Analysis & Design of RCC shear walls in the model using ETABS

Analysis & Design of RCC shear walls in the model using ETABS

 

AIM-

The etabs file for a G+6 building is provided.

Run the analysis and design the RCC shear walls

. The following challenge deals specifically with

the shear wall of size 300x1500 at grid A-11

in the structural model.

• Extract values of longitudinal steel ratio,
• boundary element length and shear reinforcing
• ratio from the design results.
• Provide cross sectional steel arrangement of
• the shear wall from its base up to terrace, in
• compliance with provisions of IS 13920 – 2016.
• AutoCAD application can be used for this exercise.
• Alternatively, it can be drawn by hand as well.
• Provide elevation drawings of the reinforcement
• details of the shear wall from base up to terrace.

 

 

INTRODUCTION-

 

A shear wall consist of web and boundry elements 

at either side .this boundry elements in shear wall 

subjected to alternate compression and tension 

when it is subjected to lateral force  [EQ]

 

-HENSE  it is necessary to provide special 

reinforcement  for boundry elements .

 

is 13920 -2016  provides guidelines on several

aspect of shear wall detailing .

 

-thickness of wall [clause 10.1.2]

-minimum ratio of wall lenth to thickness [c  10 .1.3]

-largest diameter of longitudinal steel bar [10.1.8]

-maximum spacing of horizontal and vertical reinforcement [10.1.9]

-condition of base of shear wall [10.1.10]

-minimum reinforcement in RC Shear wall [10.1.6]

From clause 10.1.4, walls can be categorised as squat walls,

intermediate walls andf slender walls as given below:

Now the minimum shear reinforcement in boundary

element of RC shear wall can be determined from the formula;

 

 

 

 

PROCEDURE -

-INTIALLY  open etabs  model .

-now , go to analysis tab and check model 

-after run and analysis .

-once analysis is completed we need to carry out design shear wall option .

-shear wall design > view revise preference .

-now  ,we need to start design .

-once ,design is completed go to display design option .

-then checked any failure in design .

-now ,we need to extract certAin  values from design 

-go to display design info > pier longitudinal reinforcement 

-go to display design info > pier reinforcing ration 

-go to display design info > pier edge / boundry zone width .

-go to display design info > pier shear reinforcing .

 

• Go to display design info --> pier shear reinforcing .

• Since, we have gathered the necessary information
• now we need to draft the details of a RC wall in AutoCAD for the wall at A11.

 

 

 

 

- Shear wall detailing calculations:

 

-since ,since we have gathered the nessary information , 

now we have gathered the necessary information ,

now we need to draft the RC WALLS ,in autocad  

for wall at A 11 .

 

-SHEAR WALLS  DETAILING CALCULATION :

 

-height of wall is  21000mm

-width of wall is 1500mm 

 

-hense ,ration is  obtained as 21000/1500 

=14 > 2 

so it is consider salender wall .

 

 

-maximum diameter of bar that it can be used from is code = 1/10  of thickness of part  =30mm 

-we take dia  of bar as 25mm .

-maximum spacing bar  should not exceed minimum of following 

 

a]1/5 x 1500 = 300 mm 

b]3x300      =900 mm 

c] 450 mm 

 

maximum spacing limited to 300mm 

 

 

 

-longitudinal reinforcement ;

-from etabs results maximum longitudinal reinforcement obtained is  13128mm^2 

-since we are using 25mm dia bars .

then no . bar required will be  13128 /490  =28 bars .

-but we are providing to additional bars in boundry elements for proper confiment i.e . total  30 longitudinal bars .

 

-hense total area of reinforment provided is  13720 mm^2 

-hense , it is safe 

 

• `ow, from the code the minimum vertical reinforcement
• required is 0.0025+0.01375$(\frac{t\mathrm{w/}}{L\mathrm{w)}}$ =0.00525,
• i.e 0.00525x300x1500 = 2362.5$m{m}^2$ which is less than actually provided hence safe`
• Now, minimum vertical reinforcement to be provided in the boundary region = 0.008 x 1500 x 300 = 3600$m{m}^{2.}$
  • The reinforcement provided for boundary element in right side = 4410$m{m}^2$and
  • At left side = 5390$m{m}^2$Both are greater than the required value i.e 3600$m{m}^2$. Hence safe.
• In the web area the minimum reinforcement provided is 0.0025x1500x300=1125$m{m}^2$
•  and the provided amount of reinofrcement in web area is 3920$m{m}^2$.Hence it is safe.

- Horizontal reinforcement: 

• From Etabs results the shear reinforcement amount is obtained as 750$m{m}^2$.
• So let us provide 8mm dia bars @ 100 mm c/c,
• then the provided area of reinforcement will be 1000$m{m}^2$. hence it is safe.
• This shear reinforcement can be provided for the entire shear wall.
• Now, we need to check for boundary element
• From clause 10.4.4, the shear reinforcement required in the bundary element can be obtained from the eqn 

•  

 

• • Ash is the area of shear reinforcement required per link.
  • Sv - spaing between the shear reinforcement = 100mm
  • h - spacing between the extreme longitudinal reinforcement in the boundary element i.e 600-80=520mm
  • fck = 25N/$m{m}^2$ and fy = 500N/$m{m}^2$.
  • Hence it is obtained as   Ash =$0.05\cdot 100\cdot 520\cdot \frac{\mathrm{25/}}{415}$= 156$m{m}^2$this for one link
  • One link has 2 legs hence area of each leg = 156/2=78$m{m}^2$
  • Hence, we can choose 10mm dia bars for shear reinforcement in the boundary element width
  • whose area is around 78.5$m{m}^2$. This can be provided at the left side of the wall.
  • Now, in the right side the boundary element width is 450$m{m}^2$so, h=450-80=370mm.
  • Hence, Ash requirement will be 
  • Ash = $0.05\cdot 100\cdot 370\cdot \frac{\mathrm{25/}}{415}$111$m{m}^2$ for each link. Hence, for one leg = 55$m{m}^2$
  • Hence we can provide 8mm dia bars for shear reinforcement in the boundary element width whose
  • area is around 50$m{m}^2$. This can be provided at the right side of the wall.
  • That is, for boundary element width special confining reinforcement to be provided is 
  • 10mm dia bars @ 100mm c/c at left side BE and 8mm dia bars @100mm c/c BE.

 

 

 

 

RESULT-

THE values of longitudinal steel ratio ,

boundry element lenth and shear reinforcing 

ratio from design result have been calculated .

-elevation drawing of of reinforcement deatail 

of shear wall from base to terrace has also been drafted 

acc. to code  is 13920 -2016.