Structural Modelling using Etabs 2018

AIM

To model and analyze the G+7 residential building from the given architectural drawing using the ETABS 2018

INTRODUCTION

• ETAB or ETABS they mean the same. Its full form is extended three-dimentional analysis of building system.
• It is an engineering software product that caters to multi-story building analysis and design.
• ETABS offers a single user interface to perfom modelling, analysis, design and reporting.There is no limit to the number of modelling windows,model manipulation views and data views.
• Basic or advanced systems under static or dynamic conditions may be evaluated by using ETABS
• ETABS modelling is the genralization that multi-story buildings typically consist of identical or similar floor plans that repeat in the vertical direction.
• Modelling features that streamline analytical-model generation,and stimulate advanced seismic systems.
• Once modelling is complete,ETABS automatically genrates and assigns code-based loading conditions for gravity,seismic,wind and thermal forces.

OBJECTIVES

• To model an apartment with all seismic considerations,based on given architectural inputs
• To know how to check the seismic performance of an apartment using ETABS

PROCEDURE

STEP:1

• Open ETABS software

• Then click on the new model and choose use built-in setting with option
• Set the display unit as Metric SI or as per the requirement
• Then click ok

• New dialogue box will appear.

• Select the custom grid spacing and then select the edit grid data

• click ok

• Then select custom story data and select edit the story data
• After clicking the edit story data option there will be another dialogue box named as the edit story data, and we need to add the stories upto the seventh floors
• Then make ground floor as master story and all other storys are similar

• The story and grids setup have been completed
• So the plan view and the 3D view has been shown below in the image

STEP:2

MATERIAL PROPERTIS

• Inorder to set the material first we need to go to the define option and there will be a drop-down list in that list there is another option called material properties

• After clicking on the material properety there will be another dialogue box named as define material, in that dialogue box just click on the option add new material

• New window will appear now define material type as concrete and grade as M30

• Click ok
• Add new material property
• New dialogue box will appear
• Select materail type and grade

• HYSD 500 for the longitudinal reinforcement
• HYSD 415 for the shear reinforcement

STEP:3

COLUMN

• Now we have to design the frame properties
• Go to the define tab there will be a drop-down list ,select section properties and from that select frame properties

• A new dialouge box will appear ,in that select add new property

• Then select the rectangular concrete section,rename it C400*600
• Change the property as M30 and change the size as C400*600

• After that another dialouge box opens

• Click on the modify/show modifiers, another dialouge box will appear on the screen fill all the relevant data

BEAM

• Now we have to design the frame properties
• Go to the define tab there will be a drop-down list ,select section properties and from that select frame properties

• A new dialouge box will appear ,in that select add new property

• Then select the rectangular concrete section,rename it B250*450
• Change the property as M30 and change the size as B 250*450

• After that another dialouge box opens

• Click on the modify/show modifiers, another dialouge box will appear on the screen fill all the relevant data

• Following the same procedure we will add another beam
• B300*500

SLAB

• Then go to define select section properties from that select slab section

• New window appears
• Select add new property,nwe dialouge box will appear

• Rename it as slab125, modelling type as membrane and change thickness as 125mm

• Similarly we will be adding the slab for the staircase of 200mm thickness
• Do the same procedure that we have done for the slab 125mm

SHEAR WALL

• Go to define --->section properties-->wall section

• Another dialouge box will appear , in that select add new property

• Another dialouge box will appear, add relevant data

STEP:4

• Draw structural members
• For that first select the mode as all stories at the right bottom corner

• So in order to use this tool to place the columns in a quick way so first go to the left side of the screen there is a option of quick draw columns

• Place the column

• Similarly add the beams

• Now similarly add the secondary beams

• Now add the secondary beams and balcony

• Add shear walls in their appropriate locations just by using etabs quick tools to draw walls and this tool is present at the left side of the screen

• Adding slab just by using the option quick draw plan/wall that are present in the left side of the screen

• Now we have to fix the connections at the base plan
• so in order to do that first we need to go to the base plan and then select all the joints

• After that just go to assign-->joints--> restraints

• another dialouge box will appear ,choose connection as fixed

STEP:5

• Click on the define and from that select the load patterns

• Define the loads like dead load , live load , brick wall load and earthquake load in x direction and eccentric earthquake loads in positive x and negative x and same loads in y direction also mension IS codes of respective loads

• Click on modify lateral load, set range from base to seventh floor,change direction and eccentricity ,seismic zone factor as 1 and time period as 0.5 seconds

• Do the same for all the earthquake loads
• Now we will be assigning the brick wall load to the structure
• For that go to define -->frame loads -->distributed

• A new dialouge box will appear
• In that give brickwall load as 3.5KN/sq.m
• Then apply

• After applying dead loads to the structure now we will be applying live load
• For that go to assign -->shell loads-->uniform

• A new dialouge box will appear and fill it with relevant data
• As we know that according to the is code 875 there is a provision which says that in residential buildings that the live load for rooms must be 2KN/sq.m

• And for the bathroom it should be3 kN/sq.m

For Rooms : 2KN/sq.m

For Bathrooms, staircase, lift:3KN/sq.m

• After that need to add floor finishes to the structure
• For that go to the assign-->shell loads -->uniform

• A new dialouge box will appear and fill it with relevant data

• After assigning the floor finish load now we will be doing the live load reduction factor according to the code
• For that go to design -->live load reduction factor

• A dialouge box appears and in that select the user defined then select define

• Then another dialouge box appears and fill it with relevent data

• Now we have to assign the mass source for this structure

• Another dialouge box appears and fill it with appropriate data

• After assigning mass source now we have to assign the diaphragm
• For that first we need to select
• then go to assign--shell-->diaphragm

• There will be another dialouge box select D1 and click on the apply and then click ok

• After assigning the diaphragm now we have to assign the load combinations
• For that go to define ---> load combination

• There will be another dialouge box in that click on the option add default combos

• Another dialouge box appears in that click on the option concrete frame design and concrete shear wall design , then click on the option ok

• Another dialouge will appear in that all ETABS generation load combination will be there

• Now select the pier labels and in order to do that first we need to go to the assign menu --->shel-->pier label

• After that another dialouge box named as pier labels will appear in that dialouge box just add the labels

• Then assign the pier labels accordingly

STEP:5

Modal Analysis

• Go to define -->load cases

• New dialouge box will appear in that select add new case

• Another dailouge box will appear enter the relevant data required

• After this we will be assigning spectrum analysis
• For that go to define --> functions-->spectrum analysis

• A new dialouge box will appear in that choose ia 1893-2016 and click on th add new function

• After clicking that new dialouge box will appear fill it with relevant data

The response spectrum load case in X direction :RSX

The response spectrum load case in Y direction :RSY

• Now after this we will check the model and will run the analysis
• So for checking the model go to analyze -->check model

• Now the model is checked and there are no warnings

• After checking the model with no warning do the run analysis

STEP:6

Reviewing the analysis results

Base Shear Check

• To check base shear go to diaplay -->show table

• Then another dialouge box will appear in that select analysis result --> structure output -->base shear
• Base reactions table will appear
• According to the codebook it is said that the response spectrum base shear must be at least equal to the same that is obtained by the linear analysis

• Go to the display tables and select the modal participating mass ratio

• Go to display ---> story response spectrum

• select story response as maximum story drifts in both x and y direction amd it should be not more tham4%

• Now open the reaction tab from the top screen there is a tab click on that tab or just press F7
• New dualouge box will appear , in that select the earthquake towards the x direction
• Then just click apply and then ok

RESULT

The G+7 residential building has been modelled and analyzed successfully using the ETABS 2018