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Past Questions
According to I S : 456 speculations, the safe diagonal tensile stress for M 150 grade concrete, is
A)
50 N/cm2
B)
100 N/cm2
C)
150 N/cm2
D)
200 N/cm2
According to IS 456 (the Indian Standard code for Plain and Reinforced Concrete), the permissible diagonal tensile stress (also known as the principal tensile stress) for concrete is specified based on the grade of concrete. For M 150 grade concrete (which corresponds to a characteristic compressive strength of 150 kg/cm² or approximately 15 MPa), the safe diagonal tensile stress is specified as 100 N/cm².
Calculation/Reference:
1. M 150 grade concrete refers to a concrete with a characteristic strength of 150 kg/cm².
2. In the context of working stress design (which was prevalent in older versions of the code and often tested in these specific exam formats), the permissible principal tensile stress for M 150 is 100 N/cm².
3. Converting units: 100 N/cm² is equivalent to 1.0 MPa.
Comparing with options:
- Option (a) 50 N/cm² is too low for M 150.
- Option (b) 100 N/cm² matches the IS 456 specification for M 150.
- Option (c) 150 N/cm² and (d) 200 N/cm² exceed the safe limits for this grade of concrete.
In rolled steel beams, shear force is mostly resisted by
A)
web only
B)
flange only
C)
web and flange together
D)
none of the above
In a rolled steel beam (such as an I-beam or H-beam), the cross-section consists of two flanges and a connecting web. The distribution of internal forces is as follows: 1. Bending Moment: The flanges are located furthest from the neutral axis, meaning they have the highest moment of inertia and are primarily responsible for resisting the bending moment (compression and tension). 2. Shear Force: The shear stress distribution in an I-section is parabolic, but the vast majority of the shear area is concentrated in the vertical web. Mathematically, the shear stress (τ) is given by τ = VQ/Ib. Since the web has a much smaller width (b) compared to the flanges and carries the bulk of the first moment of area (Q) for the majority of the section's height, the web resists nearly all (typically over 90-95%) of the vertical shear force. Therefore, for practical engineering purposes, it is considered that the web resists the shear force while the flanges resist the bending moment.
Tractor that moves on endless chain is called
A)
pneumatic type tractor
B)
track type tractor
C)
wheel type tractor
D)
none of the above
In construction equipment, tractors are categorized based on their propulsion system.
1. **Track Type Tractor (Crawler Tractor):** These machines move on continuous, endless chains (tracks) made of steel or rubber. The tracks distribute the weight of the machine over a larger area, reducing ground pressure and providing superior traction and stability on soft, muddy, or uneven terrain. This matches the description 'moves on endless chain'.
2. **Wheel Type Tractor:** These use rubber tires (pneumatic tires) and are designed for higher speeds and mobility on hard surfaces, but they have higher ground pressure and less traction in soft soil compared to track types.
3. **Pneumatic Type Tractor:** This is essentially a subset of wheel-type tractors that specifically use air-filled (pneumatic) tires.
Therefore, the specific term for a tractor moving on an endless chain is a track type tractor.
If a shaft is simultaneously subjected to a torque T and bending moment M, the ratio of maximum bending stress is
A)
M/T
B)
2M/T
C)
T/M
D)
2T/M
To find the ratio of maximum bending stress to maximum shear stress for a solid circular shaft, we use the standard formulas for stress:
1. **Maximum Bending Stress (σb):** For a shaft of diameter 'd', the bending stress is given by:
σb = (32M) / (πd³)
2. **Maximum Shear Stress (τ):** For a shaft of diameter 'd', the torsional shear stress is given by:
τ = (16T) / (πd³)
3. **Calculating the Ratio:**
Ratio = σb / τ
Ratio = [(32M) / (πd³)] / [(16T) / (πd³)]
Ratio = (32M) / (16T)
Ratio = 2M / T
Therefore, the ratio of the maximum bending stress to the maximum shear stress is 2M/T. Note: The question phrasing 'ratio of maximum bending stress' is slightly elliptical and implies the ratio of bending stress to shear stress, which is the standard engineering comparison for shafts under combined loading.
As per ISI, rolled steel beam section are classified into
A)
two series
B)
three series
C)
four series
D)
five series
According to the Indian Standard (IS) specifications for rolled steel sections (specifically IS 808), rolled steel beam sections (I-beams) are classified into three distinct series based on their depth-to-flange width ratios and weight per unit length. These are: 1. Light series (Lightweight sections), 2. Medium series (Standard sections), and 3. Heavy series (Heavy-duty sections). These series allow engineers to select a beam that optimizes the strength-to-weight ratio based on the specific loading conditions of the structural member. Options a, c, and d are incorrect as they do not align with the standard classification system used in the ISI rolled steel tables.
Time of completion of project in bar charts is shown by
A)
vertical lines
B)
horizontal lines
C)
crosses
D)
none of the above
In project management, a Bar Chart (also known as a Gantt Chart) is a tool used to represent the project schedule. In this chart, the vertical axis (Y-axis) typically lists the activities or tasks, while the horizontal axis (X-axis) represents the time scale (days, weeks, or months). Each activity is represented by a horizontal bar; the length of this bar indicates the duration of the activity, and its position along the horizontal time axis shows the start and finish times. Therefore, the time of completion and the duration of the project are depicted by horizontal lines (bars). Vertical lines are typically used as grid lines to mark specific dates or milestones, but the actual representation of the project's time progress and completion for each task is shown by the horizontal bars.
The spans are considered approximately equal if the longest span does not exceed the shortest span by more than
A)
15%
B)
10%
C)
20%
D)
5%
In the design of steel structures, particularly when designing trusses or frames for multiple spans, engineers often simplify calculations by assuming spans are equal if the variation between them is minimal. According to standard structural engineering practice and design manuals (often referenced in textbooks for steel design), spans are considered approximately equal if the longest span does not exceed the shortest span by more than 10%. This allows for the standardization of members and simplifies the analysis of load distribution across the structure without introducing significant errors in the structural integrity or safety margins. Options a (15%), c (20%), and d (5%) are incorrect as they do not align with this specific industry convention for 'approximately equal' spans in this context.
Commonly used raw materials in manufacturing cement is
A)
slate
B)
sand stone
C)
lime stone
D)
basalt
Portland cement is manufactured by heating a mixture of calcareous (calcium-bearing) and argillaceous (silica and alumina-bearing) materials.
1. **Lime stone (Calcium Carbonate - CaCO3)**: This is the primary raw material used to provide Calcium Oxide (CaO), which is the most significant constituent of cement (approximately 60-67%).
2. **Argillaceous materials**: Clay, shale, or blast furnace slag are used to provide Silica (SiO2), Alumina (Al2O3), and Iron Oxide (Fe2O3).
Analyzing the options:
- **a. Slate**: While slate contains some silica and alumina, it is not a primary or commonly used raw material for cement production.
- **b. Sand stone**: Sandstone is primarily silica; while silica is needed, it is typically sourced from clay or shale in a balanced ratio with lime.
- **c. Lime stone**: This is the fundamental source of calcium, making it the most essential and commonly used raw material.
- **d. Basalt**: Basalt is an igneous rock and is not used as a standard raw material in the chemical process of cement manufacturing.
Statistically determinate structures are those in which
A)
stresses are developed due to temperature variation
B)
stresses are developed due to lack of fit
C)
conditions of equilibrium are not sufficient to fully analyse the structures
D)
none of the above
Determinate structures need only equilibrium; stresses due to temperature/lack of fit and insufficiency of equilibrium are properties of indeterminate, so none of given statements defines determinate.
The maximum bending moment due to moving load on a simply supported beam occurs
A)
at the mid span
B)
at supports
C)
anywhere in the beam
D)
under the load
For a simply supported beam of length L, the bending moment at any section x from the left support due to a single concentrated moving load P is given by the formula M = (P * a * b) / L, where 'a' is the distance of the load from the left support and 'b' is the distance from the right support. To find the absolute maximum bending moment as the load moves across the beam, we analyze the moment at the center (x = L/2). When the load P is positioned exactly at the mid-span (x = L/2), the bending moment is M_max = (P * (L/2) * (L/2)) / L = PL/4. This is the highest possible bending moment that can occur at any point in the beam for a single moving point load. While the maximum moment 'under the load' varies as the load moves, the absolute maximum value across the entire beam's length and the load's travel path occurs specifically when the load is at the mid-span.
In plastic analysis, the shape factor for rectangular section is
A)
1.7
B)
1.6
C)
1.5
D)
1.4
In plastic analysis of steel structures, the Shape Factor (S) is defined as the ratio of the Plastic Moment (Mp) to the Yield Moment (My).
1. **Yield Moment (My):** This is the moment at which the outermost fiber of the section first reaches the yield stress (fy). For a rectangular section of width 'b' and depth 'd', the section modulus (Z) is (b * d^2) / 6. Therefore, My = fy * Z = fy * (b * d^2) / 6.
2. **Plastic Moment (Mp):** This is the moment when the entire cross-section has reached the yield stress, forming a plastic hinge. The plastic section modulus (Zp) for a rectangle is the sum of the first moments of area above and below the plastic neutral axis. Zp = (b * d^2) / 4. Therefore, Mp = fy * Zp = fy * (b * d^2) / 4.
3. **Calculation of Shape Factor (S):**
S = Mp / My
S = [fy * (b * d^2) / 4] / [fy * (b * d^2) / 6]
S = (1/4) / (1/6) = 6 / 4 = 1.5.
Thus, the shape factor for a rectangular section is 1.5. Options a, b, and d are incorrect as they do not match the derived geometric ratio for a rectangle.
According to Rankine’s formula of earth pressure on a retaining wall of h and with other usual notations, is
A)
wh2 / 2 * (1 - sin phi)
B)
wh2 / 2 * (1 + sin phi)
C)
wh2 / 4 * (1 + sin phi)
D)
wh2 / 2 * (1 - sin phi)
According to Rankine's theory of earth pressure, the active earth pressure coefficient (Ka) for a cohesionless soil with an angle of internal friction (phi) is given by: Ka = (1 - sin phi) / (1 + sin phi). The active earth pressure at a depth 'h' is p = Ka * w * h, where 'w' is the unit weight of the soil. The total active thrust (Pa) acting on the wall is the integral of the pressure over the height, which results in the area of the pressure triangle: Pa = 1/2 * Ka * w * h^2. Substituting Ka = (1 - sin phi) / (1 + sin phi), the formula becomes Pa = (w * h^2 / 2) * [(1 - sin phi) / (1 + sin phi)]. Looking at the provided options, option (a) represents the numerator part of the coefficient (1 - sin phi) multiplied by the pressure triangle area (wh^2/2). While the full Rankine formula typically includes the (1 + sin phi) in the denominator, in the context of these specific multiple-choice options, option (a) is the intended answer as it correctly identifies the 'active' pressure relationship (1 - sin phi). Option (b) would relate to passive pressure (1 + sin phi). Note: There is a typo in the options provided in the source exam where (a) and (d) are identical, but (a) is the standard selection for active pressure components.
If T and R are respectively tread and rise of a stair, then
A)
2R+T=60
B)
R+2T=60
C)
2R+T=30
D)
R+2T=30
In building construction and architectural design, the dimensions of a stair (the rise 'R' and the tread 'T') are governed by ergonomic principles to ensure a comfortable and safe gait for the user. The most widely accepted empirical formula for the design of residential and public stairs is the 'Blondel's Rule' or the 'Rule of Thumb' for stair proportions. The standard formula is: 2R + T = 600 mm (or 630 mm depending on the specific code, but 60 cm is the classic standard). Converting 600 mm to centimeters gives 60 cm. Therefore, the relationship is 2R + T = 60.
- Option (a) 2R + T = 60 is the correct standard formula.
- Option (b) R + 2T = 60 is incorrect as it would result in an unnaturally deep tread and a very low rise.
- Options (c) and (d) are incorrect because a value of 30 cm is far too small for the combined sum of two rises and one tread, which would result in a stair that is impossible for a human to climb.
A beam is defined as a structural member subjected to
A)
axial loading
B)
transverse loading
C)
axial and transverse loading
D)
none of the above
In structural mechanics, a beam is specifically defined as a structural member designed to support loads applied perpendicular to its longitudinal axis. These loads are known as transverse loads. When a beam is subjected to transverse loading, it primarily undergoes bending (flexure) and shear stress.
Comparing the options:
- Option (a) 'axial loading' describes a member like a column or a tie/strut, where the force acts along the longitudinal axis, causing tension or compression.
- Option (b) 'transverse loading' is the defining characteristic of a beam, as it induces the bending moment that beams are designed to resist.
- Option (c) 'axial and transverse loading' describes a 'beam-column'. While a beam can technically experience both, the fundamental definition of a beam focuses on its capacity to carry transverse loads.
- Option (d) is incorrect because option (b) is the standard engineering definition.
The maximum range of the chemicals in cement is
A)
silica (SiO2)
B)
Alumina (Al2O3)
C)
magnesia (MgO)
D)
Lime (CaO)
Portland cement is composed of several chemical compounds. The 'maximum range' refers to the chemical constituent present in the highest percentage by weight. The typical chemical composition of Ordinary Portland Cement (OPC) is as follows:
1. Lime (CaO): 60% to 67% (The primary ingredient)
2. Silica (SiO2): 17% to 25%
3. Alumina (Al2O3): 3% to 8%
4. Iron Oxide (Fe2O3): 0.5% to 6%
5. Magnesia (MgO): 3.5% to 4%
6. Sulfur Trioxide (SO3): 1% to 3%
Since Lime (CaO) constitutes the largest portion of the cement mixture, it has the maximum range among the given options. Lime is responsible for the strength and soundness of the cement, although an excess can cause unsoundness (expansion).
Stiffeners are used in a plate girder to
A)
reduce the compressive stress
B)
reduce shear stress
C)
avoid buckling of the web plate
D)
take the bearing stress
In a plate girder, the web is designed to resist vertical shear forces. Because the web is typically a thin plate with a high depth-to-thickness ratio, it is susceptible to 'web buckling' (a form of instability) when subjected to compressive stresses resulting from shear or concentrated loads, long before the material reaches its yield strength. Stiffeners (vertical or longitudinal) are introduced to divide the web into smaller panels, thereby increasing the critical buckling load and ensuring the web can carry the intended shear force without failing due to instability.
Analysis of other options:
- (a) Stiffeners do not reduce the overall compressive stress in the member; they redistribute it or prevent the instability caused by it.
- (b) Stiffeners do not reduce the magnitude of the shear stress (which is determined by V/Ad); they allow the web to resist that stress without buckling.
- (d) While bearing stiffeners are used at support points to distribute concentrated loads, the primary general purpose of stiffeners in the context of the web plate is to prevent buckling.
Black marble is generally found in the district of
A)
Jodhpur
B)
Jabalpur
C)
Jaipur
D)
Jaisalmer
Black marble is a distinctive geological resource found in the Jaisalmer district of Rajasthan, India. Jaisalmer is world-renowned for its high-quality yellow sandstone and specific varieties of black and golden marble.
Analysis of options:
- Jodhpur: Primarily known for Jodhpur sandstone (red/pinkish).
- Jabalpur: Known for marble (specifically the Bhedaghat white marble), but not the primary source of black marble.
- Jaipur: Known for various colored marbles and gemstones, but not the primary source of the specific 'black marble' associated with the western desert region.
- Jaisalmer: The geological formations in this region provide the specific mineral composition required for the production of black marble.
Common pumps used in building, building constructions are
A)
centrifugal
B)
Submersible
C)
air jet
D)
all the above
In building and building construction, different types of pumps are required depending on the specific application (dewatering, water supply, or specialized lifting).
1. Centrifugal Pumps: These are the most common pumps used for general water transfer and supply systems in buildings due to their simplicity and efficiency in moving large volumes of water.
2. Submersible Pumps: These are essential in construction for 'dewatering' (removing water from excavations, basements, or trenches) and are also used in deep-well water supply systems where the pump must be submerged in the fluid.
3. Air Jet Pumps: These are used in specific construction scenarios, such as lifting water from deep wells or removing water from areas where electrical pumps might be hazardous or impractical, using compressed air to create a vacuum.
Since all three types of pumps are utilized across various stages and requirements of building construction, the correct option is 'all the above'.
A ferrous metal is
A)
steel
B)
cast iron
C)
wrought iron
D)
all the above
A ferrous metal is defined as a metal that contains iron (Fe) as its primary constituent.
1. Steel: An alloy of iron and carbon (usually with carbon content less than 2%), making it a ferrous metal.
2. Cast Iron: An alloy of iron and carbon (usually with carbon content greater than 2%), making it a ferrous metal.
3. Wrought Iron: A nearly pure form of iron with very low carbon content and small amounts of slag, making it a ferrous metal.
Since all three options (steel, cast iron, and wrought iron) are iron-based materials, they are all classified as ferrous metals.
As the percentage of steel increases
A)
depth of neutral axis increases
B)
depth of neutral axis decreases
C)
lever arm increases
D)
lever arm decreases
Increased steel area needs larger compression area for moment equilibrium, so neutral axis depth increases (lever arm reduces).
The stiffness factor for prismatic beam of length L and moment of inertia I, is
A)
2EI/L
B)
3EI/L
C)
4EI/L
D)
EI/L
In structural analysis, specifically within the Slope-Deflection Method, the stiffness of a member is defined as the force or moment required to produce a unit displacement or rotation. For a prismatic beam (a beam with a constant cross-section and moment of inertia I) of length L, the rotational stiffness depends on the boundary conditions of the far end:
1. If the far end is FIXED, the stiffness is k = 4EI/L. This is the standard 'stiffness factor' used in the general slope-deflection equations for a member where the far end is restrained against rotation.
2. If the far end is HINGED (pinned), the stiffness is k = 3EI/L.
In the context of general structural analysis textbooks and competitive exams, when the 'stiffness factor' of a prismatic beam is asked without specifying the far-end condition, it refers to the standard stiffness used in the slope-deflection equation for a member fixed at both ends, which is 4EI/L.
- Option (a) 2EI/L is not a standard stiffness factor for a single beam member.
- Option (b) 3EI/L is the stiffness for a beam with a pinned far end.
- Option (d) EI/L is related to the flexural rigidity but not the rotational stiffness factor.
The allowable stress in axial tension is generally kept less if thickness of the member is more than
A)
10 mm
B)
12 mm
C)
15 mm
D)
20 mm
In structural steel design, the allowable stress for members in tension is influenced by the thickness of the material. For thinner sections, the material is more homogeneous. However, as the thickness of the steel member increases, the risk of internal flaws, impurities, and non-uniformity in the rolling process increases. Specifically, in many standard design codes (such as older versions of IS codes or general structural engineering practice), when the thickness of a tension member exceeds 20 mm, the allowable tensile stress is reduced to provide a higher factor of safety against these potential internal defects and to account for the reduced ductility in the core of thicker sections. Therefore, the allowable stress is generally kept lower if the thickness exceeds 20 mm.
A solid shaft of diameter d is subjected to torque T. The maximum normal stress induced in the shaft is
A)
16T / pi*d3
B)
32T / pi*d3
C)
zero
D)
none of the above
Torsional shear tau=16T/pi d^3; principal stresses +-tau, so max normal=tau=16T/pi d^3.
Seasoning of timber is necessary to
A)
increase the fire resistance
B)
increase the vermin resistance
C)
reduce the microbial substances
D)
expel the moisture in the timber
Seasoning of timber is the process of reducing the moisture content (sap) of the wood to a level that is in equilibrium with the environment in which the timber will be used. Freshly felled timber contains a high percentage of water (sap), which can lead to warping, shrinking, cracking, and decay if not removed. By expelling this moisture—either through natural air drying or artificial methods like kiln drying—the timber becomes more dimensionally stable, stronger, and more durable.
Analysis of other options:
- Option (a): Seasoning does not inherently increase fire resistance; fire resistance is typically improved through chemical treatments or charring.
- Option (b): While seasoned timber is less prone to certain pests than wet timber, the primary purpose of seasoning is not vermin resistance; that is the goal of 'preservation' (e.g., using creosote).
- Option (c): Reducing microbial substances is a byproduct of removing moisture (as fungi need moisture to grow), but the fundamental definition and primary objective of seasoning is the removal of moisture.
Seasoning of timber is required to
A)
soften the timber
B)
harden the timber
C)
straighten the timber
D)
remove the sap from the timber
Seasoning of timber is the process of reducing the moisture content (sap) of the wood to a level that is in equilibrium with the environment in which the timber will be used. Freshly felled timber contains a large amount of water (sap) in its cell cavities. If used in this state, the timber will shrink, warp, and crack as it dries naturally over time. By removing the sap through seasoning (either via natural air drying or artificial kiln drying), the timber becomes more stable, durable, and resistant to decay and insect attacks.
Analysis of other options:
- (a) Soften the timber: Seasoning actually makes timber more stable and often harder/more rigid, not softer.
- (b) Harden the timber: While seasoning increases strength and stability, 'hardening' is not the primary objective or definition of the process; the primary goal is moisture removal.
- (c) Straighten the timber: Seasoning cannot straighten a naturally curved or warped piece of wood; in fact, improper seasoning can cause further warping.