Do you know what gives real strength to your building ?
Human body without bone structure will be like flesh ball & will not be able to be a strong structure as it is now to do any work . Like wise buildings without framework are impossible to create.So when creating a structure it is most important to give a framework to give an identity & it must be of good quality to be strong enough.Concrete frameworks are the most common frameworks that are used in today’s modern house.The horizontal frameworks are called beams & vertical frameworks are called columns. From these two framework column is most important because it provide support to the entire building not like beam which provide support to a floor.For framework steel rods are used and there are many factors which need to be taken care during the framework construction.
Construction companies must give priorities to the strengthening of framework not only to the foundations. Therefore the guidelines must be followed to maintain the quality of framework. For this we are covering the details of dos & don’ts below here.
Steel Rods-: Plain concrete without steel or other reinforcement is strong in compression, but weak in tension .Steel is one of the best forms of reinforcement to take care of stress & to strengthen concrete to bear loads. It forms the basis concrete structure and is generally laid out in a circular cross section.
But the steel rods used in making of framework must be of good quality, It must be free from loose rust, oil paints, mud etc.,& cut, bent & fixed properly. The bar should be placed & maintained in position by using proper cover blocks, spacers,supporting bars ,laps etc.
For general house construction,6-20 mm diameter bars are used .Mild steel bars and deformed bars are used, with the latter used most commonly now a days, because of higher strength and the reduced requirement of steel.
Thermo mechanically treated (TMT) & corrosion-resistant steel bars with added features have been introduced recently. Remember to purchase ISI certified steel bars, from reputed manufacturers, regardless of the size you choose.
Lap length:- Lap length is provided at the junction where an old bar that terminates and join new extension bar. Lap length of about 50 times the diameter of the bar is considered safe. All laps should be staggered and not provided at one place. A maximum of 50% bars should be lapped per section.
If the required lap length is not available at the junction owing to space and other constraints, couplers or the correct method of welding should be used to join bars.
Anchorage length:-Also called development length.This is the additional length of steel of one structural member necessary for insertion with another member at the junction .For example, the beam with the pillar, or the pillar with the foundation. The required length is similar to the lap length mentioned above or as per design instructions.
Cover Blocks:-Cover blocks are placed to prevent the steel rods from rusting due to exposure to air, and to fix the bars in place. Sometimes during the correcting activity,the covers tend to get displaced. To prevent this tie the cover block using thin steel wires called binding wires to the steel bars. Cover should be made of cement and sand mortar. The blocks could be cubical or cylindrical in shape. Normally, cubical cover blocks are used. As a thumb rule ,a minimum cover of 2” in footings,1.5” in columns and ½” to ¾” for slabs and beams is recommended.
Shuttering:- The framework or shuttering should be rigid and closely fitted, with sufficient strength to support wet concrete. It should be leak proof to prevent the cement –sand-water mix from leaking .The face of framework should be treated with form release agents available in the market or a mixture of diesel and grease.
Now a days steel frameworks are used which is very convenient to work.
Deshuttering:- Removal of shutters (deshuttering)results in the concrete being subjected to loads and exposure to the atmosphere. If the ambient temperature is above 15 degree centigrade and the workmanship is good following striking/deshuttering period is considered as safe:
Here is the table which give the data what is the safe period to remove the shuttering:
This is total work needed to be done properly for the framework of a house to make the house last for longer period of time.If you are constructing your house you should check if this work is properly done or not.