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(tw/Lw) =0.00525,
- i.e 0.00525x300x1500 = 2362.5mm2 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 = 3600mm2.
- The reinforcement provided for boundary element in right side = 4410mm2and
- At left side = 5390mm2Both are greater than the required value i.e 3600mm2. Hence safe.
- In the web area the minimum reinforcement provided is 0.0025x1500x300=1125mm2
- and the provided amount of reinofrcement in web area is 3920mm2.Hence it is safe.
- Horizontal reinforcement:
- From Etabs results the shear reinforcement amount is obtained as 750mm2.
- So let us provide 8mm dia bars @ 100 mm c/c,
- then the provided area of reinforcement will be 1000mm2. 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/mm2 and fy = 500N/mm2.
- Hence it is obtained as Ash =0.05⋅100⋅520⋅25/415= 156mm2this for one link
- One link has 2 legs hence area of each leg = 156/2=78mm2
- Hence, we can choose 10mm dia bars for shear reinforcement in the boundary element width
- whose area is around 78.5mm2. This can be provided at the left side of the wall.
- Now, in the right side the boundary element width is 450mm2so, h=450-80=370mm.
- Hence, Ash requirement will be
- Ash = 0.05⋅100⋅370⋅25/415=111mm2 for each link. Hence, for one leg = 55mm2
- Hence we can provide 8mm dia bars for shear reinforcement in the boundary element width whose
- area is around 50mm2. 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.