form house design
TRANSCRIPT
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DDEESSIIGGNNOOFFFFAARRMMHHOOUUSSEEIINN
SSEEIISSMMIICCRREEGGIIOONN
SSEESSSSIIOONN22000033((FF))--22000077
Project Advisor:
ENGR. MUHAMMAD IRFAN-UL-HASSAN
( ASSISTANT PROFESSOR )
Submitted By:
SAFEER ABBAS 2003(F)-CIVIL-988MOHAMMAD AFZAL 2003(F)-CIVIL-982ADNAN KHALID 2003(F)-CIVIL-976MOHAMMAD AHSAN 2003(F)-CIVIL-987
Department Of Civil Engineering
University of Engineering & Technology
Lahore.
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DESIGN OF FARMHOUSE
IN
SEISMIC REGION
This project is submitted to Department of Civil Engineering,
University of Engineering and Technology, Lahore-Pakistan, for the partial
fulfillment of the requirement for the degree of
Bachelors of Science
InCIVIL ENGINEERING
Approved on: _______________
Internal examiner: Sign: ____________________________
(Project advisor) Name: Engr. Muhammad Irfan-ul-Hassan
External examiner: Sign: ____________________________
Name: ____________________________
Department of Civil EngineeringUniversity of Engineering and Technology
Lahore-Pakistan
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TTAABBLLEEOOFFCCOONNTTEENNTTSS
ARCHITECTURAL PLANS
CHAPTER 1: INTRODUCTION 1
1.1 Earthquake 1
1.2 Old concepts about an earthquake 2
1.3 Causes of Earthquake 2
1.4 Types of Earthquakes 3
1.5 Earthquake Measuring Instruments 3
1.6 How does Earthquake affect Building 4
1.7 Complexity of Earthquake Ground motion 6
1.8 Effects of Earthquakes 6
1.9 Earthquakes in Pakistan 9
1.10 Scope of Seismic design of structure 11
1.11 Objectives of Project 11
1.12 Introduction of Project 12
CHAPTER 2: LITERATURE REVIEW 13
2.1 Codes 13
2.1.1 ACI CODE
2.1.2 UBC 97
2.2 Masonry Design 24
2.3 Related Terms 27
2.3.1 Beam
2.3.3 Column
2.3.4 Slab
2.3.5 Wall & Footing
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2.4 Fundamental Assumptions for Reinforced Concrete 35
Behavior
2.5 Design Basis 35
2.6 Trend of making the earthquake resistant structures 36
2.6.1 Present Practices in Pakistan
CHAPTER 3: SEISMIC DESIGN OF STRUCTURE 38
3.1 Purpose 38
3.2 Minimum Seismic Design 38
3.3 Seismic and Wind Design 393.4 Some Related Terms 39
3.5 Construction Of Buildings In Seismic Region 43
3.5.1 Dead loads
3..5.2 Live loads
3.5.3 Dynamic / viberations loads
3.5.4 Wind loads
3.5.5 Seismic loads3.5.6 Thermal loads
3.5.7 Shrinkage and creep
3.5.8 Snow loads
3.6 Structural systems 50
3.7 Expansion and separation joints 51
3.8 Foundations and substructures 51
3.9 Method of analysis 523.10 For single to two storey houses units 52
3.10.1 Materials
3.10.2 Structural forms and building cconfigurations
3.10.3 Horizontal reinforcement in walls
3.10.4 Plinth Band
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3.10.5 Lintel Band
3.10.6 Roof Band
3.10.7 Vertical reinforcement in walls
3.10.8 Vertical joints between orthogonal walls
3.10.9 Dowels at corner and junctions
3.11 Guideline for multistory frame structure 57
3.11.1 Material types for wall
3.11.2 Foundations
3.11.3 Masonary shear walls
3.11.4 Reinforced concrete walls
3.11.5 Minimum beam , column and slab sizes
CHAPTER 4: DESIGN METHODOLOGY 59
4.1 Two-Way Slabs.
4.1.2 Design by the coefficient method
4.2 For One way slab 60
4.2.1 Design procedure
4.3 Beams 62
4.3.1 Design of structural beams
4.3.1.1 Design procedure for simply
Supported beams
4.3.1.2 Design procedure for doubly
reinforced beams
4.3.1.3 Design procedure for continuous
Beam
4.4 Design of lintels 65
4.4.1 Wall load on lintel
4.5 Columns 66
4.5.1 Design procedure for the
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Structural columns
4.6 Wall design and foundations 67
4.6.1 Design of masonary foundation
4.6.2 Thickness of wall
4.6.3 Design procedure for isolated footing
4.7 Design of stairs 69
4.8 Software used in design of
farm house as frame structure 69
4.8.1 Overview of ETABS program
4.8.2 Procedure for modeling in ETABS
STRUCTURAL PLANS
CHAPTER 5: DESIGN OF FARMHOUSE 76
A ) Manual Calculations
5.1 Walls And Foundations 77
5.1.1 Exterior wall ( W1 )
5.1.2 Exterior wall ( W1 )
5.1.3 Interior wall ( W2 )
5.1.4 Interior wall ( W2 )
5.1.5 Exterior wall ( W1 )
5.1.6 Conclusions
5.2 Design of column ( C3 ) footing 84
5.3 Design of column ( C2 ) footing 90
5.4 Design of slabs 96
5.4.1 Design of ground floor slab system
5.4.2 Design of first floor slab system
5.5 Design of beams 110
5.5.1 Non structural beams
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5.5.2 Structural beams
5.6 Design of lintels 115
5.7 Design of columns 118
5.8 Design of stairs 124
B ) Computer aided asnalysis and results 127
Drawings
CONCLUSIONS & RECOMMENDATIONS 156
REFERENCES
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1
IINNTTRROODDUUCCTTIIOONN
No natural event is more frightening than an earthquake
because earthquake strikes (damages) suddenly without giving any warning. The frame
and huge foundation of the earth shake like a coward. The destructive movements are all
over in less than a minute, leaving behind fallen dreams and broken structures.
Earthquake , like other natural disasters, have affected hundreds of thousands of persons
directly over the ages. Earthquake is a major problem for mankind, killing thousands
each year. Earthquake are causing death and destruction in a wide variety of ways, from
building collapse to conflagrations , tsunamis , landslides. In Pakistan earthquakes are not
so common compared to other part of the world but some areas of Pakistan (North and
South Himalayas) lies in the area of high seismic zone. Recently 8th
October 2005
earthquake shakes the most part of Azad Kashmir and NWFP and causes huge
destruction and loss of life.
C H A P T E R
1
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CHAPTER 1 Introduction
2
1 . 1 EARTHQUAKE
An earthquake is a disturbance or vibration of earth by different types of natural and
human induced phenomenon e.g. meteoric impact, volcanic activity, under ground
nuclear explosion, rock stress changes due to large reservoirs, and movements of tectonic
plates. During an earthquake the earth's surface starts vibrating, and rumbling and roaring
noise come from underneath and the buildings start cracking and collapsing, and the
people get frightening.
1 . 2 OLD CONCEPTS ABOUT AN EARTHQUAKE
Mythological explanations for earthquakes have included the ox who carries the earth on
one shoulder [or in some versions, one horn] and causes earthquakes when shifting the
earth to the other shoulder or horn. According to some accounts, Pythagoras suggested
that earthquakes resulted from the multitudes of dead people fighting under the earth.
1 . 3 CAUSES OF EARTHQUAKE
The sudden slip that is an earthquake results from a gradual build-up of stress inside the
earth. Basically, the rocks that make up the outer layers of the Earth, if subjected to
sufficient force, can be brought to a "breaking point". It is even easier for them to snap if
certain places are already weakened, much the way a sheet of paper will tear more readily
along a sharp crease. When the stress in a particular location is great enough to overcome
the forces holding together the rocks below us, something, effectively, "breaks" or "gives
way", and an earthquake begins. The forces needed to cause this stress and move such
large masses of rock are immense.
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Tectonics deals with structural ruptures at the plate boundaries. These plates drift very
slowly with relation to each other as they "float" on the more fluid material (the mantle)
beneath them. At their edges, they may be colliding, separating, or moving laterally past
each other. The nature of these plate to plate boundaries has a tremendous effect on the
geology, volcanic and seismic activity along the edges of each plate.Earthquakes are
therefore the result of tectonic movements. The crust of the earth consists of several very
thick plates, and at the boundaries of these plates as well as within each plate
geological discontinuities, known as faults, usually occur. The sudden relative movement
of plates at a fault engenders vertical and horizontal vibrations of the ground over a large
area, usually causing damage to structures and also loss of life.
Therefore earthquakes are the result of tectonic movements, Meteoric impact , Volcanic
activity, Under Ground nuclear explosions , Rock stresses change due to large reservoirs
1 . 4 TYPES OF EARTHQUAKES
1 )Tectonic earthquakes
2 )Interplate earthquakes
3 )Deep focus earthquakes
4 )Volcanoes
1 . 5 EARTHQUAKE MEASURING INSTRUMENTS
There are different types of earthquakes measuring instruments e.g. accelerograph,
seismograph but the principle of working of these are almost same.These instruments are
used to measure ground shaking and structural vibration during an earthquake. The basic
element of vibration measuring instrument is a transducer.Three separate transducers are
http://www.answers.com/topic/interplate-earthquakehttp://www.answers.com/topic/deep-focus-earthquakehttp://www.answers.com/topic/deep-focus-earthquakehttp://www.answers.com/topic/volcanohttp://www.answers.com/topic/volcanohttp://www.answers.com/topic/deep-focus-earthquakehttp://www.answers.com/topic/interplate-earthquake -
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required to measure the three components of motion i.e. two horizontal and one vertical.
The data can be obtained in the form of three acceleration components.
SEISMOGRAPH
SEISMOGRAM
Figure 1.1 Seismograph Figure 1.2 Seismogram
1 . 6 HOW DO EARTHQUAKES AFFECT BUILDINGS
The dynamic response of the building to earthquake ground motion is the most important
cause of earthquake-induced damage to buildings. Failure of the ground and soil beneath
buildings is also a major cause of damage. Most earthquakes result from rapid movement
along the plane of faults within the earth's crust. This sudden movement of the fault
releases a great deal of energy, which then travels through the earth in the form of
seismic waves.
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Figure 1.3showing the movement of seismic waves
The seismic waves travel for great distances before finally losing their energy.At some
time after their generation, these seismic waves will reach the earth's surface,and set it in
motion, which we not surprisingly refer to as earthquake ground motion. When this
earthquake ground motion occurs beneath a building and when it is strong enough, it sets
the building in motion, starting with the foundation, and transfers the motion throughout
the rest of the building in a very complex way. These motions in turn induce forces which
can produce damage. Ground motion at a building site is vastly more complicated than
the wave form. Compare the surface of the ground in an earthquake to the surface of a
small body of water. You can set the surface of a pond in motion--by throwing stones
into it. The firstfew stones create a series of circular waves, which soon begin to collide
with one another. After a while, interferencepatterns begin to predominate and the
originalwaves disappear. In an earthquake, the ground vibrates in a similar manner, as
waves of different frequencies and amplitude interact with one another
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1 . 7 COMPLEXITY OF EARTHQUAKE GROUND MOTION
The complexity of earthquake ground motion is due to three factors:
1)SOURCE EFFECTS
The seismic waves generated at the time of earthquake fault movement are not all
uniform.
2)PATH EFFECTS
As seismic waves pass through the earth on their way from the fault to the building
site, they are modified by the soil and rock media through which they pass.
3)LOCAL SITE EFFECTS
Once the seismic waves reach the building site they undergo further modifications,
which are dependent upon the characteristics of the ground and soil beneath the building
1 . 8 EFFECTS OF EARTHQUAKES
There are many effects of earthquakes, these include, but are not limited to,
1 )Broken windows
2 )Collapse of buildings
3 )Fires
4 )Landslides
5 )Destabilizations of the base of some buildings which may lead to collapse in a
future earthquake
6 )Disease
7 )Lack of basic necessities
8 )Human loss of life
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9 )Higher insurance premiums
+
Figure 1.4shows the broken windows Figure 1.5shows that the whole building tilted( Turkey ) on left side after the earthquake.
Figure 1.6shows that the building collapses Figure 1.7earthquake in Ahmedabadduring an earthquake in (26-01-2001)
Ahmedabad (27-01-2001)
Fault rupture tearing apart a building in Glck Naval Base
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Figure 1.8shows that the building get inserted into the ground and tilted due to earthquake. ( Bhug )
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1 . 9 EARTHQUAKES IN PAKISTAN
Major Earthquakes in Pakistan are,
Year Location
1935 Quetta (Balochistan)
1945 Makran coast (Baluchistan)
1974 NE of Malakhand, NWFP
1981 Gilgit Wazarat (Jammu & Kashmir)
1997 Near Harnai (Baluchistan),
2001 Near Bhachau (Gujarat )
2002 Gilgit
2005 Ballakot , Muzzafarabd , Kashmir
Figure 1.9 (Margala tower ) Figure 1.10(Margala tower )
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Figure 1.11 ( Muzzaffarabad)
Figure 1.12 ( Muzzaffarabad ) Figure 1.13 ( Muzzaffarabad)
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1 . 10 SCOPE OF SEISMIC DESIGN OF STRUCTURE
After 8th
October earthquake in Pakistan the importance of earthquake resistant structures
have increased. Now a day the scope of Seismic design of structures is increase because
peoples are more interested to construct earthquake resisting structures for their domestic
and commercial activity. Even if our structure is going to built at a site where there is a
minimum chances of earthquake, we have to consider the earthquake forces and then
design accordingly.
1 . 11 OBJECTIVES OF PROJECT
In this project ( DESIGN OF FARM HOUSE IN SEISMIC REGION ) the main objective is to
understand the whole design process of design practice , to under stand the special
provisions that are made to make the structure earth quake resistant according to the
seismic codes ( UBC 97 ).
In common study practice usually design of individual structural components is carried
out. The main purpose behind the project is to design the whole building by applying the
seismic provisions when only architectural drawings are given, while the engineer has to
determine the all the input data himself as many design parameters are required at
different design stages.
To understand the masonry construction of the houses in the seismic region is also the
one of the objective in this project. The objective is to get the knowledge of the different
techniques that are used in the masonry construction of the houses in the seismic regions.
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The aim is to understand, what separate things (materials) that are used in the
construction of masonry wall in the seismic region.
The objective of this project is also to understand the Computer Aided analysis and
Design of the structures. The aim is to understand how seismic loads are applied on the
structures in the computer software.
1 . 12 INTRODUCTION TO THE PROJECT
In this project (design of farm house in seismic region) we have design the walls,
foundations, slab systems, beams, lintels and columns of the farm house. Some special
measures are adopted to make this masonry building as earthquake resistant.
In our project, first we manually design the structural components of the load bearing
farm house with some extra seismic provisions and then we convert our farm house in a
frame structure and then whole design is carried out through ETABS.
In chapter 2 of this project, we discuss the codes & related articles from the different
books. Seismic provisions and their implementation for the structures have been
discussed in 3rd
chapter. Design methodologies are in chapter 4 and manual calculations
& computer aided results are done in chapter 5.
Different self made excel sheets are prepared for the design of different structural
components (beams, slabs, lintels).
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LLIITTEERRAATTUURREERREEVVIIEEWW
C H A P T E R
2The code covers the design of structural concrete used in buildings and where
applicable in structures. ACI 318-05 was adopted as a standard of the American
Concrete Institute October 27, 2004 to supersede ACI 318-02 in accordance with the
Institutes standardization procedure.UBC-97 (Uniform building Code) is adopted for
the seismic design of structures.
22..11 CCOODDEESS
22..11..11 AACCII 331188--0055
ACI 7.6.1
The minimum clear spacing between parallel bars in a layer shall be dbbut not less than
25mm.
ACI 7.6.2
Where parallel reinforcement is placed in two or more layers, bars in upper layers shall be
placed directly above bars in the bottom layers with clear distance between layers not less
than 25mm.
ACI 7.6.3
In spirally reinforced or tied reinforced compression members, clear distance between
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longitudinal bars all not be less than 1.5dbor 40mm.
ACI 7.6.5
In walls and slabs other than concrete joist Construction, primary flexural reinforcement
shall be spaced not farther than three times the wall thickness, nor 450mm.
ACI 7.10.5.2
Vertical Spacing of ties shall not exceed 16 longitudinal bar diameters, 48 tie diameter or
lest dimension of compression member.
ACI 7.12.1
Reinforcement for shrinkage and temperature stresses normal to flexural reinforcement shall
be provided in structural slabs where the flexural reinforcement extends in one direction
only.
ACI 7.12.2.1
Area of shrinkage and temperature reinforcement shall provide at least the following ratios
of reinforcement area to the gross area, but not less than 0.0014,
a) Slabs where grade 40 or 50 deformed bars are used 0.0020b) Slabs where grade 60 deformed bars are used 0.0018
ACI 7.12.2.2
Shrinkage and temperature reinforcement shall be placed not farther apart than five times
the slab thickness, nor farther apart than 450mm.
ACI 9.5.2.1
Minimum thickness in Table 9.5(a) shall apply for one-way construction not supporting or
attached to partitions or other construction likely to be damaged by large deflections, unless
computation of deflection can be used without adverse effects.
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ACI 9.5 (a) MINIMUM THICKNESS OF NON-PRESTRESSED BEAMS ORONE-WAY SLABS
Minimum thickness, h,
Simply SupportedOne End
Continuous
Both Ends
ContinuousCantilever
Members
Construction
Members not supporting or attached to partitions or other likely to be damaged by
large deflections.
Solid One-Way
Slabs1/20 1/24 1/28 1/10
Beams Or RibbedOne-Way Slabs
1/16 1/18.5 1/21 1/8
Table 2.1
ACI 9.3.2
Strength reduction factor shall as follows,
Tension controlled section 0.9Compression controlled section 0.65
ACI 9.3.2.3
Shear and torsion 0.75
ACI 10.2.2
Strain in the reinforcement and concrete shall be assumed directly proportional to the
distance from the neutral axis.
ACI 10.2.3
Maximum usable strain at the extreme concrete compression fiber shall be assumed equal to
0.003.
ACI 10.2.5
Tensile strength of concrete shall be neglected in axial and flexural calculations of
reinforced concrete.
ACI 10.3.6
Design axial load strength Pnof the compression member shall not be taken greater than
the following:
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ACI 10.3.6.1
For non pre-stressed members with spiral reinforcement conforming to 7.10.4 or composite
members conforming to 10.14
Pn= 0.85[0.85fc'(Ag Ast) + fyAst]
ACI 10.3.6.2
For non pre-stressed members with tie reinforcement conforming to 7.10.5
Pn= 0.85[0.85fc'(Ag Ast) + fyAst]
ACI 10.5.4
For structural slabs of uniform thickness, minimum area and maximum spacing of
reinforcement in the direction of the span shall be as required for shrinkage and temperature
according to 7.12.
ACI 10.9.1
Area of longitudinal reinforcement for non composite compression members shall
not be less than 0.01 or more than 0.08 time's gross area Ag of the section .
ACI 10.9.2
Minimum number of longitudinal bars in compression members shall be 4 for bars
within rectangular ties or circular ties, 3 for bars within triangular ties.
ACI 11.5.5.1
Spacing of shear reinforcement placed perpendicular to the axis of the member shall
not exceed d/2 in non pre-stressed member.
CI 11.5.5.2
Inclined stirrups and bent longitudinal reinforcement shall be so spaced that every
45o line, extending toward the reaction from mid depth of member d/2 to longitudinal
tension reinforcement, shall be crossed by at least one line of shear reinforcement.
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ACI 11.5.7.1
When factored shear force Vuexceeds shear strength Vcshear reinforcement shall
be provided to satisfy eqs 11-1 & 11-2.
ACI 15.2.2
Base area of footing shall be determined from un-factored forces and moments
transmitted by footing to soil and permissible soil pressure selected through principles of
soil mechanics.
ACI 15.4.1
External moments on any section of a footing shall be determined by passing a
vertical plane through the footing, and computing the moment of the forces acting over
entire area of the footing on one side in that vertical plane.
ACI 15.4.2
Maximum factored moment for an isolated footing shall be computed as prescribed
in 15.4.1 at critical sections located as follows:
a) At the face of column, pedestal, or wall, for footings supporting a concrete column,
pedestal or wall.
b) Halfway between middle and edge of wall, for footings supporting a masonry wall.
ACI 15.4.3
In one-way footings, and two-way square footings, reinforcement shall be distributed
uniformly across entire width of footing.
ACI 15.4.4
In two-way rectangular footings, reinforcement shall be distributed as follows:
ACI 15.4.4.1
Reinforcement in long direction shall be distributed uniformly across entire width of
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the footing.
ACI 15.4.4.2
For reinforcement in short direction in a rectangular footing a portion of the total
reinforcement given by Eq.15-1 shall be distributed uniformly over a bandwidth equal to the
length of short side of the footing. Remainder of reinforcement required in short direction
shall be distributed uniformly outside centre bandwidth of the footing.
REINFORCEMENT IN BAND WIDTH = 2
TOTAL REINFORCEMENT IN SHORT DIRECTION + 1
ACI 15.5.1
Shear strength of footings shall be in accordance with 11.12.
ACI 15.8.1
Forces and moments at base of the columns, wall, or pedestal shall be transferred to
supporting pedestal or footing by bearing on concrete and by reinforcement dowels and
mechanical connectors.
ACI 15.8.2
In cast in-situ construction, reinforcement required to satisfy 15.8.1. shall be
provided either by extending longitudinal bars into supporting pedestal, footing or by
dowels.
ACI 15.8.2.1
For cast in place columns area of reinforcement across interface shall be not less
than 0.005 times gross area of supported member.
ACI 15.7
Depth of footing above bottom reinforcement shall not be less than 150mm, for
footings on soil .
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ACI 15.6.3
Critical sections for development of reinforcement shall be assumed at the same
location as defined in 15.4.2 for maximum factored moment.
ACI 21.2.1.4
In regions of high seismic risks or for structures assigned to high seismic
performance special moment frames special structural walls shall be used resists forces
induced by earthquake motion.
ACI 21.2.3
Strength reduction factor shall be as given in 9.3.4
ACI 21.2.4.1
Specified compressive strength of concrete shall not be less than 3000 Psi
ACI 21.3.1.1
Factored axial compressive force on the member, Pu shall not exceed Agfc' / 10
ACI 21.3.1.2
Clear spans for flexural members, ln shall not be less than four times its effective depth.
ACI 21.3.1.3
Width of flexural member, bw , shall not be less than the smaller of 0.3h & 250mm.
ACI 21.3.1.4
Width of flexural member, bw , shall not exceed the width of the supporting member plus
distance on each side of supporting member not exceeding three fourth of the depth the
flexural member.
ACI 21.3.2.1
At any section of flexural member for top as well as for bottom reinforcement, the amount
of reinforcement shall not be less than eq 10.3 and the reinforcement ratio shall not exceed
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0.025.Atleast 2 bars shall be provided continuously both top and bottom.
ACI 21.3.2.2
Positive moment strength at joint face shall not be less than one half of the negative moment
strength provided at back face of joint.
ACI 21.4.1.1
The shortest cross sectional dimension measured on a straight line passing through the
geometric centroid shall not be less than 300mm
ACI 21.4.3.1
Area of longitudinal reinforcement shall not be less than 0.01Ag or more than 0.06Ag.
ACI MOMENTS COEFFICIENT
o Positive moment End spans
Discontinuous end unrestrained............................... wuln2/11
Discontinuous end integral with support ...................... wuln2/14
Interior spans .................................................................wuln2/16
o Negative moments at exterior face of first interior support
Two spans ......................................... wuln2
/9
More than two spans...................... wuln2/10
o Negative moment at other faces of interior supports............. wuln2/11
o Negative moment at face of all supports for Slabs with spans not exceeding 10 ft;
and beams where ratio of sum of column stiffness to beam stiffness exceeds eight
at each end of the span.. wuln2/12
o of exterior support for members built integrally with supports
Where support is spandrel beam ... wuln2
/24
Where support is a column .............. .wuln2/16
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ACI 3 . 2 CEMENT
ACI 3 . 2.1 Cement shall conform to one of the following specifications:
(a)Specification for Portland Cement (ASTM C 150)
(b)Specification for Blended Hydraulic Cements (ASTM C 595), excluding Types S
and SA which are not intended as principal cementing constituents of structural
concrete.
(c)Specification for Expansive Hydraulic Cement (ASTM C 845)
(d)Performance Specification for Hydraulic Cement (ASTM C 1157)
ACI 3 . 3 AGGREGATE
ACI 3 . 3.1 Concrete aggregates shall conform to one of the following specifications:
(a)Specification for Concrete Aggregates (ASTM C 33)
(b)Specification for Lightweight Aggregates for Structural Concrete (ASTM C 330)
ACI 3 . 3.2 Nominal maximum size of coarse aggregate shall be not larger than:(a)1/5 the narrowest dimension between sides of forms, nor
(b)1/3 the depth of slabs, nor
(c)3/4 the minimum clear spacing between individual reinforcing bars or
wires, bundles of bars.
ACI 3 . 4 WATER
ACI 3 . 4.1 Water used in mixing concrete shall be clean and free from injurious
amounts of oils, acids, alkalis, salts, organic materials, or other substances
deleterious to concrete or reinforcement.
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22..11..22 UUBBCC9977
22..11..22..11
BBAASSEESSHHEEAARR
According to UBC 97 1630.2.1
V = CVI x W
RT
W = Total weight of structure.
V = Design base shear at the base of structure.
Cv = Seismic coefficient based on acceleration& dependent on
soil condition & seismicity of the region
I = Seismic Importance Factor
= Its value is 1 , 1.25 , 1.5 for ordinary structure , Special & Essential structure .
R = Structural coefficient depending upon ductility and overstrength of the structure
T = Fundamental Time Period of the Structure.
Ta = Ct (hn ) 3/4
Where
Ta = Approx. time period
Ct = 0.035 for steel structure
= 0 .03 for concrete structure
= 0 .02 for other structures
hn = Total height of structure.
TB= Tme period obtained by analysis
Max. value of V is = 2.5 Ca I x WR
W = It include the dead load plus the partition load &floor finishes& cladding
In case of storage building 25% of the live load can be considered
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In case of snow load 20% of the flat roof snow load can be considered.
If flat snow load > 30 lb/ft^2
P.L = 10lb/ft^2 = F.F = cladding
Vmin = 0. 11Ca I W
Ca = similar to Cv
= Constant Value of Ca Cv can be read from table.
For seismic zone :
V = 0.8 Z Nv I x W
R
Z = seismic coefficient = 0.4 for zone 4
(Balakot, Muzaffarbad, Bagh, Quetta, Chamman, Gilgit, Malakand)
Z = 0.3 for zone 3
( Rawalpindi , Islamabad , Peshawar )
Z = 0.2 for zone 2B
(Lahore Faisalbad, Jhang)
Z = 0.15 for zone 2A
Z = 0. 075 for zone 1
(Multan, D.G Khan, Bahawalpur )
Nv, Na = near source factor for zone 4 & in conjunction with soil type
VERTICAL DISTRIBUTION OF FORCES
According to UBC 97 1630.5
Fx = ( P Ft ) Wxhxwihi
Where
Fx = Story lateral force
V = Total base shear
Ft = Additional force at the top for the participation & higher mode in the large structures.
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Ft = 0.07 T V [0. 25 V IF T > 0.07 sec
Ft = 0 if T [0. 7sec.
Wx = Storey load
Hx = Storey height
Storey Shear is ,
Vx = Ft + Fi
DRIFT RATIO / DRIFT LIMITATION / ALLOWABLE STOREY
LATERAL DEFLECTION
According to UBC 97 1630.9.2
M = 0.7 R s
Where ,
M = Max. Deflection/max.inelastic response/max. inelastic deflection.
s = Horizontal Deflection at mid height under Factored Load
R = A constant
2 . 1.2.2 MASONARY DESIGN
SLENDERNESS RATIO
R = H or l = 18
t t
For load bearing wall = 20
= 18 for non-loading bearing in case of exterior walls.
= 36 for interior wall ( non load bearing wall )
( See UBC table 21- O )
Where R = slenderness Ratio
H = Effective Storey Height
l = Length of wall
t = Thickness of wall
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ALLOWABLE COMRESSIVE STRESS ( UBC-97 2107.3.3)
The allowable compressive stress Fb is given by
Fb = 0.33 f 'm 13.8 Mpa
ALLOWABLE AXIAL COMPRESSIVE STRESS ( UBC-97 2107.3.2)
The allowable axial compressive stress Fa is given by
Fa = 0.25f 'm[1- (R/40)2] , R 29
Fa = 0.25f 'm[20/R]2 , R > 29 , R= slenderness Ratio
COMBINED AXIAL & COMPRESSIVE STRESS ( UBC-97 2107.3.4)
fa / Fa+ fb / Fb1.0
fa , fb = applied stresses
Fa, Fb = allowable strength
ALLOWABLE TENSILE STRENGTH ( UBC-97 2107.3.5)
The allowable tensile strength Ftis given by
Ft = 1 fm1/2
for tension perpendicular to bed joint7
Ft = 1 fm1/2 for tension perpendicular to head joint
15
Wherefm= compressive stress due to dead load only
ALLOWABLE SHEAR STRENGTH ( UBC-97 2107.3.6)
The allowable shear strength Fv is given by
Fv = 1 fm1/2
345 Kpa
1 2
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ALLOWABLE BEARING STRESS ( UBC-97 2107.3.8)
The allowable bearing stressFbris given by
Fbr = 0.26fm when full area is loaded
F'br= 0.38 f'm when 1/3rd or less area is loaded.
TTAABBLLEEUUBBCC1199--II--CCFFOOUUNNDDAATTIIOONNSSFFOORRBBEEAARRIINNGGWWAALLLLSS
WIDTH OF
FOOTING(inches)
THICKNESS OF
FOOTING(inches)
DEPTH BELOW
UNDISTURBED
GROUND
SURFACE(inches)
NUMBER OF
FLOORS
SUPPORTED BY THE
FOUNDATION X 25.4 for mm
12
3
1215
18
67
8
1218
24
TTAABBLLEE22..22
BEAM DETAILS
According to UBC 1921.3.1 , 1921.3.2 , 1921.5.4
COLUMN DETAILS
According to UBC 1921.4 , 1921.4.3 , 1921.4.4.4 , 1921.4.4.6 , 1921.4.4.2.
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2 . 3 RELATED TERMS
2 . 3.1 BEAM
Beam are the structural member that is subjected to a transverse loading and resists
the bending moments.
When a beam is subjected to bending moments, bending strains are produced. These strains
produce stresses in the beam, compression in the top and tension in the bottom. Bending
members must, therefore, be able to resist both tensile and compressive stresses.By
embedding reinforcement in the tension zone, we create a reinforced concrete member. Such
members can resist bending sufficiently.
TYPES OF CROSS SECTIONS W.R.T. FLEXURE AT ULTIMATE LOAD
LEVEL
1. TENSION CONTROLLED SECTION
A section in which the net tensile strain in the extreme tension steel is greater than or
equal to 0.005 when the corresponding concrete strain at the compression face is 0.003.
2. TRANSITION SECTION
The section in which net tensile strain in the extreme tension steel is greater than y
but less than 0.005 when corresponding concrete strain is 0.003.
3. COMPRESSION CONTROLLED SECTION
The section in which net steel strain in the extreme tension steel is lesser than y
when corresponding concrete strain is 0.003.
PRACTICAL CONSIDERATIONS
A ) COVER
Concrete cover is provided to protect steel against fire and corrosion and to improve
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bond strength. It reduces the wear of steel and attack of chemicals especially in
factories.
B ). SELECTION OF STEEL BARS
1 )When different diameters are selected the maximum difference can be a gap of
one size.
2 )Minimum number of bars must be at least two, one in each corner.
3 )Always Place the steel symmetrically.
4 )Preferably steel may be placed in a single layer but it is allowed to use 2 to 3
layers.
5 )Selected sizes should be easily available in market
6 )Small diameter (as far as possible) bars are easy to cut and bend and place.
C ) SPACING BETWEEN STEEL BARS
Minimum spacing must be lesser of the following
1 )Nominal diameter of bars
2 )25mm in beams & 40mm in columns
3)1.33 times the maximum size of aggregate used.
We can also give an additional margin of 5 mm.
- A minimum clear gap of 25 mm is to be provided between different layers of steel
- The spacing between bars must not exceed a maximum value for crack control
CONCRETE
Mixture of Portland cement or any other hydraulic cement, fine aggregate,
coarseaggregate, and water, with or without admixtures.
DEFORMED REINFORCEMENT
Deformed reinforcement is defined as that meeting the deformed reinforcement
specifications of 3.5.3.1, or the specifications of 3.5.3.3, 3.5.3.4, 3.5.3.5, or 3.5.3.6. No
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other reinforcement qualifies. This definition permits accurate statement of anchorage
lengths. Bars or wire not meeting the deformation requirements or welded wire
reinforcement not meeting the spacing requirements are plain reinforcement, for code
purposes, and may be used only for spirals.
CONTRACTION JOINT
Formed, sawed, or tooled groove in a concrete structure to create a weakened plane
and regulate the location of cracking resulting from the dimensional change of
different parts of the structure.
DEVELOPMENT LENGTH
Length of embedded reinforcement, including pretension strand, required to develop
the design strength of reinforcement at a critical section. ( See 9.3.3.)
EFFECTIVE DEPTH OF SECTION
Distance measured from extreme compression fiber to centroid of longitudinal tension
reinforcement.
EMBEDMENT LENGTH
Length of embedded reinforcement provided beyond a critical section.
MODULUS OF ELASTICITY
Ratio of normal stress to corresponding strain for tensile or compressive stresses below
proportional limit of material. ( See 8.5.)
MOMENT FRAME
Frame in which members and joints resist forces through flexure, shear, and axial
force.
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SPIRAL REINFORCEMENT
Continuously wound reinforcement in the form of a cylindrical helix.
STIRRUP
Reinforcement used to resist shear and torsion stresses in a structural member;
typically bars, wires, or welded wire reinforcement either single leg or bent into L, U,
or rectangular shapes and located perpendicular to or at an angle to longitudinal
reinforcement.
STRENGTH DESIGN
Nominal strength multiplied by a strength reduction factor . ( See 9.3.)
STRENGTH, NOMINAL
Strength of a member or cross section calculated in accordance with provisions and
assumptions of the strength design method of this code before application of any
strength reduction factors. ( See 9.3.1.).The basic requirement for strength design may
be expressed as follows:
Design strength Required strength
PnPu, MnMu,, VnVu
STRUCTURAL WALLS
Walls proportioned to resist combinations of shears, moments, and axial forces
induced by earthquake motions.
TIE
Loop of reinforcing bar or wire enclosing longitudinal reinforcement. A continuously
wound bar or wire in the form of a circle, rectangle, or other polygon shape without re-
entrant corners is acceptable.
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YIELD STRENGTH
Specified minimum yield strength or yield point of reinforcement. Yield strength or
yield point shall be determined in tension according to applicable ASTM standards
as modified by 3.5 of ACI code.
2 . 3.3 COLUMN
They are classified as concentrically loaded and eccentrically loaded
columns, depending on their configuration of the structural frame and the loading to which
they are subjected.
2 . 3.4 SLAB
A reinforced slab is a broad, flat plate, usually horizontal, with top and bottom surfaces
parallel or nearly so.
It may be supported by reinforced concrete beams (and is usually cast monolithically with
such beams), by masonry or by reinforced concrete walls, by steel structural members,
directly by columns, or continuously by ground.
ONE-WAY SLAB
The slab which resists the entire/major part of applied load by bending only in one
direction
5.0..
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and
L = c/c distance between supports.
BAR SPACING FOR SLABS
smaxwill be lesser of following.
1.) 3 x h (local practice is 2 x h) , for one way slabs
2.) 450 mm (local practice is 300 mm)
3.) (158300/fy) -2.5Cc
4.) 12600/fy
Where , Cc= Clear Cover
DISTRIBUTION, TEMPERATURE & SHRINKAGE STEEL FOR SLABS
Shrinkage and temperature reinforcement is required at right angle to main reinforcement to
minimize cracking and to tie the structure together to ensure its acting as assumed in design.
For Grade 300 0.2% of b x h= 0.002 As= 0.002bh
For Grade 420 0.18% of b x h = 0.0018 ..As= 0.0018bh
Smax. will be lesser of following
1 - 5 x h (field practice is 2 x h)
2 - 450 mm (field practice is 2 x h)
TWO-WAY SLAB
Slab resting on walls or sufficiently deep and rigid beams on all sides. Other
options are column supported slab e.g. Flat slab, waffle slab.
Two way slabs have two way bending.
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DESIGN METHODS
1 ).ACI co-efficient method
2 ).Direct design method
3 ).Equivalent frame method
4 ).Finite element method
MINIMUM DEPTH OF 2-WAY SLAB FOR DEFLECTION CONTROL
According to ACI-318-1963
hmin= (inner perimeter of slab panel)/180
90 mm
For fy= 300 MPa
180
LL2h
yx
min
+=
For fy= 420 Mpa
165
LL2h
yx
min
+=
According to ACI-318-2005
( )( )9m36
1500f8.0Lh
yn
min+
+=
y
x
L
Lm=
Ln = clear span in short direction
2 . 3.5 WALLS & FOOTINGS
FOUNDATION
Footings are structural members used to support columns and walls and to
transmit and distribute their loads to the soil in such a ay that the load bearing capacity of
the soil is not exceeded. Excessive settlement, differential settlement or rotations are
prevented and adequate safety against overturning or sliding is maintained
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TYPES OF FOOTINGS
Wall Footings
Isolated Footings
Combined Footings
Cantilever or Strap Footings Continuous Footings Raft or Mat Footing Pile Caps
DESIGN OF MASONARY FOUNDATION
Load is distributed at 60 degree in case of bricks & 45 degree in case of plain concrete
( a ) If the width of footing is not sufficient to accommodate the 60 degree load
distribution it will be un safe
( b ) If the width of footing is sufficient to accommodate 60 degree load distribution
which is safe but may be uneconomical
ASSUMPTIONS
1 )Load at the bottom of footing is uniformly distributed with out considering any voids
underneath the foundation.
2 )That voids may be present due to the uneven surface or uneven compaction3 )The effect of intersections is also ignored which are from perpendicular wall
4 )In case of boundary wall (property line wall) the resultant of soil pressure not coincide
with line of action of applied force that may result in over turning moment. In order to
avoid this footing is designed considering increased load by 35%.
5 )Effect of beam is also ignored.
6 )F.O.S for the bearing capacity is taken as 3 & for the backfill is 1.5.
STRENGTH OF BRICKS
Crushing strength of bricks ranges from 4.3 to 19.3 Mpa
Strength of first class brick in Punjab is 10.5 Mpa.
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25% of the strength is reduced in case of saturated condition Also more strength is
shown by machine due to the end plates effect so normally design strength is taken
half of the strength obtained by compression testing of bricks in dry condition.
So design strength =10.5 / 2 = 5.25 Mpa.
Available design strength is 70% in case of (1:3) c/s mortar.
It is 65% in case of (1:4) c/s mortar.
It is 45% in case of (1:6) c/s mortar
It is 30% in case of (mud) mortar.
Table 2.3
Mortar Compressive strength of brick1:3 4 MPa
1:4 3.4 MPa
1:6 2.4 Mpa
MUD 1.6 Mpa
STOREY HEIGHT
Storey height can be defined as the distance between plinth level & first
lateral support (as slab)
EFFECTIVE STOREY HEIGHT (H)
( 1 ) If lateral support + superimposed compressive load then
H = 0.75 x Storey height
( 2 )No lateral support + superimposed compressive load
H = 1.05 x storey height
( 3 ) No lateral support + no superimposed compressive load
H = 2 x Storey height
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22.. 4 FUNDAMENTAL ASSUMPTIONS FOR REINFORCED CONCRETE
BEHAVIOUR
The fundamental propositions on which the mechanics of reinforced concrete is
based are as follows:
The internal forces, such as bending moments, shear forces and normal, shear
stresses at any section of a member are in equilibrium with the effects of the
external loads at that section.
It is assumed that perfect bonding exists between concrete and steel at
the interface so that no slip can occur between the two materials. Hence, as the
one deforms, so must the other.
t is assumed that concrete is not capable of resisting any tension stress whatever.
2 . 5 DESIGN BASIS
The single most important characteristic of any structural member is its actual
strength, which must be large enough to resist, with some margin to spare, all
foreseeable loads that may act on it during the life of the structure, without failure or
other distress. It is logical, therefore, to proportion members, i.e., to select concrete
dimensions and reinforcement, so that member strengths are adequate to resist forces
resulting from certain hypothetical overload stages, significantly above loads
expected actually to occur in service. This design concept is known as STRENGTH
DESIGN.
2 . 6 TREND OF MAKING THE EARTH QUAKE RESISTANT STRUCTURES
2. 6.1 PRESENT PRACTICES IN PAKISTAN
Previously , in Pakistan there were no practices to make the structure earth quake
resistant and there were no consideration of the seismic forces but after the earth
quake of 8th
October 2005 special provisions are made & more consideration are
given to make the structure earth quake resistant. Now a days special provisions are
applied on the structures to make the structure earth quake resistant
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Figure 2.1 :
Columns and Beams are
provided in the masonary
structure to insure the box action
in the building of one or two
storey house and to give the
additional strength and stiffness
Figure 2.1
Figure2.2
Steel bars are provided at every
opening ( Window opening ) in
vertical directions
Figure 2.2
Figure 2.3
Columns are placed at each corner of
a building to insure the box action.
Shear stirrups
Special hook
Figure 2.3
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C H A P T E R
3
SSIIEESSMMIICCDDEESSIIGGNNOOFFSSTTRRUUCCTTUURREE
In Seismic Design of structure , we apply some special provisions on the structures such
that it can resist the earthquake forces. The aim of designing the structures
earthquakeresistant is that , the structure should be undamaged during the moderate
earthquake and it should not collapse during the severe earthquake to safe the life and
property.
3 . 1 PURPOSE.
The purpose of the earthquake provision here in is primarily to safeguard against
major structural failures and loss of life, not to limit damage or maintain function.
3 . 2 MINIMUM SEISMIC DESIGN
Structures and portions thereof shall, as a minimum, be designed and constructed
to resist the effects of seismic ground motions as provided in this division
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3 . 3 SEISMIC AND WIND DESIGN.
When the code-prescribed wind design produces greater effects,the wind design
shall govern, but detailing requirements and limitations prescribed in this section
and referenced sections shall be followed.
3 . 4 SOME RELATED TERMS
BASE
Base is the level at which the earthquake motions are considered to be imparted to
the structure or the level at which the structure as a dynamic vibrator is supported.
BASE SHEAR
It is the total design lateral force or shear at the base of a structure.
BEARING WALL SYSTEM
It Is a structural system without a complete vertical load carrying space frame.
BUILDING FRAME SYSTEM
It is an essentially complete space frame that provides support for gravity loads.
COLLECTOR
It is a member or element provided to transfer lateral forces from a portion of a
structure to vertical elements of the lateral force resisting system.
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CONCENTRICALLY BRACED FRAME
It is a braced frame in which members are subjected primarily to axial forces.
DESIGN BASIS GROUND MOTION
It is that ground motion that has a 10 percent chances of being exceeded in 50
years as determined by a site specific hazard analysis or may be determined
from a hazard map
DESIGN RESPONSE SPECTRUM
It is an elastic response spectrum for 5% equivalent viscous damping used to
represent the dynamic effect of the Design groundmotion for the design of
structure. This response spectrum may be either a site-specific spectrum based
on geologic,seismological and soil characteristics associated with aspecific site
or may be a spectrumconstructed in accordance with the spectral shape.
DIAPHRAGM
It is a horizontal or nearly horizontal system acting to transmit lateral forces to
the vertical resisting system.
ELASTIC RESPONSE PARAMETERS
Elastic response parameters are the forces and deformations determined
from an elastic dynamic analysis using an unreduced ground motion
representation.
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ESSENTIAL FACILITIES
Those structures which are necessary for emergency operations subsequent to
natural disaster.
LATERAL FORCE RESISTING SYSTEM
It is the structural system designed to resist the Design Seismic Forces.
MOMENT RESISTING FRAME
It is the frames in which members and joints are capable of resist forces
primarily by flexure.
MOMENT RESISTING WALL FRAME
It is a masonry wall frame especially detailed to provide ductile behavior.
ORTHOGONAL EFFECTS
These are the earthquake load effects on structural system common to the
lateral force resisting systems along two orthogonal axes.
OVERSTRENGTH FACTOR
It is a characteristic of structures where the actual strength is larger than the
design strength. The degree of over strength is material and system-dependent.
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PEFFECT
It is the secondary effect on shears, axial forces and moments of
framemembers induced by the vertical loads acting on the laterally displaced
building system.
SHEAR WALL
It is wall designed to resist lateral forces parallel to the plane of the wall.
SHEAR WALL FRAME INTERACTIVE SYSTEM
Uses combination of shear walls and frames designed to resist lateral forces in
proportion to their relative rigidities, considering interaction between shear walls
and frames on all levels.
SPACE FRAME
It is a three dimensional structural system, without bearing walls, composed
of members interconnected so as to function as a self-contained unit with or
without the aid of horizontal diaphragms or floor bracing system.
STORY
It is the space between the levels. Story x is the story below level x.
STORY DRIFT
It is the lateral displacement of one level relative to the level above or below.
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STORY DRIFT RATIO
It is the ratio of story drift to story height.
STORY SHEAR
It is the summation of design lateral forces above the story under
consideration.
STRENGTH
It is the capacity of an element or a member to resist factored loads.
STRUCTURE
It is an assemblage of framing members designed to support gravity loads and
resist lateral forces.
3 . 5 CONSTRUCTION OF BUILDINGS IN SEISMIC REGION
All structures and their components shall be analysed for all phases of construction for a
high degree of structural competence, reliability and ease of construction, as per the
various standards & codes
3 . 5.1 DEAD LOADS
Dead loads are the vertical loads due to the weight of all permanent structural and non-
structural components of a building, such as walls, built-in & moveable partitions, floors,
roofs, and finishes including all other permanent construction.
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Dead loads also include the weight of all fixed services equipments, such as
piping, heating & air-conditioning equipments, elevators and the weights of all
other fixed equipments.
The vertical and lateral pressures of liquids are also treated as dead loads.
Dead loads shall be calculated from the unit weights given in UBC or from
the actual known weights of the materials used.
To provide for partitions where their positions are not known on the plans, the
beams &the floor slabs (where these are capable of effective lateral distribution
of the loads) shall be designed to carry, in addition to other loads, a uniformly
distributed load per sqft of not less than one third of the weight per foot of the
finished partition but not less than 20 lb/ft2
(1 KPa), if the floor is to be used for
office purpose
DEAD LOADS
1 ).Roof Finishes including insulation
and water proofing treatment 55 psf. (2.75 KPa)
2 ).Floor Finishes:
i) Terrazzo/ Marble/ Local granite flooring 30 psf. (1.5 KPa)
ii) Ceramic/ Glazed/ Vinyl tiles flooring 30 psf. (1.5 KPa)
iii) Plain cement concrete flooring 20 psf. (1 KPa)
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3 ).Ceiling Finishes:
i) Plaster 5 psf. (0.25 KPa)
ii) False Ceiling including supporting structure 3 psf. (0.15 KPa)
4 ).Piping, Ducts, Cables: 10 psf. (0.5 KPa)
5 ).Masonry Walls as per actual location and weight
6 ).Light Partitions for Office areas 25 psf. (1.25 KPa)
7 ).Wall Finishes:
i) Plaster 5 psf. (0.25 KPa)
ii) Cladding with marble, granite etc. 15 psf. (0.75 KPa)
8 ).Fixed Service Equipments Mechanical/Electrical As per actual loads equipments for
example elevators, pumps, fan according to manufacturer's
coil units compressors etc. information.
9 ).Facades including glazing tiles etc. As per actual weight
3 . 5 .2 LIVE LOADS
Live loads are the loads superimposed by the use and occupancy of the building
not including the wind, seismic and temperature loads or dead loads.
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Live loads include loads due to intended use and occupancy of an area, personnel,
moveable equipments, lateral earth pressures, vehicle and impact loadings.
Floor live loads as per occupancy and intended use requirements. Unit live loads
are the minimum live loads for the design of the listed areas. For any area not
listed, minimum design live loads shall be in accordance with UBC. For elevators
and other moving loads, equipment manufacturer information shall be used for
wheel loads, equipment loads, and weights of moving parts. If not otherwise
specified by the equipment manufacturer, impact and lateral forces shall be in
accordance with UBC.
The floor area live load may be omitted from areas occupied by equipment whose
weight is specifically included in dead load. Live load is not omitted under
equipment where access is provided.
LIVE LOADS
1 ).Monument Deck Levels 125 psf. (6.25 KPa)
2 ).Libraries
i) Reading 60 psf. (3 KPa)
ii) Book storage area 150 psf. (7.5 KPa)
3 ).Mosques, Stairs 100 psf. (5 KPa)
4 ).Museum 80 psf. (4 KPa)
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5 ).Offices
i) Filling and storage space 100 psf. (5 KPa)
ii) Office for general use 50 psf. (2.5 KPa)
iii) Office with computing data 75 psf. (3.75 KPa)
processing and similar equipments.
6 ).
i) Corridors first floor 100 psf. (5 KPa)
ii) Corridors above first floor 80 psf. (4 KPa)
7 ).Roof
i) Accessible 40 psf. (2 KPa)
ii) Inaccessible 20 psf. (1 KPa)
3 . 5.3 DYNAMIC / VIBRATIONS LOADS
Dynamic effects caused by vibrating loads of equipment and
machinery such as pumps, fans, screens, and compressors shall be determined by
established analytical methods or design data from suppliers. It is intended to minimize
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the vibration effects as far as possible by the provision of shock absorbing materials in
accordance with supplier's Recommendations.
3 . 5.4 WIND LOAD
All loads due to the effect of wind pressure or suction shall be considered as wind
loads. The wind loads on the structure shall be calculated in accordance with
ANSI/ASCE 7 using the following formula:
qz = 0.00256 kz (IV)2
Where
V = Basic wind speed = 100 miles/hour
Kz = Velocity pressure Exposure coefficient I = Importance factor
qz = Velocity Pressure at height Z in pounds per square foot.
qz = 0.613 kz (IV)2
Where
V = Basic wind speed = 45 meter/sec
Kz = Velocity pressure Exposure coefficient I = Importance factor
qz = Velocity Pressure at height Z in N/m2
.
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3 . 5.5 SEISMIC LOADS
Earthquake load shall be computed using the ground motion values given in
Seismic Zoning Maps of the earthquake affected areas issued separately by NESPAK.
The seismic zoning maps show Peak Ground Acceleration (PGA) values for 10%
Probability of Exceedance in 50 years (500 years return period) and PGA values for 2%
Probability of Exceedance in 50 years (2500 years return period).
The PGA values shown on these maps are for firm-rock (shear wave velocity of 760
m/sec) site condition. For soil sites amplification of ground motion is introduced
therefore appropriate amplification factors should be used keeping in view the
geotechnical properties of the subsoil. Taking average shear wave velocity of 400m/sec
of the sub-soil in the earthquake affected areas, the average value of amplification factor
of 1.3 should be used.
3 . 5.6 THERMAL LOADS
The temperature effect will be investigated against a maximum differential
temperature of 20 degree centigrade for the frame structure.
In this project ( Design of farm house in seismic region ) we do not consider this load.
3 . 5.7 SHRINKAGE & CREEP
Shrinkage of reinforced concrete shall be considered as a
shortening of 0.04 inch per feet (3.33 mm per meter). This can be reduced to 0.02 inch
per feet (1.67 mm per meter), if effects of creep are included.
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3 . 5.8 SNOW LOADS
The roofs shall be designed for snow loads or live loads whichever is more
severe. Actual load due to snow will depend upon the shape of the roof and its capacity to
retain the snow; and each case shall be treated on its own merits. In the absence of any
specific information, the loading due to the collection of snow may be assumed to be 1.3
lbs/sq.ft per in (2.441 Pa per mm) depth of snow.( according toNESPAK)
3 . 6 STRUCTURAL SYSTEM
Structural elements e.g. slab, beams, columns, walls and footings are
combined in various ways to create structural systems for buildings. For the selection of a
suitable framing system for a building, the determining factors are:
a )Appearance, functional & aesthetic requirements.
b )Limitations on the size of structural members as imposed by architectural design
and practical constraints on the basis of structural considerations.
c )Clear spans and height required.
d )Loads, including special loads.
e )Availability of materials, skilled labor and construction equipments.
f ) Integration of structure with respect to architectural details, mechanical
equipment, occupancy requirements etc.
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g )Economy, not merely in structural system but also the overall economy in the
finished structure.
Except for the very simple and ordinary structure, study of several alternative systems,
materials and layouts shall be made, before the final scheme is set. From many
alternatives, the criteria for the selection of the best structural system for a building
would be its compliance with the functional and aesthetic requirements in an efficient and
in technically sound manner.
3 . 7 EXPANSION AND SEPARATION JOINTS
Arrangements of these joints shall be made on the following principles: Joints shall
be provided only to avoid extremely irregular plan shapes & to avoid excessively long
interconnected structures. In general, maximum interconnected length shall be limited to
about 150 feet (46 meter). This is acceptable only if the structure is temporarily separated
at about 65 feet (20 meter) long intervals or less by "shrinkage control pour strips" which
are left open for at least 30 days after placement of concrete on each side.
Width of joint will be at least 1 inch (25 mm).
Double columns shall be provided at isolation joints.
3 . 8 FOUNDATIONS AND SUBSTRUCTURE
The bearing capacity of the soils and other factors pertaining to foundation design
shall be evaluated as per recommendations laid down in the soil investigation report. In
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case no soil investigations are carried out, an allowable bearing capacity of 0.75 t/ft2
(8.07
t/m2
) may be adopted for small residential units.( Nespak )
The foundation and the substructure requirement depend on the soil type and the seismic
zone.
3 . 9 METHOD OF ANALYSIS
The analysis shall be carried out using computer aided methods of
analysis and design as listed below using well reputed compute software e.g..
a) SAP-2000 - Structural Analysis Programme (Static & Dynamic Finite element
Analysis of Structure).
b)STAAD-Pro - Structural Analysis and Design Program
c )Etabs Extended three Dimensional Analysis of Building Systems
3 . 10 FOR SINGLE TO TWO STOREY HOUSING UNITS
3 . 10.1 MATERIALS (for construction of houses in earthquake prone areas)
MASONRY UNITS:
- Concrete block work
- Cut-stone masonry
- Burnt clay brick
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Avoid using random rubble masonry
The bricks shall be of standard shape, burnt red, hand formed or machine made and shall
have a minimum crushing strength of 1500 psi (10 N/mm
2
). The concrete block shall be
solid blocks of 12 x 8 x 6 (300mm x 200mm x 150mm) made with 1:2:4 mix
MORTAR:
Cement-sand mixes of 1:6 and 1:4 shall be adopted for one-brick and half- brick
thick walls, respectively. The addition of small quantities of freshly hydrated lime
to the mortar in a lime-cement ratio of 1/4:1 to 1/2:1 will increase its plasticity
greatly without reducing its strength. Where steel reinforcing bars are provided,
the bars shall be embedded in a cement-sand mortar not leaner than 1:4, or in a cement
concrete mix of 1:2:4
PLASTER:
All plasters shall have a cement-sand mix not leaner than 1:6 on outside or inside
faces. It shall have a minimum 28 days cube crushing strength of 450 psi (3 N/mm2
) . A
minimum plaster thickness of 3/8 (10 mm) shall be adopted.
3 . 10.2 STRUCTURAL FORM AND BUILDING CONFIGURATION
A ) Avoid creating heavy concentrated masses, particularly at roof level (eg.
large water tanks).
B )Make sure no heavy masses are located above stairwells etc.
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C )Avoid irregular floor plan shapes to avoid torsional effects in earthquakes.
D )Make sure columns and walls are continuous between floors.
E )Make sure buildings do not have large openings (eg. for garages or shops) as
these can weaken structure and cause torsional effects.
F ) Make sure that buildings plan shape at any floor level, including ground
floor, is symmetrical.
G ) If shear walls are concentrated inside a building make sure it will not be
subject to torsional effects or design structure, to resist this.
H ) Make sure structure is not long in relation to its width (W). Avoid long
unsupported walls of longest length (L) does not exceed 3 W.
3 . 10.3 HORIZONTAL REINFORCEMENT IN WALLS
Horizontal reinforcing of walls is required in order to tie orthogonal walls
together. The most important horizontal reinforcing is by means of reinforced concrete
bands provided continuously through all load-bearing longitudinal and transverse walls at
plinth, lintel and roof-eave levels and also at the top of gables according to the
requirements stated below.
3 . 10.4 PLINTH BAND
This should be provided in those cases where the soil is soft or uneven in its properties. It
may also serve as damp-proof course.
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3 . 10.5 LINTEL BAND
A lintel band shall be incorporated in all openings and shall be continuous over all
interior and exterior walls. The reinforcement over the openings shall be provided in
addition to that of any other requirement.
3 . 10.6 ROOF BAND
This band shall be provided at the eave-level of trussed roofs and also below gable levels
on such floors which consist of joists and covering elements so as to integrate them
properly at their ends and fix them into the walls. This band is not required in case of
reinforced concrete or reinforced brick masonry slabs.
The width of the RC bands (at plinth and lintel) shall be the same as the thickness of the
wall. The minimum thickness of a load-bearing wall shall be 9 inches (225 mm). A cover
of one inch from the face of wall shall be maintained for all steel reinforcing.
The vertical thickness of the RC bands may be kept to a minimum of 6 (150 mm) with 4
(115 mm) bars as reinforcement. For economical reasons a minimum
thickness of 3 (75 mm) with 2 (65 mm)bars may be adopted.
The concrete mix is to be 1:2:4 by volume. Alternatively, it shall have a minimum
compressive cylinder strength of 2500 psi (17 N/mm
2
) at 28 days.
The longitudinal bars shall be held in position by steel stirrups 3/8 (10mm) placed 6
(150 mm) centre to centre.
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3 . 10.7 VERTICAL REINFORCEMENT IN WALLS
Steel bars shall be installed at the critical sections (i.e. the corners of walls, junctions of
walls, and jambs of doors) right from the foundation concrete. They shall be covered with
cement concrete in cavities made around them during the masonry construction. This
concrete mix should be kept to 1:2:4 by volume, or richer.
The vertical steel at openings may be stopped by embedding it into the lintel band, but
the vertical steel at the corners and junctions of walls must be taken into either the floor
and roof slabs or the roof band.
. 3 . 10.8 VERTICAL JOINTS BETWEEN ORTHOGONAL WALLS
For convenience of construction, builders prefer to make a toothed joint which is later
often left hollow and weak. To obtain full bond, it is necessary to make a sloped or
stepped joint. It should be constructed so as to obtain full bond by making the corners
first to a height of 24 inches (600 mm), and then building the wall in between them.
Alternatively, the toothed joint shall be made in both the walls in lifts of about 18 inches
(450 mm).
3 . 10.9 DOWELS AT CORNERS AND JUNCTIONS
Steel dowel bars shall be provided at corners and T-junctions to integrate box action of
the walls. Dowels are to be taken into the wall to sufficient length so as to provide their
full bond strength.
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3 . 11 GUIDELINES FOR MULTI-STOREY FRAME STRUCTURES
3 . 11.1 MATERIAL TYPES FOR WALLS
- Concrete block work units
- Cut-stone masonry units
- Reinforced Concrete walls (expensive alternative)
- Factory manufactured brick units
- Avoid using random rubble masonry
3 . 11.2 FOUNDATIONS
- Check soil type and water level.
- Use reinforced concrete strip footings under main load bearing walls and
columns.
- Soft clays and loose-medium dense sand, which is waterlogged, may liquefy
during an earthquakes. Seek specialist advice on piled foundations and
structural design.
3 . 11.3 MASONRY SHEAR WALLS
Masonry walls acting as non-structural shear walls to resist lateral shaking:
- Make sure walls are made with good strength
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- Make sure wall are build first and use shutters for columns to give strong
bonding between masonry walls and column.
- All masonry units to be bonded with mortar, of 1 part cement to 3 parts sand
- Make sure all walls are continuous from foundations to roof level.
- Make sure masonry buildings is tied to floors and columns at suitable intervals
3 . 11.4 REINFORCED CONCRETE WALLS
- These can be combined with columns to provide additional shear resistance
against earthquakes.
3 . 11.5 MINIMUM BEAM, COLUMN AND SLAB SIZES
10 ft (3 m) span concrete floor slabs, minimum depth 150 mm
15 ft (4.5 m) span beams, minimum 18 inch x 12 inch (450mm x 300mm)
Concrete columns average 12 inch x 12 inch (300mm x 300mm)
- Make sure that all main reinforcing bars in concrete are high yield deformed bars,
not plain bars.
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DDEESSIIGGNNMMEETTHHOODDOOLLOOGGYY
Over the past several decades the strength design method has largely displaced the older
service load design methods both in Pakistan and abroad because in this method, individual
load factors may be adjusted to represent different degree of uncertainty for the various
types of loads and strength reduction factors likewise may be adjusted to the precision with
which various types of strength (bending, shear, torsion, etc.) Therefore, throughout in the
design of this building, strength design is followed. In this project we design the farm house
first manually & we provide the plinth band , lintel band & roof band for making the
building earthquake resistant. Also the steel bars are provided in the masonary walls. We are
following the ACI 2005 & UBC-97 codes.We use the excel sheets for the manual
calculations.
C H A P T E R
4
Also the analysis and design results are taken from the ETABS by converting the load
bearing wall structure ( farm house ) into frame structure .
4 . 1 TWO-WAY SLABS
These are the slabs that are essentially supported on more than two faces. A term "aspect
ratio" is sometimes defined for the slab that is the ratio of shorter to longer span. For a slab
to be two-way, this ratio must lie between 0.5 and 1, both values included.
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4 . 1.2 DESIGN BY THE COEFFICIENT METHOD
A unified method in the two way slab design was presented in 1963 ACI code. Its use
spread all over the world for the design of such slabs and its continued use is permissible
under the code provision .
The method makes use of tables of moment coefficients for variety of conditions.
Unit width strip is taken in both directions. The strip is designed separately for +ve and ve
moment
2nuu LCM =
C = ACI co-efficient
u= Factored slab load
C depends upon the end conditions of slab and the aspect ratio.
Three tables are available for C
Dead load positive moment
Live load positive moment
-ve moment
4 . 2 FOR ONE-WAY SLAB
4 . 2.1 DESIGN PROCEDURE
1 ).Check whether the slab is one-way or two-way.
2 ).Calculate hminand round it to higher 10mm multiple.
i. Not less than 110 mm for rooms
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ii. Not less than 75 mm for sunshades.
3 ).Calculate dead load acting on the slab.
Dead Load = Load per unit area x 1m width.
4 ).Calculate live load acting on the slab.
Live load = Load per unit area x 1m width.
5 ).Calculate total factored load per unit strip. (kN/m)
6 ). Calculate the moments either directly (simply supported) or by using coefficient for
continuous slabs.
7 ).Calculate effective depth.
d = h (20 + ()db)
db= 10, 13, 15, generally used.
8 ).Check that
d dmin
9 ).Calculate As required for 1m width.
10 ).Calculate minimum/distribution/temperature & shrinkage steel.
11 ).Select diameter and spacing for main and steel.
12 ).Check the spacing for max. and min. spacing.
smin 90mm
if spacing is less than minimum increase the diameter of bar.
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13 ).For continuous slabs, curtail or bend up the +ve steel. For -ve steel see how much steel
is already available. Provide remaining amount of steel.
14 ).Calculate the amount of distribution steel. Decide its dia. & spacing like main steel.
15 ).Check the slab for shear.
vVcVu
16 ).Carry out detailing and show results on the drawings.
17 ).Prepare bar bending schedule, if required
4 . 3 BEAMS
All the Beams in a farm house are not a structural Beam as they are not provided to take the
transverse load (to resist the bending).They are provided to insure the box action. They are
provided to increase the ductile nature of the masonary structure. They give additional
strength and stiffness.
The minimum steel Area is provided on these Beams
min = 0.0018 for Grade 420 MPa
As min. = 0.0018 x b x h
They are provided at the Plinth Level , at the Lintel Level , at the Roof Level
4 . 3.1 DESIGN OF STRUCTURAL BEAMS
4 . 3.1.1 DESIGN PROCEDURE FOR SIMPLY SUPPORTED BEAMS
1 ) Calculate self weight of the beam
2 ) Calculate the Slab Load
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3 ) Calculate the total factored load that is subjected to beam
4 )Determine the clear span of the beam ln
5 )Find the moment
M = wu ln2
88
6 )Determine the dmin
7 )Provide a clear cover of 40mm.
8 )Calculate h.
9 )Calculate
= w x [1- [(1-0.216R/fc')]
w = 0.85 fc' / fy
R = Mu / ( bd2
)
10 )Check against min
min = 1.4 / fy
11 )Calculate the area of steel
12 )Select the no of bars according to the calculated area of steel
4 . 3.1.2 DESIGN PROCEDURE FOR DOUBLY REINFORCED BEAMS
1 ) Calculate self weight of the beam
2 ) Calculate the Slab Load
3 ) Calculate the total Factored load that is subjected to beam
4 )Determine the clear span of the beam ln
5 )Find the moment "M"
6 )Calculate dmin
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7 )If dmin is greater than the h req then design the beam as a doubly reinforced.
8 )Calcute d' / d
9 )Determine ( 600 fy ) / 1600
If ( 600 fy ) / 1600 < d' / d so compression steel will be yielded.
10 )max = 0.85 1x 3fc' / (8 fy)
11 )Calculate As1= maxx b x h ( tension steel area )
12 )Calcute a = 0.85 1 x 3d / 8
13 )Determine M1
M1= x As1x fy x ( d - ( a / 2 ))
14 )Determine M2
M2= M - M1
15 )Calculate As' = M2 / (x fy x ( d d' )) ( compression steel area )
16 )As = As1+ As'
17 )Calculate the no of bars for the tension steel area and also for the compression steel
area.
4 . 3.1.3 DESIGN PROCEDURE FOR CONTINUOUS BEAM
1 ) Calculate self weight of beam
2 ) Calculate the slab load
3 ) Calculate the total Factored load that is subjected to beam.
4 ) Calculate the moments at the ;
Negative moment at the exterior face of exterior support
Negative moment at the exterior face of the first interior support
Negative moment at the interior face of first interior support
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Exterior span positive moment
Interior span positive moment
5 )From these moments find the corresponding area of steel and then the no of bars
corresponding to the steel area
4 . 4 DESIGN OF LINTELS
4 . 4.1 WALL LOAD ON THE LINTEL
Equivalent UDL on lintel if height of slab above lintel is greater than 0.866L
UDL = 0.11 x twx L
tw= wall thickness in "mm"
L = opening size in "m"
If the height of slab above lintel is less than 0.866L
Total Wall Load + Load from slab incase of load bearing wall
UDL = ( Equivalent width of slab supported ) x ( Slab Load per unit area )
= m x KN / m2 = KN / m
After the calculation of the load the rest of the design is same as the beam
4 . 5 COLUMNS
The minimum area of steel is provided is provided in the columns of a farm house which are
provided for the purpose to insure the box action & to give additional strength to the
masonary design of a farm house. These columns are not for the purpose to take the axial
loads and moments.( Non Structural columns )
Special provisions are applied for the detailing ( Seismic provisions ).e.g Lap is provided at
the centre of the columns.
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4 . 5.1 DESIGN PROCEDURE FOR THE STRUCTURAL COLUMNS
( AXIAL LOAD + MOMENTS )
1 ) Find the PD, PL, Mux , Muy
2 )Calculate the size of the Column using the following formula
Ag = Pu +2Mux+2Muy
0.5fc' + 0.01 fy3 ) Calculate the " "
4 ) Calculate ex, ey & eox
ey = Mux / Pu , ex = Muy / Pu , eox = ex+eyx b h
5 ) Use interaction curves and charts to determine
6 ) From these value find the area of steel for the longitudinal bars and then decide the noof bars.
7 ) Check the provided
0.01 < provided < 0.03
8 ) Transverse reinforcement
9 ) Spacing of shear stirrups
10 )Calculate the lap length
l = 0.093 fy db
4 . 6 WALL DESIGN & FOUNDATIONS
4 . 6.1 DESIGN OF MASONARY FOUNDATION
W = Load per unit length of wall.
W = li 385 + ( hi ti ) x1920 + ( qi li )0.5 (kg/m)
L = Width of the footing = W 10 F(qa-10D)
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Li = Clear span of each slab or the panel ( m )
hi = Height of each floor ( m )
ti = Thickness of wall of each storey (m).
Qi = Allowable partition load (kg/m^2)
L = Width of footing in mm
qa = Allowable bearing capacity in KPa.
F = 1.0 for interior footing
F = 1.35 for exterior footing
D = Depth of bottom footing from plinth level (m)
No of Steps = L 2h t
114
4 . 6.2 THICKNESS OF WALL
If the load W is divided by compressive strength of brick it will give us wall thickness at the
section. Normally thickness of wall is expressed in no. of half bricks.
No of half bricks = W 2 /2
4500
Where
2 = 1 for interior wall
2 = 1.5 forexterior wall
(Only for 1:6 mortar)
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4 . 6.3 DESIGN PROCEDURE FOR ISOLATED FOOTING
1 )Collect all the required information i.e allowable bearing capacity , depth of footing ,
type of load coming and decide type of footing.
2 ) For service DL , LL and net allowable bearing capacity find the size of footing.
3 ) Select or assume a suitable depth of footing satisfying two way punching shear.
4 ) Calculate the net factored contact pressure "qnu" at the interface of soil and concrete
surface.
5 )Calculate one way shear in longer direction and check for its capacity.
6 ) Calculate the moment in shorter and longer direction.
7 ) Calculate the total amount of steel in shorter and longer direction and find the spacing.
8 ) Check the bearing pressure at the bottom of column.
9 ) Check the development length for the steel provided.
4 . 7 DESIGN OF STAIRS
1 ) Calculation of span of slab
2 ) Depth of slab
3 ) Loads calculation
4 ) Calculation of Moments
5 ) Steel calculations & spacing
6 ) Check for maximum spacing.
7 ) Shear check.
8 ) Detailing.
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4 . 8 SOFTWARES USED IN DESIGN OF FARM HOUSE AS FRAME
STRUCTURES
We use the software ETABS for the design of farm house as frame structure.
4 . 8.1 OVERVIEW OF ETABS PROGRAM
ETABS ( Extended Three dimentional Analysis of Building System ) is a stand-alone finite-
element-based structural analysis program with special purpose features for structural design
and analysis of building systems. The analysis methods include a wide variety of Static and
Dynamic Analysis Options. We can import our file ( Plan of a complex building ) from the
AUTOCAD to the ETABS.
4 . 8 .2 PROCEDURE FOR MODELING IN ETABS
Step 1
Begin a New Model
In this Step, the dimensions and story height are set. Then a list of sections that fit the
parameters set by the architect for the design are defined.
Figue 4.1: ETABS user interface
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A. Change the units in the lower right corner in the drop down box according to our
desired units.
B. Click the File menu > New Model command or the New Model button.
Figue 4.2:The New Model Initilization form
C. Select the Nobutton on that form and the form. The Building Plan Grid System and
Story Data form is used to specify horizontal grid line spacing, story data, and, in
some cases, template models. Template models provide a quick, easy way of starting
your model. They automatically add structural objects with appropriate properties to
your model. It is highly recommend to start models using templates whenever
possible. However, in this project , we import the drawing from the AUTOCAD .
D. Set the number of stories.
E. Type 11 ftin the bottom storey height.
F. Then click grid only
G. Click the OK button to accept your changes. When you click the OK button, your
model appears on screen in the main ETABS window with two view windows tiled
vertically, a Plan View on the left and a 3-D View on the right.The number of view
windows can be changed using the Options m