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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Arka Roy


How to find out the required amount of concrete for construction work

To find out the exact quantities of concrete for a construction project is very crucial. Given below, some useful tips for computing the quantities of concrete mix for any construction project.

How to work out the amount of concrete necessary for Slabs(along with odd shapes)

Rule of thumb: Include 1/4″ to the density of your slab for your slab concrete budget. It supposes that the job is uniformly graded to the exact depth, and the grade is properly compacted.

While examining your grade, if it is found that one spot is 4″ and other spots are 4.5″ to 5″ then it is recommended ion to settle the grade for both the job quality and your concrete budget.

Odd shapes: Convert odd shapes into rectangles and odd shapes can be located easily.

Build driveway 14′ x 20′ and your estimate will be perfect. It will be done in this way – The driveway is 16′ at the top and 12′ at the bottom. Throughout the center the width averages 14′.

Working out the Amount of Concrete Essential For Footings

Footings will seldom pursue the drawing accurately. In the soil where there are lots of gravels, the footings may fall down if big rocks are excavated.

It is assumed as a 12″*12″ footing, but check how the left side of the footing has fallen down. Compute the exact width.

The digging is too deep by the excavator, or there may be raining and the digging for footings should be deeper to get to solid soil. Therefore, it is vatal to examine different types of spots on your footing and obtain an average size. Then with the help of a calculator, works out the required amount of concrete.

House slabs on grade that are 8″ out of grade containing a 4″ slab also arranged some of the footing over the grade too.

This 12″ x 12″ footing should be computed as 12″ x 16″ so the footing is built to go over grade to attain the 4″ slab thickness.

To make calculation online, click on the following link

How to find out the required amount of concrete for construction work

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How to choose pile foundation on the basis of cost versus other foundations for construction project

Get detailed information on how to choose the pile foundations on the basis of cost vs. other foundations for construction projects and factors which impact the cost of pile foundation.

Sometimes, it becomes difficult for structural designer to take stable decision to select types of foundations like pile foundation or ordinary strip or mat foundation to be used for the structure.

The problem becomes acute while going to choose among pile foundation and traditional mat or strip foundation developed in a deeper level to fit a soil layer having desirable bearing strength.

There should be an indicator for all construction conditions under which the use of pile foundation is considered as inexpensive with reference to traditional strip and mat foundations.

This article will focus on the variations through which the decision for choosing of pile foundation over other foundation types can be taken without difficulty. This condition line is formed on the reasonably detailed cost appraisal of the foundation. The foundation cost is impacted by the following factors :-

Factors impacting the cost of Pile Foundation

Evidently, final decision for employing the type of foundation, cannot be taken on the basis of the calculation of excavation volume and concrete quantity of deep mat or strip foundation with regard to cost of piles that support the same load.

A cap is needed for Pile foundation. The density of the cap should be approx 45cm for two piles and 60cm to 120cm for two pair of piles. Plan dimensions of piling cap should be up to 2100mm2 for pile having diameter of 550mm.

With tie beams provided over one direction, the Pile caps are joined together using tie beams in more than one direction.

It is found that, the excavation cost of pile cap along with capping beams and tie beams is two times the cost of machine excavation in moderately large column bases. With the advancement of construction, the perfect structural design as well as stringent supervision is required for pile foundation.

To get more details, click on the following link

How to choose pile foundation on the basis of cost versus other foundations for construction project

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Arka Roy

Curtain Wall Design Tips For Water Penetration & Condensation

Designing curtain walls to water penetration brings huge benefits for maintaining the security, thermal performance and comfort of the structure and residents.

The rain caused by wind and condensation create huge issue and it becomes complicated to handle when curtain wall is designed together with gravity, kinetic energy, capillary action and surface tension and the chances are enhanced for water ingression.

Get the detailed information on the design of curtain wall against the infiltration of water and condensation.

Design of Curtain wall for Water Infiltration and Condensation

  • Wind driven rain and the possibility of water ingression
    • Design of curtain wall to control water penetration
    • Design of curtain walls to control condensation

Wind driven rain and possibility of water ingression

There are five different types of forces such as that contribute either partially or as a whole to the ingression of water may occur due to existence of five various types of forces like gravity, kinetic energy, capillary action, surface tension and air pressure difference.

The curtain wall is capable of resisting forces that enhances the chance of water penetration. It is dependent on glazing details, drainage details, frame construction, weather stripping and frame gaskets, perimeter flashings and sealings and interior sealants.

Wind loads create differentials pressure that may cause windblown rain. It exceeds gravity force and as a result forces water to stir ascending.

Surface tension properties and capillary effect of curtain wall elements are significantly impacted with thermal expansion of various building materials.

As for example, expansion or contraction of materials because of temperatures may tight expansion joints extremely and ultimately raise capillary action among different components of the curtain wall.

The surface tension properties of curtain wall may fluctuate because of contraction and expansion and bring about unwanted results. So, it is necessary to design movable joints, seals and gaskets to accommodate differential movements among various members.

To learn how to make design of curtain walls to manage water penetration, click on the following link


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Calculation of Cement and Sand Quantity for Plastering

The ratio and all calculations given below are according to the requirement of 12mm thick plastering.

Plastering, as we all know, removes imperfection of external walls along with maintaining the line level and the alignment. Generally, plastering is defined as a protective surface for walls. It can be many a type depending on the materials it uses such as cement plaster, gypsum plaster and lime plaster. These are the common types of plastering that are required for home construction.

Cement plaster has two main materials in its core – cement and sand. The right proportion is required to get the best outcome you expected. This plaster removes imperfections from both inner and outer walls of the construction. Knowing the right proportion is an important factor in the making the paste or mortar perfect for the walls.

The list below contains the ratio between cement and sand that you need to maintain as per the application.

  • Cement mortar ratio 1:3 – this mortar mix is not used in general applications. It can be used as a repair mortar when they are combined with a waterproofing or bonding agent.
    • 1:4 – for ceiling and external plaster.
    • 1:5 – the ratio proved to be good as brickwork mortar. It is also good for internal plaster.
    • 1:6 – this ratio can be maintained for internal plaster.


Calculate Cement and Sand Requirement for Cement Plastering:

Calculating the quantities of cement, sand and water depends on a few parameters. These bring out the logic why you need to maintain the ratio.

  • Volume of plaster requirement: the volume of plaster can be calculated by multiplying the area of the plaster and the thickness of the plastering (in this case – 12mm)
    • Mix Ratio of plaster: deciding the Mix Ratio of plastering contains complex calculation. It indicated the ratio of the volume of cement to sand. Mix ratio of plaster 1:4 means that the mixture has one part cement and 4 parts sand.

For calculating quantity, generally two methods have been applied –DLDB method and Empirical method. These two processes include steps required for a logical distribution of the materials. The calculations and measurements used in this methods based on the quantity of the materials.

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EMMA calculator for measuring electrical quantities

A generic ‘EMMA’ for work with bulk electrical quantities.

A multi-use EMMA should be applied for any ‘mass’ activity, that entails a physically quantifiable unit of construction work scope measured in tens, hundreds or thousands. As for instance, electrical cable tray or racking or cable laying/pulling are perfect individual subjects for this EMMA.

The EMMA contains 3 ‘pages’, called ‘INPUT’ (Basic data that should be entered to make EMMA functional), ‘TABLES’ (Spreadsheets used for entering target & actual progress percentages, man hours etc), and ‘CHARTS’ (Here accessed spreadsheets should be demonstrates as curves & histograms). The EMMA is applied for different purposes which are described below:

  1. To arrange target rate of progress (S-curve);
    2. To make an estimate regarding man-hours, converted to manpower requirements (histogram);
    3. To register units computed as complete every month;
    4. To register man-hours used each month, in that way automatically matching the actual rate of development and genuine handling of manpower, with premeditated rates.
    5. Besides, unacceptable trends can thus be recognized and work re-scheduled, together with automatic adjustments to manpower requirements, that will lead achievement of target completion.

Primary needs for inputting are:

  1. The projected total quantity;
    b. Meaning of the unit (eg m3);
    c. A valuation of man-hours necessary for each unit;
    d. The average number of hours to be conducted each day;
    e. The average number of days to be conducted on every week.

Subsequently, inputting should be compliant with notes provided.
Application of an EMMA will help in creating specific interest to anyone for taking liability to finish a work scope package before schedule.
6.11.B. Earthing tape, cable racks & trays, cables, terminations

The calculator demonstrated below can be employed for calculating man hours required for any one, or all, concerning the activities related to cabling which are incorporated. Besides, entering quantities, the user will be able to modify the unit manhour rates provided, for rates more in keeping with that User’s environment.

To obtain a hypothetical example, click Real-time Sync, provide secret key ‘electrified’ and click connect.

To start calculation, click on the following link

EMMA calculator for measuring electrical quantities

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RetainWall version 2.60 – A powerful software for designing a concrete or masonry retaining wall

Dhani Irwanto has developed RetainWall. It is an exclusive software that can be used for making the design of a concrete or masonry retaining wall. The wall may preserve soil or other granular material.

It examines the strength of the wall on the basis of the loads and resistances, and leads to bearing pressure, sliding, overturning and rotational stabilities. Loads which operate on the wall may include self weight, soil pressure, water pressure, live and seismic loads.
Resistances may contain base friction and cohesion, passive earth pressure, other structures or a shear key. Load and resistance factor design (LRFD) mode can be employed. If the wall is a reinforced concrete structure, the software can also produce the reinforcement design for any reinforced concrete structure wall. Besides, there is a soil pressure calculator.

This user-friendly application provides on-screen trial-and-error method and instant solution for the design. With it, any designer will be able to design the wall swiftly. Complete outputs are visible on screen or printed.

The software starts it’s operation by clicking on the specified dimensions to produce the initial dimensioning of the wall, earth surface and water levels. After that, it enters material properties of the wall, soil, water and reinforcement bars. Provided external loads contain surcharge load, seismic load as a horizontal seismic coefficient and any concentrated loads implemented on the wall if necessary. Load and resistance factors combinations are easily selected. Results of the wall stability are gained immediately. If satisfactory result is not obtained, then another trial can be produced instantly. You can also choose from options to use or not to use water, seismic or ashear key. The final results can also be printed.

The reinforced concrete design can be made instantly by applying the internal forces of the wall. It only needs bar diameters and spacings of the reinforcements.

RetainWall is compatible with metric, SI and British unit systems.

Given below, some exclusive features of the software :-

  1. Ability to design Load and resistance factors.
    b. Apply load and resistance factors combinations from AASHTO LRFD 2007, ACI 318-08 and IBC 2006.
    c. Load and resistance factors editor to change or generate new combinations
    d. Concrete reinforcement design from ACI 318-08.
    e. Force diagrams (moment, shear and normal) for every combination.
    f. Loads, resistances and reactions diagrams for every combination.
  2. Wall stabilities (bearing, sliding, overturning, rotation) for every combination.
    h. Workout nominal soil bearing resistance by applying theoretical or semi empirical methods.
    i. Ability to select active or at rest soil pressures.
    j. Ability to select elastic (rock) or plastic (soil) bearing pressures.
    k. Ability to enter user’s soil pressure coefficients.
    l. Reinforcement design for upper stem, lower stem, toe and heel.
    m. Unit systems, properties, load and resistance factors, reinforcement design method, and page setup from last editing which turn out to be the default for new design.
    n. Ability to include other loads on wall.
    o. Offer stability resistances from a shear key, toe passive soil pressure, adjacent structure, anchors or piles.
    p. Enable or disable a shear key, water or seismic.
    q. Various types of units of measurements like metric, SI and British unit systems are supported.
    r. Easy, clear, quick and simple software operation.
    s. Help facilities, can be printed to produce manual.

Click on the following link to download a trial version RetainWall version 2.60

RetainWall version 2.60 – A powerful software for designing a concrete or masonry retaining wall

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How concrete strength is impacted with different factors

The strength of concrete is impacted by various factors. The details are given below :-

Concrete porosity: Air and water are the useful substances to fill up voids in concrete. Air voids belong to pores in concrete. When concrete is blended it contains air trapped in the mix. The vibrators are used to clear out the air at the time of pouring walls.

If the concrete is less porous, it’s strength will be increased and calculated with compressive strength. The most crucial source of porosity in concrete refers to the proportion of water to cement in the mix, called the ‘water to cement ratio’.

Factors water/cement ratio: It is described as the mass of water divided by the mass of cement in a mix. As for instance, in a concrete mix if there are 400kg cement and 240litres(=240kg) of water, the water/cement ratio will be 240/400=0.6. The water cement ratio is shortened as ‘w/c ratio’ or just ‘w/c’. In mixes where the w/c is in excess of roughly 0.4, all the cement can, in theory, react with water to develop cement hydration products. If the w/c ratios are greater, it follows that the space occupied by the supplementary water over w/c=0.4 will persist as pore space filled with water, or with air when the concrete becomes dry.

As a result, when the w/c ratio become higher, the porosity of the cement paste in the concrete also upsurges. With the higher porosity, the compressive strength of the concrete will reduce.

Stability of aggregate: It is inevitable that when the aggregate in concrete is feeble, the concrete also becomes feeble. Rocks like chalk that contain low intrinsic strength, are not appropriate to be utilized as aggregate.

Aggregate-paste bond: The strength of the bond among the paste and the aggregate is vital. When no bond exists, the aggregate practically reproduces a void and the strength of concrete is decreased.

Cement-related parameters: Various parameters pertaining to the formation of the individual cement minerals and their ratios in the cement can impact the rate of strength growth and the final strengths gained.

To get more information, click on the following link


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Some newest technology to make construction process smarter

Some advanced technologies have emerged in materials science which can transform the construction industry to the next level.

As for instance, ordinary concrete is employed for different types of building applications ranging from foundations to flat surfaces. But, cracking may frequently occur for this type of concrete. If the cracking is not repaired, water can penetrate on its surface.

The problem can be resolved with a new self-healing concrete that employs bacteria to seal cracks devoid of any interference in the works. A permeable concrete that facilitates the water to gutter through it instead of pool on it is also being developed.

Other new materials are still in the testing phase. As for example, a transparent aluminum that provides the pleasing visuals of glass but the strength and longevity of metal. Transparent metal technology is also very useful for generating transparent solar panels for sustainable energy devoid of large, unappealing black rectangles on the roof.

3D printing technology is also gaining popularity among housing and construction sectors to fulfill the requirements for reasonable housing. With this technology, it is possible to 3D print a house in about a day at a lower cost as compared to conventional construction process.

Augmented reality, or AR, will play a significant role in construction. Contradictory to VR, or virtual reality, in which a person’s total field of vision is substituted with a rendered environment, AR arranges images over what’s actually come into reality.

In construction, an AR wearable will show the exact amounts to a 3D blueprint to workers as they’re on the job. The latest smart safety goggles like Google Glass, or smart helmets with a combination visor-screen are emerged in the market to make construction process superior.

Now-a-days, the drones are extensively used for surveying purposes, particularly for larger commercial projects on previously undeveloped land. With drones, it becomes easier to obtain full information on a job site rapidly efficiently.

The industry will continue to expand and advance and more improvements will occur in wearables and robotics which will provide a great impact in construction sectors.

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How to layout columns for a residence on the basis of thumb rules

In order to generate a column layout concerning a building, the following three crucial thumb rules are necessary:

  1. Size of the Columns 2. Distance between the columns 3. Alignment of Columns

Here, you will learn how the column layout of a residence is accomplished on the basis of the aforesaid three thumb rules.
Here, you will learn how the column layout of a residence is accomplished on the basis of the aforesaid three thumb rules.

Column Layout for a residence

The residential villa is built up with 1 and half floors. In the beginning, the column size 9″x12″ is utilized together with the M15 grade of concrete. To save money, the builder usually forms the columns smaller in size.

Therefore, the columns in the Floor plans remain 9″x9″ in size. The Engineer verifies that M20 grade of concrete must have been employed for Columns.

Thumb rule no1:

Size of the Columns

The size of the columns should be 9″x9″ together with the utilization of M20 grade of concrete.

Thumb rule no.2:
Space among the columns:
The space among the columns should not surpass 4.5m.

Thumb rule no.3:
Alignment of Columns
The Columns should be provided on an iron grid pattern. Therefore, no zigzag walls and zigzag beams exist which minimize complexities in the structure.

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How to layout columns for a residence on the basis of thumb rules

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