Understanding RCC – structural Beam aspects

A beam is a horizontal structure made up of Rebars[reinforcement steel] and concrete. The main purpose of beams is to

1. Bind the columns together to form the RCC structure.
2. It also allows to distribute the load to all the columns when a roof is placed over it.
3. It supports the span of roof along with columns.

This means that a beam design is more critical when you have wide spans of roof over a big room. The total length of beam between two columns needs to be reinforced with appropriate strength or diameter of rebars used. But you have to keep in mind that a thicker rebar also means more weight. So when you mason uses his knowledge of past and says we can use higher diameter just make sure you discuss with your structural engineer before doing any such steps. This also makes it critical for a structure engineer to verify whether the beam design by your rebar guys is proper.

Where do you come in ?

1. You can calculate the total length of rebar required by using structural drawing as reference. Nowadays the rebars are sold by count and not be weight. You can exactly buy the number of rods that are required as per design. Infact you can even instruct your rebar guy on how to make the cut of the rods. You know its about using minimal number of rods. You will need patience and an urge to understand or challenge yourself.
2. Note that the rebar guys use good enough approximation and sometimes directly cut the bigger lengths first and whatever is remaining try to see if its useful. So you know, sometimes you could end up wasting more rebars than required. If a full length rod is remaining normally the shop guys buyback such full remaining rods. You can discuss with shop guys beforehand.
3. Note that a rebar is of around 39 ft in length. Its diameter ranges from 8mm, 10mm, 12mm, 16mm, 20mm, 25mm. Higher the diameter higher the price. So my suggestion is study the structural drawing for the highest diameter rods first and try to optimize the requirement and lengths you need. This is more an exercise to your brain and is important because, first you understand what is happening. Second you understand what a rebar guy is doing. Third, it allows you to optimise and save money if rebar guy is missing some key aspects. Most importantly it allows you to cross check the work once it done and fix few things if there are some mistakes before you do the roof concrete. You dont want your house to suffer due to a mistake. As I always mention if you are the owner of the house and its your dream project then you will need to spend time and effort and learn. For all other people its a job and they will spend as minimal time because most probably everyone is doing multiple projects or multiple structural drawing. They may spend around 10 mins verifying the work. Because its most of the time a once in a lifetime opportunity. Whatever you learn during this time is useful to you and most importantly you can ensure that structure is built using the right drawings.

3. Sometimes you can even identify wrong structural drawings and request clarification. For example if you see a longer span and you sense that there is not enough rebars there you can clarify with structural engineer. It always helps if you are knowledgeable and can review someones work. Just remember in engineering the best work gets done by review and rework. Be open to all thoughts.

Hope the information presented clears some aspects. Here is a more complete list of articles. Do read about them

• Understanding RCC – structural RCC columns
• Understanding RCC – Reinforcement steel bar or rebar
• Understanding RCC – structural footing drawings