Reinforcement Detailing of Beams from ETABS output

Challenge 7 – Detailed design of concrete buildings -1

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.

Aim:-

• To design the beams in detail from the Etabs 2018.
• To provide details of longitudinal and shear reinforcement for the given two continuous beams.
• To calculate the value of maximum shear force in any one of the spans in the continuous beams as per clause 6.3.3 (b) in IS 13920 – 2016.

Introduction:

• Beams are horizontal structural elements used for the supporting lateral loads.
• In conventional reinforced concrete structures, beams usually receive load from the floor slab, but may also be subjected to other loads such as wall loads, finishes, services installation, etc.
• The design and detailing of RC beams involves the selection of the proper beam size and the quantity of longitudinal and shear reinforcement that will satisfy ultimate and serviceability limit state requirements.
• Afterwards, It is very important that the beam reinforcements are placed and arranged properly on site, to avoid construction error.

Procedure:

• First open the challange 7 attachment and download.
• After downloading the Challenge,open it in the etabs 2018, as shown.
• Go to design tab and click on concrete frame and select view preference.
• Next we have to check the load combinations, as shown

• Next Go to the 'Start Design/Check option and click as shown.
• Go to conrete frame and click on design info and set longitudinal reinforcing as shown below.

Provide details of longitudinal and shear reinforcement for the two continuous beams

• 3 span continuous beam along grid A.
• Now we provide 3-28 dia at the top and bottom, as shown.
• Next we provide 1-8 dia at the top supports for the continuous beam, as shown.
• The maximum Ast for the bottom support is 1766mm and bottom middle is 702 mm^2
• The maximum Ast for the top support is 1889mm and top middle is 453 mm^2

• 7 span continuous beam along grid 3.
• provide 3-22 dia at the top and bottom, as shown in the below.
• Next we provide 1-10 dia and 1-12 dia at the top supports and we provide 2-16 at the bottom middle for the continuous beam.
• The maximum Ast for the bottom support is 1061mm and bottom middle is 1493 mm
• The maximum Ast for the top support is 1915mm and top middle is 479 mm^2

Provide reasons for failure of the middle span along grid A.

• Along grid A-the is unequal span length beams alond grid A,which disturb the load distribution.Instead of equal transfer of loads their will be unequal distribution of load among three beams at grid A.
• To avoid the failure either span of all beams to be maintained same or provide additional shear links and longitudinal reinforcement at middle beam.

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.

• select the beam and rgiht click, a new tab appears.
• select an combination and click on details, select shear details.
• For UDcons56,
• Design shear force Ve=230.7 KN
• Factored shear force = 194.8 KN
• Design shear force >Factored shear force,hence analysis is correct.

RESULT:

• The beams are designed in detail (as given data) from the Etabs software.
• The details of longitudinal and shear reinforcement for the two continuous beams is provided.
• The value of maximum shear force in the continuous beams using the Etabs software is also calculated.