Reinforcement Detailing of Beams from ETABS output

Introduction:- 

Seismic force :- It is the external force applied to the structure as a result earthquake generated agitation

• In this the earthquake occured at once in a 2500 years
• Seismic cannot be determined it's a less uncertainity  
• Seismic force occure at the ground level in all the directions and it has 3degree of freedom they are 2 translational and 1 rotational force
• The base shear starts at the bottom of the buildings when the seismic load occures 

ETABS :- 

• The full form of ETABS is Extended three dimensional analysis of building system
• ETABS software was started by CSI (Computers and Structural ,Inc
• ETABS is a engineering software which is used for multistorey analysis and design
• In this software we can analyse and design the seismic load, wind load, and other loads 
• In this software we are defining and assigning the materials, frame sections, slab sections diaphragm etc.,
• This software give the proper output result to that analysed model 

• In this question the model is given in the question itself so we need to analyse and design the frame structures 
• By using an AutoCAD draw the detailing of the beam

Answers along with procedure:- 

Detailing rule of any reinforced concrete member 

• Minimum reinforcement for shrinkage and temperature 
• Reinforcement required for limiting crack width
• Ultimate limit state design rebar requirement 
• Ductility rebar requirement 

Which ever is greater should be drawn in detailing

Minimum longitudinal reinforcement as per IS 13920-2016 clause 6.2.1 As = 360mm^2

Minimum shear (or) trnasverse reinforcement  as per IS 456:2000 clause 26.5.1.6 (Assuming 1000mm spacing in the formula) Asv = 332mm^2

Development length as per IS 456:2000 clause 26.2.1 Ld = 41xdiameter of the bar

 ETABS design Procedure:- 

Step1:- 

• The ETABS model file is given in the question 
• Open the file in a ETABS software
• Click on the Run analysis

Step2:- 

• After the analysis complete then click on concrete frame design 
• And wait for some times it will give the details about reinforcement, shear, bending moment etc.,

Step3:- 

• When the concrete design has done then it shows the longitudina reinforcement 
• This is the snap shot of the longitudinal reinforcement required

Step4:- 

• After the longitudinal reinforcement 
• To see the shear reinforcement  Go to the concrete design then go to the display design information
• Then  select the shear reinforcement it shows the shear reinforcement values 
• The snap shot is inserted below

Step5:-

Longitudinal reinforcement of the beam at Grid A from ETABS (mm^2)

Shear reinforcement of the beam at the Grid A from ETABS (cm^2/1000)

 Step6;- 

Longitudinal reinforcement of the beam at Grid 3 from ETABS (mm^2)

Shear reinforcement of the beam at the Grid 3 from ETABS (cm^2/1000)

Additional reinforcement guidelines from the IS 13920-2016 clause 6

As per IS 13920-2016 clause 6.3.3(b) the sway shear force is given

Step7:- Sway shear force at right 

Sway shear force at left

The value of   V_ua ^D+L   is 70.5835 is taken from the ETABS model

The value of   V_ub ^D+L   is 70.333 is taken from the ETABS model

Here the value of M_u ^As , M_u ^Bh , M_u ^Ah , M_u ^Bs  are given by the ETABS model

+ve reprsesnts - Sagging

 -ve represesnts - Hogging

• M_u ^As  = 161.072 KN-m
• M_u ^Bh  =219.3905 KN-m
• M_u ^Ah = 233.3577 KN-m
• M_u ^Bs  = 154.5493 KN-m

Here the length is given as 4500mm by the ETABS 

so the L_AB = 4500mm  

Here the calculation is done according to the formula

 Compare V_ua  on both left and right sway then take a hiighest value in that

 Compare V_ub  on both left and right sway then take a hiighest value in that

V_ua  = 50.09KN

V_ub  = 191.015KN 

Here we are using 3L-8mm dia bars at 100mm c/c at the support and 3L-8mm dia at 175mm c/c at the midspan

Step8:- Detailing for beam along   A-1 to A-3

                                         This detailing drawing is for A-1 to A-3

Detailing for beam along   3-A to 3-B

                                         This detailing drawing is for 3-A to 3-B

Result:- 

• As per the given data the beam detailing is done by using AutoCAD
• The details of longitudinal and shear reinforcement are done for both the continuous beams
• The details of longitudinal and shear reinforcement in ETABS also calculated

Shear stress :- It is the ratio of the load applied to its unit area

• In the shear stress we can increase the load and decrease the load so that we can increase and decrease the shear stress

Shear capacity of the concrete 

• It depend on the characteristic strength of the concrete 
• The shear capacity varies with the grade of the concerete
• Instead of using a M-20 grade to this failing structure we can use high grade of the concrete only for this concrete only (M-25 or M-30)
• So that we can increase the shear capacity of the beam 
• Hence the failing structure become safe