Sanjer Bela Civil Engineering Site

Types Of Prestressing Depending Of the feature of design construction prestressing construction may be classified into number of groups. a) External Prestressing : - It is prestress a concrete by adjusting its external reactions. For a simply supported beam external prestressing can be done by jacking against abutments . Jacking can be done at proper places to produce compression in the bottom fibres and tension in the top fibres. Such an arrangement, however cannot be easily accomplished in practice as even if abutments favourable for such a layout are obtainable, shrinkage and creep in concrete may completely offset the strains unless they can be readjusted. This type of prestressing is probably suited for arch bridges having rigid abutments. b) Internal Prestressing: - in such cases prestress is provided by high tensile wire against concrete.Various variations of internal prestressings are discussed below. 1) Linear and circular prestressing: - linear prestressing is applied is in...

  What is grouting in Civil Engineering? The purpose of post tensioned tendions in prestressed concrete members is to provide permanant protection to the post tensioned steel and to develop bond between the prestressing steel and the surrounding concrete. The grout is a mixture of cement water with or without admixtures. The recommended grout mix is 1 bag (50 kg) of portland of cement water 22 kg (5 Gallons) Of water, which works out to a water cement ratio is 0.50. Sand should not be added in grout mix. Research has that confirmed that for basically horizontal tendons in rigid ducts,satisfactory quality of grout may be achieved without any admixture. Admixture should be impart the properties of low water content, good flow ability and minimum bleed. Aluminium powder and proper fineness of quality which is well dispersed can be used to obtain a 5 to 10 percent unstrained expansion of the grout. The essential qualities of a good grout are : 1. It should be sufficiently fluid in the ...

  Pile Driving Piles are commonly driven means of hammer supported by a crane by a special device known as a pile driver. The hammer is guided between two parallel steel member known as leads. The leads are carried on a frame in such a way that they can be supported in a vertical position or an incliened position. Hammers are the following types. 1.       Drop hammer If a hammer is raised by winch and allowed to fall by gravity on the top of a pile,it Is called a drop hammer. 2.       Single   acting   hammer If a hammer is raised by steam, compressed air or internal combustion, but is allowed to fall by gravity alone,it is called a single acting hammer. 3.       Double acting hammer The double acting hammer employs steam or air for lifting the ram and for accelerating the downward stroke. It operates with succession or rapid blows. 4.       Diesel Hammer ...

  Negative skin friction (NSF) refers to the phenomenon that occurs when the friction between a soil or rock surface and a pile or foundation element creates an opposite force, pulling the foundation down into the ground rather than resisting its movement. This is commonly observed in piles or deep foundations that are embedded into soft soils, especially in areas where the soil undergoes consolidation or settlement. Here’s how it works: 1.      Soil Consolidation or Settlement : In soft, compressible soils, like clay or silt, when the soil undergoes settlement (due to load or natural compaction), it can cause downward movement of the soil around a pile or foundation. 2.      Friction Development : As the surrounding soil consolidates or moves downward, the friction (skin friction) between the pile surface and the soil increases. Normally, this friction resists the movement of the pile, providing support. 3.      ...

  Drilled Concrete Piers Drilled concrete piers are used to create deep foundations for structures like residential homes, commercial buildings, and industrial facilities. They can be used in many different types of soil conditions. Applications Deep foundations Drilled piers are used to create deep foundation systems that transfer a structure's load to bedrock or soil. Unstable soil Drilled piers can be used in unstable soil conditions by socketed into more stable strata. Challenging soil conditions Bored piles can be constructed to significant depths to provide deeper foundation support in challenging soil conditions. How they are used A drilling rig is used to create deep holes. The holes are filled with reinforced concrete. The concrete must cure before the structure can be loaded. Other names Drilled concrete piers are also known as cast-in-situ piles, cast-in-drilled-hole piles, drilled shafts, and caissons. Related methods Other methods of pili...

Under Reamed Piles Under-reamed piles are a type of deep foundation used to provide support in weak or loose soil conditions. They are essentially a variation of bored piles, where the pile shaft is enlarged or "under-reamed" at specific depths to increase the load-bearing capacity of the pile. An under-ream is a bulb-shaped enlargement of the pile shaft, typically created at one or more levels below the ground surface. The enlargement is designed to anchor the pile more securely in the soil by increasing the surface area, which enhances its capacity to resist lateral and vertical loads. The enlarged section of the pile provides greater resistance to both settlement and lateral forces. Effectiveness of Under-Reamed Piles: Under-reamed piles are particularly effective in the following situations: 1.      Weak or Cohesionless Soils : They are commonly used in soils with low bearing capacity, such as clay, silt, or loose sand. The enlarged portion helps to dis...

  Drilled Piers Drilled piers are a type of deep foundation system used to transfer structural loads to deeper, more stable soil or rock. They are commonly used in areas where surface soils are weak or unstable. Here's a breakdown of their advantages and disadvantages. Advantages of Using Drilled Piers 1.      Deep Foundation Support 2.      Minimal Disturbance to Surrounding Area 3.      Adaptable to Various Soil Types 4.      Can Be Installed in Confined Spaces 5.      Customizable Length and Diameter 6.      Lower Noise and Vibration 7.     Good for Seismic and Settlement Conditions   Disadvantages of Using Drilled Piers High Initial Cost Lengthy Installation Process Risk of Soil Contamination Potential for Difficulty in Rock or Hard Soil Quality Control Issues Limited Load Capacity Dealing with Gro...