Definition of Cofferdam and its Types

The word Coffer means a trunk, casket or chest in which temporary structure built to enclose and encase an area meant for excavated for the foundation of the construction. Cofferdams are used for structural foundation in Open Water & Open Land such as bridge piers, docks, locks, dams and high ground water table. A cofferdam is a waterproof wall built around the periphery of the proposed excavation to prevent the flow of water into the excavation so that the basement may remain in dry condition.

As per the Requirement of the job-site and output need the coffer dam may be many types but some common types  of cofferdam are as under:

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

What Is Cofferdam And Its Types

1)     Earth Coffer Dams: Earth Coffer Dams are constructed in a area where the velocity of the current and depth of the water is 13 to 18 in. which is carried about 1 m above the water level. It is constructed with a mixture of clay and sand. The Side Slopes of the bank on the water side should be pitched with rubble Boulder to avoid embankment from scouring. On Completion of coffer dam the water is pumped to dry the inside surface. Sand  bag can be used in an emergency.

2) Rockfill Coffer Dams: Rockfill coffer dams made of rockfill enclose the site sometimes with dewatered. To protect against wave action the crest and the  upper part of the impervious membrane are provided with rip rap. The slopes of rockfill cofferdam can be made as steep as 1 horizontal to 1.5 vertical.

3) Single-Sheet Pile Coffer Dams: Single Sheet Coffer Dam constructed in a very small area and whose depth of water is more than 4.5 to 6m. At First Guide Piles better known as Timber Piles inserted into the firm Ground which is below water bed. Depending upon the velocity of the Current in water the Longitudinal runners spacing varies known as wales which are bolts to a timber piles at a necessary distance. Steel or Wooden Sheet inserted into the River Bed along with wales which are secured to the wales by bolts. To increasing the stability of walls against the water pressure the sheets on the two faces arc braced by trussed arrangement of struts and  Half-filled bags of sand stacked on the inside and the outside faces of the sheets. After the cofferdam is constructed, the water in the enclosed area is poured out and the construction work begun.

4) Double-wall sheet piling cofferdams: :In Large Area Single Wall Sheet Coffer Dam is not workable as it unable to resist Water Pressure thus double wall sheet piling cofferdam is constructed with a depth of water upto 12m. The distance of the both wall depend on the depth of the water, the wall should be wider depending upon the depth of the water increase to stabilize against overflowing and sliding. The Thickness of the water depend on the depth of the water, greater the depth thickness should be excess of 3m.  The Sheet piles are inserted at a reasonable depth in the Bed to prevent the leakage from the Ground Level.

5) Braced Coffer Dams : The braced cofferdams are influence  to flood damage. A braced cofferdam is prepared by operating two rows of vertical sheeting and bracing with wales and struts.  To prevent ground water from entering the foundation pit on land the Braced Cofferdams are sometimes used as land cofferdams to support the soil so as to prevent cave in. The structure is formed After the pit is dewatered. The cofferdam is removed after completion of concreting above the water level,.

7)     Cellular Cofferdams: Cellular Cofferdams are of 2 varies known as i)  Circular Type . ii) Diaphragm type

1) In Circular Type Cofferdams are constructed by filling the cell completely up-to top before the start of Construction work. The Crane and other equipment can be place requires for construction purpose without any adverse effect to the neighboring Cell due to Interlock Stress within a permissible diameter of a cell.

2) In Diaphragm type steel Sheet piles are connected Series wise.  The Distance of Straight Diaphragm is equal to the radius of the Connecting Arcs. The Cell are filled with sand, gravel and other material after inserting the cell at a required depth. The adjacent cells should be filled at approximate rate to avoid the failure of interlocks. This type of Cofferdam increases the desirable limit without increasing the Interlock stress.


What is Plastering and How Many Types of Plastering

Plastering means covering the surface area with a suitable material by masonry. The Material required for Plastering is being prepared by mixing cement with sand or fat lime with sand or surkhi in addition to sufficient quantity of water. A Fine Paste of Mortar is formed after mixing all the ingredients.

The Category of Plastering are being defined according to the Ingredient.

  1. Cement Plastering
  2. Lime Plastering
  3. Mud Plastering
  4. Stucco Plastering
  5. Moughal Plastering

1)     Cement Plastering:

Plaster is known as cement plaster, when cement is used for binding material. The Mix Ratio content of Mortar depends upon the nature of the work to be plastered. For Rich Plastering work such as Side Bathroom etc 1.3 Cement Plaster is used. On the other Hand for General Plastering of Wall 1.5 to 1.8 cement plaster mixes are used.

The joint Masonry properly raked depth 10 to 15 mm provide key to plaster for preparing the surface properly. The surface is kept wet for 6 hours with thoroughly watering. Cement Plastering may be One /Two coats as per requirement. The Mortar is dashed into uniform thickness with the help of Trowel Wooden. The Trowel wooden is removed after specified time as per Required Coats.This type of plastering specially suited for damp conditions i.e. bathrooms, etc.

2)     Lime Plastering:

The surface preparation is same as Cement Plastering but the Ingredient depends upon Coats i.e for 1 Coats 1 part of lime to 1.5 parts of sand is used, proportionately the second coat consists of two parts of lime and one part of sand and 3rd coats 4 parts of lime to one part of sand. This type of plastering is suitable for internal renderings of buildings.

3)     Mud Plastering:  

The wall surface is first prepared as cement plastering. The cow dung and cement in proportion of 3 : 2 : 1. The mud plaster is then evenly dashed against the wall surface with a wooden float. After 24 hours, the surface is tamped. To avoid developments of cracks due to hollows, tamping is compact the layer and to drive it deep into the joints. After tamping, water is sprinkled slightly and the surface is polished with a steel trowel. A thin wash of cow dung is used where small cracks have formed. Finally the surface is given a wash of fine white earth and cow-dung. This type of plastering is done on walls of temporary sheds and country side buildings.

4)     Stucco Plastering:

This is special type of plaster is used for decorative type of plastering.  The first coat also known as scratch coat consists of lime plaster 12 mm in thickness and the second coat or brown coat consists of rich lime plastering in 10 mm thickness and the final coat is  mixture of very fine lime and white ground stone ( marble or quartz), 3 mm in thickness. The proportion of ingredients for the first two coats is 1 part of cement to 3 parts of sand with 10% by weight of hydrated lime. The finishing coat consists of 1 part of cement and 2 pars of sand in which some coloring pigment is added or colored cement is used. Method of applying this plaster is same as described in case of cement or lime plastering. This type of plastering is suitable for external as well as internal surfaces of buildings.

5)     Moughal Plastering:

It is generally applied in two coats of lime mortar by mixing lime, sand and surkhi in the ratio of 4:3:1 along with glue and powdered gull nut. The surface is well wetted and the second coat of about 1.25 mm thickness is applied when the first coat is hardened. The finished plastered surface is kept wet for 3 weeks

What is Plastering and How Many Types of Plastering


Download Roofing Calculator to Calculate your Roof Work

As the construction phase of your house nears end, roofing comes into picture. Calculation of the area of the roof and the material required to complete the flooring becomes the main focus.

The calculations for the area and the materials required for the flooring can be done using a Roofing Calculator which makes troublesome process easier and faster. Just enter the dimensions of the floor and flooring material you are using, Roofing Calculator will give you the area to be covered and the material required. The cost of the material can be also be estimated.

If the shape of the roof is complicated with elevations, slopes and circular shapes, etc. then it is advised to divide the roof into simple shapes and calculate the area individually. Slope factors can also be used which are given with the calculator for your convenience.

Download Roofing Calculator

Download Roofing Calculator to Calculate your Roof Work


How to Build Rope Bridge using Quadrocopters / Flying Machine

A rope bridge is a bridge constructed chiefly of rope. In its simplest form of bridge. It can be made of one or two ropes and is bridged over a river. A traveler is enable to cross the river by being supported by the bridge and does not get swept away with the flow. One rope above another, for feet and hands, may be referred to as a commando bridge.

In this video shared by Federico Augugliaro, shows how to build a rope bridge using the flying machines, quadrocoptersin the ETH Zurich Flying Machine Arena.

Aquadcopter, also called aquadrotor, is a multirotor helicopter that is lifted and propelled by four rotors. Quadcopters are classified as rotorcraft, as opposed to fixed-wing aircraft, because their lift is generated by a set of rotors.

In this video, it can be seen that simple and structures can be built using the small flying machines. The rope used here is of Dyneema, a material having low weight-to-strength ratio and is suitable for aerial construction. The full erection of bridge is done with autonomous drones which are controlled by algorithms run on computers.

The drones are equipped such that it allows control on tension during the rope deployment while building. The external forces and torques exerted by the rope during deployment are accounted to achieve compliant flight behaviour.

The videos shows that small flying machines are capable of autonomously realizing load-bearing structures at full-scale and proceeding a step further towards real-world scenarios. Several computational tools are being developed to take this technology further, specifically addressing the characteristics of the building method. The design tools allow to simulate, sequence, and evaluate the structure before building.

Building a Rope Bridge


Post Tension of Reinforced Concrete – Detailed Process

Post tension is a technique for reinforcing concrete. Post-tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. Afterwards, once the concrete has gained strength but before the service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges of the concrete.

Post-tensioning is a form of prestressing. Prestressing simply means that the steel is stressed before the concrete has to support the service loads. Most precast, prestressed concrete is actually pre-tensioned-the steel is pulled before the concrete is poured. Post-tensioned concrete means that the concrete is poured and then the tension is applied-but it is still stressed before the loads are applied so it is still prestressed.

This video posted by FirthIndustriesNZ’s channel on YouTube captures beautifully the 10 hour process of post-tensioning the airport hangar floor in just 5 minutes. This amazing work was done by Firth for Fletcher Construction.

Construction of post-tensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. Cables are arranged as indicated by the engineer and chaired to run through the center of the slab.

Post-tensioning has several benefits like as it reduces or eliminates shrinkage cracking-therefore no joints, or fewer joints, are needed. Cracks that do form are held tightly together. It allows slabs and other structural members to be thinner. It allows us to build slabs on expansive or soft soils. It lets us design longer spans in elevated members, like floors or beams.

Post Tension Concrete


Pile Foundation and its types

When the upper layer of ground on which the construction is to be done is of weak soil, then the load of the structure needs to be transferred to the deeper layer earth. Pile foundation carries the load of the structure and transfers in to the strong soil or rocks beneath.

Pile foundation is more suitable when the structure has very heavy concentrated load or in case of high rise buildings. This foundation is capable of taking more load as compared to spread foundation.

Based on load transfer criteria, Pile foundation has following types:

1. End Bearing Piles

This type of piles take the load of the structure all the way downwards to the strong layer of soil, hence the name End-bearing Piles. Here piles act more like columns, bypassing the weaker layer and transferring the load to stronger layer. The bottom of the pile rests at the intersection of weak and strong layer.

2. Friction Piles

Friction Piles are shorter in length as compared to end bearing piles. They work on the principle of skin friction. The entire surface of the pile, cylindrical in shape, transfers the load of the structure along the length of the pile through friction to the soil. Hence the load is distributed throughout rather than being concentrated at the bottom.

Pile Foundation Types|
Image source:

Based on method of installation, Pile foundation is classified as:

1. Driven or Displacement Piles

The piles are pre-cast before being installed in the foundation. They are installed by jacking, hammering and screwing into the ground.

2. Bored or Replacement Piles

The hole is bored into the ground first, and then the piles are formed as reinforced concrete.

Based on the type of material used, Pile foundation can be as follows:

  • Timber Piles
  • Concrete Piles
  • Steel Piles
  • Composite Piles

Beam Deflection Formula Application Download

The horizontal member of any construction framework is called Beam. When this beam is subjected to loading, bending moments and internal stresses develop at different points in the beam to counterbalance the deflections due to loading.

Beam Deflection Calculator is a software which can be used to calculate deflection, slope, bending moment, shear forces and reactions in different beams like simply supported beams and cantilever beams. All you are required to do is select the type of beam, dimension of beam, type of loading and material properties. The Beam Deflection calculator brings forth the results by calculating the bending moment and shear forces, finally giving the diagrams BMD and SFD.

The different methods which are used to calculate the Beam Deflections are:

  • Double-integration method
  • Area-moment method
  • Strain-energy method
  • Conjugate-beam method
  • Method of superposition

Using Beam Deflection Calculator makes the overall procedure easier and efficient. The software can be downloaded from the below link.

Beam Deflection Formula

Download Beam Deflection Formula Application for FREE


Definition of Retaining Walls and its features

The wall designed and built for the purpose of holding back the earth of or soil on a sloppy terrain is called Retaining wall. When there is a change in elevation of ground level, the soil tends to move downwards if the angle of repose exceeds, leading to landslide. To prevent such this unfortunate event, Retaining wall is built at the edge.

Different types of Retaining walls are:

1. Gravity walls:

These are dense walls made up of concrete, stone or brick masonry. Due to their heavy weight, they are able to hold material behind and retain against failure. These wall are thick and suitable for height upto 3m. Geometry of these walls keep them stable.

2. Cantilevered walls:

Cantilever beams are made of reinforced concrete. Steel bars are cast in concrete and the shape of the wall resembles inverted T. This type of wall uses much less material and are economical. Cantilever walls are sometimes buttressed.

3. Sheet piling:

If the soil is soft and the space is tight, the Sheet Piling retaining walls are built. These are made up of steel, vinyl or wooden plank which are installed in the ground.

4. Bored pile:

Bored piles are assembled in a sequence, making Bored Pile retaining wall and the excess soil is excavated out. This type of retaining wall may also include a series of earth anchors or reinforcing beams, depending upon the project.

5. Anchored

Any of the above retaining walls are when additionally strengthened by using cables or other stays anchored in the rock or soil behind it, then it is call Anchored retaining wall. This type of wall is preferred when high loads are expected.

Retaining Walls and its features


Types of Beams, Shear Force & Bending Moment Diagram

When a beam is subjected to uneven load, beam undergoes bending producing bending moment which in turn produces stresses within the beam. Therefore, it is necessary to calculate the bending moment and shear stress developing within the beam when subjected to any type of load.

A beam is a horizontal member of a structure, which distributes the overall load of the building. Different types of beams are:

  • Simply supported beam
  • Fixed beam
  • Over hanging beam
  • Double overhanging beam
  • Continuous beam
  • Cantilever beam
  • Trussed beam

Different types of loads which might come into action are:

  • Dead load
  • Live load
  • Wind load
  • Snow load
  • Earthquake load
  • Thermal load
  • Settlement load
  • Dynamic load

Preparing Bending Moment Diagrams (BMD) and Shear Force Diagram (SFD), gives idea about the internal stresses and bending developed in structure to counter the deformation due to loading. Hence, while designing a beam of concrete we find the points of maximum SFD and BMD values. These values in turn give us the idea as to the kind of material and geometry we need to provide to resist deformation or failure in general.

The Video uploaded by Learn Engineering, explain the calculation of BMD & SFD along with detailed procedure for preparing their diagrams.

types of beams


Calculate Construction Material using Online Calculators and Designers

For any construction project, small or big, it is necessary to make initial rough estimations. Designing, calculations and estimations are to be done to know the overall budget of the project. These calculations take the maximum amount of time of the designer or the construction contractor.

To make things easier, faster and efficient, there is nowadays an option of online calculators and designers. These applications make instant cost estimations for different types of construction materials required in a construction project. All that is required is the rough data like some dimensions, some specifications and some parameters, and these software calculates the type and amount of materials required, the cost estimation and the design/ layout of the project.

Calculate Construction Material using Online Calculators and Designers

These free online services provide 45 different types of calculations. Materials for construction of pitched or mansard roofs such as rafters can be estimated. Depending upon the no. of turns, angle of rotation, span and type of staircase, a layout of stairs can be generated with the amount of material required. Concrete amount, shapes and rings can be calculated and designed using this software.

Even for building the most basic structures like walls, floor and fences of any construction project, estimation for the materials can be calculated using these online calculators. Amount of cement, concrete, gravel, accessories, tiles, plasterboard can be found depending upon the requirement. Calculations can be also be done for the excavation works.

All the calculations can be done by just entering the dimensions and parameters, extracting designs, material and cost estimations using the online calculators and designers.

Roof Calculators STAIRS Wooden Calculator
Calculation of the rafters Calculation of the stairs
Calculation of roofing materials for pitched roofs Calculation of the stairs with a 90°
Calculation of roofing materials for single-pitch roof Calculation of the stairs with a pivoting steps of 90°
Calculation of roofing materials for the mansard roof Calculation of the stairs with a rotation of 180 degrees
Calculation of the stairs with a 180-degree swivel and rotary stages
Concrete Product Calculators Calculation of ladders with three spans and smooth landings
Calculation of straight stairs from concrete Calculation of ladders for three missions and Rotary stages
Calculation of the material strip foundation Calculating the size of a spiral staircase
Calculation of the amount of material affect the Foundation
Calculation of the base plate material Building and Construction materials Calculators
Calculation of concrete rings Calculation of the amount of cement, sand and gravel for making concrete
Calculate the number of paving tiles Calculation of the volume of sawn
Calculator accessories
Fences, Walls and Floor Calcualtor Calculation of ceramic tiles
Calculation of the amount of material the House of round logs Calculation of plasterboard for walls, walls, ceilings
The calculation of the amount of material for exterior walls
Calculation of building materials for the fence Earthworks Calculartor
Calculation of brick fence Lot of complex shapes
Arch for fences Calculation of earthwork excavation for
Calculation of building materials for the floor Calculation of the well
Calculation of floor filling materials Calculation of the volume of the trench
Calculation of the canopy over the entrance Calculation of a rolled lawn
Calculation of materials for construction of swimming pools