Structural Modelling using Etabs 2018

QUESTION:

The architectural drawings for a G+7 residential building in zone 5 have been provided. The floor plan is the same for all seven-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 on the ground floor – the column/shear wall arrangement must not obstruct the 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-story drift requirements, vertical & planar irregularities, minimum shear wall requirements, maximum axial load ratio for column and shear walls, an effective moment of inertia for beams
and columns, etc.

ANS:

AIM:

• To create a model of a G+7 building using ETABS, given The architectural drawings for a G+7 residential building in zone 5. The structural model must comply with provisions of IS 1893 and IS 13920.
•  Run a modal response spectrum analysis and check the analysis results of the tabs model.

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 structure class.

• Basic or advanced systems under static or dynamic conditions may be evaluated using ETABS.

• Interoperability with a series of design and documentation platforms makes ETABS a coordinated and productive tool for designs that range from simple 2D frames to elaborate modern high-rises.

• 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.

• Analysis capabilities then offer advanced nonlinear methods for characterizing static pushover and dynamic response.

• Dynamic considerations may include modal, response-spectrum, or time-history analysis.

PROCEDURE:

STEP: 1

• First, open the tabs software.

• Next, click on the file option at the top left-side corner and select the new model, as shown below.

• After selecting the new model, the new tab opens; in that tab, we must choose the 'Use Built-in Setting option, as shown below.

• After setting the model Initialization, the templates tab will open, 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 nine-story in the Story Data, as shown below
• The nine stories are added in the Story Data, as shown below.

Step: 2

• Next, the plan views are visible on the tabs screen, as shown below.
• also open the 3D view 

Step 3

Now you can go to the file option and save the project as shown below.

STEP: 4

• 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: 5

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

• so, go to define< material properties < add new material < india< concrete < indian < M25

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

STEP: 6

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

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

 

STEP: 7

• Now, go to defint < section properties < frame sec tion < add new ... as shown below.

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

• Next, the frame section property data will be visible.

• In that, we add beam size as BEAM250x450, change the material 
• Next, we must select the Modify/Show Rebar option, as shown below.
• After selecting the Modify/Show Rebiar option, the new tab appears, in that we choose the design type as M3 Design only (Bearn)
• Next, we select longitudinal bars with the grade of HYSD500
• Next, we select Confinement bars with the grade of HYSD415

• Similarly, add new material < select Rectangular shape type in concrete, as shown below
• Next, the frame section property data will be visible, So we add column size as BEAM300x500, as shown below.
• Next, we must 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 (Bearn).
• Next, we select longitudinal bars with the grade of HYSD500
• Next, we select Confinement bars with the grade of HYSD415

STEP: 8

[REPEAT SAME STEPS AS USED IN CASE OF BEAM]

•  we have to add the column size as 400x600 in the frame section property data, as shown below.
• (Note: specify the direction of the column accordingly as shown  in the given plan)

STEP: 9

• Next FOR slab section from section properties
• go to defint < section properties < SLAB section < add new ... as shown below.

• Next, the slab properties tab will be visible.
• 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 125, which means slab with a thickness of 125mm.

• And we take the concrete grade as M25, as shown below.
• Next, we have to click the ok option.

SIMILARLY,

• Now we take the slab thickness separately for the staircase with the thickness of 200 mm

STEP: 10

• go to defint < section properties < wall section < add new ... as shown below.

• Next, we have to add the wall properties in the wall property data

STEP: 11

• Next, we must add the columns using the quick draw option below.

• Next, we need to add the beams using the quick draw tool

• Next, we need to add the secondary beams using the quick draw beams option

• Next, we add the shear walls in the required location in the residential building

• Next, we need to add the slab using the quick draw floor/wall option

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

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

STEP: 12

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

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

STEP: 13

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

• Then, after the new tab appears, we select the load pattern as Brickwall, take the uniform load as three kN/m, click the apply button, and close.

STEP: 14

• 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 apply the live load for the staircase portion, veranda, and lift core area.

• Next, we apply the live load for the remaining portions of the residential building, as shown below.

STEP: 15

• Next, we must select live load reduction factors from the design option, as shown below.

• Now we add the reduction factor by decreasing 10% from the 1st floor to the 7th floor, as shown below

STEP: 16

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

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

STEP: 17

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

• After selecting the object type option, the new tab will be visible. In that, like 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 choose D1 and click on the apply button and close

STEP: 18

• Next, we have to select the Pier label from the shell option, as shown below

• Before going to the shear wall design, we have to assign the names for the shear walls(PLP2 P3 P4 P5 P6 P7) as shown

STEP: 19

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

• After selecting the load combinations, the new tab is visible; we choose the Add Default Design Combos option.

• Next, we select "concrete frame design & concrete shear wall 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

• Next, we select the Modal cases from the Define option, as shown below
•  After selecting the Modal cases, the new tab is visible. In that, we give the modal case name Modal 1 & we provide the maximum number of modes as 20, as shown below.

STEP: 21

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

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

STEP: 22

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

• After selecting the Response spectrum, the new tab is visible, in that we choose IS 1893 2016 from the Choose function type and click on the Modify/Show spectrum option, as shown below

• After selecting the modify show spectrum option, the new tab will be visible. In that, we give the Function name as 15 FUNCTION, and the software will set the remaining details. We don't need to change any of the elements in that response spectrum function tab, as shown below

STEP: 23

• Next, we must select the Load cases from the Define option, as shown below.

• Next, the Load cases tab will be visible; in that, we select the Add new case as shown below

• Now we have to enter the details of the load case in the load case data as shown below

Now we have to do the run analysis

STEP: 24

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

• After selecting the show tables option, the new tab will be visible.
• Now we select the Base Reactions and click the ok button, as shown below.

• The Base Reactions table will be visible, as shown.