Modelling of 25 storey building with the specified properties using ETABS

QUESTION:-

Model a 25 storey building on ETABS 2018 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
• Live load on floor : 3 kN/m2

Buildings are assumed to be pinned at base.

All columns in all storey are of the same size.

All beams in all storeys are of the same size.

Carry out the following excercises:

• Check if translational fundamental natural period of vibration in both the x and y direction is approximately the following:

This check will help confirm if modelling is done correctly. Some deviations from above values is possible (± 2%). But any major deviation will suggests error in modelling.

• Check if the following provision in Table 5 of IS 1893 (part 1) – 2016, on torsional irrregularity 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

ANSWER:-

Aim:- To model a 25 storey building with the given structural properties using etabs 2018.

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
• ETABS modeling is the generalization that multi-story buildings typically consist of identical or similar floor plans that repeat in the vertical direction.
• Modeling features that streamline analytical-model generation, and simulate advanced seismic systems.
• Once modeling is complete, ETABS automatically generates and assigns code-based loading conditions for gravity, seismic, wind, and thermal forces.
• Users may specify an unlimited number of load cases and combinations.

Procedure:-

Step:-1

• First we have to oprn the etabs software.
• Next click on the file option at the left side top corner and select the new model, as shown below.

• After selecting the new model the new tab opens, in that tab we have to select 'Use Built-in Settings with' option, as shown below.

• After setting the model Initialization the templates tab will opens and, select the Grid only and press ok.
• Next we need to do the settings in Grid system data, as shown below.

• Next we need to add the stories upto 25 story in the Story Data, as shown below.

• The 25 stories are added in the Story Data, as shown below.

Step:-2

• Next the plan views are visible in the etabs screen, as shown below.
• Next we need to open the 3d-view, as shown in the below figure.

Step:-3

• Next we need to define option and select material properties, as shown below.

• After selecting the material properties the new tab appears, then we add new materials by selecting the Add new material option, as shown below.

Step:-4

• Now we need to add material type as concrete and grade as M30.

• Next we need to check the material property data, as shown below.

Step:-5

• Now we need to add material type as rebar and grade as HYSD Grade 500.

• Next we need to check the material property data, as shown below.

Step:-6

• Now we need to add material type as rebar and grade as HYSD Grade 415.

• Next we need to check the material property data, as shown below.

Step:-7

• Now we need to select the section properties and click on the frame sections, as shown below.

Step:-8

• After selecting the frame sections the new tab will be visible, in that we need to select the Add New Property, as shown below.

• After selecting the Add New Property, the new tab appears.
• In that new tab we select the Rectangular shape type in concrete, as shown below.

• Next the frame section property data will be visible, In that we add beam size as B300x400, as shown below.
• Next we need to select the Modify/Show Rebar option as shown below.

• After selecting the Modify/Show Rebar option the new tab appears, In that we select the design type as M3 Design only (Beam).
• Next we select longitudinal bars with the grade of HYSD500.
• Next we select Confinement bars with the grade of HYSD415.

• Again we have to select Rectangular shape type in concrete, as shown below.

• Next the frame section property data will be visible, In that we add column size as C800x800, as shown below.
• Next we need to select the Modify/Show Rebar option as shown below.

• After selecting the Modify/Show Rebar option the new tab appears, In that we select the design type as P-M2-M3 Design (Column).
• Next we select longitudinal bars with the grade of HYSD500.
• Next we select Confinement bars with the grade of HYSD415.

Step:-9

• Next we select the slab section option from the section properties, as shown below.

• Next the slab properties tab will be vissible, In that we select the Modify/Show Property option, as shown below.

• After selecting the Modify/Show Property option, the new tab appears.
• In that we need to put the slab name as Slab 150, it means slab with the thickness of 150mm.
• And we take the concrete grade as M30, as shown below.
• Next we have to click the ok option.

Step:-10

• Next we need to add the columns using the Quick draw columns option.

Step:-11

• Next we need to add the beams using the Quick draw beams option.

Step:-12

• Next we need to add the slabs using the Quick draw floor/wall option.

Step:-13

• Next we go to the base plan and select all base joints, as shown below.

• Next we select the Restraints from joint option, as shown below.

• Now we need to select the pin joint and click on apply and then click on close button, as shown below.

• Thus, the pin-joints are added to the base of the structure, as shown in the below figure.

Step:-14

• Next we need to select the load patterns from the define option, as shown below.

• Now we add Dead load, live load, Brickwall load, and earthquake load, as shown below.

• Next we need to select eqx and click on the Modify Lateral Load, then the new tab appears.
• In this tab select X Dir and take seismic zone factor as per code is 0.36.
• And we need to select site type as lll, as shown below.
• Next click on the ok button.
• Similarly, do this for all the seismic loads such as eqx+, eqx-, eqy, eqy+, eqy-

Step:-15

• Next we have to click on the assign option and then select shell loads, from the shell loads we select the Uniform option, as shown below.

• Here we need to consider the live load upto the 24th floor with 3kN/m^2, as shown below.

Step:-16

• Next we have to click on the assign option and then select shell loads, from the shell loads we select the Uniform option, as shown below.

• Here we need to consider the live load for the 25th floor with 1.5kN/m^2, as shown below.

Step:-17

• Now we select the object type option, as shown below.

• After selecting the object type option, the new tab will be visible, In that select the beams and click on the select button and close.

• Next we select the distributed load from the frame loads, as shown below.

• Then after the new tab will appear, In that we select load pattern as Brickwall, and then click on the apply button and close.

• Now we click on the toogle option to view the loads acting on the story, as shown in the below figure.

Step:-18

• Next, from the define option we select the mass source, as shown below.

• In the mass source tab, we select Modify/Show Mass Source option, as shown below.

• Next we add the load patterns in the Mass Source Data, as shown below.

Step:-19

• Next, from the define option we select the load combinations, as shown below.

• After selecting the load combinations the new tab is visible, In that we select 'Add Default Design Combos' option.

• Next we select concrete frame design in the Add Default Design Combinations, as shown below.

• Now we can see here that the load combinations are visible, as shown below.

Step:-20

• In the select option we select object type option, as shown below.

• After selecting the object type option, the new tab will be visible, In that select the floors and click on the select button and close.

• Next we have to select the Diaphragms from the shell option, as shown below.

• After selecting the diaphragms the new tab will appear, in that select D1 and click on the apply button and close.

Step:-21

• Next we have to check the model by clicking the check model option, as shown below.

• Next the check model tab will appears, in that we select the all options and click on the ok button.

• After the model is checked, then the warning tab will be visible and it tells that there is no warning messages, as shown below.

Step:-22

• Next we select the 'show deformed shape' option, then the new tab appears.
• In the deformed shape tab, we select live load in the load case
• Next we see the deformed shape of the structure with the live loads.

• Next we see the deformed shape of the structure with the Dead loads.

• Next we see the deformed shape of the structure with the Brickwall loads.

• Next we see the deformed shape of the structure with the earthquake loads.

Step:-23

• Next, from the display option we select the show tables option, as shown below.

• After selecting the show tables option the new tab will be visible.
• Now we select the Modal Participating Mass Ratios and click on the ok button, as shown below.

• Next the Modal Participating Mass Ratios table will be visible, as shown below.

RESULT:-

• The 25 storey building has been modelled successfully in the ETABS 2018.