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Contracting

Read Full Article                          Contract

       

An agreement which is enforceable by law is a contract. It is an undertaking given by a person (not being a Govt. servant), Syndicate or firm, for the execution of any work or supply of materials or performance of any service in this connection.

https://bristolquakers.org.uk/drova/7549                           Contractor

    

This term is applied normally to a person (other than a Govt. servant), Syndicate or firm, giving an undertaking for the execution of any work or supply of materials or performance of any service in that connection.

http://thinkmaya.com/?biorer=rencontres-femmes-92&eaf=e3             Qualification of contractor

              

The following categories of contractors are generally enlisted with P.W.D:

1.For building and roads

2.For sanitary installations and water supply

3.For electrical, and Air conditioning

4.For furniture

Each of these categories of contractors should be competent enough to deal with the work entrusted to them and have an engineering organisation to do the work. For 2 and 3  of works, contractors should have valid licence to perform the work. Each contractor is expected to have the required equipment and machinery for the job. The qualification of contractors are further adjudged from (a) their financial resources (b) their professional ability to understand and implement the contractual obligation (c) their ability to control labour (d) the income tax clearance certificate.

After the Gujarat earthquake, Govt. has introduced a bill to change the qualification required for building contractor. If the contractor is an individual then he must have civil Engg. Degree and if it a firm, then they must have civil engineers with them.

partnersuche hofheim taunus                Essentials of contracts

The essential elements of a contract are:

  1. http://www.bicialpedrete.es/?okno=conocer-personas-por-internet&cff=6c Minimum two parties: Minimum of two parties are necessary to form a contract because one person cannot enter into a contract with himself. In order to form a contract, one party has to make an offer and the other must accept it. The person who makes the offer is called the ‘promisor’ and the person who accepts the offer is called the ‘promisee’.
  2. fb connectez vous Offer and acceptance: There must be an ‘offer’ and ‘acceptance’ to the offer in any contract. Both ‘offer’ and ‘acceptance’ should be lawful.
  3. investigate this site Competent parties: The parties to a contract must be competent i.e., they are of the age of majority, of sound mind and not disqualified form contracting by any law to which they are subjected.
  4. go right here Free consent: To form a valid contract, all parties should give their free consent. Consent means that the parties must agree upon the same thing in the same sense, consent should be free unless it is induced by undue influence, fraud, misrepresentation and mistake.
  5. Intention to create legal obligation: The parties must have the intention to create a legal obligation. In a commercial agreement, an intention to create legal relations is presumed, unless the parties have expressly agreed to otherwise.
  6. Lawful object: The object of an agreement is said to be lawful if it is not fraudulent or illegal or immoral or opposed to public policy and also it should not imply injury to the person or property of another.
  7. Not expressly declared void: An agreement expressly declared to be void under any law, is not enforceable and is, thus, not a contract.

            Different types of contract

Contracts are of the following types:

(A) Item rate contract, including

(1) percentage rate contract

(2) Schedule rate contract

(3) Labour rate basis

(4) Through rate basis

(B) Lumpsum contract

(C) Combination of both item rate and lumpsum contract.

     (A) Item rate contract

In this type of contractor, the contractors have to quote the rate of each item of the work without reference to any schedule of rates. This method is adopted when a reasonably complete schedule of rates is not available for the place where the work is to be carried out or when the number of non-schedule items in the work is more.

  1. Percentage rate contract

In this type of contract, the rates for various items are fixed by the department and the contractor agrees to do the works at a percentage above or below fixed rates. This method is adopted for works at places where a reasonable and complete schedule of rates is available.

  1. Schedule rate contract

In this type of contract, the work is allotted at fixed rates for different items and the payment depends upon the quantity and kind of work done or supply made.

  1. Labour rate basis

In some cases, the contractor quotes the labour rate at some percentage above or below the rates prevailing in the area for various items of works.

  1. Through rate basis

In some cases, the contractor quotes the rates for doing work some percentage above or below the through rates.

  1. Lumpsum contract

In this type of contract, the contractors have to quote a lumpsum figure for completing the work according to the given specification, drawings etc. This type of contracts is given only in exceptional cases. The contracts must include the necessary conditions to safeguard and protect the interest of the government.

  1. Combination of both

In this contract, a fixed sum is agreed upon for the completion of a particular work by the contractor. In case of any addition or alterations, the payment is made or deducted on the basis of a schedule of rates.

        Advantages and Disadvantages

                  Item rate contract

                       Advantages

  1. This form of contract ensures a more detailed analysis of cost by the contractor and is more scientific.
  2. The contractor is required to quote rates for individual items of work and hence it is not easy to form a ring during submission of tender and to allot a work to one of the contractors without competition.
  3. This form of contract helps in smooth progress and timely completion of a work because the unworkable rated tender may be avoided.

4  Intermediate payment to contractors for the completed item is easier.

                      Disadvantages

  1. In this type of contract, there is always a loophole for a contractor to correct a rate in order to be the lowest tenderer.
  2. This type of contract is not always advantageous when the quantities of certain items are to be increased or decreased. If by anticipation or by some other source a contractor comes to known the items whose quantities are likely to be increased may quote a high price for these items and similarly can quote low prices for items likely to be decreased. In that case, the department would stand to lose heavily due to unbalanced tender.
  3. Preparation to a comparative statement of this type of tender requires more time and through scrutiny required for this type of tenders.
  4. Chances of rejection of such type of tenders are more because of human error like overwriting and cutting and not doing the initial to their overwriting and cutting in the quoted rates of items by the contractor.
  5. It requires accurate measurements of all the items of work.

                   Lumpsum contract

                         Advantages

  1. The cost of the work is known before hand.
  2. Detailed measurements of the work done or not required except in case of any addition and alteration.
  3. Since there is difficulty in making intermediate payment to contractors in this type of contract, every contractor has a tendency to complete the work quickly, resulting in the early completion of work.
  4. Proper planning and efficient management for the execution of work are more convenient.

                      Disadvantages

  1. Making an intermediate payment to contractors is not so easy.
  2. Detailed drawing with full information and specification is essential to avoid any dispute.

                  Scheduled Contract

                        Advantages

  1. The materials stored in Government are utilised.
  2. Delay of work due to non-availability of materials in the open market is avoided. Thus better progress with standard quality of materials can be maintained.
  3. The increase in the cost of work is checked in spite of any rise in the price of materials in the market.

                     Disadvantages

  1. There may be a delay in the obtaining materials from the department stores resulting in the delay in completion of the work.
  2. A large storage area is required by the department to store the materials.
  3. Theft of materials from a store, shortage of material and damage of material are constant worries for a department.
  4. Reconciliation of material is essential in this type of contract.

         Book- Civil estimating & Costing, Writer- A.K. Upadhyay

Types of Flow

               Types of flow

Fluid flows are classified as:

  1. Steady and unsteady flow
  2. Uniform and non-uniform flow
  3. Laminar and turbulent flow
  4. Compressible and incompressible flow
  5. Rotational and irrotational flow
  6. Ideal and real flow
  7. One, two and three-dimensional flow

               Steady and unsteady flow

Steady flow is that type of flow in which fluid parameters (velocity, pressure, density etc.) at any point in the flow field do not change with time. This means that the fluid particles passing through a fixed point have the same flow parameters like velocity, pressure, surface tension etc. The parameters may be different at the different cross-section of the flow passage.

Mathematically, a steady flow is defined as

             

Unsteady flow is that type of flow in which fluid parameters (velocity, pressure, density etc.) at a point changes with time.

Mathematically, an unsteady flow is defined as

             

             Uniform and Non-uniform flow

Uniform flow is defined as that type of flow in which the velocity of flow of a fluid at any instant does not change with respect to space. In other words, it is the flow in which the velocity of flow remains constant throughout the flow field at any given time.

   

Mathematically, for uniform flow

             

where     ∂ Ʋ = change in velocity

                ∂ s = length of flow in a direction, s.

Non-uniform flow is defined as that type of flow in which the velocity of flow changes with respect to space at any given time.

In other words, it is the flow in which the velocity of flow is different for a different section in the path of flow.                                 

           

Mathematically, for non-uniform flow

               

              Laminar and Turbulent flow

Laminar flow is defined as that type of flow in which each fluid particle has a definite path and paths of individual particles do not cross each other.

         

Laminar flow is also called streamline or viscous flow. This type of flow occurs in smooth pipes having the low velocity of flow. It also occurs in liquids having high viscosity.

 Turbulent flow is defined as that type of flow in which each fluid particle does not have a definite path and the paths of individual particles cross each other.

In other words, it is the flow in which fluid particles move in a zigzag path.                      

       

When a fluid is flowing in a pipe, the type of flow is determined by a non-dimensional number, called Reynold’s number.

For laminar flow, Reynold number  ˂  2000

For turbulent flow, Reynold number  ˃ 4000

             Compressible and Incompressible flow

The flow in which the density of fluid changes, due to pressure and temperature variations, from point to point during the flow is called compressible flow.

In other words, it is the flow in which the density of a fluid is not constant during the flow.

Mathematically, for compressible flow

              P ≠  constant

The flow in which the density of fluid does not change during the flow is called incompressible flow.

In other words, it is the flow in which the density of a fluid is constant during the flow.

Mathematically, for incompressible flow

              P =  constant

Liquids are generally incompressible which means that pressure and temperature changes have a very little effect on their volume. Gases are compressible fluids.

           Rotational and Irrotational flow

 Rotational flow is that type of flow in which fluid particles also rotate about their own axes while flowing along a streamline.

         

 Irrotational flow is that type of flow in which fluid particles do not rotate about their own axes while flowing.             

           

              Ideal and Real flow

An ideal flow is the flow of a non-viscous fluid. In the ideal flow, no shear stress exists between two adjacent layers or between the fluid layer and boundary, only normal stresses can exist in ideal flows.

The flow of real (viscous) fluids is called real flow. In real flow, shear stress exists between to adjacent fluid layers. These stresses oppose the sliding of one layer over another.

         One, Two and Three-dimensional flow

 One dimensional flow is the flow in which parameters (velocity, pressure, density, viscosity and temperature) vary only in one direction and the flow is a function of only one co-ordinate Axis and time. The flow field is represented by streamlines which are straight and parallel.

Mathematically, for one-dimensional flow

              

Two-dimensional flow is the flow in which fluid parameters vary along two directions and the flow is the function of two rectangular space coordinates (x and y-axis) and time. The flow field is represented by streamlines which are curves.

Mathematically, for two-dimensional flow

             

 Three-dimensional flow is the flow in which flow parameters change in all the three directions and the flow is the functions of three mutually perpendicular co-ordinate Axis (x, y, z-axis) and time. The streamlines are space curves.

              

Mathematically, for three-dimensional flow

           

Book- Fluid Mechanics(Hydraulics), Writer- A.K. Upadhyay

Classification Of Channels

             Classification of channels

Channels can be classified as:

1.Prismatic channels and non-prismatic channels

2.Natural and Artificial channels

3.Rigid boundary and mobile boundary channel

                    Prismatic channel

A channel is said to be prismatic channel if the cross-section and bed slope does not change along the length of the channel.

Example: A laboratory flume laid at a constant bed slope and uniform cross-section.

               Non-Prismatic channel

  

A channel is said to be non-prismatic channel if there is a change in cross-section and bed slope along the length of the channel.

Example: A river with varying cross-section and bed slope.

                      Natural channel

Rivers and streams are natural channels. Natural channels have the irregular cross-section. So it is difficult to define the flow depth for natural channels.

                    Artificial channel

Human-made channels are called artificial channels. Irrigation Canals, sewage pipes, aqueducts etc. are examples of artificial channels. Artificial channels have regular cross-sections like triangular, trapezoidal, rectangular, circular etc.

               Rigid Boundary channel

A channel is said to be a rigid boundary channel if the material on the bed and sides of a channel is not easily movable.

Example: concrete lined canal, a metal flume.

             Mobile Boundary  channel

A channel is said to be a mobile boundary channel if the material on the bed and sides of a channel is loose and easily movable due to the flow of water. Analysis of mobile boundary channel is more complicated due to sediment erosion, deposition and resulting in additional resistance to flow.

Book- Fluid Mechanics(Hydraulics), Writer- A.K. Upadhyay

Road pavements- Flexible, Rigid, & Semi-rigid pavement

                    Road pavement

The part of the road which is finished with a hard smooth surface is known as a pavement. It helps in making them durable and able to withstand traffic.

                Types of road pavement

                (a) Flexible pavements

        

The pavements which have a very low flexural strength and are flexible in their structural behaviour under the wheel loads are called flexible pavements. Because of the low flexural strength, the pavement deforms if the sub-grade deforms, in flexible pavments the vertical load of traffic is transmitted to the lower layers by grain to grain transfer. A well compacted granular structure forms a good flexible pavement layer.

The load transferring ability of the flexible pavement depends on the type of material and thickness of payment. The pavement thickness is so designed that the stress on the sub-grade soil is kept within its bearing capacity and the sub-grade is prevented from excessive deformations. In flexible pavement the sub-grade plays an important role as it carries the vehicle load transmitted through the pavement. The strength and smoothness of the pavement depend to a great extent on the deformation suffered by the sub-grade.

All bituminous pavements, Water Bound Macadam (W.B.M), gravel pavements etc., are the example of flexible pavements.

                (b) Rigid pavements

        

Rigid pavements are those which possess a considerable flexural strength of flexural rigidity.

A Rijid payment derives its capacity to withstand loads from flexural strength. The rigid pavement has the slab action and is capable of transmitting the loads to a wider area. The Rigid pavment does not get deformed to the shape of the lower surface as it can bridge the minor variations of the lower layer.

Cement concrete pavement is the best example of the Rigid pavement.

                (c)  Semi-rigid pavement

Semi-rigid pavements represent an intermediate state between the Flexible and the Rigid pavement. The flexural strength of such type of pavment is much lower than the concrete slab, but it derives support by the lateral distribution of loads through the pavement depth as in flexible pavement.

Lean cement concrete, soil cement and lime-puzzolanic concrete construction are examples of semi-rigid pavements.

Book- Highway Engineering, Writer- A.K. Upadhyay

Weir, Barrage, Dam

                WEIR, BARRAGE AND DAM
                            Weir
An impervious barrier which is constructed across a river to raise the water level on the upstream side is known as Weir. Here the water level is raised up to the required height and the surplus water is allowed to flow over the Weir. Generally, it is constructed across an inundation river.
                            Barrage  
When adjustable gates are installed over a weir to maintain the water surface at different levels at different times, then it is known as Barrage. The water level is adjusted by operating the adjustable gates or shutters. The gates are placed at different tiers and these are operated by cables from the cabin. The gates are supported on the piers at both ends. The distance between pier to pier is known as Bay.
                            Dam  
The high impervious barrier constructed across a river valley to form a deep storage Reservoir is known as Dam. The surplus water is not allowed to flow over the dam, but it flows through the spillways provided at some designed level.

Book- Irrigation Engineering, Writer- N N Basak

Types of water demand

              Types of water demand

The following are the various types of water demand of a town or city:

              1.Domestic demand

               

The domestic demand includes the water required in the houses for drinking, cooking, bathing, washing of clothes and utensils, sanitary blocks, private vehicles, gardening, etc. The requirement of water for domestic animals is also included in this demand. In Indian towns or cities,  the domestic consumption of water under normal condition is taken as 135 lits/day/capita  ( as per I.S: 1172- 1971). In developed countries, the water demand is very high due to their advanced lifestyle.

               2.Commercial demand

   

It includes the water demand in commercial centres like the office building, hotels, restaurants, shopping centres, cinema houses, motor garages, laundries, diaries etc. For this purpose, the demand is assumed as 25 lits to 40 lits. capita/day.

               3.Industrial demand

The industrial demand for water depends on the type of industry in the area. The number and type of industries such as cloth mill, paper mill, cotton mill, sugar mill, chemical industry, hume pipe, rolling mill, etc. should be recorded. The water demand for this purpose is generally assumed as 20% to 25% of the total water demand of the city or town.

                  4.Public demand

                   

It includes the water requirement for public places such as public sanitary blocks, parks, swimming pools, etc. The water demand for this purpose is considered as 5% of the total consumption of water in the town or city.

                  5.Fire demand

In case of any outbreak of fire in busy areas of a town or city, sufficient quantity of water may not be available for fire-fighting from the surface sources such as Pounds, ditches, open wells etc. Again these sources may not exist within busy areas of the town or city. Hence, the requisite amount of water for fire-fighting should always be kept is stored in underground reservoirs in specific places and fire hydrants should be established in main pipelines at an interval of about 100 m to 150 m. In the event of a fire, the fire brigade pump is connected to the Fire hydrant and the jet of water is thrown under high pressure over the fire.

Book-Environmental Engineering, Writer-N N Basak

Historical development of roads in India

 HISTORICAL DEVELOPMENT OF ROADS IN INDIA

                 

The history of the development of road construction is linked with the history of human civilization. The first and oldest mode of travel was footpath with people found the most convenient and the shortest way to approach to their hunting and fishing ground. People use tamed animals for transport which required bridle paths of greater width and heights. After the invention of the wheel, animal-drawn carts continued to be the popular mode of transport for quite a long time. This had necessitated providing hard surfaces for wheeled carts. The first hard surface was discovered in Mesopotamia at about 3500 B.C. A brief review of road development in India is given below.

                 Roads in Ancient India

                 

The excavations of Mohenjodaro and Harappa have established the existence of roads in India at about 3500 B.C. As per the early records,  in early periods the roads were mainly for administrative and military purposes. During Aryan period in 400 B.C., there were “Mahapathas” as a means of communications as referred in Rig Veda ( part 1, para 5). Kautilya the first Prime Minister of Emperor Chandragupta Maurya laid down rules in his book titled  Arthasastra. Rules have been mentioned regarding the depth of roads for various purposes and for different types of traffic. The punishment for obstructing roads have also been mentioned. At the beginning of 5th century, the roads had been improved by Emperor Ashoka.

                 Roads in Mughal Period

                   

The roads were greatly improved in India during the Mughal period. Many of the highway built or maintained by Mughals received great appreciation from the foreign visitors. The road from Delhi to Daulatabad was constructed by Muhammad Tughlaq. The roads from Agra to Allahabad and from Ujjain to Bijapur were constructed by Muslim emperor.

                   Roads in British Period

                   

The period covering the decision the decline of the Mughals and the beginning of the British rule was a period of neglect of the road system. During this period,  the condition of roads deteriorated. The early British interest was only in maintaining roads of military importance. William Bentinck took steps to build the modern Grand Trunk Road from Calcutta to Delhi with permanent bridges and good stones. Lord Dalhousie gave further Momentum to road construction by forming the P.W.D in place the military board in 1885. With the development of Railways, the attention of the government was shifted from road development. The work of road construction and maintenance was given secondary importance. Major Roads,  except those of military importance, were neglected and attention was mainly on the feeder Roads.

                   Appointment of   Jayakar Committee

In 1927, the central government appointed Indian road development committee under the chairmanship of M.R. Jayakar to report on the condition of the existing road and to suggest ways and means for their future development. The Jayakar committee submitted its report on 1928 with the recommendations that since the provincial governments and the local bodies unable to look after all the roads, the road development in the country should be taken up by the central government.

Historical development of roads, Book-Highway Engineering, Writer-A.K. Upadhyay

Transportation, Highway, Waterway, Airway

                           Transportation
The term transport is derived from latin word Transportare that is trans over and portare means to carry thus transport means to carry from one place to another. the term transportation idicates a Means or system of convenience and it is thus an act of transporting. 

      It is difficult to imagine those all days when people lived in a distance and could not reach to their relatives easily. The introduction of transport facilities in the modern age has narrowed down the distance between various parts of the country or world.
                         Modes of transport
  1. Land transport 2. Water transport 3. Air transport

                              

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What is Hydrology & Hydrologic cycle

                                 Hydrology

 The science of studying the different forms of water available above the earth surface or below the earth surface is known as hydrology. Even Hydrology includes those portion of the  science which deals with the estimation of runoff and its transportation from one place to another.

                            Importance of Hydrology

 The study of Hydrology is useful for the design and operation of engineering projects for the  control and use of water. The knowledge of hydrology is very essential for the applications:

(a). Determination of the capacity of a reservoir from the rainfall records and the yearly discharge  observation of a river.

(b). Determination of peak flow of a river.

(c). Determination of suitable site for hydro-electric power generation.

(d). Sources of water supply in a town or city.

(e). Methods to be adopted for the flood control.

                                  Hydrologic cycle

                   

  The water from the surface sources like lakes, rivers, ocean, etc. converts to vapour by evaporation  due to solar heat. The vapour goes on accumulating continuously in the atmosphere. This vapour is  again condensed due to the sudden fall of temperature  and pressure. Thus clouds are formed.  These clouds again causes the precipitation (i.e Rainfall).Some of the vapour is converted to ice at  the peak of the mountains. The ice again melts in summer and flows as rivers to meat the sea or  ocean. These processes of evaporation, precipitation and melting of ice go on continuously like an  endless chain and thus a balance is maintained in the atmosphere. This phenomenon is known as                  Hydrologic cycle.

                   Component of Hydrologic cycle

     1 . Evaporation

     2 . Transpiration by plant

     3 . Condensation

     4 . Precipitation

     5 . Interception

  1. Infiltration

     7 . Ground water flow

     8 . Surface flow

 Hydrology & Hydrologic cycle – Book Irrigation Engineering,   Writer – N N Basak