Modelling of 25 storey building with the specified properties using ETABS
PROJECT TITLE:
Modelling of 25 storey building with the specified properties using ETABS
AIM:
Model a 25 storey building on ETABS with structural properties as specified below. Ground floor or plinth floor level can be taken at a height of 1.5 metres from the base. Each of the successive 25 storeys has a storey height of 3 metres.
Structural Element Sizes
- Beams : 300 × 400 mm
- Columns : 800 × 800 mm
- Slab : 150 mm thick
Material Properties
- Grade of Concrete : M30
- Grade of Steel Reinforcement Bars : Fe 415
Loading
- Dead Load on beams from infill wall : 10 kN/m (Let us assume the same for roof floor in view of parapet)
- Live load on floor : 3 kN/m2 (Let us assume the same for roof floor)
a) Buildings are assumed to be pinned at the base
b) All columns in all storey are of the same size
c) All beams in all storeys are of the same size
d) Building is located on Soil type-II and in Zone-III. Assume other factors if required.
Carry out the following exercises:
- Check if the translational fundamental natural period of vibration in both the x and y direction is approximately: Tx1">Tx1Tx1= 4.4 second Ty1">Ty1Ty1= 4.2 second
This check will help confirm if modelling is done correctly. Some deviations from the above values is possible (± 2%). But any major deviation will suggest an error in modelling.
- Check if the following provision in Table 5 of IS 1893 (part 1) – 2016, on torsional irregularity satisfied:
The natural period corresponding to the torsional mode of oscillation must be less than the two fundamental translational modes of oscillation along each principal plan directions.
- Check if the two provisions of clause 7 in Table 6 (shown below) of IS 1893 (part 1) – 2016, regarding vertical irregularity is satisfied
- Check if provision on inter-storey drift limitations in clause 7.11.1.1 satisfied. Please note that this check is for Serviceability Limit State and hence is for situation when stucture is subjected to unfactored seismic base shear
INTRODUCTION:
ETABS is an engineering software product that caters to multi-story building analysis and design. Modeling tools and templates, code-based load prescriptions, analysis methods and solution techniques, all coordinate with the grid-like geometry unique to this class of structure.
PROCEDURE:
Open ETABS software choose a new model file ,a dialogue box will open choose use built-in settings with & codes & give ok.
Now model quick templates will open choose the grids ,add one more grid & give the value for x & y coordinate & give ok.
Edit story data & give ok
Now edit the stories plinth height at 1.5m+25 storey height 3m.storey 1 as labelled as master storey & all the above levels are similar to that.
Under define tab,choose material ,material type concrete & give ok.
Provide the reinforcement as HYSD grade 415 & give ok
Go to define tab >section properties>frame properties
Add new property,provide beam size 300*400
Modify reinforcement
Provide column data of size 400*400
Go to slab property under define tab & provide slab data
Define the load pattern
Define the mass source
Provide load cases & load combinations for concrete frame design
Create the column
Now to create a beam ,choose beam >beam property>all storey >select the grids to create a beam
Go to quick draw slab ,choose the property s150 & create the slab
Now to assign the load choose the beam property ,now all the beams are selected ,choose the wall & provide a load of 10KN/m
Assign the load of 3kN/m^2 to the slab
Set diaphragm & run analysis & save the file as G+25 model A
Run analysis the model is analyzed & deflection pattern ,BMD & SFD are cross checked logically.Model provide reliable results
Now the created model has been saved as G+25 model A
Now open a new file & save it as G+25 model B
Go to edit tab>edit storeys & grids >Add story>Refresh the view to see the changes>ok
Cross check the load cases are visible or not
Insure the slab & assign the diaphragm.
Run anlaysis now the deformed shape as been shown
Open a new file & save it as G+25 model c
Now provide a column of size 550*300
Assign local axis as 90 deg
Assign diaphragm & run analysis now the deformed shape is visible
Open a new file & save it as G+25 model D
Now provide a column of size 550*300
Assign local axis as 0 deg
Assign diaphragm & run analysis now the deformed shape is visible
Now open a new file & save it as G+25 model E
Go to edit tab>edit storeys & grids >Add story>Refresh the view to see the changes>ok
Go to define tab >section properties>frame properties
Providing column of size 600*600
Unhide beams & floors & apply
Go to 3d view, set building view limits
Assign diaphragm & run analysis now the deformed shape is visible
Add storey & refresh view
Define column of size 800*800
Follow the same procedure followed for model E
Set diaphragm & run analysis
Create a new file G+25 Model H
Follow the same process followed in model G
Run analysis
Assign shell loads 3.3 & run analysis
Create a another file of G+5 model k
Assign shell load of 3.6
Run analysis
RESULT:
Open model E file
Click on Display>show tables>Analysis results>Structure ouput>Modal information>modal periods and frequencies.
Building E (10 storey with various column size load)=1.12s
Building F (10 storey with various column size load)=1.86s
Building G (25 storey with various column size load)=1.84s
Building H (25 storey with various column size load)=4.57s
Building H (25 storey with 3kM/sq.m imposed load)= 4.57s
Building j (25 storey with 3.3kM/sq.m imposed load)=4.75s
Building k (25 storey with 3.6kM/sq.m imposed load)= 4.76s
Effect of building height on time period:
Building A (2 Storey)= 0.5s
Building B (5 Storey)= 1.08s
Building F (10 Storey)=1.86s
Building H (25 Storey)=4.57s
Effect of column orientation on time period:
Building B (All floor column size 400*400)= 1.08s
Building C (All floor column size 550*300)oriented in x direction= 1.03s
Building D (All floor column size 300*550)oriented in y direction= 1.14s
