Modelling of 25 storey building with the specified properties using ETABS

Aim- to model a 25 storey building in etabs and analyse it.

Procedure-

• Open etabs 2019.
• Select new model and set the model initialization> use built in setting. Specify the model as Indian code.
• 
• Set the grid system for the model.
• 
• Set the storey system for 25 floor in the system with height 3m between floors and plinth level of 1.5m.
• 
• Now add the material property in the model.
• Define>material properties>add new material>m30 and Hysd415.
• 
• Similarly define the frame sections for beam and columns.
• Define>section properties>frame sections>add new property>select rectangular section.
• Write B 300x400 and modify the the frame section data. Set the depth and width and reinforcemnet data. Similarly do it for column and slab.
• 
• Now add load patterns in the model.
• Define>load patterns>add new load.
• Dead is already defined rest of the loads are to be added.
• 
• Modify the seismic loads for eccentricity and directions.
• 
• Add mass source, define>mass source>modify mass source.
• Add the load patterns in the mass source. Dead load, wall load and live load.
• 
• Also add the load combinations for the model.
• Define>load combinations>add default load combinations.
• 
• Now add the columns, beams, and slab in the model.
• Go to 1^st floor which is master storey select all stories.
• Select quick draw columns and select C 800x800 from properties.
• Carefully place the columns on the grids intersection.
• Select quick draw beams and select B 300x400 from from property and place the beam between the columns.
• 
• Now add the slabs in the model.
• Select the similar stories option to avoid placing the slabs on the plinth level.
• Select quick draw floor and select slab 150 and place it carefully.
• 
• Go to base floor add restraint of pin foundation to the model.
• 
• Now add loads on the building.
• Select>object type>beams.
• Assign>frame loads> loads assignment.
• Select brick wall and make it 10 kn/m2 as specified.
• 
• Similarly, select> object type> floors.
• Assign> shell loads> uniform> shell load assignment.
• Select live load and set it at 3kn/m2.
• 
• Add the diaphgram to the model for centre of mass.
• 
• Now check the model for any errors.
• Run analysis on the model.
• 
• Go to display> show tables.
• Select analysis report> structure output> modal information.
• Select the modal participating mass ratio.
• 

Result-

• the translational fundamental natural period in both x and y directions is respectively 4.416s and 4.222s.
• mode 3 is 3.311 which is lesser than mode 1 and mode 2 therefore the torsional irregularity is satisfied.
• The first mode itself is having 80% of the mass participation factor therefore no need to add next two mode for x and y directions.
• But the 10% difference between 1^st mode and 2^nd mode is not satisfied.