BT-204 Basic Civil Engineering and Engineering Mechanics - Dec 2023 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
   aWhat are the contour lines and explain its various properties?
   How to answer

   • Definition of contour line (imaginary line joining points of equal elevation)
   • Key characteristics/properties: contours never cross except at overhanging cliff
   • Closely spaced contours indicate steep slope, widely spaced indicate gentle slope
   • Concentric closed contours with higher values inside indicate a hill, lower inside indicate a depression
   • Contours cross a ridge or valley line at right angles
2. 7 Marks
   bWhat do you understand by the term moment of inertia and radius of gyration?
   How to answer

   • Definition of moment of inertia (second moment of area/mass) and mathematical expression ($I = \int r^2 dA$ or $\sum m r^2$)
   • Physical significance and units (mm$^4$ or kg$\cdot$m$^2$)
   • Definition of radius of gyration ($k$): distance from reference axis where entire area/mass is assumed to be concentrated
   • Formula: $k = \sqrt{I/A}$ or $k = \sqrt{I/M}$ and units (m or mm)
3. 7 Marks
   aWrite short notes on any four of the followings:

   1. i)Shallow foundation
   2. ii)Survey stations
   3. iii)Indian Remote Sensing Satellite
   4. iv)Geodetic surveying
   5. v)Free body diagram
   How to answer

   • Shallow foundation: definition ($D_f \le B$), types (isolated, combined, strap, raft)
   • Survey stations: main stations, subsidiary stations, tie stations and their marking/selection
   • IRS: Indian Remote Sensing Satellite series (IRS-1A, Cartosat, Resourcesat), civilian remote sensing applications
   • Geodetic surveying: accounts for curvature of Earth, large areas (> 250 km$^2$), high precision
   • Free body diagram: isolated sketch of body showing all external active and reactive forces
4. 7 Marks
   bWhat is the workability of concrete? Explain those factors that affecting the workability of concrete.
   How to answer

   • Definition of workability: ease of mixing, placing, compacting, and finishing concrete without segregation
   • Water content/water-cement ratio: higher water increases workability
   • Aggregate size and shape: rounded aggregates require less water than angular ones
   • Aggregate grading and surface texture: smooth/well-graded improves workability
   • Use of admixtures: plasticizers/superplasticizers increase workability without extra water
   • Environmental factors: temperature, wind, transit time
5. 7 Marks
   aExplain nominal and design mix concrete in details.
   How to answer

   • Definition of nominal mix: fixed volumetric proportions specified by codes (e.g., M15, M20) without lab design
   • Definition of design mix: proportions determined through laboratory trials based on actual material characteristics for target strength
   • Comparison: nominal mix uses volume batching, design mix uses weigh batching
   • Economy: design mix is more economical and ensures required durability and strength
   • Applications: nominal for minor/low-grade works ($≤$ M20), design mix for high-strength/structural works
6. 7 Marks
   bWhat are the principle and applications of the remote sensing in the Civil Engineering?
   How to answer

   • Working principle of remote sensing: interaction of EMR with target, reflection/emission, sensor detection, and data processing
   • Components: energy source, transmission path, target, sensor, receiving station
   • Applications in Civil Engineering:
   • - Site selection for dams, highways, bridges
   • - Water resource management and flood mapping
   • - Urban planning and land use/land cover mapping
   • - Disaster management and environmental impact assessment
7. 7 Marks
   aDraw the shear force and bending moment diagram for simply supported beam, which carries a uniformly varying load of $15\text{ kN/m}$ and a point load of $25\text{ kN}$ on its center having span of $6\text{ m}$.

   

   How to answer

   • Calculate total UVL = $\frac{1}{2} \times 15 \times 6 = 45\text{ kN}$, acting at $2/3 \times 6 = 4\text{ m}$ from support A
   • Taking moments about A: $R_B \times 6 = 25 \times 3 + 45 \times 4 = 75 + 180 = 255 \implies R_B = 42.5\text{ kN}$
   • Vertical equilibrium: $R_A = (45 + 25) - 42.5 = 27.5\text{ kN}$
   • Plot Shear Force Diagram: parabolic variation from UVL plus vertical jump of $25\text{ kN}$ downward at mid-span
   • Find point of zero shear to locate maximum bending moment
   • Plot Bending Moment Diagram: cubic curves, maximum value calculated and marked
8. 7 Marks
   bDefine any two-field test; those are conducted on cement and sand.
   How to answer

   • Cement field test 1: Color test (uniform greenish-grey) and touch/feeling test (smooth feeling, not gritty)
   • Cement field test 2: Temperature test (hand plunged into cement feels cool) or sink test (paste floats before sinking)
   • Sand field test 1: Silt content test (mixing sand with saline water in a measuring cylinder to observe silt layer)
   • Sand field test 2: Presence of organic impurities (rubbing on palm) or bulking test
9. 7 Marks
   aWhat is the composition of cement? Explain in detail.
   How to answer

   • List oxide constituents and typical percentages: Lime (CaO, 60-67%), Silica (SiO$_2$, 17-25%), Alumina (Al$_2$O$_3$, 3-8%), Iron Oxide (Fe$_2$O$_3$, 0.5-6%), Magnesia (MgO, 0.1-4%), Alkalies, Sulfur trioxide
   • Functions of each ingredient (Lime imparts strength, Silica imparts strength, Alumina quick setting, Gypsum retards flash setting)
   • Harmful effects of excess lime, silica, or magnesia
   • Brief mention of Bogue's compounds formed ($C_3S$, $C_2S$, $C_3A$, $C_4AF$)
10. 7 Marks
    bDefine any four of the following terms:

    1. i)Law of machine
    2. ii)Initial and final setting time of cement
    3. iii)Efflorescence
    4. iv)Curing of concrete
    5. v)Plastering and pointing
    How to answer

    • Law of machine: linear relationship between effort ($P$) and load ($W$), $P = mW + C$
    • Initial and final setting time: Initial time ($\ge 30$ min) when cement starts losing plasticity; final time ($\le 600$ min) when paste completely hardens
    • Efflorescence: whitish powdery deposit on masonry surface due to soluble salts crystallizing after evaporation of water
    • Curing of concrete: process of maintaining moisture and temperature conditions for continued hydration and strength gain
    • Plastering and pointing: Plastering is covering entire wall surface with mortar; Pointing is finishing only the exposed joints of masonry
11. 7 Marks
    aWhat is the local attraction in surveying? How is it detected at any survey station?
    How to answer

    • Definition: magnetic disturbance of the compass needle from magnetic meridian due to external magnetic materials (iron ore, steel poles, electric cables)
    • Detection: by checking the difference between fore bearing (FB) and back bearing (BB) of a line
    • If $|FB - BB| = 180^\circ$, both stations are free from local attraction
    • If $|FB - BB| \ne 180^\circ$, one or both stations are affected by local attraction
    • Correction methods: method of included angles or correction calculation per station
12. 7 Marks
    bWhat are the various types of doors and windows used in the building construction?
    How to answer

    • Doors classified by arrangement of components: paneled, battened and ledged/braced, glazed/sash
    • Doors classified by operation: hinged, revolving, sliding, swing, rolling shutter, collapsible
    • Types of windows: casement window, sash window, sliding window, clerestory window, bay window, skylight, dormer window, louvered window
    • Criteria for selection: light, ventilation, security, and aesthetics
13. 7 Marks
    aDefine and derive an expression for parallel axis theorem.
    How to answer

    • Statement of Parallel Axis Theorem: The moment of inertia of an area about any axis is equal to the moment of inertia about a parallel centroidal axis plus the product of the area and the square of the distance between the two axes ($I_{AB} = I_G + Ah^2$)
    • Neat sketch showing area $A$, centroidal axis $G$, parallel axis $AB$ at distance $h$, and elemental area $dA$
    • Mathematical setup: $I_{AB} = \int (y + h)^2 dA = \int (y^2 + 2yh + h^2) dA$
    • Expansion: $I_{AB} = \int y^2 dA + 2h \int y dA + h^2 \int dA$
    • Since $\int y dA = 0$ (centroidal axis) and $\int y^2 dA = I_G$, $\int dA = A$, result follows: $I_{AB} = I_G + Ah^2$
14. 7 Marks
    bDetermine the moment of inertia of the given plane lamina about its centroidal axis as shown in the figure below:

    

    How to answer

    • Identify symmetry: The H-section is symmetric about both horizontal and vertical axes passing through the center
    • Total width = $15 + 60 + 15 = 90\text{ mm}$, total depth = $100\text{ mm}$
    • Calculation of $I_{xx}$:
    • - Two vertical flanges: $2 \times [\frac{1}{12} \times 15 \times 100^3] = 2.5 \times 10^6\text{ mm}^4$
    • - One central web: $\frac{1}{12} \times 60 \times 15^3 = 16,875\text{ mm}^4$
    • - Total $I_{xx} = 2.5 \times 10^6 + 16,875 \approx 2.517 \times 10^6\text{ mm}^4$
    • Calculation of $I_{yy}$:
    • - Web: $\frac{1}{12} \times 15 \times 60^3 = 270,000\text{ mm}^4$
    • - Flanges: $2 \times [\frac{1}{12} \times 100 \times 15^3 + (100 \times 15) \times (30 + 7.5)^2] = 2 \times [28,125 + 1500 \times 37.5^2] = 4.275 \times 10^6\text{ mm}^4$
    • - Total $I_{yy} = 270,000 + 4.275 \times 10^6 = 4.545 \times 10^6\text{ mm}^4$
15. 7 Marks
    aWrite short notes on any four of the following terms:

    1. i)Magnetic declination
    2. ii)Bow's notation
    3. iii)Plane tables
    4. iv)D-Alembert's principle
    5. v)Types of staircase
    How to answer

    • Magnetic declination: horizontal angle between true north/meridian and magnetic north/meridian (east/west)
    • Bow's notation: method of lettering spaces between forces/members in a truss in clockwise order
    • Plane tables: graphical surveying equipment where field observation and plotting are done simultaneously
    • D-Alembert's principle: dynamic equilibrium principle where inertia force ($-ma$) is applied converting dynamic problem into equivalent static problem ($\sum F - ma = 0$)
    • Types of staircase: straight, dog-legged, open well, spiral, helical, geometrical
16. 7 Marks
    bWhat do you understand by support reactions and its type? Explain shear force and bending moment for a cantilever beam.
    How to answer

    • Support reactions: reactive forces and moments exerted by supports to keep a structure in static equilibrium
    • Types of supports: roller (1 vertical reaction), hinged/pinned (2 reactions: horizontal and vertical), fixed (3 reactions: horizontal, vertical, and moment)
    • Cantilever beam definition: fixed at one end and free at the other
    • SF and BM for cantilever: usually subjected to negative (hogging) bending moment throughout
    • Example sketch: cantilever under point load or UDL with corresponding SFD and BMD shapes