Structural Modelling using Etabs 2018

                                                                  Challenge-11

                                               Structural Modelling using Etabs 2018

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 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 AAC blocks

. Finishes – floor tiles of 75 mm thickness

. Live loads as per IS 875 part 2

. 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 modal response spectrum analysis and check analysis results of the etabs model for inter-storey drift requirements, vertical & planar irregularities, minimum shear wall requirements,maximum axial load ratio for column and shear walls, effective moment of inertia for beamsand columns etc.

Please note that the column positions shown in the architectural typical floor plan are only to provide an initial starting point for modelling. Participants will have to change its size, introduce shear walls, and add new vertical elements after running the analysis. You will have to run the analysis multiple times until a structural model is obtained that meets structural code requirements without compromising architectural functions. Also, there is no one ‘correct’ structural system for this challenge. There can be multiple possible solutions for this problem.

Introduction :-

Etabs :- ETABS is one of the most powerful software tools for structural analysis. 3D modeling, visualization, and automatic code-based learning are some of the unique features of this software. ETABS also supports several analytical models like response spectrum analysis, time-history analysis, and line direct integration time-history analysis. 

Advantages :- Built-in drawing utilities: To aid the engineers in modeling, ETABS comes with a built-in feature for drawing and drafting. Some other packages also have this feature, but the quality is much better in ETABS. Extensive reports: ETABS generates detailed and comprehensive reports for every project or task you perform, be it calculation of stresses, deformation or failure analysis, and design summary. Design of concrete and steel frames: Among all the materials available to build structures, concrete and steel are by far utilized the most in terms of volume. ETABS has specialized modules that deal with concrete and steel frames to optimize your calculations and offer capacity checks for frame elements.

Aim :- To model and analyze G+7 residential plan from given architectural drawings using Etabs 2018. To Run a modal response spectrum analysis and check analysis results of the etabs model.

Procedure :- Open the ETabs software. Click the file menu and choose to create a new model option. After choosing a new model a dialogue box will appear as Model Initialization.

. Choose the built-in settings option and select the display units and codes.

. New dialogue box will appear named New Model Quick Templates.

. Select Custom Grid spacing and custom story data.

 

. After models initialization, select grid and storey inputs from new model quick templates dialogue box.

. In the dialogue box choose grid spacing and custom story data which is used to provide the input specified above.

. Now edit stories by using the user-defined story input, 26 stories are incorporated (plinth at 1.5m and 25 story with 3m height each).

. Storey 1 has been labelled as a master storey and all above levels are labelled similar to that.

. Add Story height as 3m. Number of Added stories as 4.

• So, 7 storeys are successfully added in the peoject.
• Create alll the storeys as similar to storey 1.

. Select Material properties under define tab.

. New dialogue box will appear named Define Materials.

. Select Add new Material from the window.

. Now need to add material  type as concrete and grade as M25.

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

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

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

. Now need to add material type as rebar and grade as HYSD 415. Now we need to check the material property data, as shown below.

. Now need to add material type as rebar and grade as HYSD 500. Now we need to check the material property data, as shown below.

. Now select Section Properties under Define Tab. Select Frame Sections. Select Add new properties in Frame Properties.

. Create a new Property as a beam and input values as 250X450. Select Modify/Show Rebar in Reinforcement option. Select M3 Design only (Beam). Select Reabar as HYSD415.

 . Create a new Property as a beam and input values as 300X500. Select Modify/Show Rebar in Reinforcement option. Select M3 Design only (Beam). Select Reabar as HYSD415.

. Create a new Property as a column and input values as 400X400. Select Modify/Show Rebar in Reinforcement option. Select P-M2-M3 Design (Column). Select Reabar as HYSD415.

. Create a new Property as a column and input values as 400X650. Select Modify/Show Rebar in Reinforcement option. Select P-M2-M3 Design (Column). Select Reabar as HYSD415.

. Now select Section Properties under Define Tab. Select Slab Sections. Select Add new properties in Slab Properties.

. Using the membrane properties, slab size 125 mm has been added to the list. Membrane property will help to consider only slab weights and Floor weights in analysis of structure while no stiffness component of flange advantage are considered during calculation.

. Using the membrane properties, slab size 200 mm has been added to the list for staircase. Membrane property will help to consider only slab weights and Floor weights in analysis of structure while no stiffness component of flange advantage are considered during calculation.

. Now we have to add Wall properties in wall property data.

. Now add the wall data as thickess of the wall as 250 mm, Material- M25.

. Now add the wall data as thickess of the wall as 300 mm, Material- M25.

. Now Draw columns of size 400X400 mm at the intersection of the horizontal and vertical grids and beams with quick draw Column keeping all the stories on.

. Now draw columns of size 400X650 mm at the intersection of the horizontal and vertical grids and beams with quick draw Column keeping all the stories on.

. Columns are Successfully added to the structure.

. Now Draw the Beams. Draw beams of size 250X450mm at the intersection of the horizontal and vertical grids and beams with quick draw beam keeping all the stories on.

. Beams are Successfully added to the structure.

. Next we have to Draw secondary beams.

. Next we add the shear walls in required locations in longitudinal building.

. Now Draw the Slab. Draw slab of size 125mm thickness, Draw slabs with quick draw floor/wall keeping all the stories on.

. Slabs are Successfully added to the structure.

. Now we go to base plan and select all the joints. Now we select the Restraint from joint option, as shown below.

. Now define the Load patterns. Click on the define tab and click on load patterns. Define the loads like dead load, live load, brick load, earthquake load in X direction and same loads in Y direction also. Mention IS codes of respective loads.

. Next we need to select the distributed load from the frame loads.

. Then after the new tab will appear, in that case we select load pattern as Brickwall and we take uniform load as 3.5 Kn/m an then apply.

. Next we have to click on assign option and then select  shell loads and select Uniform option.

. Here we apply 3 Kn/m2 live load for the staircase portion, verandah and liftcore area.

. Here we apply 2 Kn/m2 live load for rest of the portion in the slabs.

. Next we add  live load reduction factor from the design option.

. Now add the reduction factor as decrease of 10%from 1st to 7th floor.

. Now go to Mars Source from define tab. Modify the mars source and tick mark the required loads. Add load patterns and assign the model. Insert the dead load as multiplier to 1, live load as multiplier to 0.25 and wall load as multiplier to 1.

 

. Mars source is been added successfully.

. Now go to Load cases in define Tab.

. Now create the Diaphragm by going to the assign tab then shell and select diaphragm.

. Next we have to select the pier lable from shell option.

. WE have to assign the names for the shear wall.

. Now go to Load combinations in define Tab.

. Select add default design combos. Select concrete frame Design.

. Next we add model cases from define option.

. Give odeal case name as Model1 and we give the maximun number of modes as 20.

. Next we need to check the Model.

. After the model is checked, it will show us No warning.

. Now select the response spectrum from Functions option in define Tab.

. We choose IS 1893:2016 from choose function Type and click on Modify/Show spectrum option.

. Now go to Load cases in define Tab.

. Add new case.

. Analyse the model using analyse option then click on check model the modelled structure is verified without errors and warnings.

. Now click on display -> show tables -> Analysis result structure output -> Base Reactions

. We have to check EQ should be close to the RS , We should calculate the 

        

. Now substituting the value from the table , 

At X- direction -> ( 354.657 / 138.167) X 386.089  ->  991.04

At Y- direction -> ( 354.657 / 115.05) X 386.089 ->  1187.96

. Now we put above value as scale factor for Response Spectrum at X and Y direction.

. Now click on display -> show tables -> Analysis result structure output -> model information -> model periods and frequencies.

. Select the Story Response Plot from Display option.

. Story Response for maximum Story Drifts for x and Y direction is as per following.

X- Direction :-

Y- Direction :-

. Next we open the Base floor in Plan view.

. We have to open Reaction tab, we select the earthquake load towards in X-direction in load case.

. When we divide base shear taken up by shear wall divided by total base shear of Building will get %  of shear forces taken by Shear Wall.

Result :- Modeled and analyzed G+7 residential plan from given architectural drawings using Etabs 2018. Run a modal response spectrum analysis and check analysis results of the etabs model.