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Friday, October 20, 2017

Types of bridge and bridge components

Bridges are generally made of various types and materials and an essential part of transportation.
Bridge: It is mainly a structure which is built to stretch physical obstacles without closing the original way underneath like a body of water, valley or road etc. to make a passage over the hurdle.
There are lots of different designs from which each of them can be served for a distinct purpose and can be applied in different situations. The designs of the bridges differ as per the function of the bridge, the nature of the soil where the bridge has constructed and anchored, the material used to make it and the available funds for it.
There are mainly 4 types of bridges such as, 1) Bridges by Structure, 2) Fixed or Movable Bridges, 3) Types by Use and 4) types of Materials.
Bridges by Structure:
1. Arch bridges: The bridges use arch as a main structural element and also made with one or more articulations depended on the kind of load and stress forces endured. Ex: - “Old Bridge” in Mostar, “Bosnia and Herzegovina” and the “Hell Gate Bridge” in New York.
2. Beam bridges: They are very basic type of bridges which are supported by many beams of various shapes and sizes like inclined or V shaped. Ex: - “Lake Pontchartrain Causeway” in Southern Louisiana.
3. Truss bridges: They mainly use diagonal mesh of posts above the bridge and two most common designs are the King posts and queen posts.
4. Cantilever bridges: They are like the arch bridges in appearance but support their load through the diagonal bracing than vertical bracing and often use truss formation both in the below and the above the bridge. Ex: - “Queensboro Bridge” in New York City.
5. Tied arch bridges: Same appearance of the arch bridges but transfer weight of the bride and traffic load on the upper chord that is connected at the bottom cords in bridge foundation and these types of bridges are often called bowstring arches or bridges.
6. Suspension bridges: These kinds of bridges generally use ropes or cables from the vertical suspender for holding the weight of bridge deck and traffic. Ex: - “Golden Gate Bridge” in San Francisco.
7. Cable-stayed bridges: They use deck cables which are straightly connected to one or more vertical columns as cables generally connected to columns in two ways- harp design and fan design.
Fixed or movable types of bridges:
1. Fixed: Most of the bridges in this world are fixed and have no movable parts for providing higher clearance for river or sea transportation which flows below them. These bridges are mainly designed for staying in one place till their demolishing.
2. Temporary bridges: These bridges are made of modular basic objects which can be moved by medium or light machinery and used in military engineering or in circumstances as in time of fixing or repairing.
3. Moveable bridges: Powered by electricity and have moveable decks also.
Video Source: Sami Ullah Stanikzai
Types by use:
1. Car traffic: They are usually very common and have two or more than two lanes which are designed for carrying car and truck traffic of various depths.
2. Pedestrian bridges: They are generally found in the urban environments where car transportation way is through the soils of rough mountains, forests etc.
3. Double-decked bridges: They are naturally built to maintain as better as the traffic movement can be flowed across bodies of water or rough land. They often have large amount of car lanes and sometimes have the dedicated areas for train tracks.
4. Train bridges: Especially made for carrying one or more than one lanes of train tracks.
5. Pipelines: They can carry water, air, gas and communication cables in the water or remote lands.
6. Viaducts: They are old-fashioned structures which are created for carrying water in the prosperous areas to dry cities.
7. Commercial bridges: Modern bridges are now built as a decoration to the commercial buildings like restaurants and shops.
Types by materials: Natural materials like wood, stone, concrete and steel and some other advanced materials.

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Rajib Dey


Wednesday, October 18, 2017

Various types of cofferdam

Coffer belongs to a trunk, casket or chest in which temporary structure is constructed to surround and cover an area that is prepared for excavating of the foundation of the construction. Cofferdams are applicable for structural foundation in Open Water & Open Land like bridge piers, docks, locks, dams and high ground water table.

A cofferdam is a wall with water resistance capacity that is constructed around the boundary of the projected excavation to resist the water flow into the excavation to keep the basement in dry condition.

Given below the lists of common types of coffer dams :

1) Earth Coffer Dams 2) Rockfill Coffer Dams 3) Single-Sheet Pile Coffer Dams 4) Double-wall sheet piling coffer dams 5) Braced Coffer Dams 6) cellular Coffer dams

Categories of cofferdam:

1) Earth Coffer Dams: Earth Coffer Dams are mainly built up in an area where the velocity of the current and depth of the water remains at 13 to 18 in and it is lifted 1 m over the water level. It is built up with a by amalgamating clay and sand. The Side Slopes of the bank on the water side should have been sloped with rubble Boulder to get rid of embankment from scouring. Once the coffer dam is finished, the water is pumped to wipe the interior surface. Sand bag can be utilized in an urgency.

2) Rockfill Coffer Dams: Rockfill coffer dams are constructed with rockfill. The site is often surrounded with dewatered. To safeguard against wave action, the crest and the upper portion of the impermeable membrane are supplied with rip rap. The slopes of rockfill cofferdam is built as steep as 1 horizontal to 1.5 vertical.

3) Single-Sheet Pile Coffer Dams: Single Sheet Coffer Dam is built in a very small area and it’s depth of water surpasses.5 to 6m. Initially First Guide Piles alias Timber Piles are inserted into the firm Ground that is underneath water bed. On the basis of the velocity of the Current in water, the Longitudinal runners spacing fluctuates and it is called as wales which are bolts to a timber piles at a requisite space.

Steel or Wooden Sheet is placed into the River Bed together with wales which are fastened to the wales through bolts. To make the walls stronger against the water pressure, the sheets on the two faces arc bolstered with trussed arrangement of struts and Half-filled bags of sand piled on the internal and the external faces of the sheets. Once the cofferdam is built up, the water in the surrounded area is poured out and the construction work starts.

Various types of cofferdam

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Rajib Dey

Tuesday, October 17, 2017

How to settle density of various masonry walls in buildings

On the basis of loads and other factors, the density of masonry walls in a building is designed. Given below the details of perfect thickness of masonry walls necessary at the design phase :-

As for instance, it is suggested to utilize invariable masonry wall thickness among lateral supports. The lateral support for masonry is arranged with cross walls, pilasters, and structural frame members.

Concerning deviation of masonry in vertical direction, the distance among floors, structural frames and roofs should be taken into consideration if the density of masonry wall is different.
Masonry wall thickness modifies among floor and roof as well as various floors that is generally imposed to attain thermal, sound and fire requirements.
If the density of masonry wall is modified, it is suggested to expand the thicker wall to the lower support level.
Building code requirements and specifications for masonry structure (ACI 530-11) affirms that, when the density of masonry wall is developed hollow masonry units is modified, then it is necessary to arrange a layer or various layers of solid masonry units or entirely grouted hollow masonry units among the thicker masonry wall and the thinner masonry wall.
The objective of arranging solid masonry course among thicker and thinner masonry wall should be transmitting loads perfectly from the above wall (thin wall) to the wall underneath (thick wall).
There are various constraints and limitations which should be taken into consideration for masonry walls apart from the case where the walls are designed for reinforcements on the basis of the engineering principles.
The constraint related to masonry thickness for various masonry walls types are explained in detail.
Thickness Requirements for Load Bearing Masonry Wall: The density of load bearing masonry wall should have been minimum 304.8 mm (1 ft.) dense for maximum wall height of 10.668m (35 ft.).
Besides, the density of masonry wall should be raised by 101.6 mm (4in.) for each consecutive 10.668m (35 ft.) height or fractions of this height calculated from the top of the masonry wall.
There are different cases in which the above conditions are not applicable for load bearing masonry walls which range from stiffened masonry wall, top storey masonry wall, residential masonry wall, masonry wall of penthouses and roof structures, plain concrete and grouted brick masonry wall, hollow masonry wall, faced masonry wall, nonbearing masonry wall.
How to settle density of various masonry walls in buildings

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Rajib Dey

Friday, October 13, 2017

Different types of concrete mixes

Nominal Mixes: Earlier, specifications for concrete are set the ratios of cement and fine course aggregates. This mixes of fixed cement & aggregate ratio makes sure sufficient strength in concrete and it is termed as nominal mixes.

The strength of the nominal concrete for a specified workability fluctuates significantly because of the difference of mix components. In this type of mix, all the ingredients are prearranged and their proportions are given.

Nominal mix contains volumetric batching. It is mainly utilized for comparatively insignificant and simpler concrete works. Nominal mix concrete generally utilized for concrete of M-20 or lower.

Standard Mixes: The nominal mixes of fixed cement-aggregate ratio (by volume) differentiate greatly in strength and may leads to under or over-rich mixes. Due to this the least compressive strength is contained in various specifications. These mixes are described as standard mixes.

As per IS 456-2000 standard, the concrete mixes are divided into several grades like M10, M15, M20, M25, M30, M35 and M40. Here M denotes the mix and number to the number to the stipulated 28 day cube strength of mix in N/mm2.

The mixes of grades M10, M15, M20 and M25 conform roughly to the mix proportions (1:3:6), (1:2:4), (1:1:5:3) and (1:1:2) correspondingly.

Design Mixes: In these types of mixes, a designer indicates the performance of the concrete but the ratios of mixes are defined by the producer of concrete irrespective of the minimum cement content is set.

It is the most appropriate method for choosing the mix ratios with certain materials which contain comparatively distinct characteristics.

This method facilitates the formation of concrete keeping the proper properties most inexpensively. But this type of mix does not ensure the exact mix ratios for the standard performance.

Different types of concrete mixes

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Rajib Dey

Thursday, October 12, 2017

About the Efflorescence on Brick masonry, its causes and treatment techniques

About Efflorescence on Brisk Masonry: It is often a white or a brown green or yellow powdery material which can be observed mainly in the winter season and it is produced from the mix of soluble salts and water.

The salt would drop on brick masonry and palpable itself as efflorescence when the water disappears and the color of the efflorescence is based on type of created salt. This efflorescence might vanish in summer but remains for the whole year.

Cause of Efflorescence on Brisk Masonry: There is a unique condition of occurring efflorescence and all the conditions should be met otherwise the brick masonry would suffer. There are three main three conditions offering the best conditions for efflorescence formation on brick masonry wall which are discussed here:
• The wall should be contained with soluble salts and that could be presented in masonry brick, mortar, adjacent soil and backing material.
• Water has to present in the brick masonry wall with the contact with soluble salt for the surface where water can be evaporated and left the salt.
• This wall will acquires pore structure for permitting the migration of soluble salt for dissolving it.
• And last of all, all the above conditions should be present for creation of efflorescence.

Factors affect the Efflorescence on Brisk Masonry:
• Temperature: An effect of high temperature falls on the efflorescence as it disappears water prior to reach the brick masonry surface.
• Water: Efflorescence is also frequent in water as water takes some time to reach the surface of the brick masonry.
• Wind
• Humidity

Sources of materials cause Efflorescence on Brisk Masonry:
• Soluble salt: There are a few sources for instance brick masonry, block masonry, mortar constituents like cement, sand, lime and admixture, grout components including cement, sand, aggregates and admixtures, contacting soil and ground water. The salts may be produced as the reactions between various constituents of brisk masonry walls and all soluble salts has the capability of producing efflorescence, like carbonates silicate, sulfate and chloride.
​• Moisture: The main source of it is the rain water especially which are wind driven and penetrate considerable water quality into the well.

Detrimental effects of Efflorescence on Brisk Masonry building: It generally damages the artistic value and the maintenance of the building. But it does not affect too much in the inner side of the building.

Control over Efflorescence on Brisk Masonry: The three conditions that are responsible for this should be controlled and proper action should be taken and as they are removal so can be washed to keep the bricks safe. But the thing is only removal and cleaning is not enough so it is required to seal the wall to avoid the problem permanently.

For more information follow

About the Efflorescence on Brick masonry, its causes and treatment techniques

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Rajib Dey

Wednesday, October 11, 2017

Illustration of stress-strain curve for concrete and steel

This construction video tutorial will teach you the detailed process for creating the design of stress-strain curve of concrete and steel by adhering to the IS 456:2000. Limit State Method is used here for these curves.

As the tensile strength of concrete as compared to compressive strength is very week, it can only withstand compressive stress. Alternatively, the tensile strength of steel is very strong and it can withstand both tensile and compressive strength.

While going to design a structure located in costal area and as per IS code the minimum grade of concrete for this structure should be M30 and concrete can’t be used below this grade. It is known that 30th characteristic strength of concrete cube of size 150 mm at 28 days. The characteristic strength is represented with the symbol as fck.
The stress-strain curve for hardened cement paste is nearly linear. The aggregate is more stiff as compared to the cement paste and will consequently deform less (i.e. contain a lower strain) under the similar applied stress.
The stress strain curve of concrete remains among those of the aggregate and the cement paste. But this alliance is non-linear over the most of the range. This non-linear behavior occurs because of formation of micro-cracks for the following reasons :-
(i) At the interface among aggregate particles and cement paste due to the differential movement among the two phases, and
(ii) Inside the cement paste itself.

These cracks are developed owing to variations in temperature and moisture and the application of load.
To learn the detailed process, watch the following video tutorial.

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Rajib Dey


Tuesday, October 10, 2017

Download spreadsheet to assess wind load on solar panels

With wind load on solar Panels Analysis Spreadsheet, it becomes easier for installing Solar Panels on any roof. By applying this spreadsheet, one can verify whether it is reasonable to compute necessary ballast weight / fixings forces / roof loads from wind operating on Solar Panels (also known as solar modules, photovoltaic modules, photovoltaic panels or PV modules). The design adheres to BRE Digest 489.

This spreadsheet is user-friendly. The spreadsheet allows several automatic calculations and with the pop-up UK & Ireland map, it is possible to define the wind pressures on projected solar panels with a single click of the mouse. So, a normal house owner gets the ability to utilize this spreadsheet for making calculation of required ballast weight.

The spreadsheets can deal with the following types of Solar Panels:
Photovoltaic modules with ballast: This type of modules is free from any fixings into prevailing roof structure and therefore, it is not to get through current roof membrane. It makes the process simple for post-installing Photovoltaic arrays. The spreadsheet computes ballast weight necessary to resist uplift, sliding and overturning.
Photovoltaic modules fixed to flat or pitched roof: Pitched roofs are mostly found in UK and Ireland. For utilizing them to support PV modules it is required to settle load bearing components directly inside the roof structure. In this situation, it is necessary to workout fixing forces retaining a PV module and thus loads on a supporting roof. These calculations can be made with this spreadsheet.
The spreadsheet contains the following exclusive features :-
- Completely user-friendly;
- A normal house owner can use this excel sheet without any engineering knowledge;
- A comprehensible and easy to read output (all on a single page);
- Includes three PV classes:
1) PV modules mounted on or above pitched roofs;
2) PV stands mounted on flat roofs - free standing (with ballast);
3) PV stands mounted on flat roofs - mechanically fixed;
- Pop-up window for easy selection of wind loads inside UK and Ireland;
- Automatically works out dynamic wind pressure on the basis of site location, building size etc;
- User may overwrite dynamic wind pressure 'qs' and modify size effect factor 'Ca' if it was computed in another software;
- Automatically measures pressure coefficients for different situations;
- Covers open and enclosed support structures;
- For ballasted PV modules, spreadsheet evaluates sliding, overturning and uplift;
- For fixed PV modules, spreadsheet provides forces for which fixings should be designed;
- Live diagrams;
- Instant summary of results;
- Design is made by adhering to BRE Digest 489: 2004
Click on the following link to download the spreadsheet
Download spreadsheet to assess wind load on solar panels

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Rajib Dey

Monday, October 9, 2017

Specification of M50 concrete mix design

Concrete mix design belongs to the method of determining the ratios of concrete mix in terms of proportions of cement, sand and coarse aggregates.

As for instance a concrete mix of proportions 1:2:4 signifies that cement, fine and coarse aggregate are in the ratio 1:2:4 or the mix comprises of one part of cement, two parts of fine aggregate and four parts of coarse aggregate.

The concrete mix design proportions are both by volume or by mass. The water-cement ratio is normally stated in mass.
The mix design M-50 grade (with Admixture –Sikament) presented here is for reference purpose only. Actual site conditions may fluctuate and consequently, this should be modified as per the location and other factors.
M50 Grade concrete is mostly suitably in heavily reinforced structures to withstand dynamic loading.
Given below the specifications of M50 Concrete Mix Design
Grade Designation = M-50
Type of cement = O.P.C-43 grade
Brand of cement = Vikram ( Grasim )
Admixture = Sika [Sikament 170 ( H ) ]
Fine Aggregate = Zone-II
Sp. Gravity
Cement = 3.15
Fine Aggregate = 2.61
Coarse Aggregate (20mm) = 2.65
Coarse Aggregate (10mm) = 2.66
Minimum Cement (As per contract) =400 kg / m3
Maximum water cement ratio (As per contract) = 0.45
Mix Calculation: –
1. Target Mean Strength = 50 + ( 5 X 1.65 ) = 58.25 Mpa
2. Selection of water cement ratio:-
Suppose water cement ratio = 0.35
3. Calculation of water: Estimated water content for 20mm max. Size of aggregate = 180 kg /m3 (As per Table No. 5 , IS : 10262 ). As plasticizer is projected, water content is decreased by 20%.
Water content is taken as 180 X 0.8 = 144 kg /m3
For more details, click on the following link
Specification of M50 concrete mix design

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Rajib Dey

Saturday, October 7, 2017

IRCON INTERNATIONAL LIMITED is hiring Civil Engineer, Site Supervisor(Civil)

IRCON INTERNATIONAL LIMITED that falls under a premier Schedule “A” infrastructure government company under the Ministry of Railways. The company is involved in developing the turnkey infrastructure projects in Railways, Highways, Buildings, Power sector, etc.
The Company has a turnover of over 3200 crores in the year 2016-17. The Company has accomplished differ types of railway and highway project with high value over the years in India as well as outside of India like Malaysia, Bangladesh,Algeria, Iraq, Jordan, Saudi Arabia, Indonesia, Turkey, Nepal, Sri Lanka etc.
The Company is seeking candidates for different positions in various disciplines (Civil, Mechanical etc.) on contract basis. Given below, the details of eligibility criterion :
Age relaxations as per Govt. of India guidelines can be obtained upon fulfillment of the necessary qualification, pay & experience criteria etc.
Medical Standards: The health condition of the candidates should be good and there is no color blindness. No relaxation is permissible in health standards.
Selection Process: The Work Engineers have to appear for written exam and/or interview.
The Site Supervisors have to appear for written test.
The above posts are intended for Specific Ircon’s Projects and not for the regular establishment of Ircon. The tenure of position will be initially for one year and it is further extended as per necessity of the Company if the services of the candidates remain satisfactory.
However, the appointment is co-terminus with the project and will not be granted any right to claim absorption in regular establishment of the company or for appointment in other projects of the company.
B-1 compensation for indoor treatment for self at the place of posting only would be allowable.
B-2 Minimum PF as approved under the EPF & MP Act 1952 will be subtracted from the salary and equivalent contribution will be done by Ircon. The perks will be disbursed at the time of termination of contract.
B-3 One leave for each calendar month of service is allowed throughout the contract period. Leave can be carried forward and accrued but no leave payment for un-availed leave is permissible throughout the contract or on resignation or termination of contract. No other type of leave would be allowable.
B-4 One weekly leave and other public holiday are granted if the project office remains closed.
B-5 TA/DA are allowed if assigned on outstation duty.
B-6 Working hours will be identical as for the project.
B-7 No other perks or benefits are provided except the above.
B-8 The ex-employees of Ircon, whose services were terminated because of shutdown of projects, are eligible to apply for these posts upon fulfillment of necessary qualifications and experience. A copy of the termination letter will be delivered along with the application. This appointment will be based on their satisfactory performance and shall be co-terminus with the project. The persons so appointed for this project can’t claim for their absorption in regular establishment of the Company or for appointment in other projects of the company.
To apply online, click on the following link
Civil Engineer, Site Supervisor - Civil

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Rajib Dey

Friday, October 6, 2017

Some useful tips to select an authentic subcontractor in your construction project

In a construction project there are specific areas where a contractor requires the assistance of an expert subcontractor. The objective of a general contractor is to handle the entire activities and performance among subcontractors.

A subcontractor can be shortlisted and selected on the basis of various points like past performances, financials and other important factors.

Given below, some valuable points based on which a perfect subcontractor can be selected for any construction project.
Before going to hire a subcontractor, it is necessary to assess the scope and project requirements perfectly. The service of a subcontractor is essential if the work remains beyond your expertise area or your resources are already settled to a diverse project for which it becomes difficult to accomplish the work with internal resources.
Prior to initiate the aptitude method, the general contractor should have to establish the size of the scope that is subcontracted out as well as the resources required to execute this work. It is vital to have clear idea on this part before implementation so as to get the proper bonding and insurance coverage for you and your subcontractor.
For lengthy subcontractor scope, it is required to undertake the steps like segregating the project into smaller parts or evaluating if it is the perfect project for your organization.
As soon as it is settled that it is appropriate for your organization, let's then proceed on to shortlist and choose the proper subcontractor.
Now if it is obligatory to hire a subcontractor with the purpose of supplementing your workforce, the general contractor should have to analyze the following areas:
• Safety
• Financials
• Staffing/Organigram
• Equipment
• Project Plan and Schedule
• Past Performances
• Comparable Projects
• Letter of Recommendation or References
• Project Cost and Payment Terms
A subcontractor should be capable of supplying this information as an answer to your RFP or throughout an RFQ process.
Safety performance is considered as one of the most crucial factors for a subcontractor at the time of qualifying. Ensure to evaluate the EMR rates, OSHA recordable, time loss owing to accidents/incidents. From a contractor point of view, you should assess who is their primary safety officer, its background, and credentials. As a contractor enquire of their safety plan and program and ensure to review it in order that it goes along with your safety expectations. Safety can also comprise of environmental response and methods upon emergencies and spills.
To gather more information on other crucial points, go through the following article
Some useful tips to select an authentic subcontractor in your construction project

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Rajib Dey

Wednesday, October 4, 2017

Soil mechanics and foundation engineering – An exclusive book for civil engineers

Dr. K. R. Arora, having 25 years of teaching experience, has written an exclusive book alias soil mechanics and foundation engineering. The book is available in PDF version.

The book is specifically designed for the undergraduate students as well as the students appearing for different competitive examinations and AMIE. A huge numbers of charts and tables are provided to make the text informative for practicing engineers.

Soil mechanics and foundation engineering (geotechnical engineering) is a part and parcel of civil engineering that witnesses a significant growth. The book is enriched with the most updated information in the field. The author has accumulated the material from different sources and demonstrated them in the form of a text.
The text is segregated into two parts. The first part sheds light on the basics of soil mechanics. The second part focuses on earth retaining structures and foundation engineering. The subject matter is explained in a rational and organized way.
The book comprises of the syllabi of undergraduate courses in soil mechanics and foundation engineering prescribed by most of Indian Universities and Institutes.
With the use of simple and coherent language, the author tries to narrate the basics for the students. Basic concepts have been emphasized throughout. The special emphasis is given on the complexities faced by the students. The book is supported with the extensive range of descriptive examples to present the application of the theory to field issues. Numerical problems, with answers, are provided for practice.
Some objective type questions are provided at the end of the each chapter.
The text is plentifully exemplified with diagrams and charts. Latest IS codes are abided by, as far as possible. References are provided at the end of each chapter. Both MKS and SI units are applied in this book.
Click on the following link to download the book Soil mechanics and foundation engineering
Soil mechanics and foundation engineering – An exclusive book for civil engineers
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Rajib Dey

Tuesday, October 3, 2017

Brief overview of rise and fall table in land surveying

This construction video tutorial is very useful for land surveyor. The tutorial sheds light on the rise and fall table in land surveying. Get some useful tricks to resolve the rise and fall table.
Rise and fall method is applied to resolve the levelling to detect the variation in elevation and elevation of points..
By resolving this table, it is possible to work out the reduced level of each point captured at staff rod with leveling machine. In order to work out the reduced level of an individual point, it is necessary to compute the rise and fall of points. After that, for reduced level, the following formula is applied :-
new R.L = old R.L – Fall
new R.L = old R.L + Rise
The table contains various heads like number, B.S (back sight), I.S (inter sight), F.S (fore sight), Rise, Fall, R.L (reduced level) and remarks.
B.S - Back sight (BS) is the abbreviation for "back sight reading". It means the first staff reading captured by the surveyor as soon as the levelling instrument is arranged and levelled. B.S is normally captured on the point of known reduced level as on the benchmark or a change point. The normally applied datum is mean sea level.
Fore sight (FS) is the abbreviation for "fore sight reading". It means the last staff reading captured prior to modify the instrument to the other position. It refers to the staff reading captured on point whose RL is to be ascertained. This sight is treated as negative and assumed from Height of Instrument to find out RL of the point.
Reduced Level (RL) in surveying stands for equating elevations of survey points relating to a common assumed datum. It refers to a vertical distance among survey point and selected datum plane. Therefore, it is taken as the base elevation that is applied as reference to consider heights or depths of other important places.
To get more detailed information, watch the following video tutorial.

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Rajib Dey