METHODS OF CALCULATIONS OF QUANTITIES OF MATERIALS

Methods Of Calculations Of Quantities Of Materials

The calculations of quantities of materials can be done using various methods of estimates. The application of an individual method depends upon the design and shape of the building. The different methods are as under:

 

1. Centre line method.
2. Crossing method.
3. Out to out and in to in method.
4. Bay method.
5. Service unit method.

1. Centre line method

This method is suitable only if the offsets are symmetrical and the building is more or less rectangular in shape. The centre line of the building is determined carefully after doing deductions for repeated measurements (as explained in the next problem). This centre line acts as length for the complete calculations of the estimate.

If the deduction is not cared for the results of estimates may be wrong. All the walls should have the same section.

2. Crossing Method

In this method, lengths and breadths of the masonry walls at plinth level are taken (internal dimension of the room + thickness of the walls) for calculating quantities. The symmetrical offsets are a must as in the case of centerline method.

3. Out to out & in to in Method

This method is most practicable under all circumstances and is generally followed in the P.W.D. for computing the quantities of various items. The estimation in this book has been done using this method.

4. Bay Method

This method is useful and is generally followed in case of building having several bays. The cost of the one class room is worked out and then multiplied by the number of bays in that building. The extra cost of the end walls and difference in framing. If there is any, should be made, so as to arrive at the correct cost.

5. Service Unit Method.

This method is followed in cases such as school building where there are so many class rooms. The cost of one class room us worked out and then multiplied by the number of class rooms to be constrused. In case of Hospitals, the service unit is a bed, in case of Water Tank, it is a litre and in case of Cinema Hall, the service unit is a seat.

MEASURE EVERYTHING ONLY WITH YOUR HANDS

Measure tricks are always welcomed because we do not always have the measurement tools at touch. Generally, we need the measurements for different things on daily basis. Also, we can not always have the tools with us. For that purpose, we will give you tricks for measuring different systems like centimeters, degrees and else. For example, if you open your thumb and your index finger, the length between them will be around 18 centimeters. But, if you open the thumb and the little finger you will get additional 2 centimeters. Then, you can tell the degrees with your palm because you will have the full angle with your thumb and your little finger.

Finally, see the pictures and learn several more tricks.

POINTS TO BE REMEMBER BY SITE ENGINEER

Following are few general points to remember for civil site engineers to make the construction work easier while maintaining quality of construction.

• Lapping is not allowed for the bars having diameters more than 36 mm.
• Chair spacing maximum spacing is 1.00 m (or) 1 No per 1m².
• For dowels rod minimum of 12 mm diameter should be used.
• Chairs minimum of 12 mm diameter bars to be used.
• Longitudinal reinforcement not less than 0.8% and more than 6% of gross C/S.
• Minimum bars for square column is 4 No’s and 6 No’s for circular column.
• Main bars in the slabs shall not be less than 8 mm (HYSD) or 10 mm (Plain bars) and the distributors not less than 8 mm and not more than 1/8 of slab thickness.
• Minimum thickness of slab is 125 mm.
• Dimension tolerance for cubes + 2 mm.
• Free fall of concrete is allowed maximum to 1.50m.
• Lap slices not be used for bar larger than 36 mm.
• Water absorption of bricks should not be more than 15 %.
• PH value of the water should not be less than 6.
• Compressive strength of Bricks is 3.5 N / mm^2.
• In steel reinforcement binding wire required is 8 kg per MT.
• In soil filling as per IS code, 3 samples should be taken for core cutting test for every 100m².

Density of Materials:

Material	Density
Bricks	1600 – 1920 kg/m3
Concrete block	1920 kg/ m3
Reinforced concrete	2310 – 2700 kg/ m3

Curing time of RCC Members for different types of cement:

Super Sulphate cement: 7 days

Ordinary Portland cement OPC: 10 days

Minerals & Admixture added cement: 14 days

De-Shuttering time of different RCC Members

<tr”>Arches spanning over 6m21 days

RCC Member	De-shuttering time
For columns, walls, vertical form works	16-24 hrs.
Soffit formwork to slabs	3 days (props to be refixed after removal)
Soffit to beams props	7 days (props to refixed after removal)
Beams spanning upto 4.5m	7 days
Beams spanning over 4.5m	14 days<
Arches spanning up to 6m	14 days

Cube samples required for different quantity of concrete:

Quantity of Concrete	No. of cubes required
1 – 5 m3	1 No’s
6 0 15 m3	2 No’s
16 – 30 m3	3 No’s
31 – 50 m3	4 No’s
Above 50 m3	4 + 1 No’s of addition of each 50 m3

THINGS THAT SITE ENGINEER SHOULD KNOW

Minimum thickness of slab is 125 mm.

Water absorption should not be more than 15 %.

Dimension tolerance for cubes + – 2 mm.

Compressive strength of Bricks is 3.5 N /mm²

Maximum Free fall of concrete allowed is 1.50 m.

In soil filling as per IS code for every 100 sqm 3 sample for core cutting test should be taken.

Electrical conduits shall not run in column

Earth work excavation for basement above 3 m should be stepped form

Any back filling shall be compacted 95% of dry density at the optimum moisture content and in layers not more than 200mm for filling above structure and 300 mm for no structure

F soling is specified the soling stones shall be laid at 45° to 60° inclination (and not vertical) with interstices filled with sand or moorum.

A set of cube tests shall be carried out for each 30 cum of concrete / each levels of casting / each batch of cement.

Water cement ratio for different grades of concrete shall not exceed 0.45 for M20 and above and 0.50 For M10 / M15 contractor

For concrete grades M20 and above approved admixture shall be used as per mix design requirements.

Cement shall be stored in dry places on a raised platform about 200mm above floor level and 300mm away from walls. Bags to be stacked not more than 10 bags high in such a manner that it is adequately protected from moisture and contamination.

Samples from fresh concrete shall be taken and at least a set of 6 cubes of 150mm shall be prepared and
cured. 3 Cubes each at 7 days and 28 days shall be tested for compressive strength. The test results
should be submitted to engineer for approval. If results are unsatisfactory necessary action/rectification/remedial measures has to be exercised.

Water used for both mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalies, salts, sugar and organic materials or other substances that may be deleterious to concrete or steel. The ph shall be generally between 6 and 8.

Cement shall be tested for its setting. 
1. The initial setting time shall not be less than 30 minutes.
2. The final setting time shall not be more than 10 hours.

Slump IS 456 
Lightly reinforced 25 – 75 mm
Heavily reinforced 75 – 100 mm
Trench fill (insitu & Tremie) 100 – 150 mm (For Tremie no need of vibrator)

Curing Days Required 
Super Sulphate cement : 7 days
Ordinary Portland cement OPC : 10 days
Minerals and Admixture added cement : 14 days

Cube Samples
1 – 5 M³ : 1 No.
6 – 15 M³ : 2 No’s
16 – 30 M³ : 3 No’s
31 – 50 M³ : 4 No’s
Above 50 M³ : 4 + 1 No of addition sample for each 50 M³.

Things Site Engineers Must Know About Reinforcement and Steel Bars

Check out the Unit Weights and Conversion which will be required on construction site here

TYPES AND USES OF COMPASS

CIVIL_ENGINEERING

A compass is a navigational instrument for determining direction relative to Earth’s magnetic poles. It consists of magnetized pointer that is free to be aligned to magnetic North or true north or sometimes to an arbitrary direction based on the location of the celestial bodies. Magnetic North refers to the pole of Earth’s magnetic field. It  is the direction of the north tip of the Earth’s magnetic field and  true north  refers to the geographic north pole. The compass has been used extensive since ancient times for direction setting and for navigating across the oceans.

What is the history of the compass?

The compass was first used in India, around 1800 BC, for Navigational purposes and was known as “Matsya yantra” (which roughly translates to fish machine) because of the placement of a metallic fish in a cup of oil. The use of the magnetic compass started from 4th century in china, where a type of magnetite known as “lodestone” was used as a tool in a kind of divining magic, Geomancy. The Chinese were the first ones to have mastered the use of magnetic iron for navigation, which then rapidly spread to Europe and beyond. In the 13th century, Arabs started using the magnetic compass in navigation. The prismatic compass played a major role in the World War 1.

What are the various types of compass and their uses?

Magnetic compass: The most common type of compass is the magnetic compass, which is used to determine the direction of magnetic north. A magnetic compass is made by placing a bit of magnetized iron or steel which is set in a low friction so that it is allowed to move freely. In most compasses, the north end of the metal piece is marked with red paint so that all directions may be determined.

Gyro compass: It is a special type of compass developed in 19th century which determines the true north. A gyro compass is basically a very fast spinning wheel or ball which uses the law of conservation of angular momentum and the spinning of earth’s axis to point towards the true north. The gyro compass is commonly used in large ships and in other circumstances where the accurate prediction of true north is needed.

Astrocompass: This is another type of compass which can predict true north rather than magnetic north. This compass relies on the direction of celestial bodies to find true north, which is used in many circumstances, mainly in the far north and south poles where magnetic compass would become erratic and gyro compass stops working. The use of astro compass in determining the exact direction of true north requires the accurate information of time, date, longitudinal and latitudinal location.

Solid state compass: In this modern digital world, solid state compass are becoming more popular. These use many of the electronic magnetic sensors which would calculate the accurate direction the compass is pointing.

GPS compass: GPS compasses are rapidly replacing the use of other traditional compasses. However, most military and ships use the gyro compass or magnetic compass if GPS compass could not pick up enough satellite. GPS compasses make use of satellites in a geo synchronous orbit over the earth to distinguish the bearer’s exact location and direction they are heading. Many hikers and drivers like this compass due to its relative reliability.

Base plate compass: It is the most affordable compass. The liquid filled compass rise on the rectangular base made of clear plastic. This compass includes a magnifying lens for map reading, luminous components for low light conditions and different scales for world wide use. This compass is fine for plotting purposes.

Card compass: Card compass or marine compass is commonly used in ships and boats. It uses a fixed needle, depending on the moving compass card for directional readings since the moving card absorbs much of the motion of the boat.

Thumb compass: This compass attaches to the user’s thumb allowing the user to hold both the map and the compass in one hand while traveling at speed by bike or by canoe. It is also known as competition compass.

Prismatic compass: It is a sophisticated device designed for highly accurate navigation. The prism sighting arrangement allows the user to read the compass bearings while seeing distant objects.

TYPES AND USES:

TM 9-243TYPES AND USES – ContinuedCOMPASS  SAWThe compass saw is slightly larger than the keyholesaw. The teeth are so arranged that the blade can easilybe turned for cutting curves or holes. As with the keyholesaw, the compass saw will vary in size depending on thedesign and purpose.

COMPASS  SAW

The hacksaw is designed to cut almost any size orshape of metal object. The hacksaw uses two types ofblades, hard and flexible. The type of blade useddepends  on  the  nature  of  the  task.  The  blade  is  held  tothe saw frame by pins that fit into small holes at each endof the blade. Blade tension is adjusted by a screw andwingnut assembly at either the nose or the handle end ofthe  frame.  The  hacksaw  comes  in  various  designs,  de-pending on the purpose.

HACKSAW

TERMS USED IN LEVELLING

CIVIL_ENGINEERING

Before studying the art of levelling, it is necessary to clearly understand the following terms used in levelling:

1. Level Surface: A surface parallel to the mean spheroid of the earth is called a level surface and the line drawn on the level surface is known as a level line. Hence all points lying on a level surface are equidistant from the centre of the earth. Figure shows a typical level surface.

 

 

 

A level Surface

2. Horizontal Surface: A surface tangential to level surface at a given point is called horizontal surface at that point. Hence a horizontal line is at right angles to the plumb line at that point [Ref. Fig. ].

3. Vertical Line: A vertical line at a point is the line connecting the point to the centre of the earth. It is the plumb line at that point. Vertical and horizontal lines at a point are at right angles to each other [Fig. ].

4. Datum: The level of a point or the surface with respect to which levels of other points or planes are calculated, is called a datum or datum surface.

5. Mean Sea Level (MSL): MSL is the average height of the sea for all stages of the tides. At any particular place MSL is established by finding the mean sea level (free of tides) after averaging tide heights over a long period of at least 19 years. In India MSL used is that established at Karachi, presently, in Pakistan. In all important surveys this is used as datum.

6. Reduced Levels (RL): The level of a point taken as height above the datum surface is known as RL of that point.

7. Benchmarks: A benchmark is a relatively permanent reference point, the elevation of which is known (assumed or known w.r.t. MSL). It is used as a starting point for levelling or as a point upon which to close for a check. The following are the different types of benchmarks used in surveying:

(a) GTS benchmarks (b) Permanent benchmarks

(c) Arbitrary benchmarks and (d) Temporary benchmarks.

(a) GTS Benchmark: The long form of GTS benchmark is Great Trigonometrical Survey benchmark. These benchmarks are established by national agency. In India, the department of Survey of India is entrusted with such works. GTS benchmarks are established all over the country with highest precision survey, the datum being mean sea level. A bronze plate provided on the top of a concrete pedastal with elevation engraved on it serves as benchmark. It is well protected with masonry structure built around it so that its position is not disturbed by animals or by any unauthorised person. The position of GTS benchmarks are shown in the topo sheets published.

 

b) Permanent Benchmark: These are the benchmarks established by state government agencies like PWD. They are established with reference to GTS benchmarks. They are usually on the corner of plinth of public buildings.

(c) Arbitrary Benchmark: In many engineering projects the difference in elevations of neighbouring points is more important than their reduced level with respect to mean sea level. In such cases a relatively permanent point, like plinth of a building or corner of a culvert, are taken as benchmarks, their level assumed arbitrarily such as 100.0 m, 300.0 m, etc.

(d) Temporary Benchmark: This type of benchmark is established at the end of the day’s work, so that the next day work may be continued from that point. Such point should be on a permanent object so that next day it is easily identified.

PRECISION MEASURING INSTRUMENTS

CIVIL_ENGINEERING

Since modern production processes is concerned with interchangeable products, precise dimensional control is required in industry. Precision measurement instruments use different techniques and phenomena to measure distance with accuracy. We will discuss some of the precision measuring instruments in this section.

Vernier Calipers:

Vernier calipers are precision measuring instruments that give an accuracy of 0.1 mm to 0.01 mm. The main scale carries the fixed graduations, one of two measuring jaws, a vernier head having a vernier scale engraved on. The vernier head carries the other jaw and slides on main scale. The vernier head can be locked to the main scale by the knurled screw attached to its head. Enlarged diagram of the metric vernier scale is shown in Figure.

 

Vernier Caliper

 

To understand the working principle of a vernier caliper, let us consider that the vernier scale has got 20 divisions which equals to 19 divisions of the main scale. Thus, one smallest division of the vernier scale is slightly smaller than the smallest division of the main scale. This difference is called vernier constant for that particular vernier caliper and when it is multiplied with the smallest unit of the main scale gives the least count of that vernier.

Now, 20 vernier scale divisions (VSD) = 19 main scale division (MSD):

 

Vernier constant (VC) = 1 MSD – 1 VSD

Now, if the smallest unit of the main scale be 1 mm, the least count of the vernier scale = VC  one smallest unit of the main scale

If the smallest unit in the main scale be 0.5 mm, the least count of the vernier scale is,

To read a measurement from a vernier caliper, first the main scale reading up to the zero of the vernier scale is noted down. It will give accuracy up to the smallest division of the main scale. Now, vernier number of vernier scale division from its zero, which coincides exactly with the main scale is noted. This number when multiplied with the vernier constant gives the vernier scale reading. The actual length is obtained when the vernier scale reading is added to the main scale reading.
The caliper is placed on the object to be measured and the fine adjustment screw is adjusted until the jaws tightly fit against the Workpiece. There are vernier calipers that incorporate arrangements for measurement of internal dimensions and depth. The vernier calipers are designed to measure both internal and external dimensions.  The lower jaws of a vernier scale are used for external measurement and the upper jaws for the measurement of internal dimensions. The rectangular rod carried by the movable jaw is used for the measurement of depth.

FIRM JOINT TYPE

CIVIL_ENGINEERING

They work on the friction created at the junction of the legs. The two legs are identical in shape with the contact points equally distant from the fulcrum and are joined together by a rivet. The component parts of the calipers should be free from seams, cracks and must have smooth bright finish. The distance between the rivet centre and the extreme working ends of the legs is known as nominal size and these calipers are available in the nominal size of 100, 150, 200 and 300 mm.

Firm joint calipers are of following types :

(i) Outside caliper
(ii) Inside caliper
(iii) Transfer caliper
(iv) Hermaphrodite caliper

Outside Firm Joint Caliper:
Figure  shows the diagram of an outside firm joint caliper. Unlike spring type outside calipers, it does not have any spring. The construction is quite simple with two identical legs held firmly by the fulcrum. If direct reading is desired, a steel rule must be used in conjunction with them.

Outside Firm Joint Caliper

Inside Firm Joint Caliper:
Inside firm joint calipers are almost similar to inside firm joint caliper with the exception that it does not have any spring to hold the legs as shown in  Figure Micrometers generally make adjustment in them. Like spring type inside calipers, they are also used for comparing or measuring hole diameters, distances between shoulders, or other parallel surfaces of any inside dimensions.

Inside Firm Joint Caliper

Transfer Caliper:
These are used for measuring recessed areas from which the legs of calipers can not be removed directly but must be collapsed after the dimension has
been measured. Therefore, an auxiliary arm is provided with two legs so that it can preserve the original setting after the legs are collapsed. The nut N in Figure is first locked and the caliper opened or closed against the work. The nut is then loosened and the leg is swung to clear the obstruction leaving the auxiliary arm in position. The leg can be moved back to the auxiliary leg, where it will show the size previously measured.

Transfer Caliper

Hermaphrodite Caliper
It is also known as odd leg caliper consisting of one divider and one caliper leg. It is used for layout work like scribing lines parallel to the edge of the work and for finding the centre of a cylindrical work. It can be with two types of legs, viz. notched leg or curved legs.

Hermaphrodite Caliper

MICROMETERS

CIVIL_ENGINEERING

Micrometer is one of the most widely used precision instruments. It is primarily used to measure external dimensions like diameters of shafts, thickness of parts etc. to an accuracy of 0.01 mm. The essential parts of the instruments shown in Figure consist of

(a) Frame
(b) Anvil and spindle
(c) Screwed spindle
(d) Graduated sleeve or barrel
(e) Thimble
(f) Ratchet or friction stop
(g) Spindle clamp

Micrometer

 

 

The frame is made of steel, malleable cast iron or light alloy. The anvil shall protrude from the frame for a distance of at least 3-mm in order to permit the attachment of measuring wire support. The spindle does the actual measuring and possesses the threads of 0.5 mm pitch. The barrel has datum and fixed graduations Thimble is tubular cover fastened with the spindle. The beveled edge of the spindle is divided into 50 equal parts, every fifth being numbered. The ratchet is a small extension to the thimble. It slips when the pressure on the screw exceeds a certain amount. It produces uniform reading and prevents damage or distortion of the instruments. The spindle clamp is used to lock the instrument at any desired setting.

Procedure for Reading in a Micrometer:
The graduation on the barrel is in two parts divided by a line along the axis of the barrel called the reference line. The graduation above the reference is graduated in 1 mm intervals. The first and every fifth are long and numbered 0, 5, 10, 15, etc. The lower graduations are marked in 1 mm intervals but each graduation shall be placed at the middle of the two successive upper graduations to be read 0.5 mm. The thimble advances a distance of 0.5 mm in one complete rotation. It is called the pitch of the micrometer. The thimble has a scale of 50 divisions around its circumference. Thus, one smallest division of the circular scale is equivalent to
longitudinal movement of 0.5  1/50 mm = 0.01mm. It is the least count of the micrometer.

 

The job is measured between the end of the spindle and the anvil that is fitted to the frame. When the micrometer is closed, the line marked zero on the thimble coincides with the line marked zero on the barrel. If the zero graduation does not coincide, the micrometer requires adjustment. To take a reading from the micrometer,  (1) the number of main divisions in millimeters above the reference line, (2) the number of sub-divisions below the reference line exceeding only the upper graduation, and (3) the number of divisions in the thimble have to be noted down. For example if a micrometer shows a reading of 8.78 mm when

 

 

 

 

The various important terms used in connection with micrometers are given below.

REMOTE SENSING AND GEOGRAPHIC INFORMATION SYSTEM

CIVIL_ENGINEERING

INTRODUCTION:

Now-a-days the field of Remote Sensing and  GIS has become exciting and glamorous with rapidly expanding opportunities.  Many organizations spend large amounts of money on these fields. Here the question arises why these fields are so important in recent years.  Two main reasons are there behind this. 

1) Now-a-days scientists, researchers, students, and even common people are showing great interest for better understanding of our environment.  By environment we mean the geographic space of their study area and the events that take place there.  In other words, we have come to realise that geographic space along with the data describing it, is part of our everyday world; almost every decision we take is influenced or dictated by some fact of geography.

2) Advancement in sophisticated space technology (which can provide large volume of spatial data), along with declining costs of computer hardware and software (which can handle these data) has made Remote Sensing and G.I.S. affordable to not only complex environmental / spatial situation but also affordable to an increasingly wider audience.

REMOTE SENSING:

Meaning:

Literally Remote Sensing means obtaining information about an object, area or phenomenonwithout coming in direct contact with it.  If we go by this meaning of Remote Sensing, then a number of things would be coming under Remote  Sensor, e.g. Seismographs, fathometer etc.   Without coming in direct contact with the focus of earthquake, seismograph can measure the intensity of earthquake.  Likewise without coming in contact with the ocean floor, fathometer can measure its depth. However, modern Remote Sensing means acquiring information about earth’s land and water surfaces by using reflected or emitted electromagnetic energy.

 

From the following definitions, we can have a better understanding about Remote Sensing: According to White (1977), Remote Sensing includes all methods of obtaining pictures or other forms of electromagnetic records of Earth’s surface from a distance, and the treatment and processing of the picture data… Remote Sensing  then in the widest sense is concerned with detecting and recording electromagnetic radiation from the target areas in the field of view of the sensor instrument.  This radiation may have originated directly from separate components of the target area, it may be solar energy reflected  from them; or it may be reflections of energy transmitted to the target area from the sensor itself.

According to American Society of Photogrammetry, Remote Sensing imagery is acquired with a sensor other than (or in addition to) a conventional camera through which a scene is recorded, such as electronic scanning, using radiations outside the normal visual range of the film and camera- microwave, radar, thermal, infra-red, ultraviolet, as well as multispectral, special techniques are applied to process and interpret remote sensing imagery for the purpose of producing conventional maps, thematic maps, resource surveys, etc.

 

in the fields of agriculture, archaeology, forestry, geography, geology and others.    According to the United Nations (95 th  Plenary meeting, 3 rd  December, 1986), Remote Sensing means sensing of earth’s surface from space by making use of the properties of electromagnetic wave emitted, reflected or diffracted by the sensed objects, for the purpose of improving natural resource management, land use and the protection of the environment.

 

According to James B.Campell (1996), Remote Sensing is the practice of deriving information about the earth’s land and water surfaces using images acquired from an overhead perspective, using electromagnetic radiation  in one or more regions of the electromagnetic spectrum, reflected or emitted from the earth’s surface.

So the stages of Remote Sensing include :  

 

•  A source of electromagnetic radiation or EMR (Sun)
• Transmission of energy from the source to the surface of the earth, through  atmosphere                    
•  Interaction of EMR with earth’s surface.
• Transmission of energy from surface to Remote Sensor mounted on a platform, through atmosphere
•  Detection of energy by the sensor.
• Transmission pf sensor data to ground station  

•   Processing and analysis of the sensor data  
•    Final data output for various types of application