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

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.

AIM :

To using 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.

INTRODUCTION :

Shear wall is a structural member used to resist lateral forces, that is, parallel to the plane of the wall. For slender walls where the flexural deformation is more, shear wall resists the loads due to cantilever action. In other words, shear walls are vertical elements of the horizontal force resisting system. In this type, concrete structures are generally designed in such a way that the lateral seismic load and gravity load is bearing by consistent shear walls. These structures have no beams or columns, and the earthquake-resistant system relies solely on concrete shear walls

Shear walls possess adequate lateral stiffness to reduce interstorey distortions due to earthquake-induced motions. In this chapter, analysis of shear walls with a moment resisting frame using the Khan and Sbarounis method is discussed. When two or more shear walls are connected by a system of beams or slabs total stiffness exceeds the summation of individual stiffness. Openings normally occur in vertical rows throughout the height of the wall and the connection between wall cross-section is provided by connecting beams. Such shear walls are called coupled shear walls. The analysis of coupled shear walls by Rosman’s continuous medium method is also discussed.

PROCEDURE :

STEP 1:

• Download the given previous revit model file
• Open the revit file and the floor diagram as shown in below
• Set all stories in bottom right corner
• Select the 11A wall and go to right click and pick the shown selected object only
• Selected object image as been shown below

STEP 2:

• Go to the elevation option on top tool bar
• Next set elevation view dialouge as been opened
• Select the option 11 and apply

STEP 3:

• Go to the set display option
• And set view option dialouge box as been open
• And Select the label and then apply
• Then check the label option as viewed or not
• they as been view like p1
• Then again go set display option and unselect the label and apply

STEP 4:

• Analusis the model with help run analysis option
• After analysis as completed
• pick the shear wall design option
• the model as been design checked
• The values of the shear wall as been shown

STEP 5:

• Again go to the shear wall design option
• And pick the display design info option
• And it opened the dialouge box as display shear wall design result
• And pick the pier shear reinforcing

STEP 6:

• After selecting the pier shear reinforcing
• the values as been shown in the shaer wall
• Next we want to pick the pier edge / boundary zone walls and the value also shown in the shear wall
• Go to the edit grid story option and screen shot it for draft the reinforcing details

• right click the shear and go to the shear wall design details
• and check the details

STEP 7:

• using auto cad software to draft the reinforcement details

STEP 8:

CALCULATION :

Verification with Is13920-2016:

a) Overall height of wall h = 21000mm, Length of wall L= 1500mm

Ratio (h/L) = 21000/1500 = 14> 2

The given RC wall is slender.

b) The largest diameter than can be used in RC wall should not exceed 1/10th of thickness of wall. So 300/10 = 30mm

We used 25mm dia rebar in the detailing.

Hence OK.

c) The maximum spacing of longitudinal/ transverse rebar should not exceed (i) 1/5th of horizontal length(1)=1500/5 =300mm

(i) 3 times of thickness (t) = 3x 300 = 900mm

(ii) 450mm

So we have to adopt maximum 300mm spacing both for vertical and horzontal rebar inside RC wall.

d) Minimum horizontal reinforcement calculation as per Table-1 of IS13920-2016

(ph)min'> (Ph) min

= 0.0025 + 0.5

(hwLw-2)(ph-0.0025)>(hwLw - 2)(Pn - 0.0025)

= 0.01672 of cross section of RC wall

= 1500 x 300 x 0.01672 = 7524 sq.mm for entire RC wall height.

= 7524/ 21= 358 sq.mm /meter height of RC wall

We already provided 16mm dia at 100 mm c/c spacing which will give = 1000/100 x 2x 201= 4020 sq.mnm

Hence OK.

e) Minimum boundary reinforcement calculation as per Table-1 of IS13920-2016

(pv,be)min"> (Pv,bo) min

= 0.008

= 0.008 x 300 x 300 = 720 sq.mm

We already provided minimum 8 numbers 12mm dia rebar = 8x 113 = 904 sq.mmm

Hence OK.

f) Minimum web reinforcement calculation as per Table-1 of IS13920-2016

(PV,web)min> (Pv,web min

= 0.0025

= 0.0025 x 900 x 300 = 675 sq.mm

We already provided minimum 8 numbers 12mm dia rebar = 8x 113 = 904 sq.mmm

Hence OK.

g) Minimum overall RC wall vertical reinforcement calculation as per Table-1 of IS13920-2016

(PV,t)min"> (Pv, zt) min

= 0.0025 +0.01375

(twLw)"> (twlw)

= 0.00525 times of wall cross section

= 0.00525 x 1500 x 300= 2363 sq.mmm

We already provided minimum 24 numbers 12mm dia rebar = 24 x 113 = 2712 sq.mm

Hence OK.

h) Boundary element special confining reinforcement as per Clause 10.4.4 of IS13920-2016:

Ash=0.05vh (Fckfy)">Ash = 0.05Syh(Fakfy)

Maximunm spacing of confinement is 100mm as per drawing

h= minimum clear distance between longitudinal rebar = 150mm say

Ash=">Ash = 45 sq.mm

We already provided two closed links of 16mm dia = 2 x 201 = 402 sq.mm

Hence OK.

RESULT :

Thus we have designed the specified RC wall and detailed using AutioCAD software. Also the clauses from ductility code Indian standard IS13920-2016 are verified for the RC wall detailing.