Q46. If the eccentricity ratio is more than 1/24, then increase in the permissible stress in the design of wall subjected to eccentric loading as per code is:
  • 10%
  • 25%
  • 33 1/3 %
  • 50%

Correct Answer: B. 25%

Solution:

When the eccentricity of a load on a masonry wall is small (less than 1/24 of the wall thickness), bending stresses are considered negligible. However, when the eccentricity ratio exceeds this, bending stresses must be accounted for. To compensate for these combined stresses, design codes allow for an increase in the permissible compressive stress, typically by a factor of 25%.

Q47. A 200 mm thick brick masonry wall made of modular bricks carries an axial load of 30 kN/m from wall above and an eccentric load of 20 kN/m from RCC floor acting at a distance of 47.5 mm from the centre line of the wall. The resultant eccentricity ratio is:
  • 0.090
  • 0.095
  • 0.100
  • 0.105

Correct Answer: B. 0.095

Solution:

First, calculate the total load: P = 30 kN/m + 20 kN/m = 50 kN/m. Next, find the moment caused by the eccentric load: M = 20 kN/m * 0.0475 m = 0.95 kNm/m. The resultant eccentricity (e) is M/P = 0.95 / 50 = 0.019 m or 19 mm. The eccentricity ratio is e/t = 19 mm / 200 mm = 0.095.

Q48. The bending stress in a wall or column subjected to effective vertical load need not be considered, if the eccentricity ratio is:
  • Less than or equal to 1/24
  • Less than or equal to 1/6
  • More than 1/24
  • Less than or equal to 1/12

Correct Answer: A. Less than or equal to 1/24

Solution:

Design codes for masonry (like IS 1905) state that if the ratio of eccentricity to the thickness of the member is less than or equal to 1/24, the resulting bending stresses are minimal and can be ignored. The member can then be designed for axial compression only.

Q49. Rich cement mortars are more liable to cracking as compared to lean mortars because rich mortars have:
  • High shrinkage
  • Less strength
  • Both (A) and (B)
  • None of above

Correct Answer: A. High shrinkage

Solution:

Rich cement mortars have a higher proportion of cement. Since cement is the component that undergoes drying shrinkage as it cures, a higher cement content leads to high shrinkage. This increased shrinkage induces tensile stresses within the mortar, making it more prone to cracking.

Q50. The effective height of free standing non-load bearing wall and column respectively will be:
  • 1.0H and 1.0H
  • 1.5H and 1.5H
  • 2.0H and 1.5H
  • 2.0H and 2.0H

Correct Answer: D. 2.0H and 2.0H

Solution:

For a free-standing element (a cantilever), which is fixed at the base and free at the top, the effective height (or length for buckling calculation) is taken as twice its actual height (H). This applies to both walls and columns in a free-standing condition. Thus, the effective height is 2.0H and 2.0H.

Q51. The bending stress in a wall or column subjected to effective vertical load need not be considered, if the eccentricity ratio is:
  • Less than or equal to 1/24
  • Less than or equal to 1/6
  • More than 1/24
  • Less than or equal to 1/12

Correct Answer: A. Less than or equal to 1/24

Solution:

This question repeats the concept from Q48. Design codes for masonry (like IS 1905) state that if the ratio of eccentricity to the thickness of the member is less than or equal to 1/24, the resulting bending stresses are minimal and can be ignored. The member can then be designed for axial compression only.

Q52. For masonry built in 1 : 1 : 6 cement-lime-sand mix mortar or equivalent, the horizontal shear stress permissible on the area of a mortar bed joint is:
  • 0.15 MPa
  • 0.125 MPa
  • 0.1 MPa
  • 0.075 MPa

Correct Answer: A. 0.15 MPa

Solution:

The permissible shear stress in masonry depends on the strength of the mortar. For a 1:1:6 cement-lime-sand mix, which corresponds to a medium-strength mortar, the building codes specify a maximum allowable horizontal shear stress of 0.15 MPa (or 1.5 kg/cm²).

Q53. Direct load carrying capacity of a brick masonry wall standing freely as against when it supports an RC Slab will be:
  • More
  • Less
  • The same in both the cases
  • 100 % more

Correct Answer: B. Less

Solution:

A free-standing wall lacks lateral support at the top, making it more susceptible to buckling under a vertical load. When an RC slab rests on the wall, it provides this lateral restraint, effectively reducing the wall's slenderness and increasing its stability. Therefore, the direct load capacity of the free-standing wall is less.

Q54. The timber floor not spanning on the masonry wall but properly anchored to the wall gives:
  • Lateral restraint but not rotational restraint
  • Rotational restraint but not lateral restraint
  • Both lateral and rotational restraints
  • Neither lateral nor rotational restraint

Correct Answer: A. Lateral restraint but not rotational restraint

Solution:

When a floor is anchored to a wall, it prevents the wall from moving horizontally (in or out) at that level, thus providing lateral restraint. However, if the floor joists are not built into or continuous over the wall, the connection is typically considered pinned, meaning it does not prevent the top of the wall from rotating. Therefore, it provides not rotational restraint.

Q55. A Slab-beam floor system may be supported on brick walls or framed into a system of RC columns. The floor thickness (slab + beam web) for the same span will be:
  • Less when framed into a system of RC columns.
  • Less when supported on brick walls.
  • The same in both the cases.
  • Equal to the wall thickness or size of column.

Correct Answer: A. Less when framed into a system of RC columns.

Solution:

When a floor system is framed into RC columns, it forms a monolithic structure. This creates a rigid frame action, allowing for more efficient load distribution and negative moment development at the supports. This results in smaller required beam and slab depths compared to a system simply supported on brick walls, which acts as a series of independent, simply supported beams requiring larger depths for the same span and load.

Q56. A 200 mm thick brick masonry wall made of modular bricks carries an axial load of 26 kN/m and another load of 19 kN/m acting at an eccentricity of 45 mm. The resultant eccentricity and eccentricity ratio are respectively:
  • 19 mm, 0.095
  • 19 mm, 0.1
  • 22 mm, 0.11
  • 24 mm, 0.12

Correct Answer: A. 19 mm, 0.095

Solution:

Total Load (P) = 26 kN/m + 19 kN/m = 45 kN/m. Moment (M) = 19 kN/m * 45 mm = 855 kN.mm/m. Resultant Eccentricity (e) = M/P = 855 / 45 = 19 mm. Eccentricity Ratio = e/t = 19 mm / 200 mm = 0.095.

Q57. In brick masonry, arch action is possible only when the minimum height of wall above the top of lintel is X times the height of triangular distribution, where X is:
  • 1.00
  • 1.25
  • 1.50
  • 1.75

Correct Answer: B. 1.25

Solution:

For the arching action to fully develop above a lintel, there must be sufficient masonry mass to provide the necessary thrust restraint. Building codes and structural principles dictate that the height of the masonry above the apex of the load distribution triangle must be at least 1.25 times the height of that triangle. This ensures the arch can form and carry the load to the supports without failing.

Q58. The Basic stress in masonry unit having height to width ratio of 1.5 may be increased by a factor of:
  • 1.2
  • 1.4
  • 1.6
  • 2.0

Correct Answer: B. 1.4

Solution:

The shape of a masonry unit affects its compressive strength. The basic stress is determined for a standard unit shape. For units with a height-to-width ratio of 1.5, codes like IS 1905 allow for an increase in the basic compressive stress. This is because such a shape can exhibit improved performance. The specified multiplication factor for a height/width ratio of 1.5 is 1.4.