Statically Determinate and Indeterminate Structures

 ◆Statically Determinate Structures 

•A structure is said to be determinate it condilions of static equilibrium are sufficient to analyse the structure. 

•In determinate structures, bending moment and shear force are independent of properties of material and cross-sectional  area. 

•No stresses are induced due to temperature changes. 

•No stresses are induced due to lack of lit and support settlement.

 ◆Statically Indeterminate Structures 

•A structure is saíd to be statically indeterminate it condilions of static equilibrium are not sufficient to analyse the structure. 

•To analyse these structures, additional compatibility condilions are required. 

•In indeterminate structures, bending moment and shear force depends upon the properties of material and cross-sectional area. 

•Stresses aro induced due fo temperature variations. 

•Stresses are induced due fo lack of lit and support settlement.

Degree of Indeterminacy 

The degree of indeterminacy can be divided into: 

1. Static indeterminacy, which can bo classified as 

(a) external indeterminacy 

(b) internal indelerminacy 

2. Kinematic indeterminacy

Static indeterminacy

1. External Static Indeterminacy

It is the total number of additional equations required to determine the external forces.

In general Degree of external static indeterminacy,

Dse = r - e

where r = Number of unknown reaction components

e = Total number of equilibrium equations

For different types of structure it is given as,

(i) Plane frame or 2D frame Dse = r – 3 

(ii) Space frame or 3D frame Dse = r - 6

2. Internal Static Indeterminacy: -

It is the total number of additional equations required to determine the internal forces.

For different type of structure it is given as

(i) Pin jointed plane frame, Dsi = m – (2j -3) 

(ii) Pin jointed space frame, Dsi = m – (3j -6) 

(iii) Rigid jointed plane frame, Dsi = 3C – r’

(iv) Rigid jointed space frame, Dsi = 6C – r’

Where, m = total number of members

j = total number of joints

C = total number of cuts required for open configuration

r’ = Number of additional equation due to hybrid joints.

Total degree of static indeterminacy is the sum of internal and external static indeterminacy.

Ds = Dse + Dsi

(i) Pin jointed plane frame, Ds = m + r – 2j

(ii) Pin jointed space frame, Ds = m + r – 3j

(iii) Rigid jointed plane frame,Ds = (r - 3) + (3C – r’) OR 3m + r – 3j

(iv) Rigid jointed space frame,Ds = (r – 6) + (6C – r‘) OR 6m + r - 6j

Where, 

m = number of members

j = number of joints

r’ = number of additional equations due to hybrid joints

r = number of external reactions

Kinematic indeterminacy

Kinematic indeterminacy also known as degree of freedom (DOF) is the 

total number of independent joint displacement. A joint can have two 

types of displacements in general; rotation and linear displacement. 

Dk = aj – r + r'

(1) Pin jointed plane frame, Dk = 2j - r

(2) Pin jointed space frame, Dk = 3j - r

(3) Rigid jointed plane frame, Dk = 3j – (r + m) + r’ 

(4) Rigid jointed space frame, Dk = 6j – (r + m) + r’ 

Where, a = DOF 

j = Number of joints

m = Number of members

r = number of reactions

r’ = number of additional equations due to hybrid joints

FRICTIONS

 1. INTRODUCTION :: 

(i) When two surfaces in contact have relative motion or have tendency of motion with each other then a force acts at the point of contact of the object and this force is called frictional force. 

(ii) The force of friction is always in a direction opposite to which the body tends to move 

(iii) It is paralel to the surface 

(iv) Frictional force is independent of the area of surface in contact 

(v) The force of friction depends on the nature of material of the surface in contact. 

(vi) Friction is a non-conservative force i.e. work done against friction is path dependent. 

(vii) Generally many of us have a misconception that friction opposes the motion of a moving body but it favours the motion of a body. It opposes the relative motion between the two bodies. When a person walks forward, he pushes the ground backward. The rough surface of ground exerts a forward force which causes the motion of the person.

2. TYPES OF FRICTION 

Friction is of two types 

(a) Static friction (b) Kinetic friction 

Now let us have some discussion on these types of friction 

2.1 Static friction : 

(i) Frictional force between two surfaces when there is no relative motion between them is called static friction. 

(ii) Static friction is self adjusting in nature. It adjusts its magnitude in such a way that together with other forces applied on a body, it maintains relative rest between two surfaces. 

(iii) The value of static friction lies between 0 and μₛN i.e 0 ≤ fₛ ≤ μₛN where μₛ is coefficient of static friction and N is normal force 

(iv) There is no energy loss due to static friction. We may perform work against static friction or static friction may perform work. 

2.2 Kinetic friction : 

(i) Frictional force between the two surfaces which are in relative motion is called kinetic friction. 

(ii) The magnitude of the kinetic friction is proportional to the normal force acting between the two surfaces i.e. fₖ ∝ N   fₖ = μₖN  where μₖ is coefficient of kinetic friction. 

(iii) This force of kinetic friction always. acts opposite to the direction of motion. 

(v) Work done against kinetic friction is nonconserved i.e. converted into heat. So in case of kinetic friction, there is always an energy loss

NOTE : If nothing is specified for μₖ and μₛ then we assume that both are equal. Theoretically

μₖ < μₛ

BUILDING, CONSTRUCTION & MATERIAL

•  Gypsum is a mechanically formed sedimentary rock.
•  Quartzite is a silicious rock.
•  Slate is formed by metamorphic action on shale.
•  Heavy stone is suitable for retaining wall.
•  Hard stone is suitable for rubble masonry.
•  Soft stones is suitable for ornamental work.
•  Quartzite has most weather resisting characteristics.
•  A good building stone should not absorb water more than 5%.
•  Compact sand stone has more fire resisting characteristics.
•  Weight test is conducted on a stone used in docks and harbours.
•  Granite stone is best suited for construction of piers and abutments.
•  Crushing strength of good building stone should be more than 100mpa.
•  Specific gravity of most of the building stone lies between 2.5 to 3.
•  Pith-annular rings-heartwood-sapwood-cambium layer-inner and outer bark.
•  Shisham is hard wood and offer maximum resistance to the white ants.
•  Star shakes-the radial splits which are wider on the outside of the log and narrow towards the pith.
•  Chir and deodar yields soft wood.
•  Mulberry tree used for making of sports goods.
•  Dry rot caused due to lack of ventilation.
•  Foxiness caused due to over maturity.
•  Honey combing caused due to-seasoning.
•  Strength of the timber is maximum in the parallel direction.
•  10% to 12% is the moisture content of well seasoned timber.
•  The age of the tree can be known by annular rings.
•  1st class timber has an average life of more than 10 years.
•  1st class brick should not absorb water more than 20% when immersed in water for about 24 hours, 22% for 2nd class bricks and 25% for 3rd class bricks.
•  Crushing strength of 1st class bricks not less than 10.5N/mm^2, 7.5N/mm^2 for 2nd class bricks.
•  The main function of alumina in brick earth is to impart plasticity.
•  The percentage of alumina in good brick earth is 20 to 30%.
•  Excess of alumina in brick earth cause crack and warp on drying.
•  Excess of silica cause brittleness.
•  20*10*10 cm is the nominal size of the brick.
•  19*9*9cm is the standard size of brick.
•  50 to 60 % silica in good brick earth.
•  Silica makes the brick to retain the shape.
•  Kneading –the process of mixing the clay water and other ingredients called.
•  60 to 70% turn over in clamp burning where as 80 to 90% turn over in kiln burning.
•  Pug mill used for preparation of clay.
•  Refractory bricks used in combustion chambers.
•  The frog of the brick generally kept on the top face of masonry.
•  500 bricks required for one cubic metre of brick masonry.
•  Quick lime is calcium oxide.
•  Hydraulic lime is obtained from burning of kankar.
•  Lime and silica are the main ingredients of the Portland cement.
•  C3A is responsible for all undesirable properties of cement.
•  Le chate lier apparatus is used for testing the soundness of cement.
•  Vicat apparatus used for testing setting time of cement.
•  C3A is responsible for intial setting time of cement.
•  The intial setting time for ordinary Portland cement not less than 30minute.
•  The final setting time should be 10 hour.
•  The normal consistency of ordinary Portland cement is 30%.
•  Early attainment of strength of cement in rapid hardening of cement is due to finer grinding.
•  After storage the strength of the cement is decreases.
•  Addition of pozzolana to ordinary Portland 
• cement cause shrinkage.
•  Gypsum consists of caso4 and H2O.
•  25mm to 50mm is the slump recommended for mass concrete.
•  Low heat cement is used in massive concrete structures.
•  Calcium chloride is the common admixture to accelerate the intial setting time.
•  The basic purpose of retarder in concrete is to increase the intial setting time of concrete.
•  Gypsum is most commonly used retarder.
•  Carbon influences the maximum properties in steel.
•  Wrought iron is the purest form of iron.
•  The ultimate tensile strength of steel is 420N/mm^2.
•  0.25% of carbon in mild steel.
•  Yield stress is used for identifying the quality of structural steel.
•  Flemish bond –alternate courses of header and stretcher.
•  English bond-alternate header and stretcher.
•  The pressure acting on the stones in stone masonry should be perpendicular to the direction of bedding planes.
•  Queen closer-the brick is cut into 2 equal parts in length wise.
•  English bond is provided in masonry for carrying heavy loads.
•  Slenderness ratio-effective length to least radius of gyration, for masonry walls not more than 20.
•  The differential settlement in case of sandy soil not more than 25mm.
•  In case of foundation on black cotton soil the most suitable method is to replace the poor soil.
•  Grillage foundation is the most economical foundation to transmit the heavy load.
•  Batter pile is used to resist the horizontal and vertical forces.
•  0.9m is the minimum depth of the foundation on clay soil.
•  The bearing capacity of a water logged soil can be improved by draining the soil.
•  Depth or height of arch-is the perpendicular distance between the intrados and extrados.
•  Flat roof is constructed where the rainfall is less and temperature is high.
•  Pitched and sloping roofs are suitable for coastal region.
•  The maximum number of steps generally restricted is 12.
•  Sum of tread and rise must between 400 to 450mm.
•  Minimum width of landing should be equal to width of stairs.
•  In any good stair case the maximum and minimum pitch is 40’ and 25’.
•  Doglegged stairs are half turn stairs.
•  Horizontal projection at head and sill called horns.
•  Revolving door is suitable for entrance in an air conditioned building.
•  Attrition test determines the rate of wear of stones.
•  Efflorescence-formation of white patches on the brick surface due to presence of alkalies.
•  Vanadium steel used in the manufacture of axles and springs.
•  Neoprene is suitable for bearing of bridges.
•  To produce low heat cement it is necessary to reduce the C3A.
•  Timber can be made more fire resistant by sir abel’s process.
•  Creosote is derived from wood or coal.
•  Excess of sulphur in steel results in red shortness.
•  Distemper is used to coat interior surface not exposed to weather.
•  Putty is made up of powdered chalk and raw linseed oil.
•  The limit of proportionality is applied more in the case of mild steel.
•  The compacting factor test determines the workability.
•  The split tensile strength is 10% to 15%.
•  The approximate ratio between the strength of cement concrete 7 to that of 28 days is 2/3.
•  The moisture content of timber is 12%.
•  0.85P times amount of water is used ofr intial setting time, 0.72P for soundness cement.
•  Lime mortar is generally made with hydraulic lime.
•  The texture of sand stone is granular crystalline.
•  Seasoning of timber is required to remove sap from timber.
•  The ratio of youngs modulus of high tensile steel to that of mild steel is about 1.
•  Poly vinyl chloride is thermoplastic material.
•  King closer is related to brick masonry.
•  High alumina cement is produced by limestone and bauxite.
•  The optimum number of revolutions required for concrete mix is 20.
•  Manganese steel used in the manufacture of rails.
•  Gauged mortar is obtained by adding sand and lime.
•  1300’to 1500’ is the temperature range of cement in kiln.
•  Before testing setting time of cement one should be test for consistency.
•  The super plasticizer in a cement paste is disperse the particles, remove air bubbles and to retard setting.
•  Surkhi is added to lime mortar to impart hydraulicity.
•  Increase in fineness of cement results in increase in development of strength and leads to higher shrinkage.
•  The purpose of frog is to form key joint between brick and mortar.
•  Bricks are burnt at a temperature of 900-1200 degree Celsius.

Correction of Chain & Tape

●Corrections Chain

• Correction for standardization • Correction for slope ●Corrections Tape • Correction for standardization • Correction for slope • Correction for Pull • Correction for Sag • Correction for Temperature • Correction for MSL • Correction for misalignment.

 Youtube video

NC, CNC and DNC Machines

 6.1 Numerical Control (NC):) Numerical Control is a technique for controlling machine toolso processes using coded command instructions. These coded command instructions are interpreted and converted by NC controller into two types of signals namely; motion control signals and miscellaneous control signals. Motion control signals are a series of electric pulse trains that are used to control the positions and the speed of the machine table and spindle. Miscellaneous control signals are set of ON/OFF signals to execute the spindle rotation and direction, control of coolant supply, selection of cutting tools, automatic clamping and unclamping, etc. In motion control signals, each pulse activates a motion of one basic length-unit (BLU). 

6.2 Computer Numerical Control (CNC): CNC controls are soft-wired NC systems as control functions are controlled by software programs. Alternatively, Computer Numerical Control is the numerical control.system in which dedicated, stored program microprocessors are built into the control to perform basic and advanced NC functions. Control signals in CNC systems are in the form of binary words, where each word contains fixed number of bits, 32 bits or 64 bits are commonly used, representing different axial positions. 

6.3 Direct Numerical Control (DNC) : Direct numerical simultaneously control the operations of a group of NC machine tools using a shared computer. Programming, editing part programs and downloading part programs to NC machines are main responsibilities of the computers in a NC system. Due to high cost of mainframe computers and introduction of CNC in 1970s, the DNC system couldn't become popular in industry. The capacity of stored memory and enhanced intelligence of the built-in, low cost, and dedicated computer replaced the desirable features of the DNC systems.

Centroid

Centroid:- The plane fig. (Like Triangle, Quadrilateral, circle etc.) have only area but no mass. The center of area of such fig. Is known as centroid.

The centre of gravity of right circular cone of height "h' lies at a distance_____ from vertex along the axis of rotation (mpsc mes 2018)

 1) h/4 2) 3h/4 3) h/3 4) 2h/3

Check this pdf

⬇️

Centroid .pdf

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LEAST COUNT OF SURVEYING INSTRUMENTS:-

🎯LEAST COUNT OF SURVEYING INSTRUMENTS:-

Least count means the minimum value that an instrument can read .
1.theodolite: least count is 20".

2.Prismatic compass: least count is 30'.

3.least count of levelling staff is 5mm.

4.dumpy level: least count 5mm as it is based on staff reading thats why least count is 5mm.

5.Total station : Least count for total station for angle is 1'' & Distance is 1mm.

Bridge Design

• Spans: 
It depends upon the type of superstructure proposed.
Masonry arch : 3 to 15 m 
Slab bridges : Upto 9 m
Slab bridges : Upto 9 m
Girder and beams : 10 to 60 m
Truss bridges : 30 to 375 m with simply supported ends.
Suspension bridges : Over 500 m so for maximum span built in 1990 m 
Cable stayed bridges : 300 to 600 m

• Width of bridges:
It is based on traffic survey. It may be single lane or double lane with pedestrian platform on only one side or on both side.

• Single lane – 4.25m

• Double lane – 7.5m with kerb
• Multiple lane – 3.5m per lane

• Length of bridge:
It depends upon the waterway.

It’s the Distance between inner faces of two abutments.
[ L= (n X clear span) + (n -1)b ]

b= pier width
n= no of span
L= total bridge length

• Height of bridge:
It is 1.2 to 1.5 m above HFL.

• Piers: 
Types of piers generally used are:
     • Masonry piers
     • R.C.C. piers

• The forces acting on piers are:
Vertical load or inclined reaction from the superstructure
Water pressure
Static water pressure
Dynamic pressure due to flow of water
Impact due to cross currents
Tractive force
Wind pressure
Earthquake forces

• Foundations:
It may be spread foundation, pile foundation or well foundation.
The choice of foundation depends upon load expected and soil properties

• GLength:

In case of erodible soil, the depth of foundation is kept more than maximum scour depth, below the designed foundation depth. This depth below scour depth is called GRIP LENGTH.

• In road ways grip length > 1/3rd of max scour depth

• In railway bridges grip length > ½ of max scour depthrip 

• Handrail:
• It will eliminate the chance of user / vehicle falling down

• Imparts appearance to bridge
• Defines the width of bridge
• Vertical posts supporting handrails are provided at an interval of 2 m. They should be designed to resist a lateral horizontal force and vertical force each of 1.5 KN/m.

• Foothpath:

• Footpath provision on either side of bridge about 1.5m is must, it will carry about 108 persons/min

• Increase this width by 0.6 m per 54 persons /min

• Scouring:

• Erosion of river bed is called scouring action.

• Bridge scour is the removal of sediment such as sand and gravel from around bridge abutments or piers.

• If velocity of flow is more than critical velocity then scouring happens.

• Scoredepth is given by

[ d= 0.473(Q/f)0.33 ]

• f=1.76√(bed material size)

• Water Way:

Area through which water flows under the bridge superstructure is called waterway.
If the flow is unobstructed then its called Unobstructed Waterway- Natural waterway.
If the flow of water is obstructed then its called obstructed – linear water way.

• Abutment:

• Abutment is subjected to all forces that are acting on pier, but one additional force Earth

pressure also acts on abutment.

• Main difference between wing wall and abutment is that the live load is absent in case of wing wall.

• Abutment pier = every forth or fifth pier of arch bridge is made stronger and designed to serve all function of abutments, except earth filling.

• Afflux:

When natural water is obstructed by bridge piers or abutments, its area of flow reduces and hence

velocity increases which causes rise in head on upstream side. This rise of head on upstream side is called Afflux. calculated by

A) Merrimans formula-

Ha = [v^2/2g][(A/Ca)^2– (A/A1)]

B) Molesworth formula

Ha =[v^2/17.87 + 1/65.60][(a/A)2- 1]

• v- Natural velocity

• A- natural waterway area

• A1- enlarged area on up stream of bridge

• a- Artificial water way area

• C- Coefficient of discharge

In any case afflux should be less than 15cm.

• Maximum Flood Discharge:

 In design of bridges consideration is made that flood will occur once in 100 years , & that for

design of culvert consideration is made that flood will occur once in 20 years.

•  Measurement of discharge :

A) Direct measurement-

. Here cross section of area up to HFL is calculated and velocity of flowing water is measured by making use of surface floats.

. While measuring area of gorge at least 3 cross section are calculated and their average is reported.

. While measuring the velocity, surface float are used in case of small rivers and velocity rods

are used in case of large rivers.

B) Indirect measurements-

     • Rational Method

          . AIR/360 .............[area in H]

     • Emperical method-

         . Dickens Formula- Q = C.A3/4 (central & north India)

         . Ryves Formula- Q= CA2/3 (madras catchment)

         . Inglis Formula- Q=123A/(√(A+10.36)) (western catchment)

A-area of catchment in km2

C their respective constants

Q- flood discharge in m3/s

I- intensity of rainfall in mm/hour

R- runoff coefficient.

Testing of Brick

IS 3495 part (I) = Compressive Strength Test
IS 3495 part (II) = Water Absorption Test on Brick
IS 3495 part (III) = Efflorescence Test on Brick
IS 3495 part (IV) = Warp age Test on Brick
IS 1077 = Dimensions Test on Brick


1) Compressive Strength Test.

Take 5 Brick as sample, Fill the frog with cement mortar of (1:3) proportion, Brick immersed in water for 3day so that mortar gain the strength.
After 3 days remove this brick for water and use for test, place in compressive test machine (CTM) and Apply the load of 14N/mm2/min.,till the fracture does not occur on surface.

➤Minimum compressive strength of brick = 3.5N/mm2 or 35 kg/cm2

Compressive strength in N/mm2  = Maximum load at failure in N / Average area of the bed faces in mm2  

2) Water Absorption Test.

For this test oven dry brick is taken and its weight is measured (w').
Brick is immersed in cold water for 24hr or hot water for 5hr,
After immersion brick there weight again measured  (w")

Water absorption, percent by mass = (w"-w')/w' *100 

Note:- 24 hours Test – IS code Recommended, 5 hours Test – CPWD (not recommended by IS code)

3) Efflorescence Test on Brick.

The brick are kept in 150mm dia dish and immersed in 25mm depth of water at room temp. after all water is absorbed or evaporation it is fill again till 25mm and make to be absorbed or evaporation.

Efflorescence reported as nil, slight, moderate, heavy or serious

Nil - <1%
Slight -  <10% (the brick is covered with a thin deposit of salts.)
Moderate - 10-50% deposit of salts. 
Heavy -  > 50% deposit of salts.
Serious -A heavy deposit of salts 

4) Warp age Test on Brick

5) Dimensions Test on Brick

For this test 20 bricks are randomly selected taken arrange in the w.r.t  L*B*H
Stack length are measured for (19*9*9)
permissible limits:-
length - 368cm to 392cm
width - 174cm to 186cm
height - 174cm to 186cm


see more topic 👇

Size and Weight of Bricks.

composition of bricks.

harmful ingredients in bricks.

classification of bricks.

Brick Manufacturing.

Testing of Brick.

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Brick manufacturing

Brick manufacturing involves four stages

1. Brick clay/brick earth preparation.
2. Moulding of bricks.
3. Air drying of bricks.
4. Burning of bricks.

1) Preparation of brick earth Various steps involved in sequence are:
a. Unsoiling
b. Digging
c. Cleaning
d. Weathering
e. Blending
f. Tempering

2) Moulding
➧Hand Moulding:   a. Ground moulded
                                b. Table moulded
➧Machine Moulding

3) Drying
a. Natural drying
b. Artificial drying

4) Burning
a. Intermittent Kilns
b. Continuous Kiln

see more topic 👇

Size and Weight of Bricks.

composition of bricks.

harmful ingredients in bricks.

classification of bricks.

Brick Manufacturing.

Testing of Brick.

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Classification Of Hydraulic Turbine

⚡️Impulse turbine

Energy available at inlet kinetic energy 

1)Pelton wheel Turbine 

●High head tangential flow turbine

●Note-  Casing is only to prevent splashing of water does not form in Hydraulic function in pelton Wheel Turbine

●Nozzle at end of penstock convert pressure energy into kinetic energy

●Bucket shape double hemispherical Cup or Bowl

●Hydraulic efficiency of pelton wheel will be maximum when the velocity of wheel is the half the velocity of the jet of water at inlet u=V1/2

●Angle of deflection of the jet through bucket 165°

●Jet ratio(m)= Pitch diameter of pelton wheel(D) /diameter of jet(d)

●Number of bucket (Z) = 15+0.5m

●Speed ratio (fi) =velocity of pelton wheel (u)/ velocity of Jet from nozzle(√2gh)
= 0.43 to 0.47

⚡️Reaction turbine

Energy at inlet kinetic energy + pressure energy

●To maximize the efficiency of reaction turbine angle of absolute velocity at outlet is 90°
i.e. Vw2=0

1) Francis turbine
●Old Francis =  Inward radial flow reaction turbine ( water flows from outward to inward )
● Modern Francis = Mixed flow reaction turbine (i.e. inward radial + Axial)

2) Kaplan & propeller
Axial flow reaction turbine

●Kaplan = Vanes are Adjustable
●Propeller = Vanes are fixed to the hub and they are not adjustable

Note - Servometer used to adjustment of runner blades

⭐️Draft tube 

 Tube or pipe of gradually increasing area is used for discharging water from the exit of turbine to the tail race
Always submerged in water below Tail race level

●Converts kinetic energy into the pressure energy
●To increase  the net head on the turbine
●It permits negative head

Turbine             Sp. Speed       Head         
--------------------------------------------------------                                                                     
Pelton
1)Single Jet         10-35            >250m
2)Double Jet       35-60

FRANCIS             60-300          30-250m

KAPLAN &.        300- 1000      <30m
 Propeller
---------------------------------------------------------

⚡️Specific speed of turbine 

Speed at which turbine runs when it is working under a unit head and develops unit horsepower
 (N√p)/(H^5/4)

◆Characteristic curves of hydraulic turbine
1)Main characteristic curve constant head
2)Operating characteristic curves constant speed
3) Muchel curve or Isoefficiency curve constant efficiency

Governing of turbine operation by which speed of turbine kept constant at all condition of working

⭐️Cavitation of turbine 

When pressure falls below below Vapour pressure

●Only reaction turbine and centrifugal pumps subjected to cavitation

●In reaction turbine cavitation may occur at outlet of the runner or at the inlet of the draft tube

●In centrifugal pumps cavitation occurs at the inlet of impeller of pump Or at the suction side of the pump

Note= When Thoma cavitation factor greater than critical cavitation factor cavitation will not occur


see more topic 👇

Size and Weight of Bricks.

composition of bricks.

harmful ingredients in bricks.

classification of bricks.

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Classification of Bricks:

1. First class Bricks:

➤ These bricks are table moulded & they are burnt in kilns.

➤ These are thoroughly burnt & are of deep red, cherry or copper colour.

➤ Surface should be smooth & rectangular, with parallel, sharp & straight edges

& square corners.

➤ It should be free from flaws, cracks & stones.

➤ It should have uniform texture.

➤ No impression should be left on the brick when a scratch is made by a finger nail.

➤ Fractured surface of the brick should not show lumps of lime.

➤ Metallic or ringing sound should come when two bricks are struck against each other.

➤ First class bricks are recommended for pointing, exposed face work in masonry structures, flooring & reinforced brick work.

➤ Water absorption = 12.5% of its dry weight when immersed in cold water for 24 hours is allowed.

➤ Crushing strength ≥ 10 N/mm².

2. Second Class Bricks:

➤ These bricks have same requirements as first class brick except for the one’s listed below.

➤ These bricks are ground moulded & they are burnt in kilns.

➤ Small cracks & distortions are permitted.

➤ Second class bricks are recommended for all important or unimportant hidden masonry works & centering of reinforced brick & reinforced cement concrete (RCC) structures.

➤ Water absorption = 16-20 % of its dry weight is allowed.

➤ Crushing strength ≥ 7 N/mm².

3. Third Class Bricks:

➤ These bricks are ground-moulded & they are burnt in clamps.

➤ These bricks are soft & reddish yellow coloured.

➤ Produce a dull sound when struck with each other.

➤ These bricks are used for unimportant & temporary structures & at places where rainfall is not heavy.

➤ Water absorption = 25 % of dry weight is allowed.

➤ These have rough surface with irregular & distorted edges.

4. Fourth Class Bricks (Zhama Bricks):

➤ These bricks are over burnt & badly distorted in shape & size & are brittle in nature.

➤ Ballast of such brick is used for foundation & floors in lime concrete & road metal, because of fact that own burnt bricks have a compact structure & hence they are sometimes found to be stronger than even first class bricks.

see more topic 👇

Size and Weight of Bricks.

composition of bricks.

harmful ingredients in bricks.

classification of bricks.

Brick Manufacturing.

Testing of Brick.

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Harmful Ingredients in Bricks:

1) Lime Slaking :

➤ Due to lime slaking volume of brick increases and due to that cracking and disintegration is occurs.

2) Iron Pyrites :

➤ Presence of the Iron pyrites leads to crystallization and disintegration of bricks during burning due to the oxidation of these pyrites.

3) Alkalies :

➤ Alkali act as a flux during the burning of bricks but if it is in excess, it causes the bricks to fuse with each other thereby resulting in its twisting and warping.

➤ Presence of Alkalies also leads to efflorescence and staining in bricks.

4) Pebbles or Stones :

➤ Presence of stones and pebbles brick earth leads to the formation of weak and porous bricks, load carrying capacity of which is comparatively reduced.

5) Organic and Vegetative Matter :

➤ Presence of organic and vegetative matter helps in the burning of bricks but if they are left unburnt, it results in the formation of gases during the decomposition, which when escapes through the body of the bricks leads to the development of numerous voids, which results in decreasing of load carrying capacity of bricks.

see more topic 👇

Size and Weight of Bricks.

composition of bricks.

harmful ingredients in bricks.

classification of bricks.

Brick Manufacturing.

Testing of Brick.

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Composition of Bricks:

1. Silica (50-60%):

➤ Silica prevents the cracking, shrinkage and warping of the bricks, thereby imparts uniform shape to it.

➤ if it is in excess, it destroys cohesion between the particles, hence bricks become too brittle.

2. Alumina (20-30%):

➤ Alumina impacts plasticity to the brick earth so that it can be easily moulded in any designed shape.

➤ If it is in excess, it causes shrinkage and warping during the drying of the bricks and makes the bricks too hard during the working process.

3. Lime (4-5%):

➤Lime also prevents the shrinkage of the bricks

➤ If it is in excess, it causes the brick to melt during the burning thereby it results in loss of the shape of bricks.

4. Oxides of Iron (5-6%)

➤ Oxides of iron help silica and lime to fuse with each other, hence leads to the development of strength in the bricks

➤ It also imparts reddish brown colour in bricks.

5. Magnesia (1%):

➤ Magnesia also prevents the shrinkage in bricks and imparts yellowish tint in bricks.

see more topic 👇

Size and Weight of Bricks.

composition of bricks.

harmful ingredients in bricks.

classification of bricks.

Brick Manufacturing.

Testing of Brick.

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Size and Weight of Bricks:

Size of bricks

➤ Standard size or modular size of bricks = 19*9*9 cm

➤ Nominal size (with mortar) = 20*10*10 cm

➤ Traditional size of bricks = 9’’*4.5’’*3’’

➤ Conventional size of bricks = 23*11.4*7.6 cm

➤ Dimension of frog = 10*4*1cm

Weight of bricks

➤ It is found that the weight of 1 m³ of bricks earth is about 1800 kg. hence the avg. wt. of a brick will be about 3 to 3.5 kg.

see more topic 👇

Size and Weight of Bricks.

composition of bricks.

harmful ingredients in bricks.

classification of bricks.

Brick Manufacturing.

Testing of Brick.

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Test on concrete*

Compaction Factor Test

➤ This test is used for the concrete possessing very low workability for which slump test is not suitable.

➤ Principle of this test is based upon finding the degree of compaction achieved by the standard amount of work done by the concrete when allowed to fall from known height.

➤ This degree of compaction is represented in terms of compaction factor that represents the density ratio.

➤ Density of concrete obtained during test to the Density of fully compacted concrete.

Slump Test

•  This is most common method.
•  Frustum having top diameter 10 cm, bottom diameter around 20 cm, height of 30 cm.
•  Concrete to be tested in filled in the mould in four layers where each layer is compacted 25 no. of times with the help of rod.
•  Mould is removed immediately by lifting it in upward direction which causes the concrete to subsidize and the subsidence of the concrete is referred as slump which may also defined as difference of the height of the mould and the top level of the subsidize concrete.
•  Higher the value of slump, more is the workability.
•  This test is not suitable for the concrete which process either very high workability or very low workability.

IS CODES FOR BUILDING MATERIALS AND CONSTRUCTION

The following is that the list of a number of the IS code giving requirements for building materials:

• IS 269–1989. Specification for ordinary Portland cement.
• IS 455–1989. Specification for Portland slag cement.
• IS 516–1959. Method of tests for strength of concrete.
• IS 1123–1975. Method of identification of natural building stones.
• IS 383–1970. Specifications for coarse and fine aggregates.
• IS 432–1982. Specification for mild steel.
• IS 3495–1976. Gives specifications for building bricks.

see more topic 👇

Size and Weight of Bricks.

composition of bricks.

harmful ingredients in bricks.

classification of bricks.

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Different Types of plot in hydrology

●Mass curve:- Plot of Accumulated Precipitation Vs Time.

●Hyteo-graph:- Plot of Rainfall intensity Vs Time.

●Hydro-graph:- Plot between discharge in stream & time in chronological order.

● Flow mass curve:- Plot between cumulative discharge, Volume & time in chronological order.

●Flow duration curve:- Plot of Stream discharge Vs percentage of time the flow is equalled or exceeded.

Highway Engineering

✨15th percentile speed:-
Lower safe speed limit
(To avoid conjection )

✨50th percentile speed:-
Median speed

✨85th percentile speed:-
Upper safe speed limit
(decided speed regulation on road )

✨98th percentile speed:- Design Speed for Geometric design

SCALAR AND VECTOR QUANTITIES

◆SCALAR AND VECTOR QUANTITIES◆

●Various quantities used in mechanics may be grouped into scalars and vectors.

●A quantity is said to be scalar, if it is completely defined by its magnitude alone.

●Examples of scalars are length, area,time and mass.

●A quantity is said to be vector if it is completely defined only when its magnitude as well as
direction are specified.

●The example of vectors are displacement, velocity, acceleration, momentum, force etc.

Unit MKS, CGS, FPS

◆ UNITS ◆

      •Length (L), mass (M) and time (S) are the fundamental units used in mechanics.

       •The units of all other quantities may be expressed in terms of these basic units.

The three commonly used systems are

— Metre, Kilogram, Second (MKS)
— Centimetre, Gram, Second (CGS)
— Foot, Pound, Second (FPS).

The systems are named after the units used to define the fundamental quantities length, mass
and time. Using these basic units, the units of other quantities can be found. For example in MKS
the units for various quantities are

Quantity           Unit
Area                  m2
Volume             m3
Velocity            m/sec
Acceleration.   m/sec2
Momentum      kg-m/sec  [Since it is = mass × velocity]
Force                 kg-m/sec2 [Since it is = mass × acceleration]