What is Caisson Foundation and How is it Used in Construction

A Caisson Foundation is basically a watertight box with the top open. It is sunk into water to gain access to the bed of the stream. It is generally made of wood, steel or concrete depending upon project requirement.

Through this boxlike chamber, the workmen can make construction work at the bottom of water bodies without being hampered by the water. Accordingly, this is mainly used to place foundations at river beds.

Caissons are generally made on shore first. Then, They are launched into the water body. The caisson is then floated to the designated spot. Then they are sunk vertically to the bottom. After ensuring that the caisson is waterproof, the water inside is pumped out to dry.

Types of Caisson Foundation:

1. Box Caisson: This is the most basic type of caisson. It is made of timber, concrete or steel. It is built on shore and floated to the foundation location and sunk to the bottom. It is basically a box without the top.

2. Open Caisson: This type of caisson has neither the top nor the bottom. When made in a cylindrical shape, it looks like a well without top or bottom. It can be built in many shapes - vertical, over, or any other option.

In case of building large bridges, a bathtub-like shape is preferred. Usually open caissons are made of steel plates welded together. RCC can be also used here, as the situation requires.

3. Pneumatic Caisson: This odd type of caisson has an open bottom but closed top. This has to be forced down to the bottom of the water by means of compressed air. Thus the name is derived. A pneumatic caisson consists of a working chamber, a shaft, and an airlock. The caisson is made of inner and outer layer of steel skins. Trusses and girders join them to form a boxlike structure.

The working chamber in pneumatic caissons is 3-4 meters tall only. It is made airtight with a special seal on top. The caisson’s bottom edge has a steel edge that cuts into the riverbed. All this facilitates working within the chamber while the caisson is being sunk. People can access the caison via the airlock.

Read more

~~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~~

What are Shear Keys and How to Use Them

A building and structure has to bear not only vertical loads, but also lateral loads. This can occur due to many design or natural reasons. To counteract this lateral load, Shear Keys are used. Let us see today what exactly are shear keys and how can you use them in your construction.

A building can face a lot of lateral load due to many reasons. Some of these include earthquake loads, sliding forces, water pressure, wind pressure etc. This often occurs with bridges, retaining walls, basements, extremely tall buildings, precast buildings and culverts, masonry walls where seismic activity is stronger, and steel columns and piers.

Shear keys can be constructed by concrete in precast buildings, and of steel in steel structures. Sometimes, steel reinforcements are made to play the part of shear keys as well. They improve the lateral stability of a building.

Placement of Shear Keys: Where the shear keys will be placed differs a lot depending upon the structure they need to support. Let us discuss them below.

Bridges: In small to medium bridge structures, shear keys are placed in the abutments of the bridge. This provides lateral transverse support to the structure above during sidewise movement.

During an earthquake or similar strong lateral force application, the shear keys act as a sacrifice. Therefore, the strong seismic forces are prevented from entering the abutment piles.

They act better when they are placed on the outer side of the bridge. However, this makes them difficult to inspect or repair.

Retaining Walls: You should place shear keys at the base of retaining walls, just beneath the stem. This prevents sliding of the base during strong lateral force application.

The shear keys placed beneath the wall must be nearly twice in width than their depth for the best performance. Generally, they are 508mm by 381 mm, respectively.

Read more

~~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~~

How to erect a bridge – some vital guidelines

Given below, some necessary stages to construct a bridge in the public works sector.

Step One: The Foundations - The purpose of foundation is to disperse different types of loads of the bridge (mass, weight, overload, forces …) perfectly based on the type of the ground of the structure.

The foundations are categorized as the following two types :-

• The superficial foundations: These foundations are ideal for the bridges with level adjacent to the ground since the structures are susceptible to reduced constraints in comparison with the wind and their gravity. It is also necessary that the rocks within the structure should be strong, undecomposed and not greatly cracked.
• Deep foundations: This type of foundation is effective while the bridge starts to obtain the height. Under this situation, it occurs consistently that the soil exposes a layer more stable in depth. At the time of construction, there are three situations which produce the following three types of foundation:

a. Referred to as “good” soil, when it allows to set the foundations directly on a durable ground, is known as flat foundation.
b. Referred to as “bad then good” soil, when it is required to place four piles in the unsteady ground unless they attain the steady ground.
c. The soil becomes “unsettled”, when the quality of soil in the ground is not good. Under this circumstance, lots of piles should be installed to provide good resistance capacity severe compression.

Without resistance at depth, the support should be provided with “floating” piles.

Second Step: Construction of Supports - The number of supports (abutments and piles) required for the construction of the bridge should be affixed concurrently on both sides of the shores. These supports are generally formed with concrete and either cast in place, or prefabricated in a factory and then assembled on site.

Third Step: Assembly and Start-Up of the Superstructure - Due to the final weight of the structure, the greater or smaller spacing among every pile and the final objective of the structure, it becomes complicated to apply the concrete for the construction of the deck which, over great distances, fall down even because of its own weight and of its traffic. For this reason, the elements of metal beams are used. These are assembled jointly to build up the structure of the deck.

On every shore, the beam elements are set up through a crane and the elements are then reconstructed with welding on site (Welded I-Beams). The deck is then provided with a launching nose, finished with a ballast at the back to resist tipping. Normally, the piles are driven with winches, cables and pulleys, the deck advances at a speed of about 9m / h. Also, this solution is substituted with restraint systems to stop runaway.

Fourth Step: Pouring the Slab - The beams are provided with connectors in the factory so that the steel structure is secured to the concrete slab of the latter. As soon as the beams are installed on their final supports, the lost formwork is arranged on them along with reinforcement prior to pouring a layer of concrete with thickness of about 25cm that will be the slab of the structure.

Step Five: Finishes - To complete the work, after several months, even years of construction, the final step is to provide asphalt on the road. Asphalt stands for a very specialized type of bitumen to resist expanding of deck. Thus, even with some deformations of steel, the bitumen will not crack and retain the quality to adapt the road traffic.

Several sensors are arranged on each strategic part (deck, cable stay, piles, pylons …) and facilitate to constantly follow the state of the bridge.



Read more
~~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~~

Some best software for structural analysis and design

Now-a-days, lots of software emerge in the market to design, analyze and develop large projects rapidly. The 3D integrated structural design and analysis software become very popular amid structural designers.

These simplified structural analysis and design software are applied to increase productivity. These software facilitate the structural modeling and load analyzing more consistent and well organized, as a result the time and effort are curtailed significantly for finite element analysis.


These design/analysis software comprise of some exclusive features which range from analysis of diversified profile of structural components, modeling structure of different materials, outputting analysis and graphical files, and examining geometrical errors. Given below, the detail lists of five best software for Civil and Structural Engineering.

Analysis & Design:

STAAD Pro: It belongs to a structural design and analysis tool that is treated as the best structural analysis software for worldwide structural engineers. It is very user-friendly and contains an extensive range of essential tools essential for executing an analytical process on several structures.

STAAD Pro is further integrated with a series of other Bentley products. The models produced with STAAD Pro can be imported to OpenSTAAD in order to make the models transmittable to other third-party tools.

SAFE: This software is frequently applied in designing foundation slab systems and concrete floors. SAFE is a comprehensive package that integrated all the features of engineering design process ranging from generating layout to detail drawing production in a single, intuitive environment.

It facilitates highly advanced local appraisal of foundation systems inside greater structures and imports files from CAD, ETABS, and SAP2000.

Given below, some of the other significant advantages of the software :

1. Extensive lists of templates to swiftly set up a model
2. Post-tensioning
3. Support conditions and loadings

RISA: It is another leading 3D analysis and design tool for developing general structures like buildings, bridges, arenas, industrial structures, crane rails, and more.

It is rapid, productive and reliable. It contains an insightful interface that combines with several other products like RISAFloor and RISA Foundation. It comprises of the newest steel, cold-formed steel, concrete, aluminum, masonry and timber design codes. It consecutively offers the tools which are required to manage the multi-material projects without any difficulty.

3D Environment:

Navisworks: The design, engineering and construction management professionals use this software to get brief understanding of the project and improve the productivity and quality. It facilitates the users to open, combine, review and distribute Detailed 3D Design models in different file formats. It allows the users to import all file formats and integrate all the files to generate a model.

~~~~~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~~~~

Basic differences among AAC Blocks and Red Bricks

Red Bricks are mostly recognized materials for building all through the world since they are inexpensive, long-lasting as well as simple to deal and work with.

The other vital features of red bricks range from superior stability and strength, low weight and greater ecological green features.

AAC Blocks and Red Bricks both are essential building materials for constructing walls. Red bricks & AAC blocks are utilized in walls according to their properties, accessibility and cost. Given below, the basic differences among red bricks and AAC blocks.

01. GENERAL: Red Bricks

• A Red brick stands for a block, or a single unit of a ceramic material that is applied in masonry construction, normally amassed collectively or placed with different types of mortar to retain the bricks jointly and develop a permanent structure.
• Bricks are generally formed in common or standard sizes in mass quantities.

AAC Blocks

• The weight of AAC Blocks is light and they are cut into masonry blocks or developed larger planks and panels.
• AAC Block is comparatively homogeneous with reference to other wall unit and does not include coarse aggregate phase.

02. RAW MATERIAL: Red Bricks

• The red bricks are produced by amalgamating clay(alumina), sand, Lime, iron oxide and Magnesia.
• Natural soil is utilized for making Bricks. So, it is totally based on the quality of local soil, i.e. Top soil of Earth Crust.

AAC Blocks

• It is produced from the mixture of fly ash, cement, lime, gypsum and an aeration agent.
• The Fly ash employed in AAC Blocks production is environment friendly & cement is applied in very small amount.
• The difficulty of fly ash usage is resolved with the use of fly-ash in AAC Block.

03. Applications: Red Bricks

01. As a Structural Unit:

Red bricks are sturdy, solid, long-lasting, so, they are utilized as a structural material in various structures as given below :-

• Buildings
• Bridges
• Foundations
• Arches and cornices
• Pavements

02. As an Elegant and Finish Surface:

Bricks are utilized according to its various colours, sizes and orientations to produce diverse surface designs. As an elegant material brick is applied for the following purposes :-

• As Facing Bricks
• Architectural Purposes
• Exposed practice work

AAC Blocks

• AAC Block is applied to develop internal and external walls.
• It can also be applied as load bearing and non load bearing walls.

To get more details about other points of variations, go through the following link gharpedia.com




~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Various types of concrete mixers

The concrete is built up through a concrete mixer by mixing cement with aggregates like sand or gravel, and water. The concrete mixers attain the consistency of the mix as well as set the mix keeping the consistency unchanged.

The process for mixing the material of concrete may vary but it should be accomplished carefully to make sure that the consistency is maintained for allotment of materials in concrete mass. It can be evaluated with uniform color and reliability of concrete.

The machine that is employed for mixing concrete is called as the mechanical concrete mixer, or just concrete mixer.

Given below, two main types of Concrete Mixers:

01. Continuous Mixer: Continuous mixers are mostly found in large constructions like dams, bridges, etc., where large masses of concrete are utilized and the constant flow of concrete is needed.

02. Batch or Drum Mixer: Batch or Drum mixer is mostly recognized in construction sites. It contains a rotating drum with blades or baffles inside it. Under this type of mixer, all the materials of the desirable proportioned mix should be entered into the hopper of the rotating drum and then drum on being revolved at a specific speed combines the materials through a series of blades arranged inside. The produced mix is finally released from the drum and transported for use.

There are following two Types of Batch Mixers.

• Tilting Mixers: Tilting mixers contain a conical or bowl-shaped drum having vanes inside. They are suitable for mixes of low adaptability and for those comprising of large size aggregate. The mixing chamber that is called as drum, is designated for discharging.

• Non-Tilting Mixers: In non-tilting mixers, the axis of the mixer always remains in horizontal direction. The discharge is accomplished either by implanting a chute into the drum or by changing the direction of rotation of the drum to the reverse or hardly by partition of the drum.

To get more information, go through the this link Gharpedia.Com




~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~