Challenge

Modelling of 25 storey building with the specified properties using ETABS

TTarun Bojja25 Jun 2023

1) 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��1= 4.4 second Ty1��1= 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

ANS:

Given Data

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

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.

Step - 1:

Frist open ETABS Softwarfe

Next Select the New Model
Next select the Initalization options

1. Click the Use Built -in Setting with:

2. Ater change the Display Units, Region for Default Materilas,

Steel Section Database, Steel Design Code, Concrete Design Code,

3. Final change oppotions click ok,

Next the New Model Quick Templates Change
Unitform Grid spacing change to X and Y Direction,
Next select the Structural objects
Next Story Dimensions
Next Custom Story Data
Specify Custom Story Date : Edit story Date
Final Click Ok

Final Grid is 2D and 3D view

Step - 2:

Next selected the material properties, and enter the following
M30 Grade of concrete and Steel Fe415,

1. Go to the Define and click

2. Change the material/ Add new material

3. Select the material type

4. Select the Grade

5. After selected the cilck ok

6. Next change material properties

Step - 3:

Next go to the Define< Selected the section properties<Frame properties<Add new property<Concrete < General Data< add to the beam & column properties and After added to the click ok.