Structural Design 02 - About Steel & Concrete for Designs

 When we talk about steel, we use two types of steel for design and constructions. Tor Steel and Mild steel. Hot rolled tor steel strength is 460 Newton per square millimetres. Hot rolled mild steel strength is 250 Newton per square millimetres.

fy=460N/mm^2 & fy=250N/mm^2

In reinforcement calculation formulas we use these values.
Ex: As(req.)=M/(0.87fyz)  Here we can use fy=460N/mm^2 for reinforcement calculation.(Tor)

Say we have a stirrup or link design of a beam. We may have below equation for that.

Asv>=[(Vd-Vc)bvSv/(0.87fyv)]    Here we can use fy=250N/mm^2 for reinforcement calculation.(mild)

According to the diameter sizes, Reinforcement area of cross sections are as follows.

Nominal diameter of a bar is taken without the RIB around a rebar. It is shown in below image.

As an example we can use the above values inorder to calculate the the provided reinforcement areas in below shown beam sections as mentioned below. 

We have shown similar examples below as well.

Mild steel rebar or reinforcement bar section is circular as it doesn't have any rib. We call them as round bars. Usually we can find them in 10 mm, 12 mm, 8 mm and 6 mm diameter sizes. In house constructions, 6 mm or R6 mild steel bars are commonly used for fabricating the beam stirrups. 

When we talk about concretes, we have two major types. Mass concrete and reinforced concrete are those two types. In mass concretes we don't use reinforcements. Just Concrete. Usually we use these for screed concrete which is placed before casting a footing on the ground. The purpose of that is to level the uneven ground surface and avoiding bleeding the liquid part of foundation concrete to the ground. It passively act as an additional covering to the reinforcement as well.

Reinforced concrete is also known as structural concrete. We use several grades of concretes for constructions according to their different different mix proportions. Few of them are shown below along with their water cement ratios and cement contents.You can find this table in the British standards BS8110 table 3.4

There is a guideline for the aggregate sizes to be used in BS8110. 

We can discuss about the Reinforcement cover and it's requirement from our next article. Until then please subscribe us. Thank You!