Structural Modelling using Etabs 2018

STRUCTURAL MODELLING OF RESIDENTIAL BUILDING USING ETABS.

QUESTION:-

The architectural drawings for a G+7 residential building in zone 5 has been provided. The floor plan is the same for all 7 floor levels. Possible column positions have also been provided. Conceptualize a framing plan layout and then model the building in Etabs. The following architectural drawings have been provided:

• Typical floor plan- The location and thickness of the brick walls and the use of the space (for estimating live load) can be obtained from this plan.
• A building section through the staircase and the lift core is provided.
• Parking layout in the ground floor - the column/shear wall arrangement must not obstruct entry/exit of vehicles.

The following loadings are to be taken into account:

• Brickwall made of ACC blocks.
• Finishes - floor tiles of 75mm thickness.
• Live loads as per IS 875 part2.
• Water tank of 20 KL above the staircase at Mumty level.
• Lift machine room at mumty level above lift core.

The structural model must comply with provisions of IS 1893 and IS 13920. Run a model response spectrum analysis and check analysis results of the ETABS model for inter - storey drift requirements, maximum axial load ratio for column and shear walls, effective moment of inertia for beams and columns etc.

Answer:

Aim:- Using the ETABS 2018, to model and analyse the G+7 residential building based on the provided architectural drawings.

Introduction:-

• An engineering software programme called ETABS is designed to analyse and design multistory buildings.
• Code-based load prescriptions, modelling tools and templates, analytical approaches, and solution methodologies all work in tandem with the structure's distinct grid-like shape.
• With ETABS, systems that are basic or sophisticated can be assessed in static or dynamic environments.
• The generalisation known as ETABS modelling states that multi-story structures usually have floor plans that repeat vertically and are identical or similar to one another.
• Characteristics for modelling that simplify the creation of analytical models and replicate sophisticated seismic systems.
• Following modelling completion, code-based loading conditions for gravity, seismic, wind, and thermal forces are automatically generated and assigned by ETABS.

Procedure:-

Step1:-

• We must first launch the etabs programme.
• Next, as seen below, choose the file option in the upper left corner and choose the new model.

• The 'Use Built-in Settings with' option must be selected in the new tab that appears after choosing the new model, as seen below.

• The templates tab will open after the model initialization is set. Choose Grid only and click "OK."
• The Grid system data settings must then be completed, as indicated below.

• As seen below, we must then add up to seven stories to the story data.
• As seen below, the seven stories have been added to the story data.

Step2:-

• As seen below, the plan views are then displayed in the etabs screen.
• The next step is to launch the 3D view, as seen in the figure below.

Step3:-

• As seen below, we must next define the option and choose the material properties.

• We add new materials by selecting the Add new material option, as shown below, after choosing the material attributes, which opens in a new tab.

Step4:-

• Concrete material type and M25 grade need to be added at this point.
• The material property data must next be examined, as indicated below.

Step5:-

• We now need to add rebar as a new material type and HYSD Grade 415 as a grade.
• The material property data must next be examined, as indicated below.

Step6:-

• We now need to add rebar as a new material type and grade, which is HYSD Grade 500.
• The material property data must next be examined, as indicated below.

Step7:-

• As seen below, we must now pick the section properties and click on the frame sections.

Step8:-

• Once the frame portions have been selected, a new tab will appear. Here, we must choose Add New Property, as indicated below.

• The new tab opens after choosing Add New Property.
• As seen below, we choose the Concrete Rectangular form type in that new tab.

• The frame section property data will then become accessible. As you can see below, we have added the beam size as B250x450.
• The Modify/Show Rebar option must then be chosen, as indicated below.

• A new tab emerges after choosing the Modify/Show Rebar option, where we choose M3 Design alone (Beam) as the design type.
• We then choose longitudinal bars that have a HYSD500 rating.
• Next, we choose Confinement bars that have a HYSD415 grade.

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

• The frame section property data will then become visible. As you can see below, we have added a column size of B300x500.
• The Modify/Show Rebar option must then be chosen, as indicated below.

• A new tab emerges after choosing the Modify/Show Rebar option, where we choose M3 Design alone (Beam) as the design type.
• We then choose longitudinal bars that have a HYSD500 rating.
• Next, we choose Confinement bars that have a HYSD415 grade.

Step9:-

• As indicated below, we must next add the 400X400 column size to the frame section property data.

• As seen below, we must once more add a second column with a dimension of 400 by 600 to the frame section property data.

Step10:-

• As seen below, we next choose the slab section option from the section attributes.

• Subsequently, we may access the Slab Properties tab and choose the Modify/Show Property option, as illustrated below.

• The new tab displays when you click the Modify/Show Property option.
• That requires us to enter the slab name Slab 125, which denotes a slab with a 125mm thickness.
• And as can be seen below, we choose M25 as the concrete grade.
• We must then select the "OK" option.

• As you can see here, we are now taking the 200mm thick slab thickness for the staircase individually.

Step11:-

• Next we have to add the wall properties in the wall property data, as shown below.

Step12:-

• Next we need to add the columns using the Quick draw columns option, as shown below.

Step13:-

• The beams must then be added using the Quick Draw Beams option, as demonstrated below.

Step14:-

• The secondary beams must then be added using the Quick Draw Beams option, as demonstrated below.

Step15:-

• As indicated below, we then install the shear walls at the residential building's necessary locations.

Step16:-

• The slabs must then be added using the Quick Draw floor/wall option, as demonstrated below.

Step17:-

• We now choose every base joint in the base plan.
• Next, as seen below, we choose the Restraints from joint option.

• As seen below, we must now choose the fixed joint, click Apply, and then click Close.

Step18:-

• The load patterns must then be chosen from the define option, as seen below.

• As indicated below, we should now include the dead load, live load, brickwall load, and earthquake load.

Step19:-

• The distributed load from the frame loads must then be chosen, as indicated below.

• Following the appearance of a new tab, we choose Brickwall as the load pattern and 3.5 kN/m as the uniform load. We then click the apply button and shut.

Step20:-

• The next step is to click the assign option, choose Shell Loads, and then, as illustrated below, choose the Uniform option.

• Here, we utilise the 3kN/m^2 live load for the lift core area, varanda, and staircase section.

• We then use the 2kN/m^2 live load for the residential building's remaining sections, as indicated below.

Step21:-

• The next step is to choose the design option's live load reduction factors, as indicated below.

• As can be seen below, we now apply the reduction factor by reducing by 10% from the first floor to the seventh story.

Step22:-

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

• As can be seen below, we then include the load patterns in the Mass Source Data.

Step23:-

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

• A new tab will appear after choosing the object type choice; choose the floors there, click the choose button, and then click close.

• The Diaphragms from the Shell option must then be chosen, as seen below.

• A new tab will open after you've chosen the diaphragms; choose D1, then click the apply button to exit the window.

Step24:-

• The Pier label must then be chosen from the shell choice, as indicated below.

• As seen below, we must first give the shear walls (P1, P2, P3, P4, P5, P6, P7, and P8) names before moving on to the shear wall design.

Step25:-

• Next, as seen below, we choose the load combinations from the define option.

• The 'Add Default Design Combos' option appears in the new tab that appears when we select the load combinations.

• In the 'Add Default Design Combinations', we next choose "concrete frame design" and "concrete shear wall design," as seen below.

• As seen below, we can now see that the load combinations are visible.

Step26:-

• As can be seen below, we next choose the Modal cases from the Define option.

• Once the modal cases are selected, a new tab appears. Here, we specify the modal case name as Modal 1 and the maximum number of modes as 20, as indicated below.

Step27:-

• The model must then be verified by selecting the check model option, as seen below.

• The warning tab, which indicates that there are no warning signals, will become available once the model has been validated, as seen below.

Step28:-

• Now we select the Response spectrum from the Functions from define option, as shown below.

• This opens a new tab where we select the Response spectrum and click the Modify/Show spectrum option, as seen below. Here, we select IS 1893 2016 from the 'Choose function type'.

• You can see a new tab after choosing the modify/show spectrum option. In that tab, we set the function name to 'IS FUNCTION' and the programme will take care of the rest. As you can see, we don't need to modify any of the details there.

Step29:-

• The next step is to choose the Load cases from the Define menu, as indicated below.

• The Load Cases tab will then become accessible. Here, we can choose to "Add new case," as indicated below.

• As seen below, we must now enter the load case details in the "Load case data" field.

• Now the run the analysis, as shown below.

Step30:-

• Next, as indicated below, we choose the show tables option from the display option.

• The new tab will become accessible after choosing the "Show Tables" option.
• As seen below, we now choose the Base Reactions and press the OK button.

• As seen below, the Base Reactions table will then be displayed.
• Here we have to check that EQ should be closer to the RS, to get the closer to each other we should calculate that, (EQ/RS) x Scale factor of response spectrum.
• Now substituting the values from the table, at X-direction (2844.3648/900.7656)x(9806.65) at Y-direction (2844.6348/1002.1982)x 9806.65

• The result at X-direction is 30969.6.
• Y-direction yields 27835.15.
• In the load case data, we set the aforementioned values as the scaling factor for the response spectrum at the X and Y directions.
• The EQ is closer to the RS from the base reaction table once these response spectrum values are entered as scale factors at the X and Y directions in the load case data, as indicated below.

Step31:-

• Next, as indicated below, we choose the show tables option from the display option.

• The new tab will become accessible after choosing the "Show Tables" option.
• As indicated below, we now choose the Modal Participating Mass Ratios and press the OK button.

• As can be seen below, the Modal Participating Mass Ratios table is now displayed.

Step32:-

• As seen below, we then choose the Story response plots from the Display option.

• The maximum tale drifts at the X and Y directions should not exceed 4% for the story response.

Step33:-

• As seen below, we then select the ground floor by opening the Select Plan View menu.

• The reactions tab must then be opened. Next, we must choose the earthquake load in the X-direction (EQX) in the load scenario. Finally, we must click the OK button, as indicated below.

• As may be seen here, the base shear reactions are now visible.
• The percentage of shear forces absorbed by the shear wall can be found by dividing the base shear absorbed by the shear wall by the total base shear of the building.
• And the more shear walls we need to install to the structure if that percentage is less than 80%.

RESULT:-

• Using the ETABS 2018, the G+7 residential building has been successfully modelled and analysed.