A
STRUCTURAL DESIGN
REPORT
OF
THE PROPOSED BUILDING OF COMMERCIAL
OWNER:
TO WHOM IT MAY CONCERN
This report comprises the summary of the Commercial building of Mrs.Jasuda Rai Dharan-15 Sunsari Nepal. The reports consist of the design procedures adopted, the assumptions made, the inputs made in the design and the design output. During the design, it is assumed that the client will completely follow the architectural as well as the structural design. It is also assumed that the construction will be supervised by professional engineer.
The designer will not be responsible if any alterations to the structural system is made by the client or the contractor without the prior written permission from the designer, or the alterations to non-structural system is made such that the weight of each individual floor or the weight of the whole building is altered by more than 10% of design weight of each floor and the total weight.
The design calculations and derivations are limited to only a minimum to let the concerned people know the methodology adopted. However, the calculations may be provided to the client or concerned authorities when needed, upon request. Hence the building is safe.
Designer
……… Er. Rabin Bhattarai
Earthquake Engineer (M.E) Council No:4944 . “Civil” A
TABLE OF CONTENTS
S.N. Title
Page No.
1
Introduction
1
2
Salient features
1
3
Design Approach and Methodology
3
4
Preliminary Design
6
5
Final Analysis
7
6
Design Methodology
8
7
Analysis Output
10
1.0 Background
This report summarizes structural analysis and design of the Commercial building for Dharan Sub-Metro politician City. The analysis and design has been based on the prevailing codes that are in practice in Nepal, the National Building Code of Nepal and the IS codes at places.
2.0 Salient Features
2.1 Project Information:
Owner : Mrs. Jasadu Rai
Building Type : Commercial Building
Location : Dharan-15
Plot no. : 9571, 9566, 9569
Land Area : 1485.00 sq.ft.
Plinth Area : 1350.00 sq.ft.
2.2 Building Features:
Type of Structure: RCC Framed Structure
Storey: 2 & half storey
Storey Height: 3.175m
Total Height: 9.525 m
2.3 Site Condition:
Soil Type: III (for seismic consideration as per NBC 105)
Seismic Zone Factor: 1.0
2.4 Material Specification:
Considering Architectural, Economic and strength demands reinforced cement concrete (RCC) is used as the major structural material. The selected material also confirms the availability and ease in construction. The concrete grade used is M20 as per Indian Standard Specification. This material provides minimum grade of structural concrete and favorable for easy production and quality control as well.
Fe 500 is provided as longitudinal and shear reinforcing in Beams, Columns, foundations, and slabs wherever RCC is used.
Considerations of material for loading and strength parameter are as detailed below:
Structural Components: Concrete:
Grade: M20
Characteristic Compressive Strength: 20 N/mm2
Unit Weight: 25.0 KN/m3
Young’s Modulus of Elasticity (E): = 5000 fck N/mm2
≈ 22360680 KN/m2 (for M20)
Steel Reinforcement:
Grade: Fe 500 (for both longitudinal and shear reinforcement)
Non-Structural Components: Brick wall:
Unit Weight: 18.85 KN/m3
Strength: Not Available
Finishing:
Plaster:
2.5 Loading Details
Number of Storey 2 & half Storey Loading in General
(Gravity loads)
Structural Self Weight
Live Load for residential services
Dead load of finishing materials for floor
Panel walls 250mm & 125mm thick brick walls without openings
125mm thick brick walls with 30% openings
Partition walls 125mm thick (half brick) walls with 30 & 20% openings
Parapet walls 125 mm thick (half brick) wall height 0.8m
Live Load As per IS 875 Part II
Lateral Loading As per NBC 105:1994
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 facility is not feasible, equivalent conversion to different loading distribution is carried to load the Model near the real case as far as possible.
For lateral load, necessary calculations were performed and checked using NBC 105: 1994 for response spectrum method.
Different load combinations based on Nepal National Codes are developed and used for design purposes.
Load Combinations:
The load combinations are based on NBC 105: 1994 Static Load Combination:
1.5 DL + 1.5 LL
Seismic Load Combinations:
1.0 DL + 1.3 LL 1.25 EQ
0.9 DL 1.25 EQ
For seismic loading, mass equivalent to the load that composed of 100% of Dead load and 25% of Live load is taken into consideration.
The Earthquake lateral loads were used in the combination from the Self-Generated Load on the Seismic coefficient Method.
Modal analysis is carried out using FEM Based three dimensional analyses.
3.0 Design Approach and Methodology:
The structure is analyzed for full Finite Element. Beams and columns modeled as frame (line) elements with five and three internal stations. All floor slabs are modeled as Shell (Area) elements with sufficient and appropriate meshing. Modulus of elasticity and Poisson’s ratio for used material i.e. M20 grade concrete (as per Indian Specification) are taken accordingly and section properties used are based on Preliminary section sizing with consideration for deflection, minimum size specified and serviceability. Computation for stiffness as a whole is carried out using FEM based latest software. Full Modal Analysis is carried out up to twelve modes confirming more than 95 % seismic mass participation and it is applied for lateral seismic force distribution that generated with NBC 105 based Spectral Function for Soil Type-III.
For Section Design and Check, suitable Load combinations as suggested in NBC105:1994 and if not covered in that, IS 1893- 2002 is referred with consideration of Envelopes of internal Forces developed.
Foundation design is carried out to satisfy strength and stability requirements.
3.2 Software used: (Introduction to Analysis software)
The analysis for the structural system was carried out using ETABS 2016 ver 16.0.0 is a product of computers and structures Inc, Berkeley. It is a FEM based software having facility of RC Design based on IS-456:2000
3.3 Structural Performance:
Structural response under limit state of serviceability is thoroughly checked. The force and stiffness relationship resulting the deflection under various load cases and combined action of forces are duly evaluated. Basically short-term elastic deflection due to vertical loads and lateral deflection due to seismic forces are of major importance along with the long-term deflection of beam elements under sustained loading condition due to shrinkage and creep are also taken into account.
3.5 Deformation under Lateral Loads:
Effect of lateral load due to seismic force is analyzed using self-generated seismic load compatible with Codal provision. The distribution of lateral force at different parts of the structure is done based on the response under unit force. Using Complete Quadratic Combination (CQC) method of modal combination combines the deformations, and related forces reported.
3.6 Recommendations:
The following recommendations are made:
Materials used shall confirm minimum standard specified before use. Primarily the cement, aggregate, sand and steel shall be used that confirms to NS or IS standard. Batching, mixing, placing and curing of concrete and steel fabrication and placing
shall be done as per standard practice.
4.0 Preliminary Design
The Preliminary Design was done using the prevailing thumb rules and span consideration.
Slab: The slab is designed based on IS456:2000. The slab is designed to meet the
deflection criteria for the slab.
Beam: The beam is designed based on IS456:2000. The slab is preliminarily designed to
meet the deflection criteria as well as the moment requirements for the span.
Column: The column is preliminarily designed to meet the stiffness criteria for the
building.
Staircase: The staircase is designed to satisfy the moment requirement as well as the
deflection criteria.
The sizes of the structural components are as given below: Sizes of Structural Components:
Slab: 5” thick RCC (M20) Slab
Beam: Rectangular main Beam size- 10” X 15” (BXD)
Column: Square, size- 12”X 12” (HXB)
5.0 Final Analysis
5.1 Load Calculations:
Refer Table: Load Intensity of Building Components
Live Load: 3.0 KN/m2 (for all rooms)
Live Load: 4 KN/m2 (for staircases and lobbies)
Roof Live Load: 1.5 KN/m2 (for roof accessible), 0.75 KN/m2 (for roof inaccessible)
5.2 Seismic Lump Load:
Seismic weight: Comprises Dead Load+ 50% of Live Load (as per IS Code for live load intensity > 3 KN/m2)
Seismic wt. at ith floor level (WI) = (Total dead load of all components i.e. Beam, Slab,
Columns And Walls for ½ height above and ½ height below the floor level + 50% of live load)
n
Total Weight of the frame, W= Wi Where, n = total number of storey I=1
Seismic Wt. of Building W = 4197.85KN
Base Shear Calculation: As Per NBC 105:
Total Horizontal Base Shear V= Cd W
Where, Cd= CZIK Where,
Basic Shear Factor (C) = According to time period of vibration and Soil type Seismic Zoning Factor (Z) = For Dharan
Importance Factor (I) = According to the type of building Performance Factor (K) = for the moment resisting frame Distribution of design seismic force:
Fi = Design Seismic Force at floor Level I
Wi = seismic wt. at ith floor level
hi = height of floor i measured from base
According to NBC 105:1994
Soil type = III
Time period (T) = 0.06 H0.75
= 0.3254 Sec
C = 0.08 (from Fig 8.1 of NBC105:1994)
Z = 1.00 (for Dharan, Fig 8.2 of NBC105:1994)
I = 1.5 (for Commercial Bldg., Table 8.1 of NBC105:1994)
K = 1.00 (for Ductile Moment resisting Frame, Table 8.2 of
NBC105:1994) Cd = CZIK
= 0.12
Horizontal Base shear Vx = Vy = 0.12*4197.85 Total Horizontal Base shear Vx = Vy = 503.75 KN
5.3 Load Cases:
Dead : Self Weight of the building structural components (Beams, columns and slabs) Finish : Weight of the finishing of the slabs as well as staircases (including steps). Wall : Wall loads (inclusive of plaster)
Live : Live load in the building area elements.
Rlive : Live load in the terraces both accessible and inaccessible (not including in seismic behaviour)
EQX : Spectral Seismic Load in X – Direction EQY : Spectral Seismic Load in Y – Direction
5.4 Load Combination:
DL = 1.5Dead + 1.5Finish + 1.5 Wall + 1.5 Rlive + 1.5Live DQX = 0.9 Dead + 0.9 Wall + 0.9 Finish ± 1.25 EQX DQY = 0.9 Dead + 0.9 Wall + 0.9 Finish ± 1.25 EQY
DLEQX = 1.0 Dead + 1.0Wall + 1.0 Finish + 1.3 Live ± 1.25 EQX DLEQY= 1.0 Dead + 1.0 Wall + 1.0 Finish + 1.3 Live ± 1.25 EQY
6.0 Design of Structural Members
6.1 Design Assumptions: Foundation
The Safe Bearing Capacity (SBC) of the soil is taken to be 150 KN/m2. The depth of the
foundation is taken as 1.67 m. It is assumed that the soil below is converted to a firm base by sufficient compaction through any convenient means or as directed by the site engineer.
Beam:
The beams are assumed to be rectangular. The preliminary design of the beam is carried out considering the deflection criteria as well as the loading condition.
Slab:
The longest span slab is designed and for uniformity in construction, all the slabs are detailed according to the designed slab. The slab is designed based on IS 456:2000, for adjacent edge discontinuous. However during detailing, the torsion in the free edges is considered.
6.2 Design Methodology:
The design of beams and columns that are the structural components in the building are carried out using the results and analysis for critical responses and also checking with manual calculations is carried out. The design of the foundation is carried out based on the base reactions as obtained from the software with necessary adjustments. The design of slabs and staircases are carried out based on the prevailing design practices, following the codal provisions.
6.2 Calculation of Wall Loads.
The calculations of the loads are given in the following tables: Load Intensity of Wall
10”Thickness of wall with 1” plaster both side of wall
Full wall intensity
=18.85*0.25*(3.175-0.375)+20.4*1*0.025*(3.175-0.375)* =13.6 KN/M
20% opening Wall intensity
30% opening Wall
intensity =13.6x0.7 =9.50KN/M
5”Thickness of wall with 1” plaster both side of wall
Full wall intensity =18.85*0.125*(3.175-0.375)+20.4*2*0.025*(3.175-0.375)* =6.8 KN/M 20% opening Wall intensity =6.8*0.8 =5.4 KN/M 30% opening Wall intensity =6.8*0.7 =4.7 KN/M Parapet 5”wall Parapet wall =18.85*0.125*0.92 =2.2KN/M
7.0 ANALYSIS OUTPUT
Result from Structural models and analysis
Design Plan (Ground Floor)
8.0 Design of Members
Design of Beams and Columns
The design of beams and columns are done from the software itself. However, it is to be notified that the limitations of the design by the software have been evaluated and the adjustments have been made accordingly. The samples (summary) of the design through the software based on IS456: 2000 has been presented hereunder.
Column Reinforcement Details
Column Reinforcement
Column
Type Ground floor First floor Second-floor STIRRUPS
C-1 (12"X12") 8-16Ø 8-16Ø x 8mm DIA @ 4" C/C near joint & 6" C/C at mid C-2(12"X12") 8-16Ø 8-16Ø 4-16Ø+ 4-12Ø C-3 (12"X12") 4-20Ø+ 4-16Ø 4-20Ø+ 4-16Ø x C-4 (12"X12") 4-20Ø+ 4-16Ø 4-20Ø+ 4-16Ø 8-16Ø C-5 (12"X12") 8-20Ø 8-20Ø 4-20Ø+ 4-12Ø
ETABS 2016 Concrete Frame Design
IS 456:2000 Column Section Design
Column Element Details Type: Ductile Frame (Summary)
Level Element Unique Name Section ID Combo ID Station Loc Length (mm) LLRF
Story1 C4 141 C-12"X12" DL+FL+LL+WL+1.3LL-1.25EQX 0 3175 0.794
Section Properties
b (mm) h (mm) dc (mm) Cover (Torsion) (mm)
304.8 304.8 54.1 28.1
Material Properties
Ec (MPa) fck (MPa) Lt.Wt Factor (Unitless) fy (MPa) fys (MPa)
22360.68 20 1 500 500
Design Code Parameters
ɣC ɣS
1.5 1.15
Axial Force and Biaxial Moment Design For Pu , Mu2 , Mu3
Design Pu kN Design Mu2 kN-m Design Mu3 kN-m Minimum M2 kN-m Minimum M3 kN-m Rebar Area mm² Rebar % % 417.4856 -13.8851 -81.2021 8.3497 8.3497 2127 2.29
Axial Force and Biaxial Moment Factors K Factor Unitless Length mm Initial Moment kN-m Additional Moment kN-m Minimum Moment kN-m Major Bend(M3) 0.732464 2794 -32.4808 0 8.3497 Minor Bend(M2) 0.664085 2794 -5.554 0 8.3497
Shear Design for Vu2 , Vu3
Joint Shear Force kN Shear VTop kN Shear Vu,Tot kN Shear Vc kN Joint Area cm² Shear Ratio Unitless
Major Shear, Vu2 N/A N/A N/A N/A N/A N/A
Minor Shear, Vu3 N/A N/A N/A N/A N/A N/A
(1.1) Beam/Column Capacity Ratio
Major Ratio Minor Ratio
N/A N/A
Additional Moment Reduction Factor k (IS 39.7.1.1) Ag cm² Asc cm² Puz kN Pb kN Pu kN k Unitless 929 21.3 1633.5835 323.1396 417.4856 0.928005
Additional Moment (IS 39.7.1) Consider Ma Length Factor Section Depth (mm) KL/Depth Ratio KL/Depth Limit KL/Depth Exceeded Ma Moment (kN-m)
Major Bending (M3 ) Yes 0.88 304.8 6.714 12 No 0
Minor Bending (M2 ) Yes 0.88 304.8 6.087 12 No 0
Notes:
N/A: Not Applicable N/C: Not Calculated N/N: Not Needed
ETABS 2016 Concrete Frame Design
IS 456:2000 Beam Section Design
Beam Element Details Type: Ductile Frame (Summary)
Level Element Unique Name Section ID Combo ID Station Loc Length (mm) LLRF
Story1 B4 13 B-10"X15" DL+FL+LL+WL+1.3LL-1.25EQY 152.4 3530.6 1
Section Properties
b (mm) h (mm) bf (mm) ds (mm) dct (mm) dcb (mm)
254 381 254 0 25.4 25.4
Material Properties
Ec (MPa) fck (MPa) Lt.Wt Factor (Unitless) fy (MPa) fys (MPa)
22360.68 20 1 500 500
Design Code Parameters
ɣC ɣS
1.5 1.15
Factored Forces and Moments Factored Mu3 kN-m Factored Tu kN-m Factored Vu2 kN Factored Pu kN -56.7272 6.4527 63.3109 0
Design Moments, Mu3 & Mt
Factored Moment kN-m Factored Mt kN-m Positive Moment kN-m Negative Moment kN-m -56.7272 9.4893 0 -66.2165
Design Moment and Flexural Reinforcement for Moment, Mu3 & Tu
Design -Moment kN-m Design +Moment kN-m -Moment Rebar mm² +Moment Rebar mm² Minimum Rebar mm² Required Rebar mm²
Torsion Force and Torsion Reinforcement for Torsion, Tu & VU2 Tu kN-m Vu kN Core b1 mm Core d1 mm Rebar Asvt /s mm²/m 6.4527 63.3109 223.2 350.2 460.72 Slab Design Input Parameters
Length of shorter span (lx) = 3.74 m Length of longer span (ly) = 4.69 m
Support condition 2 Slab type = 23 = 1 (assumed) = 1.25 ly/lx = 1.25
Design two way slab
Assume grade of concrete (fck) = M 20 Assume steel (fy) = Fe 500 Thickness of marble finishing = 25.00 mm Thickness of screed = 25.00 mm Thickness of plaster = 20.00 mm Unit weight of marble = 26.70 KN/m3
Unit weight of screed = 20.40 KN/m3
Unit weight of plaster = 20.40 KN/m3
Unit weight of concrete = 25.00 KN/m3
Live load = 3 KN/m2
Assume bar diameter = 8.00 mm Effective depth of slab (d) 130.09 mm Assume, d = 96.00 mm Total depth of slab, D = 125.00 mm
Dead load calculation of slab
Dead load of slab due to concrete = 3.13 KN/m2
Dead load due to floor finish (marble) = 0.67 KN/m2
Dead load due to screed = 0.51 KN/m2
Dead load due to plaster = 0.41 KN/m2
Partition load = 1.00 KN/m2
Total dead load = 3.13 KN/m2
Dead load + Live load = 6.13 KN/m2
Design load = 9.19 KN/m2
Bending moment Coefficients Max. bending moment
x = 0.0376 Mx = 4.83 KNm
x = 0.0496 -Mx = 6.38 KNm
y = 0.0280 My = 5.66 KNm
Check depth for moment
Required depth for moment = 52.05 mm Provided depth, d = 96.00 mm
Required depth is < Provided depth
O.K. safe Area of steel
Solving quadratic equation
0.025 Ast2 + -96.00 Ast + 13008.04 = 0
0.025 Ast2 + -96.00 Ast + 17189.19 = 0
Bottom bars Top bars
Ast = 3699.35 mm2 Ast = 3651.71 mm2
Ast = 140.65 mm2 Ast = 188.29 mm2
Spacing required
8 rods @ 357.2 mm c/c Bottom bars 8 rods @ 266.8 mm c/c Top bars Spacing provided
8 rods @ 150.0 mm c/c Bottom bars 8 rods @ 150.0 mm c/c Top bars
Check for shear
Provided Ast = 334.93 mm2 p% = 0.35 k = 1.3 c' = 0.41 N/mm2 IS 456:2000 (Table 19) c = 0.53 N/mm2 Max.shear force (Vu) = 17.18 KN v = 0.18 N/mm2 c > v O.K. safe
Check for minimum steel
Minimum steel (0.12%) Provided steel 115.20 mm2 < 334.93 mm2
O.K.
Check for deflection
= 23 fs = 121.783 = 1 = 1 = 2.000 = 1 Allowable L/d = 46.00 Actual L/d = 38.96 Allowable L/d > Actual L/d O.K.
Design of Staicase
Concrete M20 20.00 N/mm2Steel Fe500 500.00 N/mm2
Riser R 0.15 m
Thread T 0.25 m
SQRT(R2+T2)/T 1.17
Effective Span l 4600.00 mm
Assumed effctive Depth d 115.00
Provide
Cover 12.00 steel Diameter 12
Overall Depth D 133.00
Take Overall Depth D 135.00 mm Effective Depth d 117.00 mm Load Calculation for Waist Slab
Self wt. of waist Slab 3.94 kN/m2
Floor Finishes 2.00 kN/m2
Live Load 3.00 kN/m2
Total Load w 8.94 kN/m2
Factored
Load wu 10.72 kN/m2
Considering 1m wide strip of Slab
Length Lef 1.1 Center 2 Right 1.13
Load/m2 5.361536 10.72 5.361536
Reaction at support 16.70118 Max. Bending Moment 34.12952
0.133fckbd2=M u
Reqd
Depth d= 113.27 mm
Provided Effective Depth (d)=117> 113.27,
Provide 12 mm dia bar
Spacing s= 139.29
Provide 12mm bar @125 c/c( Main Bar) Steel
provoded (Ast)prvd 1130.00 mm2 Provided Steel =1130mm
2 >
811.26mm2 , Hence Safe ok
Calculation for distribution bar
Steel
Required (Ast)reqd 162.00 mm2
Provide 120mm dia bar
Spacing s= 314.81
Provide 12 mm bar @150c/c Steel
provoded (Ast)prvd 255.00 mm2 Provided Steel =255mm
2 >
162.0mm2 , Hence Safe ok
Provide 12mm bar @125 c/c (Main Bar) Provide 12mm bar @150 c/c (Distribution Bar)
Slab Strip Design - Layer A - Top and Bottom Reinforcement Intensity
(Enveloping Flexural) [mm2/m] - 12 mm Ø @ 125 mm (Top), 12 Ø mm @ 125mm (bottom). Depth-20” thick
Slab Strip Design - Layer B - Top and Bottom Reinforcement Intensity
(Enveloping Flexural) [mm2/m] - 12mm @ 125 mm (Top), 12mm Ø @ 125 mm (bottom). Depth-20” thick
List of design code and Standards
1. NBC-000-114:1994 : All relevant design codes in Nepal
2. IS 456 – 2000 : Code for practice for plain & Reinforced concrete
3. IS 875 – 1987 : Code of practice for Design Loads (other than
earthquake load) for building & structures. 4. IS 1893(part-I)-2002 : Code of practice for earthquake resist design of Structures.
5. IS 13920 – 1993 : Code of practice for Ductile detailing of
Reinforced
Concrete structures subjected to seismic forces.
6. SP: 16 – 1980 : Design aids for Reinforced concrete to IS 456
-1978
