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

 

SOLUTION:

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 warnings 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

Select 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 Participation Mass 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 difference 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 Brick wall 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 

1. 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.