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1.
INTRODUCTION
1.1. Problem Statement
Analyse and design an economical and stable RCC framed building for the usage in Residential purpose using CSI-ETABS and manual calculations.
1.2. Scope
The main scope of this project is to apply standards of Nepal National building codes and IS- 456, IS-13920, IS-1893 in designing a building. These building require great extent consideration of earthquake effects on building. This building is located in seismic zone V therefore the lateral loading of earthquake considered is predominant to the effects of wind loads. Hence wind loads are not considered. Almost materials and their sizes are so chooses that these are easily available in the market.
1.3 General
This report summarizes the structural analysis and design of building of “………..” at
………. Municipality/VDC ward no………..It has planned to utilize the building as
educational aspect. The aim of design is the achievement of an acceptable probability that
structures being designed will perform satisfactorily during their intended life.
1. The building will be used dwellings or hotels so that there are Partition walls inside the building. External walls 230 mm thick and internal walls 115mm thick with 12 mm plaster on both sides are considered. For simplicity in analysis, no sloping shades are used in the building analysis even though balconies and terraces are intentionally included.
2. At ground floor, slabs are not provided and the floor will directly rest on ground. Therefore, only ground beams passing through columns are provided as tie beams. The floor beams are thus absent in the ground floor.
3. The main beams rest centrally on columns to avoid local eccentricity.
4. For all structural elements except slabs, M25 grade concrete will be used. However, higher M30 grade
concrete is used for central columns up to plinth, in ground floor and in the first floor.
5. Column size are kept in similar group to ascertain simplicity in construction.
6. The floor diaphragms are assumed to be rigid
7. Preliminary sizes of structural components are assumed by experience.
8. Tie Beams are provided in connecting the footings. This is optional in zones II and III; however, it is mandatory in zones IV and V.
9. Seismic loads will be considered acting in the horizontal direction (along the two principal directions) and not along the vertical direction, since it is not considered to be significant.
10. The analysis and design has been based on the prevailing codes that are in practice in India and Nepal, the Indian Standard code IS 1893(Part 1):2002 and the NBC (105:1994) code at places if required. This report consists of the design procedures adopted, the assumptions made, the inputs made in the design and the design output.
11. As per IS 1893(Part 1):2002, the seismic zoning of Nepal can be taken as ZONE IV and ZONE V , most severe zone of India. For our case, we take the site lies on Zone V. Hence the building is designed with great consideration towards earthquake resistant practices.
12. All dimensions are in mm, unless specified otherwise
1.4 Building Configuration and Features
The arrangements of Beams, Columns, Balcony slabs, T/B slabs, Room floors are done according as the figures shown below. Storey height for all floors is taken as 3200mm. The numbering of beams and columns are presented in Annex I
Building Type : Residential Building of ……….. Located at ……….
Structural system : RCC Space frame, ductile moment resisting frame with infill wall Plinth area covered : ……….
Column : Square size 300x300mm Rectangular size (Main beams) :230 x 355 mm Slab : 125 mm thick two way slab
Type of foundation : Isolated footing with STRAP BEAM for footing No. of Storey : Three story including stair cover
Total Height : 9.6 with stair case cover
Wall : 250 mm & 125mm thick brick masonry (1:5 C/S ratio)
Probable Partition : (Actual Partition walls are not considered but 1KN/m2 equivalent Dead Load is assumed for possible partition)
Type of Sub-Soil : II (Medium type as per NBC 105)
Bearing Capacity of soil adopted = 200 KN/m2 as per site condition.
1.5 Loads on Buildings
1.5.1 Dead Load: A constant load in a building structure that is due to the weight of the members, the supported structure, and permanent attachments or accessories. This analysis
deals with dead loads to
be assumed in the design of buildings and same is given in the-form of unit weight of
materials. The unit weight of other materials that are likely to be stored in a building should be
also included for the purpose of load calculations due to stored materials. These loads are
calculated as specified in IS875-1987(part I)
1.5.2 Live Load :The load assumed to be produced by the intended use or occupancy of a building,
including the weight of movable partitions, distributed, concentrated loads, load due to impact and vibration, and dust load but excluding wind, seismic, snow and other loads due to temperature changes, creep, shrinkage, differential settlement, etc. This analysis covers imposed loads*(live loads) to be assumed in the design of buildings. The imposed loads, used in this building analysis, are minimum loads which should be taken into consideration for the purpose of structural safety of buildings.
These
loads are calculated as specified in IS875-1987 (part II)
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1.5.3 Seismic Load: The force on a structure caused by acceleration induced on its mass by an earthquake. This load is included in design to determine the extent of seismic reinforcing. The seismic loads on the structure during an earthquake result from inertia forces which were created by ground accelerations. The magnitude of these loads is a function of the following factors: mass of the building, the dynamic properties of the building, the intensity, duration, and frequency content of the ground motion, and soil-structure interaction. The
analysis method and earthquake loads
are calculated as specified in IS1893-2002.
1.5.4 Wind Load: Wind is air in motion relative to the surface of the earth. The primary cause of wind is traced to earth‟s rotation and differences in terrestrial radiation. The radiation effects are primarily responsible for convection either upwards or downwards. The wind generally blows horizontal to the ground at high wind speeds. Since vertical components of atmospheric motion are relatively small, the term „wind‟ denotes almost exclusively the horizontal wind, vertical winds are always identified as such. Wind load on the building would be usually uplift force perpendicular to the roof due to suction effect of the wind blowing over the roof. The positive or negative force of the wind acting on the structure; wind applies a positive pressure on the windward side of the building and a negative suction to the leeward side.. This analysis ignored the wind loads as the building is located in seismic zone V and hence the earthquake loads predominant it and the height of the building is less.
2.
METHODOLOGY
The project provided to us is completed performing each section works mentioned in the contents before The following stages are involved in the analysis and design of three and half storey building.
2.1 Load Calculation
Load calculation is done using the IS 1893:2002 and NBC105: 1994 as code of standards. The exact value of unit weights of the materials from the code is used in the calculation. The thickness of materials is taken as per design requirements.
2.2 Preliminary Design
The tentative size of structural elements are determined through the preliminary design so that after analysis the pre assumed dimensions might not deviated considerably , thus making the final design both safe and economical . Tentative sizes of various elements have been determined as follows:
2.2.1 Slab
For slab, preliminary design is done according to deflection criteria span /effective depth = 26*modification factor.( IS456-2000 Art 23.2.1)
2.2.2 Beam
Thumb rule of d=L/12 to L/15 basis is adopted to consider the preliminary design of the beam section .
b/D=1/2
2.2.3 Column
Preliminary design of column is done consideration and interior column. For the load acting in the column, live load is decreased according to IS456-2000 & SP 16. Cross-sections of the columns
are adopted considering the economy. Square column section is adopted in this building project as per the internal aesthetic requirements.
2.2.4 Staircase
Stairs is designed as per drawing. Coolum for stairs boxes is not included in the grid system but they are assumed to be simply tied with main frame with beam.
2.3 Loading Patterns
Loading pattern from slab to beam is obtained by drawing 450 offset lines from each corners then obtained trapezoidal as well as the triangular loading and is converted into the equivalent UDL as described in the respective sections .The loading from cantilever slab part is converted to UDL acting in beam by dividing the total load by beam. Load from all cantilever part is converted to UDL acting in beam by dividing total load (wall UDL*total wall length) by length of the beam. Self-weight of the projected beam
2.4. Gravity Load Calculation
There are three types of loads for which the provided proposed project is designed: Dead load
Live load Seismic load
Dead load consists of the load from each element of building i.e. weight of column, beam, slab and wall. Dimensions of column, beam, and slab are taken from preliminary design and Corresponding density from code. For wall load thickness of wall is taken from plan. Live load is taken from relevant code. In case of different live loads in one panel of slab, highest value of load is taken for the panel. For seismic load whole mass lump of building is calculated from which base shear is obtained according to code.
2.5 Tools for Analysis
For analysis, different softwares are available during these days. Concerning to the project “CSI-ETABS V-15” integrated building software is used for analysis of frames. Manual analysis and design using IS456:2000 carried out for the slabs and foundations with the help of me created excel-templates made accordingly.
2.6 Design Method
Limit State Method
It uses the concept of probability and based on the application of method of statistics to the variation that occurs in practice in the loads acting on the structures or in the strength of material. The structures may reach a condition at which it becomes unfit for use for one of many reasons e.g. collapse, excessive deflection, cracking, etc. and each of this condition is referred to a limit state condition. The aim of limit state design is to achieve an acceptable probability that a structure will not become unserviceable in its lifetime for the use for which it has been intended i. e it will not reach a limit state. It means structures should be able to withstand safely all loads that are liable to act on it throughout its life and it would satisfy the limitations of deflection and cracking. We adopt limit state method for design.
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3.
FRAME DESIGN
3.1 ETABS
Analysis
3.1.1
Assignments
Materials
Table 1 - Material Properties – Concrete Concrete Grade E ν α G Unit Weight Fc Lightweight?
MPa 1/C MPa kN/m³ MPa
M20 20 0.2 5.50E-06 9316.95 25 20 No
Table 2 - Material Properties - Rebar
Name E α
Unit
Weight Unit Mass Fy Fu
MPa 1/C kN/m³ kN-s²/m⁴ MPa MPa
HYSD415 200000 1.17E-05 76.9729 7.849 415 485
Table 3 - Reinforcing Bar Sizes
Name Diameter Area
mm mm²
8 8 50
12 12 113
16 16 201
Loads
The following considerations are made for the assignment of loads on the structural model:
The loads distributed over the area are imposed on area element and that distributed over length are imposed on line element whenever possible.
Where such loading is not applicable, equivalent conversion to different loading distribution is carried to load the model near the real case as far as possible.
The imposed loading of infill walls are considered(as per architectural drwg.) as equivalent UDL with 25% to 30% deductions for openings, but the actual modelling of infill walls as equivalent Struts are not performed. Hence the stiffness of infill walls are not considered.
The Plinth Tie – Beams are designed as purely tie members for lateral loads only, not designed as flexural members as floor beams.
For simplicity of Structural analysis, Modelling of stair case is not performed & no landing beam is considered. The DL & LL load of stair case is transferred to the floor beam as equivalent UDL.
Load Patterns
Table 4 - Load PatternsName Type Self-Weight Multiplier Auto Load
Dead Load Dead 1
Live Load Live 0
Seismic Load(X) Seismic 0 IS1893 2002
Seismic Load(Y) Seismic 0 IS1893 2002
Load cases
Name Stiffness From Mass Source Load Type Load Name Scale Factor Design Load Type
Dead Preset P-delta MsSrc1 Load Pattern Dead 1 Program Determined
Live Preset P-delta MsSrc1 Load Pattern Live 1 Program Determined
EQX Preset P-delta MsSrc1 Load Pattern EQX 1 Program Determined
EQY Preset P-delta MsSrc1 Load Pattern EQY 1 Program Determined
Dead loads (DL)
Assessment of unit Dead loads
Table 7 – Assessment of unit Live Loads
Unit Weight of Concrete = 25 KN/m3
Unit Weight of Brickwork with
Plaster = 20 KN/m3
Unit Weight of Floor Finish 20 KN/m3
Probable Partition Equivqlent Dead
Load = 1 KN/m2
Beam-1 Width = 230 mm, Beam-2 Width = 230 mm,
Beam-1 Depth = 355 mm, Beam-2 Depth = 355 mm,
Height Of wall = 3200 mm
Width Of External
Wall = 250 mm Slab Thickness = 150 mm,
Width Of Internal
Page 7 of 34 Percentage of Opening on wall = 30 % Stair Area = 10.6 m2
Loads on Beams supporting Two- ways Slabs:
In case of Beams supporting two-way slabs, the load distribution is trapezoidal on long beams and triangular on short beams with base angle of 45▫ as shown in fig. The ordinates of trapezoidal and triangular loads=qLx/2.
Fig:1 Two-way slab Loading
Applications of loads on model Table 6 – Applications of loads on model
a) Beams subjected to External Wall
Dead Load = 11 KN/m
b) Line along the brick masonry partition walls
Dead Load = 6 KN/m
Length = 2743 mm
Self Weight
DL = 2 KN/m
Dead Load from Stair = 9 KN/m
(considering one-way spanning of slab) Dead Load from Wall = 11 KN/m
Live Load from Stair = 12 KN/m Additional Dead Load= 20 KN/m
(other than self-wt. load.i.e.applied on model) Additional Live Load= 12 KN/m
(due to Live load on stair.i.e.applied on model) d) Floor Slab Self-Weight DL = 3.75 KN/m2 Furnishing DL = 1 KN/m2 Possible Partition DL = 1 KN/m2 Total Additional Dead Load= 2.00 KN/m2
(other than self-wt. load.i.e.applied on model)
Imposed Load (LL)
The imposed loads on the structural system are taken from IS 875(part2)-1987 for Residential/Commercial building
Assessment of unit Live Loads
Table 7 – Assessment of unit Live Loads
Type of Building = Residential
(IS875(II)-1987; Table 1) Clause 3.1
Corridor = 3 KN/m2 Stair = 3 BedRoom = 2 Toilet/BathRoom = 2 Balcony = 3 Roof = 1.5 Terrace =
Note-1: While applying the loads on structural model rounding values are used for simplicity
Note-2: Point load consideration is ignored as the slab has sufficient rigidity to spread the concentrated load; IS875 (II) Clause 3.1
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Lateral Load Calculation (Earthquake Load)
According to NBC105:1994 & IS 1823-2002, Chitwan lies on the zone 2, V. Hence, the effect of the earthquake is predominant than the wind load. So, the frame is analysed for the EQ as lateral load. Among the methods of seismic analysis Seismic Coefficient Method defined in clause 10.1 NBC 105:1994 and equivalent IS 1893-2002 clauses 6.4.2 is used to calculate seismic coefficient. And hence lateral loads are determined
Assessment of Seismic Loading
Auto Seismic Loading
Table - Auto Seismic - IS 1893:2002 (Part 1 of 2) Load Pattern Type Directio n Eccentri city % Ecc. Overridd en Period Method Ct m Top Story Bottom Story Z Type Z Soil Type I
EQX Seismic X + Ecc. Y 5 No Program
Calculated StairCover Base Per Code 0.36 II 1 EQX Seismic X - Ecc. Y 5 No Program
Calculated StairCover Base Per Code 0.36 II 1 EQY Seismic Y + Ecc. X 5 No Program
Calculated StairCover Base Per Code 0.36 II 1 EQY Seismic Y - Ecc. X 5 No Program
Calculated StairCover Base Per Code 0.36 II 1
Table - Auto Seismic - IS 1893:2002 (Part 2 of 2)
R Period Used sec Coeff Used Weight Used kN Base Shear kN 4 1 0.0612 1145.9946 70.1349 4 1 0.0612 1145.9946 70.1349 4 1 0.0612 1145.9946 70.1349 4 1 0.0612 1145.9946 70.1349
IS1893 2002 Auto Seismic Load Calculation
This calculation presents the automatically generated lateral seismic loads for load pattern EQX according to IS1893 2002, as calculated by ETABS.
Direction and Eccentricity
Direction = Multiple
Eccentricity Ratio = 5% for all diaphragms
Structural Period
Period Calculation Method = Program Calculated
Factors and Coefficients
Seismic Zone Factor, Z [IS Table 2]
Response Reduction Factor, R [IS Table 7]
Importance Factor, I [IS Table 6]
Site Type [IS Table 1] = II
Seismic Response
Spectral Acceleration Coefficient, Sa /g [IS
6.4.5]
Equivalent Lateral Forces
Seismic Coefficient, Ah [IS 6.4.2]
Calculated Base Shear
Direction Period Used (sec) W (kN) Vb (kN) X + Ecc. Y 1 1145.9946 70.1349 X - Ecc. Y 1 1145.9946 70.1349
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Story Elevation X-Dir Y-Dir m kN kN StairCover 9.144 14.9102 0 Second Floor 6.096 43.542 0 First Floor 3.048 11.6826 0 Base 0 0 0
IS1893 2002 Auto Seismic Load Calculation
This calculation presents the automatically generated lateral seismic loads for load pattern EQY according to IS1893 2002, as calculated by ETABS.
Direction and Eccentricity
Direction = Multiple
Eccentricity Ratio = 5% for all diaphragms
Structural Period
Period Calculation Method = Program Calculated
Factors and Coefficients
Seismic Zone Factor, Z [IS Table 2]
Response Reduction Factor, R [IS Table 7]
Importance Factor, I [IS Table 6]
Site Type [IS Table 1] = II
Seismic Response
Spectral Acceleration Coefficient, Sa /g [IS
6.4.5]
Equivalent Lateral Forces
Seismic Coefficient, Ah [IS 6.4.2]
Calculated Base Shear
Direction Period Used (sec) W (kN) Vb (kN) Y + Ecc. X 1 1145.9946 70.1349 Y - Ecc. X 1 1145.9946 70.1349
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Story Elevation X-Dir Y-Dir m kN kN StairCover 9.144 0 14.9102 Second Floor 6.096 0 43.542 First Floor 3.048 0 11.6826 Base 0 0 0
Page 14 of 34
Load Combinations
The load combinations are based on NBC105:1994, clause 4.4 for Limit state design method. The following load combinations are used during analysis.
Table 9- Load Combinations
S.N. Name
Load
Case/Combo Scale Factor Type Auto
1 1.Combo1.5(DL+LL) Dead 1.5 Linear Add No
Live 1.5 No
2 5.Combo (DL+1.3 LL-1.25EQY) Dead 1 Linear Add No
Live 1.3 No
EQY -1.25 No
3 6.Combo (0.9DL+1.25EQX) Dead 0.9 Linear Add No
EQX 1.25 No
4 7.Combo (0.9DL-1.25EQX) Dead 0.9 Linear Add No
EQX -1.25 No
5 8.Combo (0.9DL+1.25EQY) Dead 0.9 Linear Add No
EQY 1.25 No
6 9.Combo (0.9DL-1.25EQY) Dead 0.9 Linear Add No
EQY -1.25 No
7 4.Combo (DL+1.3 LL+1.25EQY) Dead 1 Linear Add No
Live 1.3 No
EQY 1.25 No
8 3.Combo (DL+1.3 LL+1.25EQX) Dead 1 Linear Add No
Live 1.3 No
EQX 1.25 No
9 2.Combo (DL+1.3 LL-1.25EQX) Dead 1 Linear Add No
Live 1.3 No
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Geometry Assignments
Table 10 – Geometry Assignments
Story Diaphragms Slab thickness All Rigid 125 mm
Story Mesh Option Beams/Lines Wall Edges Further Subdivide Max Element Size
mm
All Auto Cookie Cut Yes Yes Yes 300
Other Assignments
1) 100mm2 steel sections is overridden to beam section at top for ductile reinforcement
consideration.
2) Minimum rebar sizes and numbers are overridden
for beam 12mm dia and 4 numbers of bars
for column 16mm dia and 8 number of bars
3) In every floor slabs are interconnected to act as a diaphragm.
3.1.2 Analysis Preparation
Selection of Analysis Sections
Preliminary design is carried out to estimate approximate size of the structural members.
Grid diagram is the basic guiding parameter for analysis (both approximate and exact)
and is presented below.
Slab
For limit state of serviceability (deflection) criteria,
Span / depth ratio < α β γ δ λ
Where
α, β, γ ,δ, λ are modification factors given by IS 456: 2000
α = 26, for continuous slab [IS 456: 2000, CL: 23.2.1(a)]
β = 1, for span < 10m, [IS 456: 2000, CL: 23.2.1(b)]
γ = 1.24, for pt = 0.5% (assumed) [IS 456: 2000, CL: 23.2.1(c)]
S. N.
Design
Type Story Section Type Analysis Section
Design
Procedure Design Section 1 Column All* Concrete Rectangular COL300*300 (4-16,4-12) Concrete Frame Design COL300*300 (4-16,4-12) 2
Beam All Tie Beams
Concrete Rectangular BM 230*300 Concrete Frame Design BM 230*300 3 Beam All*** Concrete Rectangular BM 230*355 Concrete Frame Design BM 230*400
δ = 1, for pt = 0% [IS 456: 2000, CL: 23.2.1(d)]
λ= 1, for rectangular section [IS 456: 2000, CL: 23.2.1(e)]
Take Overall depth (D) = 150 mm
Beam
For main beam
Depth of beam = (1 / 13) * Longest span [IS 456: 2000 CL 22.2]
The section of main beam = 230 * 355 mm, 230*400 mm
Column
For main column
d = H/8 to H/10
D= 3200/ (8 to 10)
= 400 mm to 320 mm
Adopt Size of Column
= 350* 350 mm and 400*400 mm
3.1.3Analysis Outputs
Base Reactions
Table Base Reactions and Foundation Groups
S.N. Joint Label FX FY FZ MX MY Foundation Group kN kN kN kN-m kN-m 1 1 11 9 359 9 15 F2 2 2 11 2 240 14 15 F1 3 3 6 1 420 15 11 F2 4 4 3 2 210 12 8 F1 5 5 2 8 337 9 7 F2 6 6 7 10 610 9 11 F3 7 7 7 5 559 13 11 F3 8 8 2 5 305 11 7 F2 9 9 5 6 665 11 10 F3 10 10 2 6 343 10 6 F2 11 11 5 10 391 8 10 F2 12 12 2 8 196 7 7 F1 13 13 10 8 221 8 14 F1 14 14 12 7 385 11 17 F2 15 15 11 5 326 13 15 F2
Storey Drifts
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Storey Drift ratio for all storied are checked as defined in clause 7.11.2, IS 1893-2002.It is found that storey drift ratio for all stories are within permissible limit 0.004. OK. All the reaction forces, drifts and deflections are shown in ANNEX-I
Base Reactions are used to Design Foundation
Sections Forces
Typical analysis forces of beam/column and slab are presented below. All the beam/column
forces are presented in
ANNEX-IIFig:5 Direction of forces in Beam
Fig:6 Direction of Forces in Column
Storey Maximum Drift
Stair Cover 0.000789
Second Floor 0.000605
Fig:7 Axial Force Diagram in Columns of Elevation B
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Page 21 of 34
Fig:10 Resultant Bending Moment (1-1 and 2-2 ) contour in First Floor Slab
3.2 Design Outputs
Preliminary designed sections are provided and the structure is checked for different load
combinations. The detail check and pass of all the message is shown in
ANNEX-III3.2.1 Typical Output of Critical Sections
ETABS 2015 Concrete Frame Design
IS 456:2000 Column Section Design(Envelope)
Column Element Details
Level Element Section ID Length (mm) LLRF
First Floor C7 COL300*300 (4-16,4-12) 3048 0.701
Section Properties
b (mm) h (mm) dc (mm) Cover (Torsion) (mm)
300 300 56 30
Material Properties
Ec (MPa) fck (MPa) Lt.Wt Factor (Unitless) fy (MPa) fys (MPa)
22360.68 20 1 415 415
Design Code Parameters
ɣC ɣS
1.5 1.15
Longitudinal Check for Pu - Mu2 - Mu3 Interaction
Column End Rebar Area mm²
Rebar
% D/C Ratio
Top 1257 1.4 0.603
Bottom 1257 1.4 0.606
Design Axial Force & Biaxial Moment for Pu - Mu2 - Mu3 Interaction
Column End Design Pu kN Design Mu2 kN-m Design Mu3 kN-m Station Loc mm Controlling Combo kN kN-m kN-m mm Top 600.9743 7.929 -12.0195 2693 1.5 (DL+LL) Bottom 610.0605 -4.8085 12.2012 0 1.5 (DL+LL)
Shear Reinforcement for Major Shear, Vu2
Column End Rebar Asv /s mm²/m Design Vu2 kN Station Loc mm Controlling Combo Top 332.53 0.2183 2693 0.9DL-1.25EQY Bottom 332.53 0.2183 0 0.9DL-1.25EQY
Shear Reinforcement for Minor Shear, Vu3
Column End Rebar Asv /s mm²/m Design Vu3 kN Station Loc mm Controlling Combo Top 332.53 21.706 2693 0.9DL-1.25EQY Bottom 332.53 21.706 0 0.9DL-1.25EQY
Joint Shear Check/Design
Joint Shear Ratio Shear Vu,Tot kN Shear Vc kN Joint Area mm² Controlling Combo
Major(Vu2) 0.507 0 0 0 DL+1.3LL+1.25EQX
Minor(Vu3) 0.507 0 0 0 DL+1.3LL+1.25EQX
Beam/Column Capacity Ratios
1.1(B/C) Ratio Column/Beam Ratio SumBeamCap Moments kN-m SumColCap Moments kN-m Controlling Combo
Page 23 of 34 1.1(B/C) Ratio Column/Beam Ratio SumBeamCap Moments kN-m SumColCap Moments kN-m Controlling Combo Major33 0.653 1.685 0 0 0.9DL-1.25EQY Minor22 0.432 2.547 0 0 0.9DL-1.25EQY
ETABS 2015 Concrete Frame Design
IS 456:2000 Beam Section Design (Envelope)
Beam Element Details
Level Element Section ID Length (mm) LLRF
First Floor B10 BM230*355 2743.2 1
Section Properties
b (mm) h (mm) bf (mm) ds (mm) dct (mm) dcb (mm)
230 355 230 0 60 60
Material Properties
Ec (MPa) fck (MPa) Lt.Wt Factor (Unitless) fy (MPa) fys (MPa)
22360.68 20 1 413.69 413.69
Design Code Parameters ɣC ɣS
1.5 1.15
Flexural Reinforcement for Major Axis Moment, Mu3
End-I Rebar Area mm² End-I Rebar % Middle Rebar Area mm² Middle Rebar % End-J Rebar Area mm² End-J Rebar % Top (+2 Axis) 227 0.28 212 0.26 262 0.32 Bot (-2 Axis) 212 0.26 212 0.26 212 0.26
Flexural Design Moment, Mu3
End-I Design Mu kN-m End-I Station Loc mm Middle Design Mu kN-m Middle Station Loc mm End-J Design Mu kN-m End-J Station Loc mm Top (+2 Axis) -5.1633 150 -0.8944 1828.8 -25.512 2593.2 Combo 1.5 (DL+LL) 0.9DL-1.25EQY 1.5 (DL+LL)
End-I Design Mu kN-m End-I Station Loc mm Middle Design Mu kN-m Middle Station Loc mm End-J Design Mu kN-m End-J Station Loc mm Bot (-2 Axis) 4.3834 532.2 5.4108 1828.8 3.2232 2211 Combo 0.9DL-1.25EQY 0.9DL-1.25EQY 0.9DL-1.25EQY
Shear Reinforcement for Major Shear, Vu2 End-I Rebar Asv /s mm²/m Middle Rebar Asv /s mm²/m End-J Rebar Asv /s mm²/m 442.08 378.52 446.36
Design Shear Force for Major Shear, Vu2 End-I Design Vu kN End-I Station Loc mm Middle Design Vu kN Middle Station Loc mm End-J Design Vu kN End-J Station Loc mm 47.2187 150 0.0394 1828.8 48.9573 2593.2 DL+1.3LL-1.25EQX DL+1.3LL-1.25EQX DL+1.3LL-1.25EQX
Torsion Reinforcement Shear Rebar Asvt /s
mm²/m
505.54
Design Torsion Force Design Tu kN-m Station Loc mm Design Tu kN-m Station Loc mm 4.386 2593.2 4.386 2593.2 1.5 (DL+LL) 1.5 (DL+LL)
3.1.2
Summary of Design Sections
Column
The brief description of column sections is tabulated below. The detailed column section reinforcements are presented in Column Schedule attached in structural drawing section of this report
Structural drawings are explained in ANNEX-IV
Table: 12 Column Sizes and Brief Rebar Schedule
Column Sizes Rebar Area Rebar numbers Ties Remarks
mm*mm mm2 1 300*300 8mm Φ,6-legged ties @ 100mm at joint and @150mm at middle of column
Ties spacing explained here is a general idea
proper spacing is presented in column
schedule
1257 4-16,4-12
Page 25 of 34
**Column Framing Plan and Column Schedule are attached in structural drawing sheets.
Beam
All the sizes of beams and their labels and corresponding rebar are tabulated in Beam Rebar Table attached with this report in structural drawing section (ANNEX-IV). Mainly the adopted structurally passed sections are tabulated below
Table:13 Types of Adopted Beams and Their Sizes
Beams Width (mm) Depth(mm)
Main Beams 230 355
Staircase stair landing Beams 230 355
Tie Beams 230 230
4
.
SLAB DESIGN
4.1 General
Slabs are plate elements forming floors and roofs of buildings and carrying distributed
loads primarily by flexure. A staircase can be considered to be an inclined slab. They
may be supported on walls or beams or in the columns. The beam supporting the slabs
are considered stiff and do have deflections relative small as that compared to the slabs.
The slabs supported on the wall or beams are called edge supported slab.
4.1.1 Types of Slab
Slabs are classified according to the manner of the support
a) One-way Slab spanning in one direction
b) Two-way slab spanning in two direction
c) Circular slab
d) Flat slab
e) Ribbed slab
Two-way slabs are analysed and designed for this building
4.1.2 Methodology of slab design
Important information regarding the design of slab according to IS456:2000
1. Slab is designed for 1m wide strip
2. Temperature reinforcement (Ast min) = 0.12% bD for deformed bars along the
transverse direction to the main bars (Cl.26.5.2.1)
3. Cover minimum = 25mm
4. If Ly/Lx < 2, two way slab is designed
Design Steps for two way restrained slab
1. Effective depth (d) is taken from the preliminary design
2. Find out the loading
3. Find out the effective span
Leff = lo+ t
= lo + d whichever is less
4. Bending moment is calculated according to Annex D IS 456:2000
Mux = αx * wu * (lx)
2Muy = αy * wu * (lx)
2αx and αy are the bending moment coefficient from table 26 (IS 456: 2000)
Mux and Muy are the moments on the strips of unit width spanning lx and ly
respectively.
Lx and ly are the length of shorter span and longer span respectively.
5. Find out the area of the steel
Mu = 0.87 *fy *Ast*(d- (fy*Ast/fck * b))
6. Find out the spacing for the arrangement of steel.
Sv = 1000 * ( П / 4 * Φ
2) / Ast
7. Check for development length according to cl. 25.2.1 IS 456:2000
8. Check for deflection according to cl.23.2.1 IS 456:2000
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4.2 Analysis and Design of Two-way slab
Table: 14 Two-way Slab Sizes and Bottom Main Reinforcement
Calculations of sample slab are presented in ANNEX-V
DL (KN/m2) LL (KN/m2) Lx (Short Span)_mm Ly (Long Span)_mm fy (N/mm2) fck Mpa Overal thickness of slab (mm) clear cover (mm) S1 5.750 2.000 4000 4700 415 20 125 20 535 10 125 209 8 300 126 8 300 S2 5.750 2.000 3700 4700 415 20 125 20 512 10 125 179 8 300 126 8 300 S3 5.750 2.000 3700 4000 415 20 125 20 416 10 125 142 8 300 126 8 300 S4 5.750 2.000 3000 4000 415 20 125 20 386 10 125 93 8 300 126 8 300 Atx mm2 φ (mm) c/c spa.(mm) Reinforcements along Long
span (Middle Strip)
Reinforcements along ANY Span (Column Strip)
Slab group
Er. Buddhi Sagar Bastola, NEC 7059 'CIVIL' A
Atx mm2 φ (mm) c/c
spa(mm) Aty mm2 φ (mm) c/c spa.
Table : Slab Dimensions and Rebars Positive Moment Side
Client
Reinforcements along short span (Middle Strip)
Table : DL (KN/m2) LL (KN/m2) Lx (Short Span)_m m Ly (Long Span)_m m fy (N/mm2) fck Mpa Overal thickness of slab (mm) clear cover (mm) S1 5.750 2.000 4000 4700 415 20 125 20 614 10 125 286 8 300 126 8 300 S2 5.750 2.000 3700 4700 415 20 125 20 593 10 125 244 8 300 126 8 300 S3 5.750 2.000 3700 4000 415 20 125 20 484 10 125 189 8 300 126 8 300 S4 5.750 2.000 3000 4000 415 20 125 20 440 10 125 124 8 300 126 8 300
Reinforcements along Long span (Middle Strip)
Reinforcements along ANY Span (Column Strip)
Slab group
Er. Buddhi Sagar Bastola, NEC 7059 'CIVIL' A
Atx mm2 φ (mm) c/c
spa(mm) Aty mm2 φ (mm) c/c spa. Atx mm2 φ (mm) c/c spa.(m m)
Slab Dimensions and Rebars
Client ………
Reinforcements along short span (Middle Strip)
5.
FOUNDATION DESIGN
5.1 General
Foundation are the structural element that transfer the loads from the building or individual columns to the earth. The scope of foundation design is to consider the excessive settlement, rotation, differential settlement and safety against sliding /overturning of foundation.
5.1.1
Types of Footings
a) Isolated Footing: used for single column and may have square rectangular or circular shapes
b) Strip Footing: Wall footing
c) Combined footing: supports two or more columns
d) Raft/Mat foundation: Support all columns. Used when soil bearing capacity is low and sum of individual footing area is more than 50% of plinth area.
e) Pile/Well foundations: minimum three piles are capped to support the structures. Well foundations are used in bridge foundations.
Selection of footings is made from experience but for economical foundations following factors governs the major.
- Bearing capacity of soil and N-values of SPT - Permissible differential settlement
- Soil strata
- Type of structures and loadings on them
Here the type of footing adopted is an isolated footing of size ……….
5.1.2 Bearing Capacity of soil
The total load per unit area under the footing must be less than permissible bearing capacity of the soil. Foundations must be designed to resist vertical loads, horizontal loads and moments. Typical net bearing capacity of different soil types are described below.
Rock: 3300KN/m2 to 450 KN/m2
Non-cohesive soil: 450 KN/m2 to 100 KN/m2 Cohesive soil: 450 KN/m2 to 50 KN/m2.
Here the safe bearing capacity adopted is a minimum 200KN/m2 for the proposed site.
5.1.3 Depth of Foundation
Factors
-Seasonal weather change e.g. erosion and movement of upper soil -Lateral earth pressure required to resist horizontal loads.
-safe bearing capacity
Minimum depth of foundation = p/γ [(1-sinΦ)/ (1+sinΦ)] ²
Φ=angle of repose of soil, p= gross bearing capacity, γ = density of soil However minimum depth of 500mm is mandatory.
Here the depth of foundation adopted is a minimum of 1 m from the existing ground level.
5.2 Analysis and Design of Foundation
The reaction forces are obtained from ETABS analysis and the corresponding designs are made manually with the help of EXCEL template following the criterion of IS: 456-2000.
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Here the safe bearing capacity is taken on the basis of categorization of site soil and peripheral geographical/hydrological features. Experiences with similar soil type and location as the determination of proper value is out of the scope of this report. The design parameters are shown in below and corresponding drawing are also attached in structural drawing section of the architectural report.
Table: 15 –Foundation design assignment of forces and output results.
Calculations of major footings are presented in ANNEX-VI 20 200 415 S.N. F-Group # Joint Labels FZ MX MY Bar Φ Spacing c/c kN kN-m kN-m Lx (mm) Ly (mm) Depth (mm) (mm) (mm) Bar Φ No .. 1 F1 2,4,12,13 250 14 15 1250 1200 1000 12 200 10 0 2 F2 1,3,5,8,10, 11,14,15 500 15 15 1700 1600 1000 12 200 12 0 3 F3 6,7,9 750 13 11 2100 2000 1000 12 200 20 4
Note: 1.Foundation are grouped so as to make simplicity in construction.
# F-Group(1) = [Fz=0 to 250 KN] ,F-Group(2) = [Fz=250 to 500 KN] ,F-Group(3) = [Fz=500 to 750 KN],F-Group(4) = [Fz=750 to 1000 KN], F-Group(5) = [Fz=1000 to 1250 KN],F-Group(6) = [Fz=1250 to 1500 KN],
2. Minimum dowels of 10 mm bar is provided in each face of column(4 numbers)
3. All footings have 75mm brick/stone soling and 75mm PCC base from where the depth of footings is so defined in this table. Client Location Date ………. ………. ……… Cocrete Strength MPA Bearing Capacity of Soil (KN/m2) Rebar Strength MPA
Fig: 11 Joint Labels at footing
6
. CONCLUSION
The purpose of this building is mainly residential as well as small scale of commercial with limited resources. Hence due to high cost of soil investigation actual borehole site exploration and the determination of bearing capacity of soil is omitted and adopted with the experience and visual inspection of site and local possibilities. The frame system analysis is made with an well powered software ETABS V17.Attempts are made to economise and simplified the construction ensuring earthquake safety and adopting common materials, common sections, and schedules. Design process is interactive process of selecting frames and checking for loads considered. Final safe checked and passed model with possible minimum sizes of frame members and minimum reinforcement is adopted. However this design is safe against earthquake no doubly, however more iteration are avoided in selection of members which make a little costly but not more than 10%.
Page 31 of 34
Foundations and Slabs are designed manually with the help of excel- design templates made on the basis of IS 456:2000.Client is suggested to employ supervisor in the construction periods to ensure the quality control of works/materials within a limit. All necessary calculations; analysis results and design outputs are presented in annexes as a Adarsha.pdf version of soft copy file.
REFERENCES
Books and Journals
1) Jain, A.K- R.C.C Limit State Design, Nem Chand & Bros, Roorkee, 1990 2) Shah & Kale- R.C.C Design, Macmillan India Limited
3) Ashok k. Jain- Advanced Structural Analysis, Nem Chand & Bros, Roorkee, 1990 4) S.S. Bhavikati-Structural Analysis- II, Vikas Publishing House Pvt. Ltd.
5) V.N. Vazirani- Analysis of Structures-II, Khanna Publishers
6) S. Ramamrutham-Theory of Structures, Dhanpat Rai Publishing Company 7) www.csiamerica.com
8) Bothara,Jitendra Kumar- Protection of educational buildings against earthquake,NSET-Nepal publication 9) Shrestha, Hima -Retrofitting of common Frame structural houses, NSET-Nepal publication
Codes
1) I.S. 456-2000 -Code of Practice for Plain and Reinforced Concrete 2) I S. 456-1978 -Design Aids for Reinforced Concrete ( S.P.-16 ) 3) S.P.34-1987 - Handbook on Concrete Reinforcement and Detailing 4) I S 1893-2003 -Criteria for Earthquake Resistant Design Structure
5) I S 13920-1993 -Ductile Detailing of Reinforced Concrete Structures subjected to Seismic forces
6) I S 875-1987 -Code of practice for Design Loads for Buildings and Structures Part 1- Dead Loads
Part 2- Imposed Loads
7) NBC 105 :1994- Seismic Design of Building in Nepal 8) NBC 108 :1994- Site Consideration for Seismic Hazards
9) NBC 201 :1994 - Mandatory Rules of Thumb Reinforced Concrete Buildings with Masonry Infill
Tools
CSI-ETABS V.17: The frame analysis and design of this building is made with CSI-ETABS software choosing the integrated IS codes of standards. The innovative and revolutionary ETABS is the ultimate integrated software package for the structural analysis and design of buildings. Incorporating 40 years of continuous research and development, this latest ETABS offers unmatched 3D object based modelling and visualization tools, blazingly fast linear and nonlinear analytical power, sophisticated and comprehensive design capabilities for a wide-range of materials, and insightful graphic displays, reports, and schematic drawings that allow users to quickly and easily decipher and understand analysis and design results. The entire building structure was analyzed for gravity (including P-Delta analysis), wind, and seismic loadings utilizing ETABS version 8.4, from Computers and Structures, Inc (CSI). Major success story of software are shortly explained below.
- ETABS is used in the structural design of the Burj Dubai in the United Arab. The Burj Dubai Tower is the world‟s tallest structure, passing all previous height records. The entire building structure was analyzed for gravity (including P-Delta analysis), wind, and seismic loadings utilizing ETABS version 8.4, from Computers and Structures, Inc (CSI).
- ETABS is used in the design of the new Museum for African Art on Fifth Avenue in New York
Microsoft Office Excel Templates: The Design of Foundations and Slabs are made with Excel-Template prepared by myself. The so prepared design templates are based on IS 456:2000 - Code of Practice for Plain and Reinforced Concrete
ANNEXES
1. ANNEX-I-Base Reactions and Drifts/Deflection Of Structural Elements (Soft Copy) 2. ANNEX-II-Frame Section Forces (Soft Copy)
3. ANNEX-III-Design Outputs (Soft Copy)
4. ANNEX-IV-Structural Drawings (Soft as well as Hard Copy) 5. ANNEX-V- Calculations of Sample Slabs (Soft Copy) 6. ANNEX-VI-Calculations of Sample Footings (soft Copy)
