WHAT ARE THE ADVANTAGES OF PRESTRESSED CONCRETE OVER R.C.C?
(JOB INTERVIEW QUESTION)
Concrete weak in tension and strong in compression. Therefore, Reinforcement concrete system has been created to overcome the weakness of concrete with rapidly development in construction, the concrete technology has to walk parallel with this development. Therefore, the Prestressed concrete was created to overcome the limit of reinforcement concrete span.
Prestressed concrete is a concrete construction material which is placed under compression prior to it supporting any applied loads or defined as Structural concrete in which internal stresses have been introduced to reduce potential tensile stresses in the concrete resulting from loads
The prestressing of concrete has several advantages as compared to traditional reinforced concrete without prestressing. A fully prestressed concrete member is usually subjected to compression during service life.
This rectifies several deficiencies of concrete.
Serviceability and Strength
1-Reduces occurrence of cracks .
2-Freezing & thawing durability is higher than non prestressed concrete
3-Section remains uncracked under service loads
4-Reduction of steel corrosion
5-Increase in durability.
6-Full section is utilized
7-Higher moment of inertia (higher stiffness)
Less deformations (improved serviceability).
8-Increase in shear capacity.
9-Improved performance (resilience) under dynamic and fatigue loading.
10-In areas where there are expansive clays or soils with low bearing capacity, post-tensioned slabs-on-ground and mat foundations reduce problems with cracking and differential settlement.
11-Reduces self weight of building thereby reducing the lateral load resisting system. 12-Suitable for use in pressure vessels, liquid retaining structures.
Application
1-High span-to-depth ratios
2-They do not crack under working loads, and whatever cracks may be developed under overloads will be closed as soon as the load is removed, owing to the cambering effect of pre-stress.
3-This becomes an important consideration for such structures as long cantilevers. Under live loads the def section is also smaller because of the effectiveness of the entire un-cracked concrete section.
4-Larger spans possible with prestressing (bridges, buildings with large column-free spaces)
5-Post-tensioning allows bridges to be built to very demanding geometry requirements, including complex curves, and significant grade changes.
6-Another advantage of post-tensioning is that beams and slabs can be continuous, i.e. a single beam can run continuously from one end of the building to the other.
7-Crack control helps in constructing high performance water tanks
8-More aesthetic appeal due to slender sections
9-Applications of various prestressed techniques enable quick assembly of standard units such as bridge members,building frames, bridge decks providing cost-time savings
Economy
1-Rapid construction
2-Better quality control
3-Reduced maintenance
4-Suitable for repetitive construction
5-Multiple use of formwork
6-There is also a definite savings stirrups, since shear in post-tensioned concrete is reduced in the inclination of the tendons, and the diagonal tension is further minimized bathe presence of pre-stress.
7-A lower building height can also translate to considerable savings in mechanical systems and façade costs.
8-Thinner slabs mean less concrete is required. It means a lower overall building height for the same floor-to-floor height.
9-Pre-tensioning is suitable for precast members produced in bulk.
10-The high tensile strength & precision of placement gives maximum efficiency in size & weight of structural members.
