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.

INTRODUCTION :

• The design and construction of reinforced concrete building shall be governed by the provision of IS 456:2000
• Steel reinforcement of grade Fe 415 or less can be used
• strong steel is not preferable to low strength steel in earthquake - prone regions because the typical stress-strain curve of low steel shows the following advantages a)Long yield b)greater breaking strain c)less strength gain after the first yield

PROCEDURE :

• First we have to open challenge 07 page and download the challenge
• Open it in the etabs as shown below

• Next we have to check the load combinations as shown below
• Next we have to start the beam design by selecting start design/check option as shown below,
• After the complete of the beam design we need to selevt the display design info option as shown below,
• after selecting the display option , the new tab appears in that we select the longitudinal reinforcing in the design output and click on the ok button as shown below
• Next longitudinal reinforcement details as appears

LONGITUDINAL REINFORCEMENT

• The top as well as bottom reinforcement shall consists of atleast two bars through out the member length
• Analysis need to be done
• Concrete design is done for this model
• 3 Span continous beam along grid A

At the top ,

Maximum at end support 2046 mm^2

Minimumat end support 938 mm^2

Ast for 32 diameter = 804.24

Ast for 25 diameter = 490

Ast for 20 diameter = 314

Ast for 16 diameter = 201

Ast for 12 diameter = 113

Maximum at the mid support is 511 mm^2

• 2 bars of diameter 32mm and 1 bars of 25mm satisfies the over all Ast
• 2 * T32 = 1608 mm^2
• T25 = 490 mm^2
• 2 * T32 + T25 = 2098mm^2

(OR)

• 2 bars of diameter 32mm and 1 bars of 20mm satisfies the overall Ast
• 2 * T32 = 1608 mm^2
• T20 = 314 mm^2
• 2 * T32 + T20 = 1922mm^2

7 Span continous beam along Grid 3

At the top :

• Maximum at the end support is 1105 mm^2
• Maximum at the mid support is 1501 mm^2
• 2 bars of diameter 32mm and 1 bars of 25mm satisfies the over all Ast
• 2 * T32 = 1608 mm^2
• T25 = 490 mm^2
• 2 * T32 + T25 = 2098mm^2

At the bottom :

• Maximum at the end support is 1105 mm^2
• Maximum at the mid support is 1501 mm^2
• 2 bars of diameter 32mm satisfies the over all Ast
• 2 * T32 = 1608 mm^2

SHEAR REINFORCEMENT :

The detailing is done by complying IS 13920 - 2016 As per the output area of rebar , The two beams are drawn using auto cad

FOR GRID A,

Hogging capacity of beam = -288knm

sagging capacity of beam = 163knm

shear force for 1.2 (Dl+Ll) combination

Shear force from Etab analysis = 93.8Kn

Clear span 5.375

As per IS 13290 - 2016 Clause 6.3.3

sway shear at left = 970.9 KN

sway shear at right = 905.8KN

FOR GRID 3,

Hogging capacity of beam = -233KNM

Sagging capacity of beam = 161KNM

shear force for 1.2 (Dl+Ll) combination

Shear force from Etab analysis = 71.4Kn

Clear span 4.5

As per IS 13290 - 2016 Clause 6.3.3

sway shear at left = 93.8KN

sway shear at right = 49KN

• After providing the beam reinforcement details , we select the beam right click on the beam then the new tab apperas as shown below
• Next we need to click on the details option in concrte beam design tab as shown below
• Next shear details will be visible as shown below

RESULT ;

• The beams are designed succefully from the etabs sofware
• Provided the details of longitudinal and shear reinforcement for the two continous beam
• And also calculated the value of maximum shear force in the continous beam using the Etabs sofware .