Flat roofs are easier in construction and maintenance. A flat roof is more stable against high wards. It has a better architectural appearance and it has good insulation properties.

Flaking is a defect in plastering. It is a formation of a very loose mass of plastered surface due to poor bond between successive coats. This is obtained due to poor workmanship.

Explanation:

Due to torque, shear stresses are developed in two mutually perpendicular planes.

(i) In plane of cross-section in circumferential direction.

(ii) Normal to plane of cross-section in longitudinal direction.

The shear stress produced by torque varies from zero at centre of cross-section to maximum at surface in circumferential direction. Shear stresses in direction normal to cross-section plane are always complementary in nature and have equal magnitude.

NOTE: There is no shear stress in radial direction.

From figure we can see that normal to plane of cross-section in longitudinal direction, stress is compressive and since longitudinal stress (shear stress) is complimentary with equal magnitude is maximum at surface, refore maximum compressive stress will be equal to maximum shear stress.

Normally 12 mm thick plastering is done for brick masonry and 20 mm thick plastering is done for stone masonry. The plastered surface is n cured by sprinkling water over surface for one or two weeks.

For hollow circular shaft, outside diameter = 120 mm; d = 120-2�20 = 80 mm
polar moment of inertia = ?/32 � (120⁴? 80⁴).
J = 16.36 � 10⁶ mm⁴.

The velocity of approach is defined as velocity with which water reaches notch or weir before it flows over it. This velocity of approach creates an additional head ?ha? equal to Va2 / 2g and effect head over notch is increased to H+ha.

Casing is an airtight chamber covering impeller. The different types of casing
i.Volute casing
ii.Vortex casing
iii.Casing with guide blades.

3 number of rain gauge stations should be installed an area between 250 to 500 km².

Shear stress is produced when shaft is subjected to pure twisting (torsion). The shear stress due to twisting moment is zero at axis of shaft.

A divide wall is a long solid wall constructed perpendicular to axis of weir. It provides a straight approach to scouring sluices. By preventing formation of cross currents, it protects body wall of weir.