This document is a structural design report for a proposed residential building in Kirtipur, Nepal. It provides details on the structural system, materials, design codes followed, load calculations, structural dimensions, analysis, and design procedures. The building will be a 3.5 story ductile moment resisting frame structure with reinforced concrete beams, columns, slabs, and footings. Load calculations are provided for dead and live loads according to Nepalese codes. Analysis was conducted using ETABS software to calculate member forces and design seismic loads. The report concludes with sample output data from the structural analysis.
1. A
REPORT ON
STRUCTURAL DESIGN OF RESIDENTIAL BUILDING
Of
Ms. Kalpana Thapa
SUBMITTED TO:
Kirtipur Municipality,
Ward no-7, Kirtipur,
September, 2016
2. GENERAL
1.1 INTRODUCTION:
This report is prepared on request from Ms. Kalpana Thapa to be submitted to Kirtipur Municipality
as the partial requirement for the application for building construction permit. This Report
describes in brief the Structural Aspects and Design Report of the proposed Residential Building at
Tusal, Kirtipur.
The building will be used for the residential purpose and will be designed for maximum of three
and half story. The structural design is intended to be based primarily on the current Nepal Building
Code of Practice.
1.2 STRUCTURAL SYSTEM FOR THE BUILDINGS
The structural system for the buildings have been evolved on the basis of various aspects like
functional requirements of the building, durability and life span of building, cost effectiveness and
other design criteria requirements specified by discussions on number of meetings with client.
The buildings will be designed as a Ductile Moment Resisting Frame structure, meaning frames in
which members and joints are capable of resisting forces primarily by flexure. The frames will be
detailed to provide ductile behavior and comply with the requirements given in NBC 105.
Element Sizes and Details
Initially, for the purpose of load calculation following section will be assumed
Typical floor height is 2.84m. And the floor height for the ground floor is 2.84 meter.
Roof and Floor Slab = 125 mm thick
Staircase slab = 150 mm thick
Beams along Longitudinal direction = 230mm* 355mm
Beams along traverse direction = 230 mm x 355 mm,
Columns = 300 mm x 300 mm
Wall: - A 1 brick (230mm) and ½ brick (115mm) wall is used.
1.3 RELEVANT CODES FOLLOWED FOR DESIGN
The main design standards followed for structural design are given below, indicating their area of
application.
For Loading:
NBC101-material specification
NBC102-unit weight of materials
NBC103-Imposed load
For Design of Reinforced Concrete:
NBC105-seismic design of buildings in Nepal
3. 1.4 COLUMN GRID PLAN WITH GRID NAMES AND CENTER LINE DIMENSIONS
1.6. DESIGN BASIS
1.6.1. General
The reinforced concrete members are designed in accordance with Nepal Building Code. Other
relevant codes as mentioned in the list above were also followed for specific items of work.
Grade of Concrete and Cover to the Reinforcement
The appropriate grade of concrete and nominal cover to reinforcement is governed by the
following main considerations:
• Durability of Concrete
• Fire Resistance
• Corrosion Protection to the Reinforcement
• Bar Size
• Nominal maximum aggregate size
• Proposed Grade of Concrete & Cover to Reinforcement
Considering the nature of soil as observed in site during previous excavation for the site and the
exposure conditions, fire rating, durability requirements etc. mentioned in NBC, the proposed
grade of concrete for all the reinforced concrete members is M20, and clear cover to
reinforcement for various items are as follows:
• Floor and plinth Beams 25mm
• Columns & Pedestals 40mm
• Slabs 20mm
• Footings 50mm
4. 1.6.2. Materials
Materials used as constituents of concrete shall be as per clause of NBC101. The properties of
hardened concrete shall be as per NBC and other relevant clauses shall be considered. For 43 or 53
grade Ordinary Portland Cement conforming to NBC; gain of additional strength beyond 28 days is
uncertain and thus age factor as indicated in NBC will not be considered.
1.6.3 Reinforcement
The following types of reinforcement bars shall be used:
1. Thermo-mechanically treated (TMT) Confirming to IS: 1786-1985 (fy = 500 MPa)
2. Deformed bar Confirming to IS: 1786-1985 (fy = 415 MPa)
Reinforcement Bars of size 8 mm, 10 mm, 12 mm, and 16mm will be used. Welded wire mesh shall
not be used for structural members. Only lapped splices shall be used.
1.6.4. Admixtures
The concrete slump shall in general be in the range of 75mm and 125mm depending on
reinforcement congestion, ambient temperature and other placement, transporting and
compaction considerations.
1.6.5. Cement
Use of blast furnace slag cement as per NBC is recommended for all elements of the structure
constructed underground. The superstructure may have OPC cement conforming to NBC.
1.6.6 Structural Dimensioning
In addition to the requirements of loads and stresses the minimum structural dimensions are also
governed by other considerations like fire resistance, size of aggregates, reinforcement detailing,
etc. Minimum width of beams & columns shall not be less than 250mm from above requirements.
The minimum thickness of any structural element shall conform to NBC. The minimum thickness of
various elements shall also meet the fire resistance requirements of IS: 8110-Part 1-1985. All the
reinforced concrete elements of the building will be designed for mild condition of exposure and a
fire resistance of 1.5 hours.
The minimum thickness at the tip of strap footings shall be at least 200mm from the point of view
of reinforcement detailing.
The slope at top of the footings shall be not steeper than 1: 2.5 in order to obtain well compacted
concrete throughout the footing.
LOAD CALULATION
A.DEAD LOAD CALCULATION
1. Unit Weight of materials
Reinforced concrete = 25 KN/m3
Brick masonary = 18.85 KN/m3
Screed = 20.4 KN/m3
Cement plaster = 20.4 KN/m3
marble = 26.7 KN/m3
2. Floor Loads
Thickness of structural slab = 0.125 m
Thickness of screed = 0.025 m
Thickness of celing plaster = 0.0125 m
Thickness of marble = 0.02 m
Dead Load of structural slab = 3.125 KN/m2
Dead Load of screed = 0.51 KN/m2
5. Dead Load of cement plaster = 0.255 KN/m2
Dead Load of marble = 0.534 KN/m2
Total dead load of floor finishes = 1.299 KN/m2
Dead load of partion walls = 1 KN/m2
Total dead load = 5.424 KN/m2
3. Heights of Beams, Walls & parapet walls
Depth of Beam in Longitudinal direction = 0.4 m
Depth of Beam in transverse direction = 0.355 m
Height of each story of building = 3.2 m
Height of parapet wall = 1 m
4. Dead Loads of Walls
Dead load of 230mm thick wall in longitudinal direction = 12.14 KN/m
dead load of side plaster of exterior
wall(12.5mm+25mm)thick = 2.14
KN/m
Total dead load (Long. Dir.) = 14.28 KN/m
Dead load of 230mm thick wall in tranverse direction = 12.33 KN/m
dead load of side plaster of exterior
wall(12.5mm+25mm)thick = 2.18
KN/m
Total dead load (Traves. Dir.) = 14.51 KN/m
Dead load of 230mm thick wall with 30% in longitudinal
direction = 10.00
KN/m
Dead load of 230mm thick wall with 30%in tranverse
direction = 10.16
KN/m
Dead load of 115mm thick wall in long. Direction = 6.07 KN/m
Dead load of 115mm thick wall in trans. Direction = 6.17 KN/m
Dead load of parapet wall 4" thick = 2.16775 KN/m
B. Live Load
Calculation
Live load in bedroom ,
living room = 2 KN/m2
Live load in corridor,
staircase, balconies = 3 KN/m2
Roof live load access = 1.5 KN/m2
roof live load not access = 0.75 KN/m2
6. Load Pattern Definitions
Name Type Self-Weight Multiplier Auto Load
Self Dead 1
Finishes Dead 0
4"wall Dead 0
9" wall with opening Dead 0
Parapet wall Dead 0
Staircase Dead 0
roof live Live 0
Floor live Live 0
EQx Seismic 0 User Coefficient
EQy Seismic 0 User Coefficient
Partition Dead 0
9" wall Dead 0
1.7 Design and Detailing for Seismic Forces
Calculation of Lateral Seismic Load per NBC Code
A three dimensional modal analysis of the structure will be carried out using a Seismic Coefficient
method. ETABS 2015 software will be used for analysis as well as the design of beam, column slab
and isolated footings. The software has the capability to calculate seismic load as per the NBC
specifications.
Calculation of Seismic Weight of a frame:
Seismic wt. at any floor level(Wi)= (Total Gravity Loads due to Beam, Column, lab, wall etc+25 %of
live Load)
Total Seismic Weight of the Frame, Wt=∑Wi ,
Seismic weight of each story is calculated by ETABS 2015 on the basis of mass source parameter in
which a factor of 1.00 has been assigned to the dead loads and a factor of 0.25 has been assigned
to the live loads on floors except for the roof on which no live load will be considered for seismic
load calculation as per codal provision.
1.7.1Methodology
The design base shear is computed by ETABS 2015 in accordance with the NBC code
Mass source
7. Name
Include
Elements
Include
Added
Mass
Include
Loads
Include
Lateral
Include
Vertical
Lump at
Stories
IsDefault
Load
Pattern
Multiplier
MsSrc1 False False True True False True True Self 1
MsSrc1 False False True True False True True Finishes 1
MsSrc1 False False True True False True True 4"wall 1
MsSrc1 False False True True False True True
9" wall
with
opening
1
MsSrc1 False False True True False True True
Parapet
wall
1
MsSrc1 False False True True False True True Staircase 1
MsSrc1 False False True True False True True Floor live 0.25
MsSrc1 False False True True False True True Partition 1
MsSrc1 False False True True False True True 9" wall 1
MsSrc1 False False True True False True True
weather
shed
1
The seismic weight and base shear generated by ETABS2015 is shown below:
Load Pattern Type Direction Top Story Bottom Story C K
Weight Used
kN
Base Shear
kN
EQx Seismic X slope 2 Base 0.08 1 4574.5784 365.9663
EQy Seismic Y slope 2 Base 0.08 1 4574.5784 365.9663
1.8 Load Cases and Combinations used for analysis
Following Load combinations are to be used as per clause 4.5 of NBC 105:
1. 1.5*DL + 1.5*LL
2. DL+1.3ll ±1.25EQ
3. DL ±1.25EQ
4. 0.9DL ±1.5EQ
25% of LL as reduced live load RLL is to be considered when combined with EQ Load. Similarly,
earthquake load is to be considered in two horizontal directions X and Y and in each direction, the
load will be reversible, i.e. in +X and +Y directions.
1.9 Control of Deflection
In order to control deflection of structural elements, the criteria given in clause 23.2 of IS 456:2000
is proposed to be used.
To control overall deformation due to earthquake load, the criteria given in clause 7.11 of IS
1893:2002 is applied.
1.10 Control of Cracking
In order to avoid excessive cracking in the flexural members, maximum diameter and spacing of the
reinforcement is restricted as per the detailing rules indicated in clause 26.0 IS: 456-2000.
1.11 Masonry Walls
Masonry walls have been treated as non-structural infill panels. Therefore, the structural safety of
these walls is ensured by treating them as one way / two way slab panels spanning between
adjoining beams and columns. These walls are designed as un-reinforced masonry as per` IS: 1905-
1987 and IS: 4326-1993.
8. While external walls are provided with shear connector reinforcement on the underside of upper
beams and sides of columns the internal partition walls are connected to roof slabs using dry
packing mortar between top of walls and soffit of slab / beam.
1.12 Site conditions:
• Soil Type : Gravel mixed soil
• Allowable Bearing Capacity : 150 KN/sq m
1.13 Design procedure:
• Adopt initial size of members on the basis of Architectural and serviceability
requirement.
• Analysis the structure in design load.
• Conform the section on deflection criteria.
• Design for stresses
• Conform with construction criteria
ANALYSIS PART
2.1 Design Software
A three dimensional analysis of the structure was carried out using a Seismic Coefficient method.
ETABS2015 software was used for analysis of the model as well as the design of beam, column, slab
element and foundation.
2.2 Output data results
Some of the important sample output data are presented below:
2.2.1 BASE REACTIONS –(UNIT KN METER)
Load Case/Combo
FX
kN
FY
kN
FZ
kN
MX
kN-m
MY
kN-m
MZ
kN-m
X
m
Y
m
Z
m
Dead 0 0 2442.4899 15763.0913 -16682.6092 0 0 0 0
Finishes 0 0 564.3398 3642.0529 -3920.9003 0 0 0 0
4"wall 0 0 47.9532 473.1546 -308.2914 0 0 0 0
9" wall with opening 0 0 450.2609 2860.82 -3099.1103 0 0 0 0
Parapet wall 0 0 159.8501 1067.3417 -1077.7011 0 0 0 0
Staircase dead 0 0 304.8 1950.72 -1092.9518 0 0 0 0
roof live 0 0 156.7739 994.7425 -1155.581 0 0 0 0
Floor live 0 0 566.8187 3636.2371 -4016.4055 0 0 0 0
EQx -365.9663 0 0 0 -2863.0317 2316.5772 0 0 0
EQy 0 -365.9663 0 2863.0317 0 -2390.2694 0 0 0
Partition 0 0 42.064 273.9169 -286.2312 0 0 0 0
9" wall 0 0 304.0135 1383.2796 -1896.8453 0 0 0 0
weather shed 0 0 186.5613 1179.7262 -1312.4524 0 0 0 0
11. Elevation along grid 2-2
DESIGN OF SLABS
Slab Size 4.95mX3.88m
lx = 4.95 m ly/lx = 0.78
ly = 3.88 m
fck = 20
fy 415
Overall depth of slab
= 0.125 m
Depth of slab = 0.1 m
DL = 2.345 KN/m2
LL = 2 KN/m2
TOTAL = 4.345 KN/m2
Factored load = 6.5175 KN/m2
12. at
edge at mid
alpha x = 0.055 0.042
alpha y = 0.047 0.035
Mx = 8.783 6.707 KN-m
My = 7.506 5.589 KN-m
d = 56 49 mm
52 45 mm
DEPTH OF SLAB IS OK
Shorter Span
Negative moment (Support) = 8.783
Positive Moment (Mid Span) = 6.707
Longer
Span
Negative moment (Support) = 7.506
Positive Moment (Mid Span) = 5.589
Reinforcements
Shorter Span
Support = 8 dia @ 150mm c/c
Mid Span = 8 dia @ 150mm c/c
Longer
Span
Support = 8 dia @ 150mm c/c
Mid Span = 8 dia @ 150mm c/c
Ast = 213 161 mm2
181 133 mm2
Ast, min = 150 mm2
Isolated Footing
1 Footing Size Design
Load Pu 574 KN
Design Load P 421 KN
Moment in x dir Mux 0 KN-m
Moment in y dir Muy 0 KN-m
Column size cx 300 mm
cy 300 mm
SBC q 150 KN/sqm
13. Footing Size required A req 2.81 sqmm
Footing Size Provided
L 1.70 meters
B 1.70 meters
Area Provided A prvd 2.89 meters
Zx 0.82
Zx 0.82
Net upward pressure Nup 146 KNm2
Footing Size OK
2 Slab Design
lx 0.700
ly 0.700
Bending Moment in x dir Mx 54 KN-m
Bending Moment in y dir My 54 KN-m
Concrete fck 20 MPa
Steel fy 415 MPa
Minimum Depth
Required dmin 139
Depth Provided D 400 mm
Clear Cover c 50 mm
Effective Cover d' 56 mm
Effective Depth d' 344 mm
Area of Steel
Spacing c/c in mm
12# 16# 20#
443 sqmm
255 c/c 454 c/c
709
c/c
443 sqmm
255 c/c 454 c/c
709
c/c
Ast across x direction
12 mm
dia
@ 150 mm
c/c
754 sqmm
Ast across y direction
12 mm
dia
@ 150 mm
c/c
754 sqmm
3 One Way Shear along x direction
Vu1 132 KN
ζv 0.226 MPa
ζc 0.269 MPa
14. Vc1 157 KN
One Way Shear Check
OK
4 One Way Shear along y direction
Vu1 132 KN
ζv 0.226 MPa
ζc 0.269 MPa
Vc1 157 KN
One Way Shear Check
OK
5 Two Way Shear
Vu2 541 KN
ζv 0.610 MPa
ks*ζc 1.118 MPa
Vc1 991 KN
Two Way Shear Check
OK
L= 1.70 meters
300
B= 1.70 meters
300
15. 400mm
150 mm
12 mm
dia
@ 150 mm
c/c
12 mm
dia
@ 150 mm
c/c
DESIGN OF COMBINE FOOTING
GRID
DESIGN CALCULATION:
LOAD ON COLUMN C1 W1 = 247.018 KN FCK 20 MPA
LOAD ON COLUMN C2 W2 = 95.366 KN
SELF WT. OF FOOTING 34.2384 KN
TOTAL DESIGN LOAD ON FOOTING(P)= 376.6224 KN
S.B.C OF SOIL = 150 KN/M2
REQ.AREA OF FOOTING = P/S.B.C 2.510816 M2
FOOTING SIZE PROV. L = 2 M B = 1.5 M
AREA OF FOOTING PROVIDED = 3 M2
AREA PROV > AREA REQ.
CENTER TO CENTER DIST. BET.COLUMN(b) = 1.676 M
GEOMETRIC CENTER ,G.C =b/2 0.838 M
(X)DIST. OF C.G OF COLM.FROM CENTER OF FOOTING(X)=W2Xb/(W1+W2)=
0.466825 M
PROJ.a1 FROM CENTER OF COLUMN (C2)=
a1 =(L/2-X) = 0.533175 M
PROJ.a2 FROM CENTER OF COLUMN (C1)=
a2=(L-a1-b) = -0.20917 M
NET UPWARD PRESSURE(QNET)=(W1+W2)/(A PROV)=
114.128 KN/M2
MINI.ECCEN.Emin =.02M 0.02 M
MOMENT DUE TO Emini = 6.84768 KN-M
AVAILABLE ECCEN, =(b/2-x)= 0.37117 M
MOMENT DUE TO AVAILABLE ECCE.= 139.79281 KN-M
CONSIDERING FULL WIDTH OF FOOTING
BM CALCULATION:
QNET = 114.128 KN/M2
MAX PRESSURE =QNET+6XM/BXLXL 120.97568 KN/M
MINI PRESSURE = QNET-6XM/BXLXL 107.28032 KN/M
STRIP PRESSURE(q)=QNETXB = 171.192 KN/M
SHEAR FORCE V1=qxa1= 91.275292 KN
V2 =W1-V1 155.74271 KN