Reinforcement Detailing of Beams from ETABS output
Aim
To provide the longitudinal and shear reinforcement details for the two span continuous beam
To find out the reason of failure of the middle span along grid A and possible way to resolve
To calculate the maximum shear force in any one of the spans in both the continuous beams as per Cl 6.3.3(b) in IS 13290-2016
Design of RC Beam in Etabs
Once the models and the load parameter were assign then go for check model and confirm is their any warning in the model. If no warnings presents means the model is Ok
Now Run the analysis and Frame design using the following Load Combinations
Then Design and check whether the members were passed
From the Display Design Info of Design Frame Check the Longitudinal reinforcement
From the Display Design Info of Design Frame Check the Shear reinforcement
The flexural and shear reinforcement details were noted from the above out put and corresponding details were draft through autocad for Grid A and Grid 3 beams with the standard specifications followed by IS 13920-2016
Grid A
Maximum Ast at support Top as 1804 sq mm
Maximum Ast at Mid Top as 452 sq mm
Maximum Ast at Support Bottom - 1679 Sq mm
Maximum Ast at Mid Bottom 451 Sq mm
There Provide 3#28mm dia at Top and 2#28mm dia + 1#25mm dia at bottom
Grid 3
Maximum Ast at support Top as 1590 sq mm
Maximum Ast at Mid Top as 430 sq mm
Maximum Ast at Support Bottom - 969 Sq mm
Maximum Ast at Mid Bottom 1151 Sq mm
Therefore provide 3#25mm dia at bottom and 2#25mm+ 1#28mm dia at top
Design of RC Beam in Etabs
According to IS 456:2000 the maximum permissible shear stress for M25 grade concrete is 3.1MPa.
From Etabs Out put result the middle span of Grid A reaches its limit, therefore it shows the sign of overstressed
This can be resolved either by reducing the cross section of beam element or by increasing the grade of concrete thus help to limit the shear stress.
Calculate value of 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
The shear demand force on Etabs as 154 kN
According to IS 13920-2016 the sway shear at left and right as 244 kN
Conclusion
Thus the model has been design and corresponding RC beam details were done as per IS 13920 standards.