Common thumb rules for civil engineering works

 Thumb Rules is very important for any civil engineer, Site engineer or civil supervisor to obtain instant decisions on the construction site. By applying thumb, the engineers can get the solution with a simple mathematical formula and take proper decisions wherever required. Before applying these thumb rules, it should be kept in mind that the thumb rule can only provide fairly accurate results never the correct results.

The following types of thumb rules for civil engineers are commonly used in construction work :-

Thumb rule for measuring the Concrete Volume relating to the area:
The volume of concrete necessary = 0.038 m3/square feet area.

As for instance, if Plan Area = 40 x 20 = 800 Sq. m., total necessary volume of concrete will be as follow :-
= 800 x 0.038m3 = 30.4m3

Thumb rule for Steel quantity necessary for Slab, Beams, Footings & Columns:
Essential quantity of steel in residential buildings = 4.5 Kgs – 4.75 Kgs / Sq. Ft.
Essential quantity of steel in commercial buildings = 5.0 Kgs-5.50 Kgs/Sq. Ft.

Thumb Rules For Civil Engineers recommended by B N Datta for the Steel quantity that will be applied for several members of the building :-

Proportions of Steel in Structural Members:

1) Slab – 1% of the total volume of concrete
2) Beam – 2% of the total volume of concrete
3) Column – 2.5% of total volume of concrete
4) Footings – 0.8% of the total volume of concrete

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Published By
Rajib Dey
www.constructioncost.co
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Basics of Cement Concrete for beginners

 Numerous individuals imagine that cement and concrete are a similar item – they are definitely not. Cement is a dry powdered synthetic that, when blended in with water, gradually responds to shape another hard, strong compound. Then again, concrete is a blend of cement mixed with water and different sizes of aggregates. The cement and water structure a glue that sticks the aggregates together when it solidifies.

Concrete, in its newly blended state, is a plastic serviceable blend that can be framed into practically any alluring shape. It starts to gradually harden when blended, yet stays plastic and serviceable for a few hours. This is a long enough period to permit it to be put and wrapped up. After it takes its underlying set, it keeps on picking up quality for a considerable length of time and some of the time years if dampness keeps on being available.

Concrete has two parts; aggregate and glue. Aggregates for the most part are of two sizes; fine and coarse. Fine aggregates are those with molecule sizes littler than about 5mm, generally known as sand, which can be common or fabricated. Coarse aggregates are those with molecule sizes more prominent than about 5mm. Rock, squashed stone and impact heater slag are among the most regularly utilized coarse aggregates.

Glue is made out of cement, fly ash, water and now and then entrained air. The cementing property of the glue results from a synthetic response between the cement and water. This response is called hydration. It is a response that requires time and good states of temperature and dampness.

Curing is the giving of great temperature and dampness conditions over some undefined time frame sufficiently long to permit the hydration procedure to move toward culmination. With appropriate curing, hydration happens quickly from the outset, and afterward diminishes gradually for quite a while. This permits the concrete to grow great quality and strength. Keep in mind, concrete needs proceeded with dampness to solidify appropriately. It ought not dry out excessively fast.

The compressive quality of concrete, estimated by how much power is required to squash it, is significant in the plan of structures. In asphalts and different sections on ground, the structure is normally founded on flexural quality, (i.e; how much power the concrete can withstand in twisting before it breaks). In either case, the chief variables influencing quality are the water-cement proportion and the degree to which hydration has advanced.

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Published By
Rajib Dey
www.constructioncost.co
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The role of Site Engineer & Project Engineer in a construction project

 Site engineers and project engineers frequently work in tandem on a job performing various things. Both play important role for major projects with equally significant liabilities.

Comparing Site Engineers to Project Engineers: Both the site engineers and project engineers take diverse liabilities for accomplishment for different types of construction projects.

Site engineers have sound technical skills which can be applied for specific engineering aspects of the project. Project engineers supervise the general operation of the project. They acquire the resource orders, deal with clients, and coordinate with designers and other engineers.

Given below, the basis differences among site engineers and project engineers :-

Liabilities of Site Engineers vs. Project Engineers

Site engineers perform according to a designer's plans, engineer's specifications and city codes to execute their jobs. Conversely, the project engineers perform very intimately with management and planners in an consultative manner to produce blueprints that fulfill the objectives of the clients as well as city and state codes.

Site Engineers: The site engineers may possess an office somewhere, but in several occasions they are active at the job site ensuring specific jobs are accomplished perfectly and with adherence to code.

These engineers examine that a building's wiring is completed properly, the plumbing will not leak, or the walls will not fall. They also have to rationalize modifications to orders, redrawing alternate plans and settling technical problems instantly and within the budget.

Given below, the liabilities of a site engineer:

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Rajib Dey
www.constructioncost.co
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Some useful tips to examine concrete formwork in job site

 The finalized inspection of concrete formwork should be examined prior to set the reinforcement bars in exact location. By implementing perfect form work, honey combing, blow holes, grout less or discoloration of concrete can be circumvented and consequently the finished surface of concrete becomes superior.

Prior to commencement of concreting work, shuttering surface should be fully cleansed and does not contain any defect/deposits in order to provide rightly straight smooth concrete surface. Shuttering surface does not contain any damage and unnecessary roughness to its surface.

While building concrete form work, the following should be examined properly.

1. Any member to be retained in position once the general dismantling is completed, should be labeled perfectly.
2. The applicable materials should be thoroughly examined in order that no incorrect items/rejects are utilized.
3. When excavations exist nearby reformatory and strengthening action should be undertaken to impact the safety of form work.
4. The quality of bearing soil should be strong and it should be arranged properly and the sole plates should bear well on the ground. Sole plates should be perfectly placed on their bearing pads or sleepers. The bearing plates of steel props should not be deformed. There should be adequate bearing areas for the steel sections on the bearing members.

5. There should be proper safety provisions to get rid of impact of traffic, scour caused by water and accidental impacts.
6. To maintain proper strength and durability of form work at intermediate stage, bracing, struts and ties should be provided together with the advancement of form work. Avoid ‘Tilting and overturning of steel sections.
7. While applying customizable steel props, no damage and evident bents should be observed; steel pins should be arranged, restricted latterly near each end.
8. Screw adjustments of adaptable props should not be over extended.

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www.constructioncost.co
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Some useful tips to work out the length of the bent bars

 While fabricating reinforcing bars with bends, the straight bar is primarily cut to a length that is under the sum of the specified dimensions of the bent bar.

The variation among the detailed length and the cut length belongs to the “bend curvature deduction” and called as various names like gain, creep, and gyp. Usually, the fabricators and programmers get the bend curvature deduction from a bend deduction table.

In the following table 1, the deductions for 45- and 90-degree bends of common bar sizes are provided.

Figure 1 illustrates a No. 8 (No. 25) bar with a standard hook and sides estimating 1 ft 4 in. and 4 ft (400 and 1220 mm). The detailed length of this bar is obtained by summing up the two sides, or 5 ft 4 in. (1620 mm). From Table 1, the deduction for a 90-degree bend on a No. 8 (No. 25) bar is 2-1/2 in. (65 mm). So, in such a case, the cut length of the bar should be 5 ft 1-1/2 in. (1555 mm).

The usual standard for working out the cut length of a bar is along the actual centerline of the bar, that is equivalent to the neutral axis of the bar cross section before bending. The cut length of a bent bar is less than the sum of the finished dimensions due to the following reasons :-

with a easy-to-follow mathematical calculation.

If the exterior fibers of the bar are elongated easily, the inner fibers of the bar are constrained by friction against the bending mandrel, so, the neutral axis shifts inward approaching the mandrel. It is critical to measure this component. The inconsistency arises from computing the lengths on the basis of the actual centerline is not very important.

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Rajib Dey
www.constructioncost.co
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What are the maximum bearing capacity of various types of soil

 In this construction video tutorial, one will be familiar with how to determine maximum bearing capacity of various types of soil.

Safe Bearing Capacity of Soils is defined as the maximum strength of loading that the soil will bear securely devoid of the risk associated with shear failure.

The bearing capacity of soil refers to the maximum average contact pressure among the foundation and the soil which should not lead to shear failure in the soil.

In the jobsite you will be provided with drawings along with soil investigation report. From soil investigation report, you can get various information about the soil upon which the building will be constructed like number of fillings in the soil, the bearing capacity of soil, bearing pressure of soil to undergo.

There may be some errors in the report or higher value for bearing capacity.

In this video, you will learn how to find out maximum bearing capacity of soil and tally this figure with the soil test report to check for any discrepancy.

In the video, there are two heads like soil type and safe bearing capacity of soil. In soil type, there are different types of soil like combination of soft, wet and muddy clay, fine/loose or dry sand, soft clay, black cotton soil, moist or sand clay mix, loose gravels, compacted gravels, soft rock, sand or lime stone, hard rock/granite/trap etc. For each type of soil, the maximum safe bearing capacity is provided.

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Rajib Dey
www.constructioncost.co
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How to Test the Consistency of Cement

 Definition: The standard consistency of cement paste is the level of water required, where the plunger infiltrates into the cement paste of about 5mm to 7mm from the base of the shape and in the other word consistency of cement is the base measure of water required to start a synthetic response among water and cement to frame a paste.

A Minimum quantity of water required to initiate the chemical reaction between water and cement to form a paste is known as consistency of cement. The cement consistency which will allow the Vicat plunger to penetrate to 5-7 mm point from the bottom of Vicat mould is known as standard consistency. For reference purposes, the standard consistency of a Portland cement fluctuates between 25–35%.

Significance: We as a whole realize that the strength of concrete relies upon the quality Cement. To get the necessary cement strength, we need to include the perfect measure of water. Water underneath standard security won't start the concoction response among water and cement, which will build the strength of cement.

Water less than the standard consistency would not initiate the chemical reaction between water and cement resulting in the strength of cement. Water more than the consistency results in excess water and strength reduction. That’s why it is important to know the standard consistency of cement material. On the other hand, overabundance of water over steadiness brings about abundance moisture and loss of strength. In this manner it is essential to know the standard consistency of cement.

Different tests on cement:

1. Fineness test of Cement by dry sieving method with 90 micron strainer
2. Adequacy test of cement by Le Chatelier

Reasons for the Test: We know that the cement we used on our site is mostly affected by the following

1. Weather Conditions.
2. Excessive combination of Silica. One of the cement ingredients which determines the initial and final setting time of cement paste.
3. The fineness of cement.
4. Manufacturing Defects.

By Standardising the consistency of cement, we know how much water is required to produce an effective cement which will eventually produce good quality concrete. Standard Consistency of an ordinary Portland cement varies between 25-35%. That means we need 25% of water in volume to make a standard consistency of cement.

For Example, If we need to calculate the amount of water required for a 200 g of cement which has 30% consistency means then we need 200*30% = 60g water to prepare a standard consistency. This is what we are going to find in this test.

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www.constructioncost.co
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Standard 2BHK Flat RCC Design And Calculation

 Today, let us design an average plan of a general 2BHK apartment. What's more, we should just take dead and live loads. Include wind loads and seismic loads as indicated by zone in the wake of rehearsing with dead and live load.

The thought is basic – Slab lays on beams. Beams lay on columns and Columns lay on footings. So design slab first, at that point utilize the load from load to design beams. Beams will put load on columns. Also, columns on footings.

Essentials:

Architectural drawing
IS codes – 456, 875 (I and II)
Soil report
Logical mini-computer (A scientific calculator will suffice)
MS Excel – for quicker counts. Many design workplaces use Excel format sheets. Try not to consider them to be designing programming. They are only for quicker computations and limit blunders.

We should begin the RCC design and calculations now.

Design Plan:

1. Imprint columns.
2. Join columns to check essential beams. There will be tertiary beams laying on essential beams.
3. Imprint all beams. Number them.
4. Presently mark slabs. Slabs with comparative measurements will be denoted the equivalent.
5. Design slabs. Use loads from IS:875 section 2, call it 'w'. Discover the depth and territory of steel. We'll do enumerating later.
6. Presently beams will be determined each separately. To begin with, how about we figure for tertiary beams, i.e beams laying on different beams. Accept, the depth and width of all beams are 500 mm and 300 mm individually. Draw power dia for each beam.

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Some vital tips for the selection of proper foundation types

In order to maintain the longevity of a building, the most vital step is to explore foundation types and select the most suitable foundation for your building project.

FOUNDATION TYPES FROM THE GROUND UP: As per the Soil Mechanics in Engineering Practice, a foundation means the lower segment of a building structure that transmits its gravity loads to the earth. This foundation is selected based on the following factors -

1. Ground/soil conditions
2. Types of loads from the building structure

GROUND/SOIL CONDITIONS - Soil investigation is performed for the following purposes :

• Nature and type of soil
• Depth of various layers of soil
• Bearing strength of the soil at different levels
• Level/slope of the ground

As for instance, when the soil adjacent to the surface does not have the capacity to sustain the structural loads, hard strata (soil layer with adequate load bearing strength) should be selected and most often deeper foundations are essential. Otherwise, with the existence of homogeneous stable ground, a shallow foundation is suitable.

LOAD TYPES FROM BUILDINGS: Loading conditions severely impact the selection of foundation types which are based on the type of building for your project, location/ecological factors and the type of structural construction materials effective for your project. The following factors are mainly responsible for raising loads and constructing deeper foundations:

• High-rise/multi-story buildings
• Susceptibility to strong winds or earthquake zones
• Reinforced concrete buildings

PUT THE PIECES TOGETHER: As soon as the soils are examined and loads types are established for the building project, then put the pieces together and opt for the best foundation type for the project. These main foundation types comprise of the following :-

• Spread/wall footings.
• This type of foundation is applicable where the base is broader as compared to a normal load bearing wall.
• The broader base allocates the weight from the building structure across a larger surface area and enhances the longevity of the building.
• Drilled pier/deep foundation.

• This type of deep foundation is useful for transmitting greater loads from the building structure to hard rock strata.
• This type of foundation can minimize the amount of ground disturbance whereas provides protection against earthquakes and wind forces. It is also suitable where highly expansive soils exist near surface.
• Post-tensioned slab foundation.
• This type of foundation extends over the entire area of the building to sustain loads from columns and walls.
• It can be utilized on expansive soils.

Source: http://constructioncost.co/

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