Reinforcement Detailing of Beams from ETABS output
Detail design of beams in Etabs 2018.
The ETABS file for a G+4 building is provided. Run the analysis and design the RCC Moment ResistingFrame. The following challenge deals specifically with two continuous beams in the 1st floor.
1) 3 span continuous beam along grid A
2) 7 span continuous beam along grid 3
Address the following issues thereafter.
• Provide details of longitudinal and shear reinforcement for the two continuous beams. Sketch the beam elevation details or draft it using autocad software. A sample of how beam elevation details is prepared in consultancy firms is provided below. Participants can prepare it as per their preference:
• Provide reasons for failure of the middle span along grid A. What are the possible ways this issue can be resolved?
• 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. Also, confirm these values from shear force demand calculated by ETABS.Please note that if longitudinal reinforcement provided is more than required (as per ETABS results), the shear force demand will vary from what is provided by ETABS.
Procedure:
I. First download the challenge file
II. Open the file in the etabs
III.
IV. Check the model and run the analysis
V.
VI. Next check for the load combinations
VII.
VIII. Next click on the start beam design as shown in the figure below
IX.
X.
XI. Next click on the display design info
XII.
XIII. And here select the longitudinal reinforcement
XIV.
XV. It will be displayed as shown in the figure below
XVI.
Reinforcement diagram
I. Along the grid A
a) Maximum Ast for the bottom support 1925 and bottom middle 789
b) Maximum Ast for the top support 2045 and top middle 511
Here provide the 3 bars of 20mm (942) and 5 bars of the 16mm (1004) at bottom
And provide the 4 bars of 20mm (1256) and 4 bars of 16 mm at top (804)
Next right click on the beam and check the sear details
As per clause 6.3.3.3 provide the 3 legged stirrups of dia 10mm with spacing 95mm along the entire length of the beam.
II. Along the grid 3
a. Maximum Ast for the bottom support 1042 and bottom middle 1501
b. Maximum Ast for the top support 1940 and top middle 485
Here provide the 2 bars of 12mm (226) and 4 bars of the 16mm (804) at bottom
And provide the 3 bars of 20mm (942) and 5 bars of the 16mm (1004) at top
Next right click on the beam and check the sear details
As per clause 6.3.3.3 provide the 3 legged stirrups of dia 8mm with spacing 100mm along the entire both ends of the beam. And 3 legged stirrups of dia 8mm with spacing 150mm mid span
Provide reasons for failure of the middle span along grid A. What are the possible ways this issue can be resolved?
the beam has failed due to the weak shear reinforcement as the high shear force is acting on the beam.