Project 2_Design & Analysis of a Hostel building at Guwahati, Assam

Question

In this project, participants will get to experience the entire design process from modelling, analysis, design, and preparation of construction drawings. The architectural drawings of a G+3 RCC building is provided. The following information on the building is to be used:

• Location – Guwahati, Assam
• Function – Hostel block in an academic institute

The walls will be made of AAC blocks. Other loadings are to be calculated as per the architectural drawings. 

The buildings rests on type 3 soil. Piles of length 10 meters and 500 mm diameter with a load-carrying capacity of 280 KN is to be used. 

The ground floor level will be at a height of 2 meters above the existing site level to avoid floodwater enter the building.

M25 grade of concrete with Fe500 for longitudinal reinforcement and Fe 415 for shear reinforcement is to be used. 

The following design IS codes will be required for reference:

• IS 875 part 1
• IS 875 part 2
• IS 13920
• IS 1893
• IS 2911 part 2
• IS 456
• SP 34

Students will have to produce the following:

• Etabs model for the two blocks on either side of the expansion gap
• Foundation details illustrating the pile & pile cap reinforcement
• Tie beam details connecting the pile caps
• Column reinforcement
• Framing plan for typical floor
• Beam reinforcements for ground floor

Answer

Aim:To design and analysis of G+3 hostel building in ETABS and foundation in SAFE

Introduction:

• The procedure and anaylsis and design of given building will depend on the type of building, its complexity, the number of stories etc.
• First architectural drawings of the building are studied, structural systems is finalized, sizes of structural members are decided and brought to the knowledge of the concerned architect.
• The procedure for structural design will involve some steps which will depend on the type of building and also its complexity and time available for structural design.

Following data is needed before designing the structural design:

1. A set of architectural drawings
2. Soil investigation report
3. Location of place or city in order to decide wind and sesimic load condition
4. Data for lifts, water tank on top of the building and roof loadong ad its features.

Procedure:

ETABS MODEL

Step - 1) Open ETABS and Set up the Model

• Open ETABS from the desktop shortcut or by searching for it from the start menu.
• Once the software is up and running, click on the new model option.
• Once you click on the new model, a dialogue box will pop up where you can set up the codes and units to be used in your project.
• Thus, do the needful settings and click ok to start modelling the first building in this project.

Step - 2) Setting up the Grid Data

• To set up the grid data, you need to click on the custom grid option.
• Once you do that, a menu with all the grid settings will open up.
• In the same menu, you can fix the length, numbers of grids in both the orthogonal directions, spacing between all the vertical and horizontal grids, etc.

Step - 3) Fixing the Story Data

• Similar to what we did while setting up the grids, click on the custom story data option.
• Then, specify the base level, plinth level, height of each floor, and the number of floors to be included in the model.
• Thus, we have arranged for a building with a 2m Ground floor height from the base.
• Also, you need to fix a master story and all the similar storeys in the same menu.
• And for our project, story one is the master and all other remaining floors are similar storeys.
• Once, you do this, your model is set to be executed in ETABS with the grid and storeys as specified.

Step - 4) Defining the Material Properties

• It is important to set details of the materials you are going to use for the project in ETABS.
• And for our model, we have to use the M25 grade concrete and Fe415,Fe500 HYSD steel as per the specifications.
• So, in order to define the same, go to define → material → properties → add new → concrete/steel → grade → ok.
• However, since we have already specified the Indian Standard Codes of practices, the M25 concrete and 415,500 steel is added by default into the project.

Step - 5) Defining Section Properties 

• We are using the rectangular concrete sections for all the structural elements like beams, columns, and slabs.
• So, we need to define that in ETABS software so that it allows us to use these sections repeatedly throughout the project.
• And to do so, go to define → section properties → frame sections → concrete rectangular.
• Then, a dialogue box will appear on your ETABS screen where you can specify the column/beam dimensions and the type of reinforcement (HYSD415,HYSD500) to be used in the model.
• So, you can define both columns and beams from the same menu.
• Now, to define the slab section, again go to define → section → slab.
• Again a menu will open up where you need to set the slab specifications required for the project.

Beams 450 × 650 mm

Columns 450 × 650mm

Slab 125mm, Stair slab 200mm

Step - 6) Execute the Modelling

• Now that we have defined everything from materials to beams, columns, and slabs to be needed for our structure,
• we can go ahead and draw each structural element as per the specifications.
• And to do that, we can use the commands in ETABS named quick draw tool.
• As the name suggests, you can draw all the beams, floors, and columns with the help of this tool.
• All you need to do is select the relative tool that is quick draw columns for drawing columns and vice versa. Then choose the section from the dropdown list.
• Then, simply go to the grid system in plan view and start clicking on the grid locations where you want to build these structural elements.
• So, the same approach was followed and the following beams, floors, and slabs were drawn in our ETABS model.

Step -7) Define the Load Patterns

• After completing the model, now we need to list down the types of loads that are expected on the structure during its service period.
• And to do so, go to define → load patterns  → add loads.
• Here, you can add all the loads and for our project, we are having the dead load, super dead load (Brick wall load), live load, and the earthquake load in x and y directions.
• Also, you need to define the mass source by adding 100% of dead and super dead load as well as 25% of the imposed or live load.

Step - 8) Generate Load Combinations

• Go to define → load combinations → default combinations  → check the convertible option.
• A list of load combinations will appear which you can look at and modify anytime during the project if needed.

Step -9) Assign Loads to the Structural Members

• You can select a particular structural member from the model and assign it the load that is imposed on it.
• For example, select the beam and assign a udl of super dead load due to the brick walls resting upon it.
• Thus, a similar technique is used and the loads on beams and slabs are assigned as follows:
• Dead Load on beams from infill wall : 10kN/m
• Live load on Floor : 2kN/m²
• Brick wall on freame loads :3.5kN/m²

Step - 10) Assign the Floor Diaphragm

• Select the Slab125,Stair slab200slab section from the select option.
• Go to assign  → shell → diaphragm.
• Select the default D1 diaphragm already incorporated in ETABS and press ok.
• It is now done, and you can see the centre of mass for our model has been automatically calculated as we assigned the floor diaphragm.

Step - 11) Run Analysis

• Now that everything with regards to our first model is complete, we can proceed to run the analysis for this building.
• But we'll have to first save our project before running the analysis so do it at the preferred location within your system.
• Then, you can simply press F5 on your keyboard or click on the arrowhead available on the ETABS screen to run the analysis for the current model.

Step - 12) Check the Design & export the model to SAFE 

• Now beam design and column design by selecting start design option
• After tha we select Design → Display design information 
• Also check for shear reinforcement
• And for column we need 2340sq.mm reinforcement required.
• Export base floor load and load from above in SAFE.

SAFE MODEL (Foundation Design)

Step 1) SAFE  Design 

• Open the safe software 
• Click on the new model 
• In that choose single footing option → ok
• After that fill all information like this → ok 
• After exporting ETABS model to SAFE then import file 

Step 2) Show the load 

• Now go to Display → Show load
• Dead above load 

Step 3) Data Given

• Soil type → 3
• Piles of length → 10m
• Pile dia → 500mm 
• Load carrying capacity → 280KN
• Pile cap → slab type → mat → 500mm thick 
• Column cap slab → stiff 500mm thick 
• So,firstly define → slab property

Step 4) Assign beam,Point spring data & Add the load combination

• Go to Assign → RC beam section of tie connection of foundation is 600X500mm.
• Go to Assign → point spring data .
• For bearing pressure checking the service Load combination is considered.
• For flexural design the ultimate load combination is considered.

Step 5) Add the soil & pile properties

• Define the soil
• Draw the points for the reference of the pile
• Draw piles and assign the point springs
• Draw columns below the loads

Step 6) Run the analysis & check the properties

• Run the analysis
• Safe bearing capacity from reaction 
• Punching shear design
• Strip forces & Flexural reinforcement

Step 7) Design reinforcement

• Since load was heavy the model divided to 3 pasts and analysis was done.

Result: G+3 Hostel building design and analyse is done in ETABS & the foundation design and analysis in SAFE also done.