fluid mechanics and concrete technology one liner important notes for objective

FLUID MECHANICS-

 Pascal second is the unit of dynamic viscosity.

 An ideal fluid is frictionless and incompressible.

 Cm^2/sec is the unit of kinematic viscosity.

 NS/m^2 is the unit of dynamic viscosity.

 Kinematic viscosity=(dynamic viscosity/mass

density).

 Surface tension of water increases with

decrease in temperature.

 Centre of buoyancy is always coincide with the

centroid of the volume of fluid displaced

 A floating body is said to be in a state of stable

equilibrium when the meta centric height is

above the centre of gravity.

 Stream lines and path lines always coincide in

case of steady flow.

 Equation of continuity is based on principle of

conservation of mass.

 The pitot tube is used to measure stagnation

pressure.

 Venturi meter is used to measure the discharge.

 The major loss of energy in long pipes is due to

friction.

 The losses are more in turbulent flow.

 Trapezoidal shape is the best hydraulic section.

 The height of the hydraulic jump is equal to

the difference in conjugate depth.

 Rayleigh lines are based on momentum and

continuity.

.CONCRETE TECHNOLOGY

&STRUCTURES-

 Bleeding-separation of water or water cement

mixture from the concrete.

 Segregation-separation of aggregates from the

concrete.

 Workability of the concrete directly

proportional to the grading of the aggregate.

 Workability of the concrete inversely

proportional to the time of transit.

 Approximate value of shrinkage strain is

0.0003.

 Air entrainment in the concrete increases

workability.

 Strength of the concrete increases with

increase in fineness of cement.

 Characteristic strength of concrete is given by

0.7 (fck)^(1/2).

 The compressive strength of 100mm cube is

more compare to the 150mm cube.

 Modulus elasticity of concrete is

5700(fck)^(1/2).

 Increase in moisture content in concrete

reduces the strength in concrete.

 The purpose of accelerator is to cause early

setting and hardening.

 Gypsum is most commonly used admixture.

 The percentage of voids in cement

approximately 40%.

 The strength of concrete after one year as

compare to the 28 days is 20 to 25% more.

 Modulus of rupture of concrete is the measure

of flexural tensile strength.

 In order to obtain the best workability

rounded shape aggregates used.

 Bulking of sand is maximum if moisture

content is about 4%.

 Finer grinding affects only the early

development of strength.

 Poisons ratio increases with richer mix.

 1% of voids in concrete reduces the strength by

5%.

 The fineness modulus of fine aggregate is in the

range of 2-3.5.

 The factor of safety of steel is lower than

concrete.

 For a reinforced concrete section the shape of

the shear stress diagram is parabolic above

neutral axis and rectangular below neutral axis.

 Modulus of elasticity of steel as per IRC 456-

1978 is 200kn/mm^2.

 M15 grade of concrete is used in reinforced

concrete.

 Heavily reinforced sections the workability of

the concrete is above 0.92.

 In case of hand mixing of concrete extra

cement is added is 10%.

 For walls, columns and vertical faces of

members the form work removed after 1-2 days.

 According to IS 456-1978, the column or strut

is the member whose effective length is greater

than 3 times lateral dimension.

 Slenderness ratio for short column is <12.

 The ratio of the diameter of reinforcing bar

and the slab thickness is 1/8.

 According to IS456-1978, the maximum

reinforcement for columns is 6%, 4% for

beams and 0.12% for slabs.

 Maximum distance between the expansion

joints is 45m.

 Minimum thickness of load bearing RCC wall

should be 100mm.

 One way slab ratio of long span to short span>2.

 Two way slab the ratio of long span to short

span is <2.

 Modular ratio is 280/3cbc.

 The purpose of providing the reinforcing bar

is to resist bond stress.

 12mm is the minimum diameter of longitudinal

bar.

 The load carrying capacity of a helically

reinforced column as compare to the tied column

is 5% more.

 Counter fort type retaining wall is suitable for

height beyond 6m.

 T shaped retaining wall mainly consists of

three cantilevers.

 While designing the pile has column one end is

fixed and other end is hinged.

 The design yield stress of steel according to the

IS 456-1978 is 0.87fy.

 According to IS 456-1978, the maximum

compressive stress in concrete is taken as

0.446fck.

 Partial safety factor for steel is 1.15 and 1.5 for

concrete.

 0.0035 is the maximum strain.

 The creep strains are caused due to dead load

only.

 The effect of creep on modular ratio is to

increase it.

 A beam curved in plan is designed for bending

moment, shear and torsion.

 Normally pre stressing wires are arranged in

the lower part of beam.

 3*10^-14 is the coefficient of shrinkage.

 Cold drawn wires has high tensile strength.

 In concrete use of angular aggregates in place

of natural aggregates affects flexural tensile

strength.

 Ratio of compressive strength to tensile

strength is increases with age.

 The grading of fine aggregates is divided into

4 zones.

 Endurance limit of mild steel is approximately

0.5.

 Soundness test gives unsoundness due to free

lime only.

 Vee bee test used for very low workability.

 0.9 is called medium workability.

 0.36 water cement ratio required for full

hydration of cement.

 Addition of sugar in concrete results in

increasing the setting time about 4 hour.

 7 days required for minimum curing.

 M20 grade of concrete is used for the structures

exposed to the sulphate attack.