Question 1

King-post and queen-post trusses: identify the incorrect statement

Accepted Answer

Introduction / Context: Traditional roof trusses are named for their central vertical members. Knowing how many posts each type contains is basic to selection, detailing, and measurement for roofs of different spans. Given Data / Assumptions: King-post truss: classic single central post. Queen-post truss: two posts with a straining beam between them. Span suitability generally: king-post for shorter spans; queen-post for moderate spans. Concept / Approach: The incorrect statement is the one that says a queen-post truss has only one vertical post. By definition it has two. The other statements match standard truss descriptions and typical span guidance (though span limits vary with material and design). Step-by-Step Solution: Confirm king-post: one central vertical → true.Check queen-post: two verticals with straining beam → true.Identify the incorrect claim: “one vertical post” for queen-post → false.Therefore select option b as incorrect. Verification / Alternative check: Standard structural handbooks depict one-post and two-post configurations for king and queen trusses, respectively. Why Other Options Are Wrong: a and c are correct statements.d (None) is invalid because an incorrect statement exists.e is generally correct: queen-post spans exceed king-post spans in many traditional timber cases. Common Pitfalls: Interchanging the names; assuming “queen” implies a single larger post rather than two posts. Final Answer: A queen-post truss has one vertical post is the incorrect statement.

Question 2

Concrete construction — safe stripping time for beam formwork (including props) According to standard building practice for cast-in-place reinforced concrete, the formwork to beams — including the supporting props — should be removed only after appr…

Accepted Answer

Introduction / Context: Correct formwork striking (removal) times are crucial for structural safety and surface quality in reinforced concrete construction. Beams carry significant bending and shear, and their soffit formwork and props support fresh concrete until adequate strength develops. This question checks recognition of the conservative, widely taught timeframe for removing beam formwork including props. Given Data / Assumptions: Ordinary Portland cement, normal ambient temperature, and curing. No accelerators or steam curing; no special high-early-strength mixes. General site practice for typical spans (if spans are large, even longer times may be adopted). Concept / Approach: Codes and textbooks provide indicative stripping periods: sides of beams and columns can be struck early (when concrete can support its own edges), slabs with props are commonly kept for 7–14 days depending on span, and beams/arches require the longest duration because the soffit and props carry flexural loads until the concrete gains sufficient strength. A conservative classroom value often cited for beam formwork including props is about 21 days under normal conditions. Step-by-Step Solution: Identify element type: beam → higher bending → longer prop retention.Relate to strength gain: concrete typically reaches a major fraction of its 28-day strength by day 21 under normal curing.Apply conservative site guidance: remove beam formwork including props ≈ 21 days. Verification / Alternative check: Many syllabi and handbooks tabulate indicative periods: sides of beams ~1–2 days; slab props ~7–14 days (span dependent); beam props ~14–21 days (span dependent). In the absence of span data, the safer answer is 21 days. Why Other Options Are Wrong: 3 or 7 days are too early for beam soffit props in ordinary conditions. 14 days may suffice for shorter spans, but 21 days is the safer, commonly taught value when span is unspecified. Common Pitfalls: Ignoring span length and temperature effects on stripping time. Removing props early because side shutters were removed without distress. Final Answer: 21 days.

Question 3

Low-cost housing layout — typical specification for one-room quarters For standard one-room residential quarters adopted in many public-works schemes, which of the following specifications are commonly used?

Accepted Answer

Introduction / Context: Public housing and institutional accommodation often follow standardized layouts to control cost and ensure functional usability. One-room units (single-room tenements) are specified with typical dimensions and arrangements that balance daylight, ventilation, and economy. Given Data / Assumptions: Basic one-room dwelling with a front verandah. Block planning favors repetition (row of quarters) for services and access. Dimensions stated are typical, not absolute code minima. Concept / Approach: Standard sizes streamline material usage and maintain livability. Verandahs provide shaded transition space and improve cross-ventilation. Repetition in a row optimizes plumbing, electrical routing, and site utilization while keeping circulation simple. Step-by-Step Solution: Assess plan type: repetitive row → six quarters in a line is common.Check room sizes: 3.5 × 3.0 m or 4.2 × 2.5 m meet basic furniture and circulation needs.Confirm verandah: ≈ 2.0 m width ensures functional use.Therefore, all listed specifications are consistent with common practice. Verification / Alternative check: Departmental schedule-of-accommodation booklets often publish similar module sizes for low-cost housing and labour quarters. Why Other Options Are Wrong: Each of (a)–(c) is correct; hence the comprehensive answer is (d) “All the above”. Common Pitfalls: Ignoring local bylaws for setbacks and minimum room sizes/height. Overlooking accessibility and service shaft planning in repetitive blocks. Final Answer: All the above.

Question 4

Bridge substructure in sandy soils — best-suited foundation type for flyovers For the construction of flyovers (bridge structures) on sandy soil deposits, which foundation type is generally provided to safely transmit loads and control settlements/s…

Accepted Answer

Introduction / Context: Flyovers and highway bridges impose heavy concentrated loads and must also resist scour, lateral forces, and differential settlement. Choice of foundation depends on subsoil profile and hydraulic conditions. In sandy strata, especially where depth to dense sand varies or scour is possible, deep foundations are preferred. Given Data / Assumptions: Bridge/flyover piers on sand deposits (potentially variable density and groundwater). Need for reliable capacity and settlement control under repetitive traffic loads. Exposure to potential scour around foundations in open channels or culverts. Concept / Approach: For most flyovers, pile foundations (driven precast, cast-in-situ bored, or continuous flight auger) are adopted in sandy soils. Piles transfer loads to deeper dense strata and provide group action and stiffness; they also accommodate construction above traffic. The listed shallow alternatives—strap, raft, combined, or a generic “pier footing”—are typical of building foundations and are seldom used for highway flyover piers on sands due to higher risk of settlement and scour unless exceptional site conditions exist. Step-by-Step Solution: Identify structure type: flyover pier → heavy concentrated loads and scour considerations.Assess soil: sand → variable density; potential for liquefaction or scour.Select foundation: piles are standard; not among the given options.Therefore, among listed choices, “None of these” is correct. Verification / Alternative check: Bridge design manuals and standard drawings show pile caps with pile groups for piers/abutments on sands; shallow raft/strap/combined footings are unusual for flyovers unless bearing strata are exceptionally competent and scour is absent. Why Other Options Are Wrong: Strap/combined footings are building solutions for closely spaced columns. Raft spreads loads but remains shallow and sensitive to scour. “Pier footing” as a shallow spread footing is rarely suitable in sandy, potentially erodible conditions. Common Pitfalls: Confusing substructure element (pier) with its foundation type (piles/wells/caissons). Ignoring seismic/liquefaction checks for sandy profiles. Final Answer: None of these.

Question 5

Subsurface investigation — auger boring basics (applications and limits) Which combination of statements correctly describes hand/portable auger boring as used in geotechnical site exploration?

Accepted Answer

Introduction / Context: Auger boring is a simple, low-cost method to obtain shallow subsurface information for foundations, utilities, and environmental screening. Understanding where it works best prevents wasted effort and unsafe holes. Given Data / Assumptions: Use in near-surface soils for small projects or preliminary exploration. Equipment ranges from hand augers to portable power-driven rigs. Focus on soils above the groundwater table for unsupported holes. Concept / Approach: Augers cut and lift soil by helical blades. In cohesive and self-supporting soils the hole walls remain stable without casing, making auger boring efficient. Below the water table or in loose sands, holes collapse unless cased. Economically, the method is attractive up to a few metres; beyond that, more capable drilling methods are preferable. Typical tool diameters for site work lie in the 7.5–30 cm range, matching sampling and in-situ test requirements for small projects. Step-by-Step Solution: Confirm simplicity and historical use → (a) true.Check applicable soils and water table limitation → (b) true.Depth economy threshold ≈ 5 m for small rigs → (c) true.Common auger sizes 7.5–30 cm for portable rigs → (d) true.Therefore, “All the above” is correct. Verification / Alternative check: Most geotechnical manuals specify hand augers for cohesive soils and caution against use below water table without casing. Equipment catalogs confirm typical diameter ranges. Why Other Options Are Wrong: Each individual statement is correct; selecting any single one misses the comprehensive nature of auger boring practice. Common Pitfalls: Attempting auger boring in loose saturated sands without casing support. Expecting undisturbed samples from simple augering without proper samplers. Final Answer: All the above.

Question 6

Building stones — which has the lowest crushing strength? Among the following commonly known stones, which one typically exhibits the least crushing (compressive) strength and is therefore the weakest for structural use?

Accepted Answer

Introduction / Context: Selection of stone for construction depends heavily on compressive strength, durability, and weathering resistance. Understanding the relative strengths of common stones helps in choosing suitable applications and avoiding failures. Given Data / Assumptions: Typical ranges of compressive strength for unweathered rock types. Laboratory-tested values at standard moisture content. Comparative, not absolute, assessment. Concept / Approach: Granite, slate, and many sandstones are strong to very strong rocks. Marble (metamorphosed limestone) generally has moderate to high compressive strength. Chalk is a soft, porous limestone with very low compressive strength, unsuitable for load-bearing masonry without special treatment. Step-by-Step Solution: Review typical strengths: granite and slate → high; sandstone → moderate to high; marble → moderate; chalk → low.Identify the weakest among the list → chalk. Verification / Alternative check: Rock mechanics tables report chalk strengths often an order of magnitude lower than compact limestones or granites, confirming chalk as the least strong in crushing. Why Other Options Are Wrong: Granite and slate are commonly used for heavy loads. Marble, while not as strong as granite, exceeds chalk. Many sandstones exceed chalk strength substantially. Common Pitfalls: Confusing decorative value (marble) with structural strength. Assuming all limestones are similar; chalk is a weak variety. Final Answer: Chalk.

Question 7

Bricklaying — name of a brick laid with its length parallel to the wall face In brick masonry, what do we call a brick that is placed so that its longer dimension runs parallel to and appears on the exposed face of the wall?

Accepted Answer

Introduction / Context: Bond patterns in brickwork, such as stretcher and header courses, rely on the orientation of bricks. Correct terminology ensures proper specification, quantity take-off, and construction sequencing. Given Data / Assumptions: Standard rectangular bricks are used. Face of the wall shows either the long face (stretcher) or the short face (header). Closer bricks are used only to adjust bond at ends. Concept / Approach: A stretcher is a brick laid so that its longer face is visible on the wall face; a header shows the short face. The distinction underpins English, Flemish, and other bonds where courses alternate or mix stretcher and header orientations for structural interlocking. Step-by-Step Solution: Identify orientation: length parallel to wall face → stretcher.Eliminate alternatives: header is the short face; closer is a cut brick used near quoins for bond. Verification / Alternative check: Any masonry handbook illustrates stretcher vs. header clearly in bond diagrams. Why Other Options Are Wrong: Header exposes the short face, not the long one. Closer is not an orientation but a cut piece to maintain bonding. Common Pitfalls: Confusing modular sizes with face orientation; names depend on orientation, not absolute dimensions. Final Answer: Stretcher.

Question 8

Combined footing design — verify geometry and area from load data and SBC Two reinforced concrete columns of sizes 50 cm × 50 cm and 60 cm × 60 cm carry 80 t and 120 t respectively. The centre-to-centre spacing between the columns is 5.00 m. The all…

Accepted Answer

Introduction / Context: Combined footings are used when two columns are close and individual footings would overlap or when eccentric loading must be balanced. The footing is proportioned so that the resultant of column loads passes through the centroid of the footing area, keeping soil pressure uniform (or linearly distributed without tension). Given Data / Assumptions: Column loads: 80 t and 120 t; spacing = 5.00 m. Soil bearing capacity (allowable) q_allow = 20 t/m². Projection limit beyond the smaller column = 0.25 m. Neglect footing self-weight, or include a small allowance folded into rounding. Concept / Approach: The total area A needed is approximately total load divided by allowable pressure. The centroid of the two loads from the smaller column equals the weighted average of positions. The footing length is chosen so that the centroid of area coincides with the resultant load location; width follows from A = L * B within projection constraints. Step-by-Step Solution: Compute total load W = 80 + 120 = 200 t.Area A ≈ W / q_allow = 200 / 20 = 10 m². Allowing ≈10% for self-weight and rounding → about 11 m².Centroid of loads from the smaller column: x̄ = (080 + 5120) / 200 = 600 / 200 = 3.00 m → matches (a).Limit the near-side projection to 0.25 m; choose an overall length L so that the load resultant coincides with the footing area centroid. A practical solution consistent with the options is L = 7.00 m.Width B = A / L ≈ 11 / 7 ≈ 1.57 m → matches (d). Verification / Alternative check: With L = 7 m and B ≈ 1.57 m, the centroid of the rectangular area is at 3.5 m from either end. By arranging the smaller-column face 0.25 m from the near end, the smaller-column centre lies at 0.25 + 0.25 (half column) = 0.50 m from the end; hence the centroid of loads at 3.00 m from that centre puts the resultant at 3.50 m from the same end, aligning with the area centroid. Why Other Options Are Wrong: Each individual statement (a)–(d) is correct; together they form a consistent design set, so the best choice is “All the above”. Common Pitfalls: Forgetting to include projection and column sizes when positioning the footing. Not checking for shear and bending after sizing based on area alone. Final Answer: All the above.

Question 9

Stair terminology — inclined member supporting treads and risers In stair construction, what is the name of the inclined structural member at the ends of the treads and risers that supports them along the slope of the stair?

Accepted Answer

Introduction / Context: Stairs consist of several parts with specific roles and names. Correct terminology helps in detailing, fabrication, and site communication. The inclined edge members are especially important because they carry the stair loads and define its geometry. Given Data / Assumptions: Conventional stair with treads and risers. Inclined edge/support member present. Focus on structural supporting function. Concept / Approach: The inclined member that supports the treads and risers is called the string or stringer. A baluster is a vertical post supporting the handrail; a beam is a generic horizontal structural element; “header” is not a standard stair term for the stringer in building practice. Step-by-Step Solution: Identify stair component providing longitudinal support → string/stringer.Eliminate baluster (railing component) and beam (generic).Select “String (stringer)” as the correct term. Verification / Alternative check: Fabrication drawings and site terminology consistently use “stringer” for steel/wood stair side members; concrete stairs have similar sloping edges within the slab. Why Other Options Are Wrong: Baluster relates to the handrail, not structural tread support. “Header” is not the correct stair component here. “Beam” is too general and typically horizontal. Common Pitfalls: Confusing stringer with “nosing” (front edge of tread). Ignoring load paths from stringer to landings and supports. Final Answer: String (stringer).

Question 10

Ground improvement — increasing bearing capacity of waterlogged soils When a site suffers from high groundwater (waterlogged conditions) that reduces bearing capacity, which of the following methods may be used to improve the soil so it can safely s…

Accepted Answer

Introduction / Context: Waterlogged soils exhibit low effective stresses, leading to reduced shear strength and bearing capacity. Improving such soils can involve changing water conditions, modifying soil structure, or adding binders. The best solution depends on soil type, depth, and project constraints. Given Data / Assumptions: Shallow foundations affected by high groundwater. Soil type ranges from cohesionless to cohesive deposits. Objective is to improve bearing capacity and reduce settlements. Concept / Approach: Lowering the groundwater level via drainage increases effective stress, directly improving bearing capacity. Compaction densifies granular soils, raising friction angle and stiffness. Grouting fills voids and bonds particles in coarse soils; chemical stabilization (lime, cement, other reagents) alters plasticity and strength particularly in fine-grained soils. Often, a combination is used for best results. Step-by-Step Solution: Assess soil and groundwater: waterlogged → low effective stress.Choose drainage where feasible to reduce pore water pressures.Apply compaction in granular layers; use vibro-compaction or stone columns if suitable.Consider grouting or chemical stabilization for specific soil types and depths. Verification / Alternative check: Case histories show significant bearing capacity increases after dewatering and compaction; lime/cement treatment of clays improves unconfined compressive strength and reduces settlement. Why Other Options Are Wrong: They are not wrong individually; all listed methods can be appropriate depending on the soil and project. Common Pitfalls: Attempting compaction in saturated clays without prior drainage or stabilization. Ignoring environmental impacts of chemical additives or grout migration. Final Answer: All of these.

Question 11

Foundation choice for layered clays — firm clay over deep soft clay During site investigation, a thick layer of fairly firm clay is encountered overlying a deep, soft clay stratum. For such a soil profile supporting a building, which type of foundat…

Accepted Answer

Introduction / Context: Layered soil profiles often dictate the most economical and safe foundation type. When a reasonably firm clay layer of adequate thickness lies at the surface, while a softer clay extends deeper below, designers aim to distribute loads within the firm layer and avoid excessive stress transmission to the weaker stratum. Given Data / Assumptions: Thick, fairly firm clay near the surface; deep soft clay underneath. Building loads are spread over an area (no extreme point loads beyond raft design capability). Conventional settlement control and bearing checks are required. Concept / Approach: A raft (mat) foundation spreads loads over the entire footprint, reducing contact pressure and making better use of the firm upper clay layer. It mitigates differential settlement by plate action. Pile foundations would transfer loads to deeper strata; if those strata are soft for great depth, piles become long and uneconomical or may settle. Grillage foundations are usually for isolated heavy columns on relatively shallow competent layers and are less effective for uniform distribution over soft underlying clay. Step-by-Step Solution: Check near-surface competence: thick firm clay → suitable for raft bearing.Assess deeper profile: deep soft clay → avoid driving stresses deep; spreading loads is preferable.Select raft foundation to utilize the stronger upper layer and control settlement. Verification / Alternative check: Plate-on-elastic-foundation analyses and settlement calculations typically show reduced maximum contact pressures and improved uniformity with rafts on firm-over-soft profiles. Why Other Options Are Wrong: Piles would require deep penetration into weak strata or reaching very deep firm layers, often uneconomical. Grillage focuses load under discrete columns and does not address broad-area settlement control. “None” is incorrect because raft is a standard solution here. Common Pitfalls: Ignoring long-term consolidation of the deeper soft clay; preloading or staged construction may still be needed. Overlooking groundwater effects and basal heave in excavations. Final Answer: Raft foundation.

Question 12

Herringbone bond in brickwork and paving In building construction, the herringbone bond is a distinctive zig-zag laying pattern. For which application is the herringbone bond most commonly and appropriately used in practice?

Accepted Answer

Introduction / Context: The herringbone bond is a decorative brick-laying pattern where bricks are laid at alternating angles to create a “V” or zig-zag motif. While many bonds are primarily structural (English, Flemish, header, stretcher), herringbone is best known for its aesthetic and functional performance in pavements and floor panels, where load is primarily distributed in-plane and the interlocking angles help resist lateral movement. Given Data / Assumptions: Question asks for the most appropriate and common use of the herringbone bond. Context: practical construction, not purely theoretical possibilities. Comparison is with wall bonds used to ensure through-bonding and structural action. Concept / Approach: Wall bonds (English, Flemish) are designed to secure through-ties across wall thickness, reduce continuous vertical joints, and increase loadbearing capacity. Herringbone’s diagonal placement is not intended to provide through-bonding in thick walls; instead it provides a high-friction, visually appealing surface, ideal for pavements, courtyard floors, and ornamental inlays. The angled bricks dissipate shear and reduce the tendency for blocks to “walk” under traffic. Step-by-Step Solution: Identify herringbone: an angled, interlocking, non-through bonding arrangement.Assess suitability in walls: lacks the systematic header-stretcher arrangement required for through bonding in thick walls.Recognise flooring/paving advantages: aesthetics, shear resistance, and stability under in-plane loads.Select the use-case that aligns with practice: ornamental panels/patterns in floors and pavements. Verification / Alternative check: Historic and modern masonry guides depict herringbone primarily for pavements, infill panels in timber framing, and decorative flooring—rarely as the principal bond for thick, loadbearing walls due to bonding limitations. Why Other Options Are Wrong: walls thicker than four bricks: requires strong through-bonding not provided by herringbone. architectural face finish to loadbearing walls: the face may look attractive but fails to ensure internal structural bond. all the above: overstates its suitability; primary correct use is floors/paving. none of these: incorrect because flooring/paving is correct. Common Pitfalls: Confusing decorative face patterns with structural bonding; assuming any beautiful pattern is appropriate for thick loadbearing walls. Final Answer: ornamental panels and patterns in brick flooring and paving

Question 13

Stair design — compute number of treads from storey height and riser A building’s first storey height is 3.2 m. If each riser is 13 cm, determine the required number of treads for the stair (assume a single run between floor levels, so treads = rise…

Accepted Answer

Introduction / Context: Basic stair geometry links total storey rise, riser height, and number of risers/treads. In most building layouts, the number of treads in a straight flight equals the number of risers minus one, because the upper floor or landing serves as the final “step.” This question tests correct interpretation of stair arithmetic and common design convention. Given Data / Assumptions: Total storey rise H = 3.2 m = 320 cm. Chosen riser r = 13 cm. Single run between ground floor and first-floor landing; top landing is the last step level. Hence number of treads = number of risers − 1. Concept / Approach: First compute the number of risers as H / r. If this is not an integer, round to the nearest practical integer (commonly up to the next integer to avoid an over-tall riser). Then convert to treads using the conventional relationship. Check that the resulting going (tread depth) meets comfort rules (e.g., 2r + g ≈ 600–650 mm) though this question focuses only on count. Step-by-Step Solution: Compute risers: n_r = 320 / 13 = 24.615…Practical riser count: n_r = 25 (round up to keep each riser ≤ 13 cm).Number of treads: n_t = n_r − 1 = 25 − 1 = 24.Therefore, the stair requires 24 treads. Verification / Alternative check: If 24 risers were used, each riser = 320 / 24 ≈ 13.33 cm, which exceeds the specified 13 cm. Using 25 risers keeps risers at or below the target value; with a landing at the top, treads remain 24. Why Other Options Are Wrong: 12, 18, 30: Not consistent with the computed riser count. 25: Corresponds to risers, not treads; the correct treads are one fewer. Common Pitfalls: Equating treads to risers without subtracting one for the top landing; failing to round up the riser count to meet the maximum riser constraint. Final Answer: 24

Question 14

Door/window terminology — vertical member through the middle of a shutter frame In joinery, what is the vertical member running through the middle of a window or door shutter frame called?

Accepted Answer

Introduction / Context: Understanding joinery terms is essential for detailing, procurement, and site communication. A shutter (door or window) comprises vertical and horizontal members that hold panels or glazing. The correct identification of these members avoids mistakes in fabrication and installation. Given Data / Assumptions: The question refers to a vertical member located within the middle of the shutter width. Standard door/window shutter components are considered. Conventional nomenclature is used. Concept / Approach: Stiles are the vertical outermost members at the edges of a shutter. Rails are the horizontal members (top, lock, bottom). A mullion is a vertical intermediate member that divides a shutter or window into multiple panels or lights. A reveal is the side face of a wall opening, not a part of the shutter frame; “post” is a general structural term not specific to shutter construction. Step-by-Step Solution: Identify member location: vertical and internal (not at the edges).Match to terminology: internal vertical divider = mullion.Exclude other terms: stile (edge), rail (horizontal), reveal (opening face), post (generic). Verification / Alternative check: Standard joinery drawings label vertical internal divisions as mullions and horizontal divisions as transoms. Why Other Options Are Wrong: style (stile): edge vertical member, not middle. reveal: masonry/finishing term, not a shutter member. post: generic; does not denote the shutter’s middle vertical member. none of these: incorrect as “mullion” is correct. Common Pitfalls: Spelling confusion between “stile” and “style”; mixing up mullions with transoms (which are horizontal). Final Answer: mullion

Question 15

Temporary working platforms in building — name the system What is the term for the temporary, rigid framework with platforms that enables masons and workers to operate safely at various heights during construction?

Accepted Answer

Introduction / Context: Temporary works are vital to construction safety and productivity. Among these, scaffolding provides access and working platforms along building facades or inside structures so trades can perform masonry, plastering, painting, and installation tasks safely. Given Data / Assumptions: Requirement: safe elevated working platform with guardrails and access. System must be temporary and rigid enough to support workers and materials. Common temporary works terms are provided as options. Concept / Approach: Scaffolding is a modular, temporary structure of standards, ledgers, transoms, and decks (planks) with toe boards and guardrails. Dead and raking shores are temporary supports used to carry loads during alterations or to shore up walls; underpinning strengthens or replaces foundations. Only scaffolding satisfies the function of providing elevated working platforms. Step-by-Step Solution: Identify required function: working platform at height.Map to terminology: scaffolding provides platforms, access, and edge protection.Exclude shores/underpinning: those are for temporary support, not platforms. Verification / Alternative check: Construction safety codes specify scaffold classes (tube-and-coupler, system scaffold, suspended, mobile towers) precisely for this purpose. Why Other Options Are Wrong: dead shore: vertical props for temporary support, no working platforms. raking shore: inclined props bracing walls, not walkable decks. underpinning: foundation strengthening, unrelated to access. none of these: incorrect because scaffolding is exactly the described system. Common Pitfalls: Confusing shoring (support) with scaffolding (access) due to similar temporary nature on site. Final Answer: scaffolding

Question 16

Cavity wall terminology — name of the inner section In a cavity wall consisting of two parallel leaves separated by an air gap and tied together, what is the inner section (the leaf on the room side) generally called?

Accepted Answer

Introduction / Context: Cavity walls are formed by two thin masonry leaves with a cavity in between, connected by metal or polymer ties. The system improves thermal insulation, moisture resistance, and sometimes sound attenuation. Correct naming of the components is important for detailing ties, damp-proof courses, and finishes. Given Data / Assumptions: Two masonry leaves: one external (weather face) and one internal (room face). Leaves are linked by wall ties across the cavity. Question asks the name of the inner section. Concept / Approach: The two parts of a cavity wall are called “leaves.” The inner portion is the inner leaf; the outer portion is the outer leaf. A buttress, pilaster, or pillar denotes projecting or isolated structural elements and is unrelated to the twin-leaf configuration. While the most precise term is “inner leaf,” some texts and schedules refer to each as a “leaf wall.” Given the options provided, “leaf wall” denotes the correct component. Step-by-Step Solution: Identify cavity wall anatomy: two leaves with ties and a cavity.Name the inner element: inner leaf (termed as a leaf wall in options).Exclude other structural terms (buttress, pilaster, pillar) as they are different elements. Verification / Alternative check: Standard details label the interior masonry leaf supporting internal finishes and services as the “inner leaf.” Why Other Options Are Wrong: buttress/pilaster/pillar: represent projecting or columnar supports, not the inner leaf of a cavity wall. none of these: incorrect because “leaf wall” corresponds to the intended component here. Common Pitfalls: Confusing general masonry terms with cavity wall nomenclature; overlooking that both sides are called leaves. Final Answer: leaf wall

Question 17

Sand piles for ground improvement — typical construction features Which statements correctly describe sand pile construction and usage for improving foundation performance?

Accepted Answer

Introduction / Context: Sand piles (a form of granular piles) are installed to improve weak or compressible soils by providing reinforcement, drainage, and densification. They are common under individual footings and heavily loaded columns where settlement control is required. Given Data / Assumptions: Granular piles are formed in pre-bored holes or by displacement. Compaction and controlled moisture are necessary for target density. Concrete caps or plug zones are used to spread load into the granular column. Typical application is under column footings or heavily loaded spots. Concept / Approach: Well-compacted moist sand achieves higher relative density and stiffness, enhancing load-sharing and reducing settlement. A concrete top cap provides a firm seat for footings and prevents surface ravelling. Granular piles also function as vertical drains, accelerating consolidation when combined with preloading in cohesive soils. Step-by-Step Solution: Confirm compaction: densification is fundamental → (a) true.Moist placement improves compaction energy transfer → (b) true.Concrete top length (about 1 m) used for capping and load transfer → (c) true in many specifications.Usage under columns to curb settlement and increase bearing → (d) true. Verification / Alternative check: Ground improvement manuals illustrate sand/granular piles with top plugs, preload options, and their role as drainage inclusions. Why Other Options Are Wrong: Any single statement alone is incomplete; all listed practices together best characterise sand piles. Common Pitfalls: Neglecting quality control of relative density; omitting the top cap; assuming granular piles behave like rigid piles (they are deformable inclusions). Final Answer: all of the above

Question 18

Concrete bed for foundations — factors governing required depth The depth (thickness) of a plain concrete bed beneath a footing depends primarily on which of the following design and construction factors?

Accepted Answer

Introduction / Context: A plain cement concrete (PCC) bed below a footing provides a level, clean, and slightly stiffened base to spread construction loads and protect reinforcement from soil contamination. Determining its depth requires an understanding of load transfer, edge stresses across its projection, and the compressive and shear capacity of the concrete. Given Data / Assumptions: PCC bed projects beyond the edges of the structural footing. Bearing pressure from soil acts upward on the underside of the bed. Concrete class (mix) influences compressive and shear strength. Concept / Approach: The bed acts as a load-spreading slab. Larger projections increase bending and shear demand near edges, necessitating greater thickness. Higher soil pressures raise the internal stresses in the bed. Stronger mixes permit thinner beds, while weaker mixes require more thickness to satisfy stress and minimum thickness criteria for constructability and durability. Step-by-Step Solution: Assess plan projection → greater overhang elevates bending moments in bed.Estimate soil pressure under working loads → higher pressure demands larger thickness.Select concrete mix → strength and workability influence minimum depth.Therefore, all listed factors (projection, pressure, mix) govern the required bed depth. Verification / Alternative check: Design charts or simple slab-on-elastic-foundation checks confirm the relationship between projection, pressure, and thickness, consistent with common handbooks. Why Other Options Are Wrong: Picking any single factor ignores the multivariate nature of bed design. none of these: incorrect because all listed factors apply. Common Pitfalls: Using arbitrary bed thickness without checking projection and soil pressure; disregarding local specifications for minimum thickness and cover. Final Answer: all the above

Question 19

Empirical proportion between offset and depth of concrete bed Let a (in cm) be the plan offset (projection) of a concrete bed beyond the footing edge, and d (in cm) be the depth (thickness) of that bed. Choose the commonly used empirical relation be…

Accepted Answer

Introduction / Context: For PCC leveling beds and plain concrete projections beneath footings, simple empirical rules are often used at the estimation stage to size thickness relative to the bed’s plan offset a (the overhang beyond the footing). These rules roughly account for bending and shear in the projecting portion under soil pressure. Given Data / Assumptions: a = plan offset (projection) in centimetres. d = depth (thickness) of concrete bed in centimetres. Rule-of-thumb proportion relates d to a for preliminary sizing. Final design should be checked by structural calculations and local codes. Concept / Approach: The projection behaves somewhat like a cantilever under upward soil reaction. A moderate fraction of the projection used as thickness offers a practical balance between strength and economy. The relation d ≈ 0.445 a is a commonly cited thumb rule for preliminary estimates, subject to verification. Step-by-Step Solution: Identify purpose: preliminary sizing for PCC bed thickness.Use the empirical proportion d = 0.445 a for first-pass estimates.Plan to refine with bending/shear checks considering soil pressure and concrete strength. Verification / Alternative check: Comparative checks using simple cantilever bending under uniform reaction show that thickness proportional to projection provides acceptable preliminary stresses, which detailed design can fine-tune. Why Other Options Are Wrong: d = 0.557 a or 0.775 a: overly conservative for typical PCC beds, inflating quantities. d = 0.250 a: too thin for many practical projections. none of these: incorrect since a standard thumb rule exists. Common Pitfalls: Treating thumb rules as final design; ignoring edge cases such as very high soil pressures or poor-quality concrete requiring thicker beds. Final Answer: d = 0.445 a

Question 20

Measuring depth of foundation excavations in the field Which instrument is generally used to measure the depth of excavation for foundations with reference to a benchmark or formation level?

Accepted Answer

Introduction / Context: Accurate control of excavation depth is essential to ensure the footing reaches design levels, achieves the required bearing stratum, and maintains uniformity across the site. Survey instruments and accessories are used to check levels relative to site benchmarks. Given Data / Assumptions: The measurement is relative to a benchmark or desired formation level. Standard site surveying tools are available. Practical site procedure is being queried. Concept / Approach: Depth is best controlled by taking level readings with a levelling instrument and a levelling staff placed at the excavation bottom. The difference between the reading and the benchmark-based reference gives the excavation depth or the reduced level of the bottom. A steel tape only measures linear distances locally and does not reference elevation unless a datum is established and maintained, which is less robust on uneven ground. Step-by-Step Solution: Set up a level instrument (auto level/dump level) near the excavation.Hold the levelling staff on the excavation bottom to take a backsight/foresight reading.Compute reduced level or depth relative to benchmark.Adjust excavation until the readings match the design formation level. Verification / Alternative check: Boning rods can be used for trench grade control in small works, but staff+level provides higher accuracy and is standard for foundations. Why Other Options Are Wrong: ranging rod: used for aligning straight lines, not level measurement. steel tape: measures length, not elevation relative to a datum. boning rod: for trench line/grade by sighting, less precise for depth to benchmark. none of these: incorrect because a levelling staff is correct. Common Pitfalls: Measuring depth from variable ground points without referencing a fixed benchmark; ignoring instrument errors and staff misreadings. Final Answer: levelling staff

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