Structural Analysis and Design of Commercial cum Residential

Building

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OBJECTIVE

• To analyse and design a multi-storey R C building.

• Analysis and design is done with the aid of Staad.Pro software.

• To gain design knowledge on various structural elements like beam, column, slab, foundation etc.

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SCOPE• Design using software can be useful if any

additional modification has to be done in the structure during its future life.

• To study how analysis and design is to be carried out in Staad.Pro

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SOFTWARE’S USED

–AUTOCAD 2016–STAAD.Pro–STAAD.Foundation

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STAAD.Pro - Software used for the analysis and

design of the building

AUTOCAD 2016- Used for drafting and detailing of the designed structural elements.

STAAD.foundation - It enables engineers to analyze and design the underlying foundation for the structure that are created in STAAD.Pro.

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STAAD.Pro

• It allows structural engineers to analyze and design virtually any type of structure through its flexible modeling environment, advanced features and fluent data collaboration.

• The main advantages are advanced automatic load generation facilities for wind, area and moving loads.

• Isometric and perspective views with 3D shapes, joint, member or elements can be obtained.

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AUTOCAD 2016

• Computer Aided Design which are computer based tools used to assist designers, engineers, architects in their design activities.

• CAD is used as preparing architectural drawings and interior design and modelling.

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SITE DETAILS• Site is located at NCC road, Ambalakunnu, in

Trivandrum District.• Plot Area : 1214.4m²• Plinth area• Basement Floor: 200.06 m²• First Floor

• Residential Area: 152.64m²• Commercial Area: 73.3m²

• Parking Area : 95.4 m2

• First and second Floor area : 239.75m²8

• The basement floor is designed for parking and as well as for the residence of the caretaker of the building .

• Ground floor are exclusively for commercial and for residential purpose.

• 1st , 2nd and 3rd floors are for residential use only.

BUILDING DETAILS

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• Total height : 14.2m• Each Floor Height : 3m• Roof Height : 2.2m

• No. of Columns: 19 • No. of Beams : 98 (per floor)

• Seismic Zone : Zone 3

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SITE PLAN11

BASEMENT FLOOR PLAN12

GROUND FLOOR PLAN13

FIRST AND SECOND FLOOR14

TOWER ROOM 15

TERRACE PLAN16

ELEVATION 17

SECTION - A A 18

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BORE LOG DETAILS

• Four holes were taken at the site by auger boring.

• SPT was conducted at regular intervals of depth and soil samples were collected for identification and tests.

• BH1 and BH2 were at the rear side of the plot.

• Loose gravelly fill soil was found upto 2.3m depth was found below upto about 5.5m depth.

• SPT values in it at 3m and 4.5m depth were 8 and 7 in BH1, and less than 1 and 4 in BH2.

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• Very hard weathered soil was found below.

•In BH3 at the middle region, fill soil and loose sandy layer below gave SPT values 3, 15 and 5 at 1.5m, 3m and 4.5m depths respectively.

•Very hard soil below gave SPT value more than 80 at 5.8m depth.

•In BH4 at the front region also loose soil was upto 5.5m depth and hard weathered soil was found below.

•Water table was at less than 2m depth.

•Pile foundation is recommended for the building. 22

Description of soil Depth(m)

Thickness of soil layer

Standard PenetrationTest

Depth N

BH 1Gravel FillFine sand and silt, yellowFine sand, GrayFine sand size, hard white

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2.31.53.04.56.0

040807

>80BH 2Gravelly soil, looseSandy loam, GrayHard soil, Gray and Yellow

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1.53.04.56.0

02<0104

>100BH 3Gravelly soilFine sandFine sand and clay, GrayHard soil, Fine sand size, Gray

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1.53.04.56.0

031505

>80BH 4Gravelly filled, looseFine sandSandy loam, GrayFine sand size, White hard

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1.53.04.56.0

010510

>8023

Designing Features

• Slabs• Beams• Columns• Retaining Wall• Stair Case• Foundation

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Type of Support : Fixed Support• Size of beam :

B1- 0.4 x 0.45B2 - 0.5 x 0.3

• Size of column :C1 -0.4 x 0.6C2 - 0.45 x 0.6

• The material used : Concrete• M25 concrete is used

Fe415 steel is used 25

Codes Used• IS 456 : 2000 (Plain and reinforced concrete)• IS 875 : 1987 (Design loads) Part 1 - dead loads -Unit Weights of Building Materials

and Stored Materials Part 2 – Imposed Loads Part 3 – Wind Loads Part 5 - Load Combination • IS 1893(part 1) : 2002( Earthquake resistant design of

structures)• IS 13920 : 1993 ( RC Structures subjected to seismic force)• Design aids for IS 456 (SP16)

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Load Calculation

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DEAD LOAD• Dead load of wall = Unit weight x Wall thickness x height

= 18 x 0.2 x3 = 10.8 kN/m

• Dead load of Slab = Unit weight x Slab thickness = 25 x .15

= 3.75kN/m²• Floor Finish = 1kN/m²

• Total Dead Load of Slab = Dead load of Slab + Floor Finish = 3.75 + 1 = 4.75kN/m²

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• Dead load of Parapet = Unit weight x Parapet thickness = 19 x 0.1 x 1 = 1.9 kN/m

• Dead load of Staircase = 15 kN/m

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Sl. No OCCUPANCY CLASSIFICATION UNIFORMLY DISTRIBUTED LOAD kN/m2

1 Living rooms, bed rooms 2.0

2 Dining rooms, Cafeterias and Restaurants 4.0

3 Kitchen and laundries 3.0

4 Corridors, Passages, but not less than 3.0

5 Staircase 3.0

6 Toilets and Bathrooms 2.0

7 Balconies

Same as rooms to which they give access but with a

minimum of 4.0

LIVE LOADLive Load for Residential Building

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Live Load for Commercial Building

Sl. No OCCUPANCY CLASSIFICATIONUNIFORMLY DISTRIBUTED LOAD kN/m2

1 Retail shops 2.0

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SEISMIC DEFINITION & CALCULATION

• The impact of earthquake on structures depends on the stiffness of the structure, stiffness of the soil media, height and location of the structure, etc.

According to IS 1893 -2002, Seismic Parameters

• According to Annex E, IS 1893(Part 1): 2002, Trivandrum belongs Zone III.

• Zone Factor, Z = 0.16 ( Annex E,1893(Part 1))• Time period in x, T =

= 0.459sec

• Time period in z, T = = 0.459sec 32

Seismic Parameters33

WIND ANALYSIS• Wind loads depend on the velocity of the wind at the location of the structure,

permeability of the structure, height of the structure etc.

• Wind analysis is done based on recommendations given in IS 875(Part 3), 1987 The design wind speed can be calculated as:

Vz = Vb k₁ k₂ k₃ (clause 5.3.1)

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where,Vb - Basic Wind speed in m/s

Vz – Design wind speed at any height z in m/s

k₁- probability factor( from table 1,clause 5.3)

k₂-Terrain, height and structure size factor(from table 2, clause 5.3.2)

k₃ – Topography factor(clause 5.3.3)35

from Appendix A, IS 875(Part 3), 1987Basic Wind speed, Vb - 39m/s , for trivandrum

k₁- 1.06 ( for important building) k₂- 1.042 k₃- 1

Since the length and width of the structure is less than 20m, according to IS 875(3: 1987) the structure falls under class A, category 2.

Vz = 39 x 1.06 x 1.042 x 1 = 43.07 m/sThe design wind pressure at any height above mean ground level shall be obtained by,

Pz = 0.6 Vz2 ( clause.5.4) = 0.6 x 43.072

= 1.11 kN/m2

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LOAD COMBINATION

1. 1.5(DL+LL) 2. 1.2(DL+LL+WLX) 3. 1.2(DL+LL+WL-X) 4. 1.2(DL+LL+WLY) 5. 1.2(DL+LL+WL-Y) 6. 1.5(DL+WLX) 7. 1.5(DL+WL-X) 8. 1.5(DL+WLY) 9. 1.5(DL+WL-Y) 10. 0.9DL+1.5WLX 11. 0.9DL+1.5WL-X 37

• The load combination between dead load, live load, seismic load and wind load are auto generated in Staad.Pro.• As per IS 875(Part 5), 1987, the load combination are

16. 1.2(DL+LL+EQY) 17. 1.2(DL+LL+EQ-Y) 18. 1.5(DL+EQX) 19. 1.5(DL+EQ-X) 20. 1.5(DL+EQY) 21. 1.5(DL+EQ-Y) 22. 0.9DL+1.5EQX 23. 0.9DL+1.5EQ-X 24. 0.9DL+1.5EQY 25. 0.9DL+1.5EQ-Y 26. DL+0.5LL 27. 1.5DL+0.75LL

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12. 0.9DL+1.5WLY 13. 0.9DL+1.5WL-Y 14. 1.2(DL+LL+EQX) 15. 1.2(DL+LL+EQ-X)

Where, DL – dead load LL – live load EQX – earthquake load in X-direction EQ-X – earthquake load in (-X)-direction EQZ – earthquake load in Z-direction EQ-Z – earthquake load in (–Z)-direction WLX – wind load in X direction WLZ – wind load in Z direction

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SOIL PRESSURE• The pressure exerted by the retaining material is proportional

to its density and to the distance below the earth surface.

• Rankine's equation for active earth pressure is given asp = Kₐ

where, - density of retained material = 18kN/m³h - depth of the earthKₐ - coefficient of active pressureKₐ =

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- Angle of repose= 30˚

Kₐ = = 0.33

h = total height of the floor - thickness of base slab thickness of base slab = = 3/12

= 0.25h = 3 - 0.25 = 2.75m

p = Kₐ = 0.33 x 18 x 2.75 = 16.335kN 

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MODEL GEOMETRY

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• The nodes were assigned and the corresponding beams were added.

• The columns were produced by translational repeat.

• The section properties and support details were added.

• Load case details were assigned and analysis were done.

3D VIEW

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Bending Moment Diagram

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Shear Force Diagram & Deflected Shape

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DESIGN DETAILS

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FOUNDATION

• Pile foundation is provided.

• Design of pile cap was done using STAAD.foundation.

• Pile of diameter 50cm is used in the building.

• M 35 concrete and Fe 415 steel are adopted for design. The support reactions from analysis results are used for the design.

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• The support reactions from STAAD.Pro software was imported to STAAD.foundation and the pile cap was designed by entering the pile diameter and load bearing capacity of pile.

• Piles having 2 and 3 pile caps are provided on supports,

based on support reaction.

• Foundation design is done on STAAD.foundation.

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50Pile cap detailing (2 piles)

In X direction- 25mm dia bars @ 290mm c/cIn Z direction- 12mm dia bars @ 130mm c/c

51Pile cap detailing (3 piles)

In X direction- 25mm dia bars @ 135mm c/cIn Z direction- 25mm dia bars @ 130mm c/c

52General Arrangement of Pile Caps

CONCRETE DESIGN

• IS 456 is used for concrete designFc = 25000kN/m²clear cover = 0.04m for column = 0.03m for beamsFymain = 415000kN/m²Max main reinforcement = 25mmMax sec reinforcement = 16mmMin main reinforcement = 12mmMin sec reinforcement = 10mm

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BEAM DESIGN

54Reinforcement Detail of Critical Section

Bending Moment Diagram of Critical Section

Shear Force Diagram of Critical Section

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56Beam Detailing

COLUMN DESIGN

Design Details of Column C157

Bending Moment Diagram of Column

Axial force of Column 58

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SLAB DESIGN

• Slabs are plate elements having their depth much smaller than other two dimensions.

• They usually carry a uniformly distributed load from the floors and roof of the building.

• Slab of thickness 150 mm is used in the building and were designed as two-way slab.

• Grade of concrete M 25 is assumed for slab design.

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Longitudinal ReinforcementArea obtained from STAAD.Pro, A= 279mm2

Provide 10mm dia barsa= Пd2/4 = 78.53mm2

Spacing of bars: 1000 280 mmProvide 10mm dia bars at 280 mm c/c distance

Transverse ReinforcementArea obtained from STAAD.Pro = 460 mm2

Provide 10mm dia barsa= 78.53mm2

Spacing of bars: 1000 170mmHence provide 10mm dia bars at 170 mm c/c distance

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62Two Way slab

STAIRCASE DESIGN• The staircase comprises of flight of steps generally with one

or more intermediate landings provided between the floor levels.

• Dog-Legged Staircase is designed.

• Grade of concrete = M25

• Unit weight of concrete = 25 kN/m2

• Rise = 150mm• Thread = 300mm• Width of landing = 2m• Width of steps = 2m

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Astmin= ( 0.12 x b x D)/100

= 210mm Spacing = ast/Ast

Ast = 455.39mm² Asumming 8mm dia bars = 50.26/455.39 =110.03~ 110mm

Hence provide 8mm dia bars @ 110 mm c/c

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RETAINING WALL• Retaining walls are structures used to retain earth or loose

material which would not be able to stand vertically by itself.

Clear = 50mmEmax = 25mmEmin = 12mmFc = 25N/mm²Fy = 415N/mm²Hmax = 25mmHmin = 12mmVmax = 25mmVmin = 12mm

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• Retaining wall was defined as surface with a thickness of 250 mm in STAAD.Pro. The results obtained from are:

Horizontal reinforcement – Provide 12 mm dia bars @ 450 mm c/c

Vertical reinforcement – Provide 12 mm dia bars @ 450 mm c/c

Minimum spacing = 300mm

Therefore provide Horizontal reinforcement – Provide 12 mm dia bars @ 300

mm c/c.Vertical reinforcement – Provide 12 mm dia bars @ 300 mm

c/c. 67

CONCLUSION• The project helped to gain knowledge about the

software package STAAD.Pro and AUTOCAD 2016.

• All the requirements of KBR was followed during the execution of work.

• Detailing of each designed structural member was done using AUTOCAD 2016.

• All the aspects of design was met while analysing and designing of the structure was done using STAAD.Pro.

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REFERENCE• [1] “Design aids for reinforced concrete” SP 16-1980, Bureau

of Indian Standard, New Delhi.

• [2] “Structural Safety of Building – Loading Standard Code of Practice”, IS 875-1964

• [3] IS 456:2000(Plain and Reinforced Concrete Code)• [4] IS 875-Part-1(1987)-“Code of practice for design

loads(Dead load)”

• [5] IS 875-Part-2(1987)-“Code of practice for dead load(Live load)”

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• [6] IS 875-Part-3-“Wind loads on buildings and Structures”• [7] IS 875-Part-5- “Code of Practice for design loads(Special

loads and Combination)”• [8] IS 1893-1(2002)-“Criteria foe earthquakeresistant design of

structures”• [9] B.C Punmia, Ashok K. Jain; “Reinforced Concrete Structures

Volume I & II’, Standard publishers Distributors, Delhi – 6”• [10] Dr. N. Krishna Raju; “Design of RC Structures”, CBS

Publishers and Distributors, New Delhi, 2006• [11] S. Ramamrutham and R. Narayan; “Design of Reinforced

Concrete Structures.” (conforming to IS 456).

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Thank You

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