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 (show in the etabs model). 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: ETABS is an engineering software product that caters to multi-story building analysis and design. Modeling tools and templates, code-based load prescriptions, analysis methods and solution techniques, all coordinate with the grid-like geometry unique to this class of structure.

PROCEDURE:

1. Open the etabs file attached with the challenge.

2. Select the shear wall near A by drawing a window, go to elevation view and select the 11 to see the selected shear walls. By clickling view display select the label from pier so that we can see whether it is assigned or not.

3. Now its good to start we start by running analysis, for that we need to save with a proper name. Next we click on the shear wall design option to see the values of longitudinal reinforcing areas.

4. Go to the design shear wall option and select the display design info option from that pier shear reinforcing is selected and applied to get shear values. Then we also check the boundary widths.

5. Now we go to edit stories and grid systems from edit option and take story data also for the design of the shear wall.

6. After the reinforcing details are noted, we are begining with the specification and using the guidelines check on the design of the shear wall.

• Classification of shear wall as per IS 13920-2016 Clause 10.1.4
• Slender wall

h_w / L_w = 21000/1500 = 14>2

• Min. net vertical reinforcement as per IS 13920-2016 Table-1

= 0.0025+0.01375(300/1500) which we multiply with the top view of the wall as it is vertical reinforcement we get

= 2363mm^2

• Min. Vertical reinforcement within boundary element table-1

1440mm^2 on left (600mm width boundary element)

1080mm^2 on right(450mm width boundary element)

• Minimum horizontal reinforcement in shear wall per IS 13920-2016 Table 1

(ρ_h)_min = 0.0025 + 0.5((h_w/L_w)-2) (ρ_h – 0.025)

ρ_h = 750/(300*1000) = 0.0025

h_w = 21000

L_w = 1500

(ρ_h)_min = 0.0025 + 0.5 (21/15 – 2) *0

(ρ_h)_min = 0.0025 which is the same 750 mm²/m

• Max dia of the rebar for shear wall as per IS 13920-2016 Clause 10.1.8

1/10th of wall thickness = 300/10 = 30mm

where commercial rebar dia used to be 25mm which can be adopted

• Confining reinforcement spacing for boundary elements as per IS 13920-2016 Clause 10.4.4

1. 1/3 of min member dimension = 300/3 =100mm
2. 6 times smalles main rebar = 6*25=150mm
3. 150mm permissible if vertical bars are spaced at maximum 200mm

Max spacing of confining reinforcement in boundary element 150mm

• Confining reinforcement within boundary element as per IS 13920-2016 Clause 10.4.4

A_sh = 0.05 S_v h f_ck/f_y

S_v = 150mm, h= 1000mm

A_sh = 452mm²

7. With the above procedure we are detailing the reinforcement of the shear wall.

8. The drafting is completed using the autocad software which is shown below.

9. 28 no. of 25mm dia main bar + 2 no. of 12mm dia additional boundary element bar.

RESULT: The model was taken from the challenge, from which the details are noted and checked with the guidelines and designed the shear wall.