BT-204 Basic Civil Engineering and Engineering Mechanics - Jun 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 do you understand by the term 'levelling'? Explain 'reciprocal levelling' in details.
   How to answer

   • Define levelling as the art of determining relative heights of points on earth surface
   • Explain purpose and principle of reciprocal levelling across obstructions like rivers
   • State equations eliminating instrument collimation error and earth curvature/refraction errors: $h = \frac{(h_a - h_b) + (h'_a - h'_b)}{2}$
   • Provide schematic diagram showing instrument positions and staff readings at points A and B
2. 7 Marks
   bWhat is the purpose to provide the foundation and describe its various types in details?
   How to answer

   • Define foundation and state its main purposes (load distribution, stability against overturning, preventing differential settlement)
   • Classify foundations into shallow and deep foundations
   • Explain types of shallow foundations: isolated footing, combined footing, strip footing, raft/mat foundation
   • Explain types of deep foundations: pile foundation, pier foundation, caisson/well foundation
   • Provide sketches of common foundation types
3. 7 Marks
   aWrite short notes on any four of the followings: i) Remote sensing ii) Contour lines iii) Type of surveying iv) EDM v) Survey station
   How to answer

   • Remote sensing: data acquisition from a distance via sensors and electromagnetic radiation
   • Contour lines: imaginary lines connecting points of equal elevation, characteristics of contours
   • Type of surveying: based on instrument (chain, compass, plane table, theodolite) and purpose (geodetic, plane, cadastral, topographical)
   • EDM: principle of electronic distance measurement using modulated light/microwaves
   • Survey station: main, subsidiary, and tie stations used in surveying network
4. 7 Marks
   bExplain the 'auto level' with a neat sketch.
   How to answer

   • Define auto level (automatic level) and its operating principle
   • Explain internal optical compensator (pendulum prism system) that maintains a horizontal line of sight automatically
   • Describe key components: telescope, circular bubble, leveling screws, compensator, horizontal circle
   • Draw a neat labeled sketch of an auto level
5. 7 Marks
   aWrite notes on the following with neat sketch: i) Mid ordinate rule ii) Average ordinate rule iii) Trapezoidal rule iv) Simpson's rule
   How to answer

   • Mid-ordinate rule: formula $\text{Area} = d \sum h_m$ with sketch
   • Average ordinate rule: formula $\text{Area} = \frac{\sum O}{n+1} \times L$ with sketch
   • Trapezoidal rule: formula $\text{Area} = d \left[ \frac{O_0 + O_n}{2} + O_1 + O_2 + \dots + O_{n-1} \right]$ with sketch
   • Simpson's one-third rule: conditions (odd number of ordinates) and formula $\text{Area} = \frac{d}{3} [ (O_0 + O_n) + 4\sum O_{\text{even}} + 2\sum O_{\text{odd}} ]$ with parabolic boundary sketch
6. 7 Marks
   bExplain concurrent and non-concurrent co-planer forces in details.
   How to answer

   • Define coplanar forces (forces lying in the same plane)
   • Explain concurrent coplanar forces: lines of action meet at a single point; state equilibrium conditions ($\sum F_x = 0, \sum F_y = 0$)
   • Explain non-concurrent coplanar forces: lines of action lie in same plane but do not intersect at a common point; state equilibrium conditions ($\sum F_x = 0, \sum F_y = 0, \sum M = 0$)
   • Illustrate both systems with neat force diagrams
7. 7 Marks
   aDraw the shear force and bending moment diagram for simply supported beam, which carries a uniformly distributed load of $10\text{ kN/m}$ and a point load of $20\text{ kN}$ on its center having span of $5\text{ m}$.

   

   How to answer

   • Calculate support reactions: by symmetry, $R_A = R_B = \frac{10 \times 5 + 20}{2} = 35\text{ kN}$
   • Compute shear force at critical sections: left support ($+35\text{ kN}$), just left of center ($+10\text{ kN}$), just right of center ($-10\text{ kN}$), right support ($-35\text{ kN}$)
   • Draw Shear Force Diagram (SFD) with linear slopes and vertical drop of $20\text{ kN}$ at center
   • Compute bending moments: $M_A = M_B = 0$; center $M_C = 35(2.5) - 10(2.5)(1.25) = 87.5 - 31.25 = 56.25\text{ kNm}$
   • Draw Bending Moment Diagram (BMD) as a parabolic curve reaching peak of $56.25\text{ kNm}$ at center
8. 7 Marks
   bDefine any two-laboratory test, those are conducted on bricks and cement.
   How to answer

   • Select any two standard tests (e.g., Compressive strength of bricks, Fineness test of cement, or Standard consistency of cement)
   • For test 1: state apparatus, procedure, and standard limiting value
   • For test 2: state apparatus, procedure, and standard limiting value
9. 7 Marks
   aList out the various stages for the construction of a building and list out the various building materials used in construction works with brief details.
   How to answer

   • List stages of building construction: site investigation, excavation, foundation, plinth beam, superstructure (columns/beams/masonry), lintel & slabs, plastering, flooring, doors/windows, finishing/painting
   • List key building materials: cement, sand/fine aggregates, coarse aggregates, bricks/blocks, reinforcement steel, timber, paints
   • Briefly describe functions and characteristics of each material
10. 7 Marks
    bDiscuss plastering and pointing in Civil Engineering construction works.
    How to answer

    • Define plastering: covering rough surface of walls with mortar to provide smooth and durable finish
    • Discuss objectives of plastering and types (lime, cement plaster)
    • Define pointing: finishing of mortar joints in exposed brick or stone masonry
    • Discuss types of pointing: flush, struck, V-grooved, keyed, recessed pointing
    • Highlight differences between plastering and pointing
11. 7 Marks
    aDefine the method of joints and method of section to analyze a plane truss with a suitable example.
    How to answer

    • Define method of joints: isolating each joint and applying $\sum F_x = 0, \sum F_y = 0$
    • Define method of sections: cutting truss into two parts through max 3 unknown members and applying $\sum F_x = 0, \sum F_y = 0, \sum M = 0$
    • Provide a simple triangular or Pratt/Warren truss example
    • Demonstrate step-by-step calculation for forces using both methods
12. 7 Marks
    bDefine the following terms with respect to concrete: i) Workability ii) Segregation iii) Bleeding iv) Proportion in concrete
    How to answer

    • Workability: ease with which concrete can be mixed, transported, placed, and compacted without segregation
    • Segregation: separation of constituent materials (coarse aggregates) from the mortar paste
    • Bleeding: upward migration of water to the surface of freshly placed concrete
    • Proportion in concrete: ratio of cement : fine aggregate : coarse aggregate (e.g., M15 is 1:2:4, M20 is 1:1.5:3) to achieve desired strength and durability
13. 7 Marks
    aWhat are the various types of bonds used in the construction of brick masonry?
    How to answer

    • Define bond in brick masonry (arrangement of bricks to eliminate continuous vertical joints)
    • Explain English bond: alternate courses of headers and stretchers; queen closer used next to quoin header
    • Explain Flemish bond: each course consists of alternate headers and stretchers (Single and Double Flemish)
    • Briefly mention Stretcher bond, Header bond, and Garden wall bond
    • Provide sketches showing elevation and plans of English and Flemish bonds
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

    • Divide T-section into two rectangles: Flange ($80 \times 20\text{ mm}$) and Web ($20 \times 65\text{ mm}$)
    • Calculate areas: $A_1 = 80 \times 20 = 1600\text{ mm}^2$, $A_2 = 20 \times 65 = 1300\text{ mm}^2$; $A = 2900\text{ mm}^2$
    • Determine centroid $\bar{y}$ from base: $y_1 = 65 + 10 = 75\text{ mm}$, $y_2 = 32.5\text{ mm}$; $\bar{y} = \frac{1600(75) + 1300(32.5)}{2900} = 55.95\text{ mm}$
    • Apply parallel axis theorem to find $I_{xx} = (I_{G1} + A_1 d_1^2) + (I_{G2} + A_2 d_2^2)$
    • Compute $I_{yy} = \frac{20(80)^3}{12} + \frac{65(20)^3}{12} = 853333.3 + 43333.3 = 8.97 \times 10^5\text{ mm}^4$
15. 7 Marks
    aDefine the following terms: i) True bearing and magnetic bearing ii) Fore sight and back sight iii) Local attraction iv) Errors in chain surveying
    How to answer

    • True bearing: horizontal angle with geographic north meridian; Magnetic bearing: horizontal angle with magnetic north
    • Back sight (BS): first staff reading taken after setting up instrument; Fore sight (FS): last staff reading taken before moving instrument
    • Local attraction: disturbance of magnetic needle caused by local magnetic bodies like steel, iron pipes, transmission lines
    • Errors in chain surveying: personal, instrumental, and natural errors; compensating vs cumulative errors
16. 7 Marks
    bWhat do you understand by reversible and irreversible machines? Explain with suitable examples.
    How to answer

    • Define reversible machine: machine capable of doing work in reverse direction when effort is removed; efficiency condition $\eta > 50\%$
    • Define irreversible / self-locking machine: machine that cannot do work in reverse direction when effort is removed; efficiency condition $\eta < 50\%$
    • Provide derivation/justification: $\text{Work lost in friction} = W \left( \frac{1}{\eta} - 1 \right)$
    • Give practical examples: reversible (simple pulley system), irreversible/self-locking (screw jack, worm and worm wheel)