Project 2
Complete structural analysis and design of the sample precast building (G+6) in Bhopal, M.P., India using ETABS
Key Highlights:
- Collaboration of course content from week 07 - Week 12
- Interpretation of framing plans to develop the analytical model
- Preparation of analytical model in ETABS: Geometry
- Preparation of analytical model in ETABS: Loads
- Analyzing the structural behavior of the model
- Checking the deflections, reaction uplift, story drifts in the analytical model
- Element design of every structural member
- Design for precast connections
Deliverables:
- Error free ETABS model of the building
- Element design of structural members
- Connection design of precast connection (sketches)
- Complete calculation report of the building
Answer:
Continuation from Project 1
Creation of Load combinations
Assigning the Loads to the structure
View of Brick wall load assign at all floors = 10.35 KN/m
View of Brick wall load assign at Terrace floor = 5 KN/m
Assigning Shell load to slabs = 4 KN/m2
View of load applied
Shear wall placement is identified after addressing the weak portion in the building to attain stability for modes
Create Mass source data
For Dead load multipler = 1
For Live load multipler = 0.5
as per IS 13920 for load > 3 KN/m2
Define load patterns
For Earthquake loads
EQ X
FOR EQ X+
FOR EQ X-
FOR EQ Y
FOR EQ Y+
FOR EQ Y-
WIND LOAD assign in Wind X+
Wind X-
Wind Y+
Wind Y-
Create Pier labels for the Shear walls
Go to Assign > Shell assignment > Pier label
Create Pier labels and assign them
P1,P2,P3,P4,P5,P6 for 6 shear walls
Define Diaphragm
for the slab to get as combined structure with Beams and columns
Assign Diaphragm for all the floors
View of Diaphragm assignment
again create new load combinations
Now the Model for ERRORS
It is observed that there are no warings and errors for the structure.
Now for the Precast structure it is obvious that all the joints of Beams and columns are Pinned
also the floors and walls are to be pinnedin each and every floor
so in ETABS Model it is necessary to make edge releases for all the joints
To create joints go to Assign > Shell assign > Edge releases
Selet the Floors,walls
To create joints go to Assign > Frame assign > Edge releases
Selet the Joints of beams and columns
View of Pinned joints at all the floors,walls,Beam-column Joints
Now Analyse the Structure
Analyse > RUN Analysis
Select the Modal Participation factor for the analysis
Modal ParticipationMass Ratios are observed for the Precast structure
The First Modal Participation Mass Ratio has Time period = 0.764 and Reaction in X direction = 0.6952 = 69%
The Second Modal Participation Mass Ratio has Time period = 0.552 and Reaction in Y direction = 0.6436 = 64%
The Third Modal Participation Mass Ratio has Time period = 0.368 and Reaction in Z direction = 0.6689 = 66%
The Participation mass ratios are observed in the certain range that is permissible with the Time period for
Zone 2 Building
Also the Difference between the Modal mass ratios is also in the range with the differece of approximate 5 %
The structure is very much stable for the first two modal participation ratios but the third modal ratio need to be some enhanced.
View of the Results:
Displacement results for the Model
Dead load = 1.75mm (Maximum and Minimum)
Live load =0.4mm (Maximum and Minimum)
Brick wall load = 1.6mm Maximum
= -1.5mm Minimum
Earthquake load EQ X
= 20mm Maximum
= 1.8mm Minimum
Earthquake load EQ Y
= 20mm Maximum
= 1.8mm Minimum
Wind load X+
= 10mm Maximum
= 0.9mm Minimum
Wind load X-
= 10mm Maximum
= 0.9mm Minimum
Wind load Y+
= 14mm Maximum
= 1.3mm Minimum
Wind load Y-
= 14mm Maximum
= 1.3mm Minimum
BASE REACTIONS
Base Reactions for Dead load are observed with in the near ranges of 145 KN to 680 KN
Base Reactions for Live load are observed with in the near ranges of 15 KN to 96KN
Base Reactions for Brick wall load are observed with in the near ranges of 78 KN to 515 KN
Base Reactions for Earthquake load are observed with in the near ranges of 11 KN to 87 KN EQX
Base Reactions for Earthquake load are observed with in the near ranges of 20 KN to 390 KN EQX+
Base Reactions for Earthquake load are observed with in the near ranges of 8 KN to 380 KN EQX-
Base Reactions for Earthquake load are observed with in the near ranges of 53 KN to 440 KN EQY
Base Reactions for Earthquake load are observed with in the near ranges of 107 KN to 386 KN EQY+
Base Reactions for Earthquake load are observed with in the near ranges of 84 KN to 416 KN EQY-
Base Reactions for Wind load are observed with in the near ranges of 5 KN to 215 KN Wind X+
Base Reactions for Wind load are observed with in the near ranges of 18 KN to 150 KN Wind X-
Base Reactions for Wind load are observed with in the near ranges of 7 KN to 260 KN Wind Y+
Base Reactions for Wind load are observed with in the near ranges of 7 KN to 280 KN Wind Y-
Maximum story Drift:
Maximum story Displacement for Dead load 1.8 mm
Maximum story Displacement for Brick wall load 1.6 mm
Maximum story Displacement for EqX+ load 19 mm
Maximum story Displacement for EqX- load 21 mm
Maximum story Displacement for EqY load 13.5 mm
Maximum story Displacement for EqY+ load 19 mm
Maximum story Displacement for EqY- load 14 mm
Maximum story Displacement for Brickwall load 430 mm
STORY SHEAR:
Maximum story Shear for Brick wall in EQ X+ = -430 KN
Maximum story Shear for Brick wall in EQ X- = -430 KN
Maximum story Shear for Brick wall in EQ Y+ = -600 KN
Maximum story Shear for Brick wall in EQ Y- = -600 KN
Maximum story response SPEC-X
Maximum story response SPEC-Y
Scaling of Base shear for conversion of Equivalent Lateral Force Method to Modal Response Spectrum Analysis Method (MRSA)
Standard scale factor in ETABS = 9806.65
The scale factor purpose is to match the Values of ELF method and MRSA method.
Scale Factor for SPEC X = (430.9361/6491.1475)*9806.65 = 651.046
Scale Factor for SPEC Y = (602.0431/6093.6457)*9806.65 = 968.88
Scale factor Multiplier for SPEC X = 651.046
Scale factor Multiplier for SPEC Y = 968.88
It is observed the Final scale of this MRSA method match with the ELF method
ie. EqX , EqY values of Base shear which are highlighted below are matched with the SPECX and SPECY values.
Story Shear achieved after calculation with scale factor SPEC X = 440 KN
Story Shear achieved after calculation with scale factor SPEC Y = 620 KN
DESIGN OF ELEMENTS from values obtained in ETABS:
Concrete design and Check
Design Values of Beam elements:
Beam B16 Size 230*600mm
Reinforcement required
Longitudinal Reinforcement Ast = 366+366 = 732 mm2
Shear Reinforcement = 471 mm2
Design Values of Column elements:
Beam C11 Size 500*500mm
Reinforcement required
Longitudinal Reinforcement Ast = 2000 mm2
Shear Reinforcement = 554 mm2
View of column reinforcement
Design Values of Wall elements:
Shear Wall P6 (Pier Label)
Length = 720 mm
Thickness = 250 mm
Reinforcement required details are mentioned from the ETABS Model here.
