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Explanation: 

Tender: It refers to an invitation to bid for a project. It is offered in writing to execute the work as specified by the owner. Tendering usually refers to the process whereby governments and financial institutions invite bids for large projects that must be submitted within a finite deadline.

Schedule of rates: It is the list of rates of various items. It is a document containing a detailed description of all the items of work (but their quantities are not mentioned) together with their current rates.

Analysis of rates: In order to determine the rate of a particular item, the factors affecting the rate of that item are studied carefully and then a rate is decided for that item. This process of fixing the rate of an item is termed an analysis of rates or rate analysis.

Abstract Estimate: An abstract estimate is prepared in order to enable the authority competent to give administrative approval to the expenditure.

No detailed knowledge is required to prepare abstract estimates or approximate estimates.

Explanation:

The different forms of joints are as follows:

Single riveted lap joint: In this, the plates to be joined are overlapped at the ends and a single row of rivets is placed in the middle of the lap

Double riveted lap joint: This type of joint will have two rows of rivets. The overlap is large enough to accommodate two rows of rivets

Single strap butt joint: A separate piece of metal called STRAP is used to hold the edges of the components together; This joint is also used for joining the edges of components together

Double strap butt joint: Double straps are used for riveted butt joints

Further the joint may be either chain or staggered depending upon the bolt/rivet pattern.

Explanation:

Explanation: 

Guniting: 

• It is a process of applying mortar or concrete under pressure with a cement gun, resulting in highly strong concrete. It is also used to restore concrete that has been damaged by fire, earthquakes, or chemicals.

Prestressing: 

• It is the introduction of a compressive force to the concrete to counteract the tensile stresses that will result from an applied load. Prestressing is done by the following methods:

1. ​Pre-tensioning
2. Post-tensioning

​Screeding:

• Screeding is the process of flattening the poured concrete surface into a smooth and flat layer prior to finishing the surface.
• Screeding is only the first step in finishing concrete, and it is not intended to produce a completely smooth final surface.

Concept:

Bulking of sand:

The increase in moisture of sand increases the volume of sand. The reason is that moisture causes film of water around sand particles which results in the increase of volume of sand. For a moisture content percentage of 5 to 8 there will be an increase in volume up to 20 to 40 percent depending upon sand. If the sand is finer there will be more increase in volume. This is known as bulking of sand.

The important facts in connection with the bulking of sand are as follows:

(1) When moisture content is increased by adding more water, the sand particles pack near each other and the amount of bulking of sand is decreased. Thus the dry sand and the sand completely flooded with water have practically the same volume. (2) The coarse aggregate is little affected by the moisture content. (3) One of the reasons of adopting proportioning by weight is the bulking of sand as proportioning by weight avoids the difficulty due to the bulking of sand. (4) The bulking of sand should be taken into account when volumetric proportioning of the aggregates is adopted. Otherwise, less quantity of concrete per bag of cement will be produced, which naturally will increase the cost of concrete. Also, there will be less quantity of line aggregate in the concrete mix which may make the concrete difficult to place.

Honey combing, segregation and bleeding are the defects occur in concrete.

Explanation: 

Ballast:

• Ballast is a granular material made up of broken stone or brick or kankar/gravel etc. which is placed below the sleeper and is used to transmit the load from the sleeper to the subgrade.
• Type of Ballast:

1. Broken stone ballast
2. Gravel Ballast
3. Sand Ballast
4. Brick Ballast
5. Blast Furnace Slag Ballast

• Broken stone is the best material for the ballast. Igneous rocks such as granite, quartz, etc. are used for broken stones. The size of broken stones varies from 1.9 cm to 5.08 cm.
• The functions of ballast are:

1. Load transfer
2. To provide Drainage
3. To Impart elasticity to the track.
4. To Impart longitudinal and lateral stability to the sleeper.
5. To absorb shock and vibration.

Explanation:

Filtration is the process in which fine suspended particles and flocs are removed from the water. It also removes organic matter and dissolved solids from water. Filtration is carried out in units termed filters.

Type of Filters: 1. Gravity Filter 2. Pressure Filter

1. Gravity Filter: 

• Gravity filters are those in which the head required to flow water through filter media is provided by the height of water above the filter media itself.

Gravity filters further classified into

1. Slow Sand Filter
2. Rapid Sand Filter

(A) Slow Sand Filter: (SSF)

• It utilizes water from a source or plain sedimentation tank, as in coagulation-aided sedimentation, effluent leads to frequent choking of filler media and requires frequent cleaning which increases operational cost.
• A gravel layer is provided at the bottom to support the sand medium.
• The depth of tank is 2.5 m to 3.5 m
• Fine sand is used as filter media.
• Effective size of grain (D₁₀) = 0.2 - 0.3 mm
• Coefficient of uniformity (C_u) = 1.8 - 2.5/3
• Bacteria removal efficiency is 98 - 99%

(B) Rapid Sand Filter: (RSF)

• The working of RSF is the same as SSF.
• As the size of filter media is comparatively bigger than SSF and filter media is poorly graded, impurities are able to penetrate in the lower part of filter media.
• Hence surface cleaning is not sufficient thus Back Washing is done.
• Effective size of grain (D10) = 0.35 - 0.55 mm
• Coefficient of uniformity (Cu) = 1.3 - 1.7
• Bacteria removal efficiency is 80 - 90%

2. Pressure Filter: 

• Gravity filters are those in which the head required to flow water through filter media is provided by the external application of pressure
• These are less efficient than RSF.

Concept:

Velocity/ Speed:

• The rate of change of displacement/distance of a body is called the velocity/speed of that body.
• Velocity is a vector quantity that has both magnitudes as well as direction.

Acceleration:

• The rate of change of velocity is called the acceleration of the body.
• Acceleration is also a vector quantity.
• The slope of any velocity-time graph gives an acceleration of the body.

Displacement:

• The minimum path length between two points is called displacement.

Distance:

• The total path length between two points is called distance.

Concept:

Slack time 

• It is the amount of time a task can be delayed before the project finish date is delayed. Thus, the slack is the difference between event times denoting the range within which an event time can vary.
• The Earliest Expected Time (TE) is the time when an event can be expected to occur earlier.
• The Latest allowable occurrence time (TE)is the latest time by which an event must occur to keep the project on schedule (without delaying the project).
• Event slack is defined as the difference between the latest event and the earliest event times. i.e. Slack = TL - TE
• Slack is defined as the difference between the latest occurrence time and earliest occurrence time.
• It is also given by the difference between the Latest allowable time and the earliest completion time.

Important Points

Positive slack: When TL > TE. It indicates the project is ahead of schedule meaning thereby the excess resources.

Zero slack: When TL = TE. It indicates that the project is going on schedule meaning thereby adequate resources.

Negative slack: When TL < TE. It indicates the project is behind schedule meaning thereby the lack of resources.

Concept:

• Network models can be used as an aid in scheduling large complex projects that consist of many activities.
• If the duration of each activity is known with certainty, then the Critical Path Method (CPM) can be used to determine the length of time required to complete a project.
• If the duration of the activities is not known with certainty, the Program Evaluation and Review Technique (PERT) can be used to estimate the probability that the project will be completed by a given deadline.

Difference between PERT and CPM (Critical Path Method)