Modelling of 25 storey building with the specified properties using ETABS

Aim : Modelling of 25 storey building with the specified properties using ETABS

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. Basic or advanced systems under static or dynamic conditions may be evaluated using ETABS. For a sophisticated assessment of seismic performance, modal and direct-integration time-history analyses may couple with P-Delta and Large Displacement effects. Nonlinear links and concentrated PMM or fiber hinges may capture material nonlinearity under monotonic or hysteretic behavior. Intuitive and integrated features make applications of any complexity practical to implement. Interoperability with a series of design and documentation platforms makes ETABS a coordinated and productive tool for designs which range from simple 2D frames to elaborate modern high-rises.

• Etabs is totally run based on the IS codes which are IS - 456 ,IS - 800 , IS 1893..

Project is totally analyzing and modelling by the etabs software the requirements are mentioned below

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.

Procedure :

• open the Etabs software create new sheet with built in settings units are metric SI .
• create the grids in x direction with A -E and in Ydirection 1-4 with the spacing of 4m
• enter the story data and ceate 25 stories each with 3 m height .
• define the the material properties of concrete as M30 grade and steel as HYSD 415.
• define the section proerties of frame properties are Beam size is 300 X 400 mm and columnn size is 800X800mm .
• similarly define the slab properties are thickness is 150mm.
• also define the load pattrens as dead ,live load , wall (superdead load) ,EQ x and EQ y those are seismic loads .
• next , use quick drawa option draw the columns,beams,slabs (which are not assign to base and plinth stories) based on the grids.
• then we have to assign the joints at the bottom of columns here they given pinned connection.
• after that assign the loads - frame loads to beams which are wall loads with 10 kN/m and shell loads to the slabs which are live loads with 3 kN/m2.
• also assign the mass sources to the all stories.and assign diaphroms to the floors for centre of mass for slabs.
• then modelleing is completed start the run analysis (F5).
• check resulsts and deviations and diagrams of structure.
• Results are given below.

• enter the story data and ceate 25 stories each with 3 m height .

Checking results :

1.Check if the translational fundamental natural period of vibration in both the x and y direction is approximately: Tx1Tx1= 4.4 second 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.

• the translational fundamental natural period of vibration in X direction is 4.416 and in Ydirection is 4.222 .this check is obsolutely fine.

2.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.

• The natural period corresponding to the torsional mode of oscillation is less than the two fundamental translational modes of oscillation along each principal plan directions the value is 3.211.so its fine.

3.Check if the two provisions of clause 7 in Table 6 (shown below) of IS 1893 (part 1) – 2016, regarding vertical irregularity is satisfied

• 1.which is stisfying the clause 65 % mass participation factor , we got in x direction was 80.42 % and Ydirection plane was 80.84 %.
• 2. the difference of two principal plan directions having at ,least 10 % of larger value , it is not satisfying with two values it less then 10 %.

4.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

• the story drift is not exceeding the 0.004 in the x and y directions we got 0.00149 and 0.001625 so its also fine.