Reinforced Concrete In previous post we discussed about RCC Steel buildings, Structral engineering. hope all you get clear structure idea about our line. surveying & Engineering Desining Information many more available in this post. Reinforced Concrete Is Strong in Compression Weak in Tension and Steel in Strong in Tension. Reinforced Concrete Uses Concrete to Resist Compression and to Hold Bars in Position and Uses Steel to Resist Tension. Tensile Strength of Concrete Is Neglected (I.e. Zero ) Reinforced concrete Beams Allows Crack Under Service Load.
Pre stressed concrete is a form a concrete about initial compression concrete before applying the externa load so that stress from external loads are counteacted in the desied way during the service period. steel tendon wants to gain its original length and tensile stresses are transformed into a compressive stress in the concrete. Now after loading there are two kinds of forces on the beams internal prestressing force and external forces.
What Is Pre-Stressed Concrete?:
Internal Stresses Are Induced to Counteract External Stresses. Introduce Permanent Acting Forces in Conc. to Resist Elastic Forces Under Loads.
Concept of Pre-Stressing:
The Concept of Pre Stressing Was Invented Years Ago When Metal Brands Were Wound
Around Wooden Pieces to Form Barrels. the Metal Brands Were Tighten Under Tensile Stress Which Od. Creates Compression Between Staves Allowing Them to Resist Internal – 3s Weds Seared Liquid Pressure.
Principle of Pre-Stressing:
Pre-Stressing Is a Method in Which Compression Force Is Applied to the Reinforced Concrete Section. The Effect of Pre Stressing Is to Reduce the Tensile Stress in the Section to the Point Till the Tensile Stress Is Below the Cracking Stress. Thus the Concrete Does Not Crack. It is Then Possible to Treat Concrete as a Elastic Material. The Concrete Can Be Visualized to Have Two Compressive Force. Internal Pre-Stressing Force. External Forces. These Two Forces Must Counteract Each Other. Compressive stresses are induced in prestressed concrete either by pretensioning or post-tensioning the steel reinforcement.
Pre-Stressed Concrete: Methods
There Are Two Basic Methods of Applying Pre-Stress to Concrete Member
Pre-Tensioning — Most Often Used in Factory Situation
Post-Tensioning — Site Use
Prestressed concrete has experienced greatest growth in the field of commercial buildings. For buildings such as shopping centers, prestressed concrete is an ideal choice because it provides the span length necessary for flexibility and alteration of the internal structure. where we use Pre stressed concrete buildings, Pre-stressed concrete has experienced the greatest growth in the field of commercial buildings. For buildings such as shopping centers, pre-stressed concrete is an ideal choice because it provides the span length necessary for flexibility and alteration of the internal structure.
Types of Pre-Stressing:
Pre-Tensioning in Pre-Tension, the Tendons Are Tensioned Against Some Abutments Before the Concrete Is Place. After the Concrete Hardened, the Tension Force Is Released. the Tendon Tries to Shrink Back to the Initial Length but the Concrete Resists It Through the Bond Between Them, Thus, Compression Force Is Induced in Concrete. Pretension Is Usually Done with Precast Members Tendon Anchorage Jack
in Post Tension, the Tendons Are Tensioned After the Concrete Has Hardened. Commonly, Metal or Plastic Ducts Are Placed Inside the Concrete Before Casting. After the Concrete Hardened and Had Enough Strength, the Tendon Was Placed Inside the Duct, Stressed, and Anchored Against Concrete. Grout May Be Injected into the Duct Later. This Can Be Done Either as Precast or
Take Full Advantages of High Strength Concrete and High Strength Steel Need Less Materials Smaller and Lighter Structure. No Cracks Use the Entire Section to Resist the Load Better Corrosion Resistance. Good for Water Tanks and Nuclear Plant Very Effective for Deflection Control Better Shear Resistance
Disadvantages Compared to Rc:
Need Higher Quality Materials, More Complex Technically, More Expensive, Harder to Re-Cycle.