Structural Modelling using Etabs 2018

The architectural drawings for a G+7 residential building in zone 5 has been provided. The floor plan is the same for all 7 floor levels. Possible column positions have also been provided. Conceptualize a framing plan layout and then model the building in Etabs. The following architectural drawings have been provided:

• Typical floor plan – The location and thickness of the brick walls and the use of the
  space (for estimating live load) can be obtained from this plan
• A building section through the staircase and lift core is provided
• Parking layout in the ground floor – the column/shear wall arrangement must not
  obstruct entry/exit of vehicles.
  The following loadings are to be taken into account:
• Brickwall made of AAC blocks
• Finishes – floor tiles of 75 mm thickness
• Live loads as per IS 875 part 2
• Water tank of 20 KL above the staircase at Mumty level
• Lift Machine room at mumty level above lift core

The structural model must comply with provisions of IS 1893 and IS 13920.
Run a modal response spectrum analysis and check analysis results of the ETABS model for inter-storey drift requirements, vertical & planar irregularities, minimum shear wall requirements,maximum axial load ratio for column and shear walls, effective moment of inertia for beams
and columns etc.

Please note that the column positions shown in the architectural typical floor plan are only to provide an initial starting point for modelling. Participants will have to change its size, introduce shear walls, and add new vertical elements after running the analysis. You will have to run the analysis multiple times until a structural model is obtained that meets structural code requirements without compromising architectural functions. Also, there is no one ‘correct’ structural system for this challenge. There can be multiple possible solutions for this problem.

AIM:

To model an apartment with all seismic consideration, based on given architectural input and to know how to check the seismic performance of an apartment using ETABS

INTRODUCTION:

To model and analyse the G+7 residential building with the given architectural drawing using ETABS

Data required for Etabs analysis-

• Pinned support, base + 9 story (ground to terrace) + 1 mumty
• Column 300x600mm & 300X750, beam 300x450mm, slab 150mm thick, shear wall 300mm thick
• Live load 2kN/m2, floor finish 1.5kN/m2, wall load 3.5kN/m, water tank 20KL over mumty equivalent to 200KN overall load

Conceptual design consideration before analysis-

• Re-entrant and cut-out check and modification (compromise)
• Vertical irregularity (soft story)
• Planar irregularity (looks symmetrical)
• 2% shear wall area with respect to build area
• Stiffness modifier for column, beam & shear wall (0.35 for beam, 0.7 for vertical)

Key point to remember while modeling-

• No slab, no wall load in ground floor
• Proper end releases in beams as per engineer intent
• No interior wall load in terrace
• Comparison of static and dynamic forces and revising the factor

PROCEDURE:

STEP 1) Create Model Reference in AutoCAD

• Changed the column size, position & orientation without disturbing the parking area and floor area, it doesn’t affect the floor area and parking area
• Created shear wall according to my opinion
• This drawing is used as a reference drawing for etabs model
• I have overlapped the floor plan to the new designs plan

STEP2) Create New Model in ETABS

• Click on New Modal from ETABS home interface
• Select Unit Built in Setting from Modal Initialization dialog box
• Change display unit as METRIC SI
• Region for default Material as INDIA
• Steel selection database INDIAN
• Steel design code IS-800:2007
• Concrete design code IS-456:2000 enter OK

STEP3) Create Grids

• A new dialog box opened as New Modal Quick Templates
• Select Custom Grid Spacing and click on the Edit Grid Data
• Modify the X & Y Grid Data from the Grid System Data dialog box and click OK

STEP4) Add Building Storey

STEP5) Define Material

• The grid arrangement of the new modal will open
• Go to Define and click Material Property
• Define Material dialog box will open, click on Add New Material
• Add New Material dialog box will open, select Material Type Concrete and ensure Grade M30 click OK
• Material Properly Data dialog box will open, click OK
• Again, click on Add New Material
• Add New Material dialog box will open, select Material Type Rebar and select Grade HYSD 550 & 415 click OK
• Material Properly Data dialog box will open, click OK

STEP6) Add Column, Beam & Shear Wall

• Go to Define tab, and select Frame Section from Section Property
• Click on Add New Property from Frame Properties dialog box
• Click on Rectangular Section for Beam from Frame Property Shape Type
• Change the Property Name as B300X500 and Material M30 and section dimension Depth as 500 & width as 300 from Frame Section Property Data, click on Modify/Show Rebar under Reinforcement
• Change Design Type and Rebar Material, click OK
• Again, Add New Property for Column and select Rectangular Section
• Change the Property Name, Material and Dimension and Modify/Show Rebar similarly

STEP7) Add Slab

• Go to Define, Select Slab Section from Section Property
• Click on Add New Property for Slab
• Change the Property Name, Slab Material, Modeling Type and Thikness of Slab

STEP8) Load Pattern

• Go to Define and select Load Patterns
• Add Wall & Floor Fininsh Load as Super Dead type
• Simalry add EQX & EQY Load as Seismic type and select IS-1893:2016
• Modify the lateral load and uncheck the other direction except X for EQX and Y for EQY

STEP9) Define Mass Source

• In Define tab Select Mass Source
• Click on Modify/Show Mass Source
• Check mark only Specified Load Pattern
• Add wall, live and dead load

STEP10) Response Spectrum

STEP11) Check Load Case

• Go to Define and select Load Cases
• Check load cases and click OK
• Modify the model

STEP12) Load Combinations

• Go to Define select Load Combinations
• Add Default Design Combination
• Check on Concrete Frame Design,Concrete shear wall Design and Convert To User Combination

STEP13) Draw Column and Shear wall

• Select Quick Draw Column
• And change the Properties

STEP14) Assign Load

• Select all Beam
• Assign Frame Load as a Distributed
• Load Pattern Name Wall and Uniform Load 3.5kn/m
• Similarly select slab
• Assign shell load as uniform
• Load Pattern Name live and Uniform Load 2 kn/m
• Added floor finish and water tank load

STEP 15) Add Diaphragms

• Select Slab
• Assign Shell as Diaphragms

STEP 16) Base Support

• Goto the base plan
• Select all the joitns
• Assign>joints>restrian
• Select fast restrain and click ok
• All the joints are fixed

STEP 16) Assign Peir Lebal

• From define added pier labels
• Assign one by one on shear wall

STEP 17) Add live load Reduction factor on each floor

STEP 18) Check Modal and Run The Analysis

• Here I got no warning so that modal ok, we can run analysis
• After completion of anaysis we got max. & min. deflection

STEP 19) Check Result

• Form table checked the modal infromation and compare the result
• First two fundamental modal mass grater than the torsional mode
• Modal mass participation for first 3 modes dominates at least 65% (Achieved for X-axis only)
• Mode-1 and Mode-2 differs by 10% (Achieved)
• Principal modes be greater than Torsional mode (Achieved)
• Inter story drift ratio limited to 0.004 (Achieved)

RESULT:

To model and analyse the apartment with all seismic consideration, based on given architectural input and to check the seismic performance of an apartment using ETABS and attach the modal