Challenge

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

KKrishna Moorthy M11 Dec 2022

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 Model, Analysis and design the Frame structure using ETABS Software & Foundation using SAFE Software.

Introduction:-

ETABS is an engineering software product that helps to analysis and design the multi strorey building.
SAFE represents the state of art in three dimensional finite element technologies for structural engineering.
Here, in this project we are carrying out the design analysis of a G+3 RCC building situated in Guwahati, Assam using ETABS software and then foundation design is carried out using SAFE software.

Building Design:

Given Data:

1) Location – Guwahati, Assam. It is Located in the Seismic Zone V.

2) Hostel block in an academic institute

3) Walls are made of AAC Blocks. Hence, Wall load to be 4.5kN/m.

4) Concrete - M25 Grade

5) Longitudinal Reinforcement - Fe500

6) Shear Reinforcement - Fe415

Lets Assume,

Building is Pinned Support at base.
Column - 450 x 650mm, Beam - 400 x 500mm, Slab - 150mm and Slab at Staircase - 200mm.
Floor Live Load - 2 kN/m², Terrace Live load - 1 kN/m², Floor Finish + Ceiling Finish - 1 kN/m², All Partition wall load - 3.5 kN/m and Roof Balcony wall load - 1kN/m.

Procedure:-

Step 1:-

Open ETABS Software, and select New Model from File Tab.

A Model Initialization window opens, in that giev input as shown below.

Then New Model Quick Templates window opens, Now select Custom Grid Spacing and Edit Grid Data.

Now select Custom Story Data and set Story data as shown below.
Model Grids and level created succesfully.

Step 2:-

Now Select Material Properties from Define Tab. And click Add New Material.

Define Concrete Grade as M25 as shown below.

Similarly Define Rebar Grade as Fe500 and Fe 415.

Then Define Section Properties under Define Tab, Select Frame Sections as shown below.

Click Add New Property and Select Rectangle Section.

Define Column Section as C450x650 and select material as M25.
Then Click Modify/Show Rebar and select P-M2-M3 Design (Column) as shown below.

Similarly define Beam B400x500 and modify Rebar.

Now Define Slab Sections, and give Slab thickness as 150mm for all slab and give 200mm thickness for Staircase slab.

Step 3:-

Select Load Pattern in Define Tab, add Dead load, Live load, Brickwall load, floor finish load and

Earthquake loads in X and Y direction.

Then Modify the Earthquake loads as shown below.

Select Live Load Reduction factor under Design Tab.
Reduce the loads by 10% for each floor as shown below.

Now go to Load cases from Define tab, select Modal case, then click Modify/ Show Case.
Then Set the Modal Cases as shown Below.

Now select Load Combination, a pop-up window opens, in that select Add Default Design Combos.
Then Select Concrete Design Frame, Now Load combination automatically generated.

Then Define Mass Source as Shown below.

Step 4:-

To draw Column on Grids, first we need to select All Stories Option in bottom of window.

Then Select Quick Draw Column icon in Draw toolbar.
And select Column C450x650.

Place the columns at its appropriate loaction as shown below.

Then Change the Rotation of column as required from Assign Tab.
Select Local Axes in Frame option, then change the angle as 90 degree as shown below.

Now select the Quick Draw Beams/Columns icon in draw toolbar.
Select the Beam as B400x500.

Then Place the Primary beams at loaction.

Add Secondary Beams by using Replicate tool as shown below.

Draw Floors by selecting the icon Quick Draw Floor/Wall tool.
Then select Slab 150.

Similarly draw Staircase slab by selecting Slab-STR.

Step 5:-

Select all Beams, and go to Assign Tab, select Distributed load in Frame Loads.

A New pop-up window appears, Select Brickwall Load and give value as 3.5kN/m.

Similarly, assign Brickwall load to Balcony wall of 1 kN/m.

Then select slab and Assign Floor Finish load (1 kN/m²) and Live load (2 kN/m²).

Now Select all Slabs from Select Tab as shown below. Select Floor Option.

Now to we have to Assign Diaphragms.
To that first go to Assign Tab, select Diaphragms in Shell option.

Then select D1. Click OK.

Step 6:-

To Run Analysis first we have to Check Model as shown below.
It has to show No Warnings.

Add Response spectrum from Define Tab.

Define Response spectrum as IS 1893:2016.

Now go to Load Cases and define RSx and RSy Response spectrum loads as shown below.

Now Click Run Analysis.

Step 7:-

Now Select Show Table Display Tab. To see the Modal Periods.

The Sum First Three modes is greater than 65%. Hence the model safe.

Then select Story Response Plots, and see Story drift with Earthquake load.

Both X and Y Direction Story Drift value is lesser than 0.004. Hence safe.

Step 8:-

Now Select Start Design/ Check in Concrete design tool.

It indicates some beams are red in colour it shows those beam are failed.

To change the beam section properties, first we need to unlock the model
And then add New Beam Section and assign the beams.
Then again Run analysis and check the design.
Repeat the same process until the beam gets passes.

To see the shear reinforcement requiremet, select Display Design info.
And select Shear reinforcement.

Provide reinforcement details for beam D4-E4 and Column D4.

Foundation Design:

Given Data:

1) Location – Guwahati, Assam. It is Located in the Seismic Zone V.

2) Hostel block in an academic institute

3) Pile Length - 10m

4) Pile Diameter - 500mm

5) Pile Thickness - 800mm

6) Load Carrying Capacity of each pile - 280kN

7) Concrete - M25 Grade

8) Longitudinal Reinforcement - Fe500

Lets Assume,

Center to Center distance betwwe the Pile to be 2.5 times the pile diameter - 1250mm
Edge distance from pile to be 1 time the pile diameter - 500mm

Point Spring Modulus (k) = AE/L

= 196349 x 25000 / 10000

= 490872.5 N/mm

= 490872.5 kN/m