or bearing stiffeners) ensure uniform load transfer across the joint. Using both is standard practice when section depths differ, preventing stress concentrations and secondary bending at the splice. Step-by-Step Solution: Recognise geometric mismatch: upper section shallower.Introduce filler plates to match depth and provide planar clamping surfaces.Provide bearing plates to ensure proper compressive load transfer.Therefore choose “Both filler plates and bearing plates”. Verification / Alternative check: Steel design handbooks illustrate splice details with filler and bearing elements where section sizes change. Shop drawings typically call out plate thicknesses to equalise depths and ensure contact surfaces. Why Other Options Are Wrong: Filler plates only: alignment improved, but bearing may be inadequate. Bearing plates only: load may transfer, but geometric mismatch remains for splice plates. Shim washers: not appropriate as the primary solution for depth differences. Common Pitfalls: Forgetting to extend filler plates to the full contact area. Not machining bearing surfaces where required for high loads. Final Answer: Both filler plates and bearing plates.

Question 6

Fillet welds at the sides of a base: What is the predominant internal action experienced by the weld metal when fillet welds are placed along the sides of a base connection (e.g., base plate to a supporting member)?

Accepted Answer

Introduction / Context: Fillet welds are widely used to join base plates, stiffeners, and brackets. Understanding the primary stress in the weld throat helps size the weld and check capacity against code-allowed stresses. Given Data / Assumptions: Fillet welds along the sides of a base connection (e.g., base plate to supporting steel). Typical axial or shear loads transmitted through the joint. No unusual torsional demand unless explicitly stated. Concept / Approach: The design of fillet welds is typically governed by shear stress on the effective throat area of the weld. While local components of tension/compression may exist under eccentric or combined loading, the controlling check for most base side fillet welds is shear on the throat and fusion faces, as per common design provisions. Step-by-Step Solution: Identify the load path from base plate to supporting member.Resolve resultant into shear across the weld throat.Select the stress type used for capacity checks: shear. Verification / Alternative check: Weld design chapters compute required weld size by V = allowable_shear * throat_area, confirming shear as the governing stress for typical fillet welds at bases and stiffeners unless strong eccentricities cause additional bending distribution around the weld group. Why Other Options Are Wrong: Tension/compression: normal stresses can appear locally but are not the primary basis for standard fillet throat design. Bending or torsion: may act on the weld group as a whole in eccentric cases but the elemental weld check remains shear on the throat. Common Pitfalls: Ignoring eccentricities that produce additional weld group moments. Underestimating effective throat (0.707 * leg size) in capacity calculations. Final Answer: Shear.

Question 7

Cantilever fillers (deflection/control rule): For cantilever filler members in steel construction, the recommended limit for span-to-depth ratio (L/d) should not exceed which of the following values to maintain stiffness and serviceability?

Accepted Answer

Introduction / Context: Span-to-depth guidelines are used by designers to ensure members are sufficiently stiff without requiring detailed deflection checks at preliminary stages. Cantilever members are more flexible than simply supported ones, hence stricter L/d limits are adopted to control tip deflection and vibration. Given Data / Assumptions: Member is a cantilever “filler” (secondary) beam or bracket-like element. Serviceability (deflection) is the controlling criterion for preliminary sizing. Uniform steel properties and typical building loading assumptions. Concept / Approach: Cantilevers experience larger deflections for the same span and depth compared with simply supported beams. Hence, designers use a smaller L/d limit, commonly near 8 for initial sizing. This helps ensure adequate stiffness; the final design still requires verification against actual loads and deflection limits set by the project specifications. Step-by-Step Solution: Recall rule-of-thumb L/d values: simply supported members often 12–20; cantilevers typically tighter.Adopt conservative preliminary limit for cantilevers: L/d ≈ 8.Select 8 from the provided options. Verification / Alternative check: Textbook tables and practice guides list tighter deflection control for cantilevers, often suggesting L/d around 8–10 to limit service deflections and end rotations without immediate detailed analysis. Why Other Options Are Wrong: 4: very conservative and may be uneconomical in many cases. 12, 16, 20: these are more typical of simply supported beams and are generally too slender for cantilevers at the preliminary stage. Common Pitfalls: Using simply supported span-to-depth limits for cantilevers and facing excessive end deflection. Ignoring non-structural constraints (e.g., cladding tolerances) that demand stiffer members. Final Answer: 8.

Question 8

Steel design – Effective length for lateral–torsional buckling For a simply supported steel beam whose ends are restrained against torsion, and whose compression flange at the supports is only partially restrained against lateral bending, the effect…

Accepted Answer

Introduction / Context: Lateral–torsional buckling of steel beams depends on how well the compression flange and the member are restrained at the supports. Design codes tabulate an “effective length” factor to convert the actual span into an equivalent buckling length used for capacity checks. Given Data / Assumptions: Beam is simply supported for vertical bending actions. Ends are restrained against torsion (warping/twist prevented). Compression flange at supports is only partially restrained against lateral movement. We need the effective length expressed as a fraction of physical span. Concept / Approach: Effective length factors reduce from 1.0 as end restraints improve. With torsion restraint present but only partial lateral restraint of the compression flange, tabulated factors are typically about 0.85 of span, reflecting improved stability compared with an unrestrained flange. Step-by-Step Solution: Identify restraint condition: torsion restrained + partial lateral restraint → intermediate restraint case.Use tabulated factor for this case: Le ≈ 0.85 × span.Select option matching 0.85 × span. Verification / Alternative check: Design handbooks and summary tables of end-restraint cases consistently show factors near 0.85 for the stated condition, higher than fully restrained (≈0.7–0.75) and lower than unrestrained (1.0). Why Other Options Are Wrong: L = span assumes no beneficial restraint. 0.70–0.75 correspond to stronger flange restraint. 1.25 × span implies adverse conditions (not applicable here). Common Pitfalls: Confusing flexural effective length (for column buckling) with lateral–torsional buckling effective length; ignoring flange bracing at intermediate points. Final Answer: L = 0.85 × span

Question 9

Designation of rolled steel beams in India Rolled steel beams are designated by the Indian Standard series together with which two key parameters?

Accepted Answer

Introduction / Context: Section designation standards enable quick communication of a member’s size and mass. In Indian practice, rolled beams (e.g., ISMB, ISUB, ISHB) include both the depth and the linear mass so that designers can identify geometry and weight during selection. Given Data / Assumptions: Indian Standard section series (e.g., ISMB) is used. Typical catalogue entry: ISMB 300 @ 44.2 kg/m. We need the two parameters stated after the series name. Concept / Approach: The conventional order is depth (in mm) followed by weight per metre (kg/m). This succinctly conveys size and self-weight implications without listing the entire sectional table every time. Step-by-Step Solution: Recall common notation: “ISMB 300 @ 44.2 kg/m”.Identify parameters: depth = 300 mm; weight per metre = 44.2 kg/m.Thus, the designation uses depth of section and weight per metre. Verification / Alternative check: Standard steel tables and supplier catalogues follow this same practice. Why Other Options Are Wrong: Flange width/web thickness are not part of the short designation; the order “weight then depth” is not the conventional format. Common Pitfalls: Confusing designation with full sectional properties (e.g., Ix, Zx, r). Those are referenced separately in design checks. Final Answer: Depth of section and weight per metre

Question 10

Effective length of a fillet weld for strength calculations For a straight fillet weld, the effective length used in design is taken as the actual overall length:

Accepted Answer

Introduction / Context: Design strength of fillet welds uses the effective throat over the effective length. End portions of fillet welds do not develop full throat due to start/stop craters and stress distribution, so a length reduction is applied. Given Data / Assumptions: Straight fillet weld of uniform size. Design per traditional working stress approach with length reduction for end returns. “Size of weld” means leg size (e.g., a). Concept / Approach: Standard practice takes the effective length as the actual length minus two times the weld size to discount the under-strength at the two ends. This gives a conservative net length participating at full capacity. Step-by-Step Solution: Identify reduction: two ends × (one size each).Compute effective length: Leff = Lactual − 2a.Use Leff in strength = throat * Leff * allowable stress. Verification / Alternative check: Code commentaries and steel design handbooks present the same reduction for isolated fillet weld segments. Why Other Options Are Wrong: Subtracting one size underestimates the end effects; adding sizes is unconservative; taking full actual length ignores known end weaknesses. Common Pitfalls: For overlapping or returned welds, details may restore some end capacity; however, unless detailed otherwise, the standard 2a reduction applies. Final Answer: minus twice the size of weld

Question 11

Riveted joint design – number of rivets required A joint uses rivets with strengths (per rivet) of 3425 kg in single shear, 4575 kg in bearing, and 5025 kg in tearing of the connected plate. If the member must carry 35 tonnes, how many rivets are re…

Accepted Answer

Introduction / Context: In riveted (or bolted) connections, the usable capacity per fastener is the least of the shear capacity of the fastener, the bearing capacity against the plate, and the net-section tearing capacity of the plate. The total number of fasteners is determined by dividing the required factored load by this governing (minimum) capacity. Given Data / Assumptions: Shear strength per rivet = 3425 kg. Bearing strength per rivet = 4575 kg. Tearing strength per rivet (plate) = 5025 kg. Total load = 35 tonnes = 35000 kg. Concept / Approach: The limiting (governing) mode is the one with the smallest capacity. The design number of rivets n is the smallest integer such that n * Rmin ≥ total load. Step-by-Step Solution: Find governing capacity: Rmin = min(3425, 4575, 5025) = 3425 kg.Compute required rivet count: n = 35000 / 3425 = 10.22…Round up to next integer: n = 11. Verification / Alternative check: Check total shear capacity with 11 rivets: 11 * 3425 = 37675 kg ≥ 35000 kg → OK. Why Other Options Are Wrong: 10 gives only 34250 kg, which is less than 35000 kg; 12, 13, 15 are conservative but not the minimum meeting the requirement. Common Pitfalls: Using average of capacities instead of the minimum; forgetting to convert tonnes to kg; rounding down instead of up. Final Answer: 11

Question 12

Eccentrically loaded bracket – force on a rivet due to moment A bracket is loaded by a force P with eccentricity e. If a rivet lies at a radial distance r_n from the group centroid, the additional resisting force on that rivet due to the moment is:

Accepted Answer

Introduction / Context: For riveted or bolted connections subjected to an eccentric load, the load can be decomposed into a resultant force at the centroid and a moment about the centroid. The moment is resisted by a system of forces in the fasteners proportional to their distance from the centroid. Given Data / Assumptions: Eccentric load P acting at eccentricity e from the centroid of the rivet group. Rivet at distance r_n from the centroid. Linear elastic distribution; fastener forces from moment vary linearly with radius. Concept / Approach: The total resisting moment from the group equals the applied moment M = P * e. With a linear law F_n = C * r_n, the moment balance gives Σ(F_n * r_n) = C * Σ(r_n^2) = P * e. Solving for C yields C = (P * e) / Σ(r^2), and the force in the nth rivet is F_n = C * r_n. Step-by-Step Solution: Write applied moment: M = P * e.Assume force distribution: F_n ∝ r_n → F_n = C * r_n.Impose moment equilibrium: Σ(F_n * r_n) = C * Σ(r_n^2) = P * e.Solve for C and substitute: F_n = (P * e * r_n) / Σ(r^2). Verification / Alternative check: Check dimensions: numerator has force × length × length, denominator length^2 → force, consistent. Why Other Options Are Wrong: Forms lacking Σ(r^2) ignore group stiffness; inversions like (P * e) / r_n or multiplying by r_n^2 misrepresent the linear distribution assumption. Common Pitfalls: Combining direct shear from P/number of rivets and moment-induced forces incorrectly (they must be vectorially combined per rivet). Final Answer: F = (P * e * r_n) / Σ(r^2)

Question 13

Continuity requirement – approximately equal spans in continuous members In continuous structural members, spans are considered approximately equal if the longest span does not exceed the shortest span by more than:

Accepted Answer

Introduction / Context: Simplified analysis and detailing rules for continuous beams/girders often assume “approximately equal spans.” This allows use of standard bending moment coefficients and distribution rules. Given Data / Assumptions: We compare the extreme spans within a continuous series. Criterion is expressed as a percentage difference relative to the shortest span. Concept / Approach: When span variations are small, support moments and distribution factors do not deviate drastically from tabulated “equal-span” values. A widely adopted threshold is 10%, beyond which redistribution may be significant and specific analysis is recommended. Step-by-Step Solution: Define tolerance: (Lmax − Lmin) / Lmin ≤ 0.10.Apply to select percentage value among options.Choose 10% as the standard “approximately equal” criterion. Verification / Alternative check: Many handbooks stipulate 10% as a practical limit for using equal-span coefficients without notable error. Why Other Options Are Wrong: 5% is unduly restrictive; 15–25% allow excessive variation, undermining equal-span assumptions. Common Pitfalls: Applying equal-span tables to irregular layouts with larger variations, leading to inaccurate moment distribution. Final Answer: 10%

Question 14

Channel section orientation and radius of gyration When a large value of radius of gyration is not required, how are a pair of channel sections typically arranged?

Accepted Answer

Introduction / Context: Built-up members using channel sections can be oriented to tailor the principal radii of gyration. The flange orientation affects stiffness about both principal axes and the torsional properties. Given Data / Assumptions: Two identical channels are combined. Goal: not to maximize the radius of gyration; a more compact arrangement is acceptable. Concept / Approach: Placing channels with flanges outward increases the radius of gyration about the minor axis, which is beneficial when buckling about that axis governs. Conversely, placing flanges inward reduces the spread of material, giving a smaller radius of gyration. Step-by-Step Solution: Assess objective: large r not required → choose compact orientation.Compact orientation corresponds to flanges inward (toe-to-toe).Therefore select “Channel flanges kept inward”. Verification / Alternative check: Section property calculations show reduced Iy (and hence ry) when flanges are brought closer together. Why Other Options Are Wrong: Flanges outward increases r (contrary to intent); back-to-back without specifying flange direction is ambiguous; spacer-separated webs generally increase r. Common Pitfalls: Assuming any built-up orientation always improves buckling; the layout must match the design objective. Final Answer: Channel flanges kept inward (toe-to-toe)

Question 15

Elastic versus plastic behaviour under axial tension A 20 mm diameter steel bar is subjected to an axial tensile stress of 2300 kg/cm² and exhibits a total strain of 0.004. If Young’s modulus E = 2.1 × 10^6 kg/cm², the bar is operating in which rang…

Accepted Answer

Introduction / Context: Hooke’s law states that in the elastic range, strain is proportional to stress with the constant of proportionality being Young’s modulus. Deviations from this linear relation indicate yielding or plastic deformation. Given Data / Assumptions: Applied stress σ = 2300 kg/cm². Measured strain ε = 0.004 (dimensionless). Young’s modulus E = 2.1 × 10^6 kg/cm². Concept / Approach: In the elastic range, ε_elastic = σ / E. If the observed strain greatly exceeds σ / E, the response is not purely elastic and plastic strain is present. Step-by-Step Solution: Compute elastic strain prediction: ε_elastic = 2300 / (2.1 × 10^6) = 0.001095 (approx.).Compare with observed: ε_observed = 0.004.Since 0.004 » 0.001095, significant plastic strain exists → behaviour is plastic/nonlinear. Verification / Alternative check: Apparent modulus from the data: E_app = σ / ε = 2300 / 0.004 = 5.75 × 10^5 kg/cm², far below E, confirming yielding. Why Other Options Are Wrong: Elastic range would require ε ≈ 0.0011; “at yield point exactly” cannot be inferred from one data pair; “perfectly plastic plateau” implies near-constant stress at large strain, not demonstrated by the single reading. Common Pitfalls: Using percentage strain units inconsistently; forgetting strain is dimensionless; assuming any deviation is measurement error rather than plasticity. Final Answer: In the plastic (nonlinear) range

Question 16

Steel design – deflection control: For a simply supported steel beam carrying a single concentrated load at midspan, the beam will be considered safe in deflection if the span-to-depth ratio (L/d) satisfies which of the following?

Accepted Answer

Introduction / Context: Serviceability in steel beams is often controlled by deflection limits rather than strength. For a simply supported beam with a central point load, empirical span-to-depth limits are widely used to get a quick check on deflection without detailed calculations. Given Data / Assumptions: Beam: simply supported. Loading: single concentrated load at midspan. Material: structural steel; elastic behavior assumed. Serviceability criterion: standard building practice limits for instantaneous deflection. Concept / Approach: Maximum elastic deflection for a central load is y_max = W * L^3 / (48 * E * I). For rectangular sections, I is proportional to d^4, so deflection varies strongly with depth. Traditional design guides give ready-reckoner limits on L/d to ensure y_max stays within permissible limits (commonly around L/325 to L/360 for floors). For a central point load, a conservative quick check is L/d less than about 19. Step-by-Step Solution: Identify beam condition: simply supported with central point load.Recall conservative rule: L/d must be below an approximate limiting value.For this loading, a common check is L/d < 19.Select option matching this requirement. Verification / Alternative check: Using y_max = W * L^3 / (48 * E * I) and target y_max ≈ L/325 to L/360 leads to depth estimates agreeing closely with an L/d limit near 19 for a single midspan load. Why Other Options Are Wrong: < 24: too lenient for a central point load; may exceed target deflection. > 19 or > 24 or > 37: larger L/d means shallower beams and more deflection, not “safe.” Common Pitfalls: Confusing limits for uniformly distributed load with those for point loads. Ignoring composite action or finishes that can change deflection behavior. Final Answer: < 19

Question 17

Tension members – net area of double-angle section: For double angles in tension placed back-to-back and connected to either side of a gusset plate, the effective sectional area for design equals which of the following?

Accepted Answer

Introduction / Context: In steel design, the tensile capacity of a member is governed by its net section across the line of fasteners. For built-up members like back-to-back double angles on either side of a gusset, the connection layout determines how much area is deducted for holes. Given Data / Assumptions: Two equal angles, placed back-to-back. Connected on either side of a single gusset plate. Rivet/bolt holes occur in the connected legs only. Concept / Approach: Net area = gross area − sum of hole areas along the critical section. Since the load is transferred through the connected legs, holes in those legs reduce the area resisting tension. Unconnected legs do not have hole deductions along the critical section through the connection. Step-by-Step Solution: Determine gross area: sum of both angles’ areas.Locate critical section: through the line(s) of holes in the connected legs.Compute net area by subtracting hole areas from the gross area. Verification / Alternative check: Design standards consistently define tensile strength using net section accounting for fastener holes; detailing rules ensure shear lag and block shear checks are also satisfied. Why Other Options Are Wrong: Gross area (no deductions) overestimates capacity. Adding hole area is non-physical. Multiplying gross area by hole area is meaningless dimensionally. Common Pitfalls: Forgetting to consider stagger (use of pitch and gauge) when holes are staggered. Ignoring block shear which may govern instead of simple net area. Final Answer: the gross area minus area of rivet (bolt) holes

Question 18

Terminology in floor systems: In building structures, a major primary beam supporting secondary members is commonly referred to as which of the following?

Accepted Answer

Introduction / Context: Floor systems often use a hierarchy of members: joists or secondary beams supported by major primary beams, which in turn transfer loads to columns. Correct terminology helps avoid detailing and communication errors on drawings and schedules. Given Data / Assumptions: “Major beam” means the primary supporting member in a framing bay. Secondary beams or joists frame into the major member. Concept / Approach: Conventionally, the principal beam carrying the secondary framing is termed a girder. “Floor beam” and “main beam” may be used broadly, but in strict usage a floor beam can itself be secondary, and “main beam” is generic without distinguishing hierarchy. The clearest, standard term is girder for the primary member. Step-by-Step Solution: Identify member hierarchy: primary vs. secondary.Apply standard nomenclature: primary = girder, secondary = beam/joist.Choose the term most specifically denoting the major primary member. Verification / Alternative check: Coding systems and typical steel manuals use “girder” for primary beams supporting other beams; general arrangement drawings reflect the same convention. Why Other Options Are Wrong: “Floor beam” and “main beam” are less precise; not always reserved for primary members. “All the above” would blur important distinctions in detailing and specification. Common Pitfalls: Interchanging terms in calculations and schedules leading to misfabrication. Final Answer: a girder

Question 19

Internal actions in beams: The couple developed within a beam section by longitudinal compression at the top and tension at the bottom is called what?

Accepted Answer

Introduction / Context: When a beam bends, external loads create an external bending moment. Internally, the compressive and tensile resultants form an opposing couple that resists the applied moment. Knowing the correct terminology is vital for analysis and design communication. Given Data / Assumptions: Beam under bending in the elastic range. Linear strain distribution and a neutral axis within the cross section. Concept / Approach: The external bending moment must be balanced by an internal resisting couple. The internal couple that the section can develop based on its stress distribution and section modulus is called the moment of resistance. The term “bending moment” refers to the external action, not the internal resistance. Step-by-Step Solution: External loads → external bending moment on a section.Internal stresses (compression and tension) form a couple.This internal couple is the moment of resistance which equals the applied bending moment at equilibrium. Verification / Alternative check: In elastic analysis, M = σ * Z, where σ is the extreme fiber stress and Z is section modulus; this expression is precisely the section’s moment of resistance. Why Other Options Are Wrong: “Bending moment” denotes the external action, not the internal resistance. “Flexural stress moment” is non-standard terminology. “None of these” is incorrect because a standard term exists. Common Pitfalls: Using external and internal moment terms interchangeably. Final Answer: moment of resistance

Question 20

Effective length of compression members: For a compression member of physical length L that is held in position and restrained in direction at both ends (i.e., effectively fixed at both ends), the effective length is approximately equal to which val…

Accepted Answer

Introduction / Context: Column buckling strength depends on effective length, which captures end restraints. Better end restraint reduces the effective length factor and increases buckling capacity. Recognizing standard effective length factors is essential in steel design. Given Data / Assumptions: Prismatic compression member. End conditions: held in position and restrained in rotation at both ends (fixed–fixed idealization). Euler-type buckling concept for effective length. Concept / Approach: Effective length Le = K * L, where K is the effective length factor. Typical values: pinned–pinned K ≈ 1.0, fixed–free K ≈ 2.0, fixed–pinned K ≈ 0.7–0.8, fixed–fixed K ≈ 0.5–0.7 depending on code conservatism and real restraint. Many steel design guides adopt about 0.65–0.7 for ideal fixed–fixed; 0.67 L is a common rounded value used in problems. Step-by-Step Solution: Identify end condition: both ends restrained in position and direction.Adopt K ≈ 0.65–0.7 for fixed–fixed.Select the closest listed value: 0.67 L. Verification / Alternative check: Euler buckling load is proportional to 1 / Le^2; reducing Le to about two-thirds increases capacity by roughly (1 / 0.67^2) ≈ 2.2 times compared to a pinned–pinned column, which aligns with expectations. Why Other Options Are Wrong: L: corresponds to pinned–pinned, less restraint. 0.85 L: closer to fixed–pinned, not fixed–fixed. 1.5 L or 2 L: represent poor restraint or cantilever case; not applicable. Common Pitfalls: Assuming perfect fixity in practice; real joints may justify K values slightly above the ideal. Final Answer: 0.67 L

Steel Structure Design Questions