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CIV 223
Reinforced Concrete Structures - I
Spring 2016
Office hours: Sunday 11:00 - 1:00
بسم هللا الرحمن الرحيم
Dr. Alaa Helba
2
Lecture # 1
Introduction
Course introduction
Concrete Materials
Properties of hardened concrete
Properties of Reinforcing Steel
Loads on R.C. Buildings
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CIV 223
COURSE INTRODUCTION
Reinforced Concrete Structures - I
Room # 124 Main Block, Faculty of Engineering
E-mail: [email protected]
Tel. No. : 050-2770140 Extension 221
Office Hours: 11:00 to 1:00 p.m. Sunday.
Course Lecturer: Dr. Alaa Helba
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Typical Structural Elements of a Skeletal R.C. Building
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Typical Structural Elements of a Skeletal R.C. Building
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Typical elements of
R.C buildings
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Load Transfer
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Typical RC Structural System
Reinforced Concrete Structures Any structural element in a skeletal R.C.
building or bridge should be designed
to carry the expected EXTERNAL
LOADS safely and economically.
column SUPPORT column SUPPORT
Span = L
P w Loads from: slabs
walls
o.w. of beam
Simple R.C. Beam
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The External Loads cause some
deformations which cause
INTERNAL STRAINING ACTIONS at
different sections of the structural
element depending on the SPAN
and the structural system used.
Reinforced Concrete Structures
The resulting Internal straining actions:
[ Normal Forces (N.F.), Shearing Forces
(S.F.) and Bending Moments (B.M.) ]
should be resisted by the STRENGTHS
of the SECTIONS (Dimensions) and the
MATERIALS (Concrete & Steel) used
in construction.
Reinforced Concrete Structures
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Reinforced Concrete Structures
COURSE Contents
Properties of Hardened Concrete
Properties of Reinforcing Steel.
LOADS on R.C. Structural elements.
Cases of Loadings (For Design).
1- Introduction
Properties of Materials and Loads
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COURSE Contents 2- Fundamentals of R.C. Analysis & design
Egyptian Code Requirements for safety.
Analysis & Design of R.C. Sections:
R.C. Sections subjected to Bending Moments.
R.C. Sections subjected to shear Q.
R.C. Sections subjected to Axial Loads N.
COURSE Contents 3- Analysis & Design of different elements:
Beams.
Columns.
R.C Slabs
4- Details of Reinforcement of
different R.C. Elements and Structures.
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TEXT BOOK
Attendance at Lectures and sections is Compulsory.
More Course Details
Mid-Semester Exam 20%
Class work 40%
End of Semester Exam 40%
COURSE Work and Exams
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Topic Topic
Week 1 Introduction Week 9 Sections under shear.
Week 2 Reinforced Concrete Fundamentals -
Week 10 Shear reinforcement
Week 3 Methods of design in Egyptian Code;
Week 11 Design of sections under axial forces - Columns;
Week 4 Behavior of R.C beam Under loads up to failure
Week 12 R.C. Columns
Week 5 Analysis and Design using limit states method;
Week 13 R.C. Slabs
Week 6 Sections subjected to bending moments;
Week 14 R.C. Slabs
Week 7 R.C. Beams Beams with T-section
Week 15 Reinforcement details; Bar
development
Week 8 M-term Exam
Week 16 Final Exam
R.C. Structures
Materials and Loads
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Concrete
Concrete materials
o CEMENT
o WATER
o COARSE AND FINE AGGREGATES
o ADMIXTURES (if required).
Concrete Mix
The aim is to mix the above materials in
measured amounts to make concrete that is
easy to: TRANSPORT, PLACE,
COMPACT, and FINISH
And which will SET, and HARDEN, to
give a strong and durable product.
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CEMENT The cement powder, when mixed with water, forms a paste. This paste acts like glue and holds or bonds the aggregates together.
Concrete Materials properties
Production of Portland Cement
(modern dry-process)
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TYPES OF PORTLAND CEMENT
Standard Specification for Portland Cement
provides types of Portland cement as follows:
Ordinary Portland cement - OPC
Rapid Hardening(High early strength)-RHPC
Sulfate resistance or Sea-Water Cement
Low heat of hydration - LHPC 25
AGGREGATES
There are two basic types:
COARSE : crushed rock or gravel
FINE: fine and coarse sands
Concrete Materials properties
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Aggregates should be:
STRONG And HARD
Durable
Chemically Inactive
Clean
Well Graded
Concrete Materials properties
WATER, Water should be:
clean, fresh and free from any dirt,
unwanted chemicals or rubbish that may
affect concrete.
ADMIXTURES
they are mixed into the concrete to
improve some of its properties, i.e the
time concrete takes to set and harden, or
its workability
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Concrete Materials properties
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Factors affecting the concrete
properties
CEMENT CONTENT - WATER CONTENT
WATER to CEMENT Ratio
As the Water to Cement
ratio INCREASES, the
strength and durability
of hardened concrete
DECREASES.
To increase the
strength and durability
of concrete, decrease
the Water-Cement
ratio
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Compacting Concrete
WHY COMPACT?
Properly compacted
concrete is more dense,
strong and durable. Off-
form finishes will also be
better
Curing of Concrete
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Effect of curing HOW LONG TO CURE Concrete keeps getting HARDER AND STRONGER over TIME.
Household concrete jobs MUST be cured for at least 3 DAYS.
For better strength and durability, cure concrete for 7 DAYS.
The LONGER concrete is cured, the closer it will be to its best possible strength and durability.
Effect of Curing
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Properties of concrete
The four main properties of concrete are:
WORKABILITY التشغيلية
COHESIVENESS التماسك
STRENGTH المقاومة
DURABILITYالتحملية ضد الظروف الجوية
THE COMPRESSION TEST
Compressive strength measures the concrete
ability to resist loads. Commonly specified
as a characteristic strength of concrete
measured at 28 days after mixing (fc’ in
USA & fcu in Egypt).
Cylinders (150 mm diameter x 300 mm
high) according to American specification,
in Egyptian specification the molds are
cube (150mm x150mm) are tested
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Compression Test (Standard Cylinders)
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Standard Cubes prepared for testing
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Standard Cubes
150x150x150 mm
Hardened Concrete Properties
Stress-Strain Behavior in Compression
e
Ec
0.002 0.003
0.45fcu
fc
fcu 300 mm
150 mm
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Hardened Concrete Properties
Compressive Strength, fcu
Normally use 28-day strength for
design strength
Poisson’s Ratio, n
n ~ 0.15 to 0.20
e
Ec
0.45fcu
fc
fcu
Hardened Concrete Properties
Modulus of Elasticity, Ec
Corresponds to secant modulus at 0.45 fcu
Where Ec and fcu in N/mm2
cuc fE 4400
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Concrete Properties
Maximum useable strain, ecu Egyptian Code: ecu = 0.003
Used for flexural analysis
e
Ec
0.45fcu
fc fcu
ecu = 0.003
Concrete Properties
Typical Concrete Stress-Strain Curves in Compression
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Concrete Properties
Tensile Strength
Modulus of Rupture, fctr
Code Eq.
N/mm2
Test:
2
6
bh
M
I
Mcf r
cuff ctr 6.0
P
fr
Mmax = P/2*a
unreinforced
concrete beam
Concrete Properties
2. Tensile Strength (cont.)
Splitting Tensile Strength, fct
Split Cylinder Test
P Concrete Cylinder
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Concrete Properties
2. Tensile Strength (Splitting Test)
dL
Pfct
2
Concrete Properties
Shrinkage: Due to water loss to atmosphere (volume loss).
* 80% of shrinkage occurs in first year
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Concrete Properties Creep
Deformations (strains) under sustained loads.
Like shrinkage, creep is not completely reversible.
P
P
L
dL, elastic
dL, creep
=dL/L
Behavior of Different Types R.C. beams under Flexure – Why steel rft.
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Concrete Reinforcing
Concrete - No Useful Tensile Strength
Reinforcing Steel - Tensile Strength
Steel Location
“Place reinforcing steel where
the concrete is in tension”
Grades: OMS Ordinary Mild Steel
HTS High Tensile Steel
CTS Cold Twisted Steel HTS & CTS
Reinforcing Steel Size
Standard Diameters (in mms)
6, 8, 10, 12, 16, 18, 22, 25, 28, 32, 38, 40
Grades (fy / fu in N/mm2)
240/360 OMS and 280/420 OMS
350/520 deformed HTS
400/600 deformed CTS
fy Steel Yield Strength
fu Steel Ultimate Strength
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Steel Reinforcement
Es = Initial tangent
modulus
= 200 kN/mm2
(for all grades)
Stress
Strain 0.20
GR 240/350
GR 400/600 (less ductile)
Es
1
Note: Steel GR 240/350 has a longer yield plateau
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Types of Loads on R.C. Buildings
Weight of all permanent construction
Constant magnitude and fixed location
Dead Loads
Examples:
Weight of the Structure
(Walls, Floors, Roofs, Ceilings, Stairways)
Fixed Service Equipment (Piping weights, Cable
tray, Etc.)
Live Loads
Loads produced by use and
occupancy of the structure.
Maximum loads likely to be produced
by the intended use.
Not less than the minimum uniformly
distributed load given by Code.
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Environmental Loads (if any)
Earthquake
Wind
Soil Pressure
Snow Loads
Temperature Differentials
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Types of Loads (w.r.t. direction)
Gravity (Vertical):
Dead
Live
Impact
Snow
Lateral (Hal)
Wind
Earthquake
Soil lateral pressure
Thermal
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Basic Behavior
Gravity
Load
Lateral
Loading
Lateral deflection
(sway)
Wind or
earthquakes
Vertical deflection
(sag)
Dead, Live, etc.
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Transferring of Gravity Loads
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Transferring of Gravity Loads
Example
Plan
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Transferring of Gravity Loads
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Calculation of Loads transferred to column
I- Loads on Slabs
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2- Live Loads on Different Buildings
Residential Buildings Administration Buildings Schools and Hospitals Bookstores and Warehouses
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Loads on slabs
Example
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Calculation of Loads transferred to column
II- Loads of Beams
Assume total depth of beam as follows:
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