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

AIM-

• To extract values of longitudinal steel ratio, boundary elements length and shear reinforcement from design results.
• To provide cross section steel arrangement from base to terrace w.r.t IS 13920-2016.
• To provide elevation drawings of reinforcement details of shear walls from base to terrace.

PROCEDURE -

1. Open the given ETABS file and Run Analysis :

2. Display > Show tables > Structure output > Modal Info > Modal Participating Mass Ratios :

3. Elevation > Base

4. Display Support/Spring Reactions> case> EQX ( Earthquake in X direction ) :

5. It will show the shear force values as following :

• The summation of the values divided by the Total Base Shear will give the % shear forces taken up by the shear walls.
• This percentage should be more than 80%, if not we need to add more shear.
• Also, 25% shear is taken up by the Moment Resisting Frames.

6. Total Base Shear is calculated by : Display > Show tables > Structure output > Base Reactions:

Here, at EQX the total base shear is given as -2479.9576.

7. Select Elevation > 11 ( grid A11 ) ;

8. Shear wall design > View shear wall references > OK :

9. Shear wall design > Load combinations :

10. Shear wall design > Design start/check :

11. Shear Wall Design > Display Design Info : Pier Reinforcing ratios : Extract the values from output results :

12. Shear Wall Design >Display Design Info > pier Shear reinforcing :

13. Shear Wall Design >Display Design Info > Pier Edge/Boundary Zones :

14. Right Click on any shear wall and the following details will be displayed -

CALCULATION OF SHEAR WALL DETAILS WITH ACCORDANCE TO IS 13920 2016 -

a.

• Overall height of wall h = 21000mm
• Length of wall L = 1500mm
• Ratio of h/L = 14 > 2
• Hence the wall is of type = Slender.

b.

• Largest Diameter that can be used in shear walls should not exceed 1/10th of thickness of wall = 300mm thickness
• 300/10= 30mm
• 12mm bar is used for detailing so OK.

c. the maximum spacing of shear should not exceed [CLAUSE 10.1.9]

• 1/5th horizontal length of wall = 1500/5 = 300mm
• 3 times thickness of wall = 30 X 3 = 900mm
• 450mm

Hence adopt 300mm spacing for both vertical and horizontal reinforcement.

d. Minimum horizontal reinforcement in RC shear wall - [ CLAUSE 10.1.6 Table 1 ]

• 
• (use 1st one )
• 0.0025 + 0.5 (21000/1500)(0.029X1500X300)
• = 0.01672 X cross section of wall
• = 0.01672 X 1500 X 300 = 7524 mm^2
• 7524/21 = 358 mm^2/m height of wall

Hence , provide 16mm dia at 100mm c/c spacing.

thus , 1000/100 X 2 X 201 = 4020 mm^2 .OK

e. Minimum boundary reinforcement calculation as per [CLAUSE 10.1.6 Table 1]

• 
• (use 2nd )
• 0.008 X 300 X 300 = 720mm^2/m

Provided minimum 8 bars of 12mm dia. 8X113 = 904mm^2 . OK

f. Minimum web reinforcement [CLAUSE 10.1.6 Table 1]

• 
• (use 3rd)
• 0.0025 (1500-300-300) X300
• 0.0025 X 900 X300
• 675mm^2/m

g. Minimum RC wall vertical reinforcement [CLAUSE 10.1.6. Table 1]

• 
• (use 4th)
• 0.0025 + 0.01375 (300/1500)
• = 0.00525 X cross section of wall
• 0.00525 X 1500 X 300 = 2362 mm^2/m

Provided min 24 bars of 12mm dia = 24 X 113= 2712 mm^2/m, OK

h. Boundary element special confining reinforcement [CLAUSE 10.4.4]

• Max spacing of confinement is 100mm
• 
• = 45mm^2/m
• h = min clear distance between longitudinal rebar = 150mm

Provide 2 closed links of 16mm dia

2 X 201 = 402 mm^2/m , OK

CONCLUSION -

The Design of RC SHEAR WALL is done in accordance with IS 13920:2016.