lecture # 1 introduction · lec. # 1 -17 civ 223 - dr. a. helba sp.2016 effect of curing how long...

Feb-16

Lec. # 1 - CIV 223 - Dr. A. Helba sp.2016 1

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

Feb-16


3

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

Feb-16


5

Typical Structural Elements of a Skeletal R.C. Building

6

Typical Structural Elements of a Skeletal R.C. Building

Feb-16


Typical elements of

R.C buildings

8

Load Transfer

Feb-16


9

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

Feb-16


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.


Feb-16



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

Feb-16


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.

Feb-16


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

Feb-16


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

Feb-16


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.

Feb-16


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)

Feb-16


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


Feb-16


Aggregates should be:

STRONG And HARD

Durable

Chemically Inactive

Clean

Well Graded


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

28


Feb-16


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

Feb-16


Compacting Concrete

WHY COMPACT?

Properly compacted

concrete is more dense,

strong and durable. Off-

form finishes will also be

better

Curing of Concrete

32

Feb-16


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

34

Feb-16


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

Feb-16


Compression Test (Standard Cylinders)

37

Standard Cubes prepared for testing

Feb-16


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

Feb-16



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


Modulus of Elasticity, Ec

Corresponds to secant modulus at 0.45 fcu

Where Ec and fcu in N/mm2

cuc fE 4400

Feb-16


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

Feb-16


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

Feb-16


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

Feb-16


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.

Feb-16


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

Feb-16


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

Feb-16


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.

Feb-16


Environmental Loads (if any)

Earthquake

Wind

Soil Pressure

Snow Loads

Temperature Differentials

58

Types of Loads (w.r.t. direction)

Gravity (Vertical):

Dead

Live

Impact

Snow

Lateral (Hal)

Wind

Earthquake

Soil lateral pressure

Thermal

Feb-16


Basic Behavior

Gravity

Load

Lateral

Loading

Lateral deflection

(sway)

Wind or

earthquakes

Vertical deflection

(sag)

Dead, Live, etc.

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61

Transferring of Gravity Loads

62


Example

Plan

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64

Calculation of Loads transferred to column

I- Loads on Slabs

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65

2- Live Loads on Different Buildings

Residential Buildings Administration Buildings Schools and Hospitals Bookstores and Warehouses

66

Loads on slabs

Example

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67

Calculation of Loads transferred to column

II- Loads of Beams

Assume total depth of beam as follows:

68

lecture # 1 introduction · lec. # 1 -17 civ 223 - dr. a. helba sp.2016 effect of curing how long...

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