Challenge

Reinforcement Detailing of Beams from ETABS output

Challenge 7

Aim:

To design Beam in ETABS software and to design the RCC Moment Resisting Frame
To calculate the maximum shear force in any one of the spans in both the continuous beams as per Clause 6.3.3 (b) in IS 13920 – 2016.

Introduction:

Beams are horizontal structural members that are used to support the lateral load. The beams usually receives load from the floor slab, but, the load intensity to the beams include the loads from the walls, finishes and the self weight of the beam. So it is the first priority to calculate the load.
After this the amount of reinforcement required, the cross-sectional area of a single steel bar, that is going to be provided in the beam as per their diameter, he number of the bars required for bending etc are found out.
After these steps, we find out the nominal shear stress and permissible shear strength depending upon the dimensions, and the percentage of tensile reinforcement. If the nominal shear strength exceeds the permissible shear stress, shear reinforcement is to be designed.
It is also verified that the nominal shear stress should not exceed the maximum shear strength, either the section is redesigned.
Checks for deflection and cracking is done.
And at last, the complete design process, the detailed design datas and cross-section of beam showing the reinforcement is provided.

Procedure:

Download and open the downloaded ETABS file
Check model and Run analysis is done
Select Design > concrete frame design >Select design combination
Now again select Design> Concrete frame design > Start design/check
From the Design menubar, select concrete frame design> Display Design info.
Now change to Longitudinal reinforment as the design output, click apply and then ok
From the Design menubar, select concrete frame design> Display Design info.
Now change to Shear reinforcing as the design output, click apply and then ok
Now click on the beam and right click, then select detailing option, we will get the details about the beam, including the shear force and reinforcement
For continuous beams in the 1st floor-3 span continuous beam along Grid A
Beam 33
Beam 34
Beam 38
For continuous beams in the 1st floor-7 span continuous beam along Grid 3
Beam 24
Beam 25
Beam 69
Beam 70
Beam 73
Beam 14
Beam 16

Calculation Results:

2 bars of 32mm dia is provided at the top
At the bottom also 2 bars of 32 mm dia is provided.
In the middle of the beam (ie from the beams B63 to B70 to B73) in addition to 2 bars of 32mm dia bars, 1 bar of 25 mm is also provided at the top

Result:

The reasons for failure of the middle span along grid A is mainly due to high shear stress, this can be avoided to an extreme by reducing the depth of the beam, which in turn reduces the requirement of stiffness. And the high shear stress can be also controled by changing the grade of concrete used.
Maximum shear force obtained from ETABS software is 174.1134 KN

Ship work like this
in your own course.