Reinforced concrete Design-Chapter1.pdf pdf

Reinforced concrete Design-EGCV2210
Design of Structures1-CECE2240
“Design of Structural Elements” Third Edition By Chanakya Arya
Engineering Department
Civil Section
Sem1 AY 2023-24
Lecturer- Umar.Sabhapathy

Academic Integrity: Guidelines
English
• Definition: Avoidance of plagiarism, maintenance of
academic standards and honesty
• Instances of Plagiarism:
• Copying full or part of other’s work directly
• Copy-Paste of statements from multiple sources
(electronic or print material).
• Presenting a work, done in collaboration with other,
as independent work.
• Using one’s own work presented previously,
borrowing statistics from other person and
fabrication of data.
• Contract cheating / outsourcing
• Punishments:
• Student can be asked to repeat submitted work or
something similar to ensure authenticity of work
submitted originally
• Zero mark in assessment/assignment/report
• Warning letter / Dismissal from college
Arabic
•
‫التعريف‬
:
‫األك‬ ‫المعايير‬ ‫على‬ ‫والحفاظ‬ ‫األدبية‬ ‫السرقة‬ ‫تجنب‬
‫اديمية‬
•
‫االنتحال‬ ‫على‬ ‫أمثلة‬
‫األكاديمي‬
:
•
-
‫مباشرة‬ ‫منه‬ ‫جزء‬ ‫أو‬ ‫بالكامل‬ ‫اآلخرين‬ ‫عمل‬ ‫نسخ‬
•
-
‫متعددة‬ ‫مصادر‬ ‫من‬ ‫البيانات‬ ‫ولصق‬ ‫نسخ‬
(
‫أو‬ ‫إلكترونية‬ ‫مواد‬
‫مطبوعة‬
)
•
-
‫مستقل‬ ‫كعمل‬ ‫اآلخرين‬ ‫مع‬ ‫بالتعاون‬ ‫عمل‬ ‫تقديم‬
-
‫ا‬ً‫ق‬‫مسب‬ ‫تقديمه‬ ‫تم‬ ‫الذي‬ ‫الخاص‬ ‫العمل‬ ‫استخدام‬
-
‫وتلفيق‬ ‫آخر‬ ‫شخص‬ ‫من‬ ‫اإلحصاءات‬ ‫استعارة‬
‫البيانات‬
-
‫عمل‬ ‫تقديم‬
‫أنه‬ ‫على‬ ‫أخرى‬ ‫جهات‬ ‫من‬ ‫عليه‬ ‫الحصول‬ ‫أو‬ ‫شراؤه‬ ‫تم‬
‫ذاتي‬ ‫عمل‬
•
‫العقوبات‬
:
•
-
‫أ‬ ‫العمل‬ ‫بإعادة‬ ‫القيام‬ ‫الطالب‬ ‫من‬ ‫يطلب‬ ‫أن‬ ‫المادة‬ ‫لمحاضر‬ ‫يحق‬
‫و‬
‫الطالب‬ ‫عمل‬ ‫من‬ ‫للتأكد‬ ‫الكلية‬ ‫في‬ ‫له‬ ‫مشابه‬ ‫شيء‬
•
-
‫عالمة‬
"
‫صفر‬
"
‫في‬
‫التقييم‬
/
‫التقرير‬
/
‫المشروع‬
•
-
‫كتابي‬ ‫انذار‬
/
‫الكلية‬ ‫من‬ ‫الفصل‬

‫والسالمة‬ ‫الصحة‬ ‫تعليمات‬
HSE
Orientation
Prepared by: Laith Alfairuz
- HSE Assistant Trainer (Engineering Department – Mechanic Section)
- Chairperson of HSE Committee
Laith.alfairuz@shct.edu.om

‫الطارئة‬ ‫الحاالت‬ ‫في‬ ‫اإلخالء‬ ‫خطة‬
Emergency Evacuation Plan
ELC
Emergency
NO.
Number
‫الرقم‬
‫أرقام‬
‫الطوارئ‬
Campus
Security
2685288
8
‫الجامعة‬ ‫أمن‬
Campus
Clinic
26852998 ‫الجامعة‬ ‫عيادة‬
Maintenan
ce team
26852894 ‫الصيان‬ ‫فريق‬
‫ة‬
Civil
defense
9999 ‫المدني‬ ‫الدفاع‬
“Design of Structural Elements” Third Edition By Chanakya

‫الطوارئ؟‬ ‫جرس‬ ‫سماع‬ ‫عند‬ ‫تتصرف‬ ‫كيف‬
What you have to do when you hear the
emergency alarm?
1
-
‫التحلي‬
‫بالهدوء‬
‫وعدم‬
‫اإلرتباك‬
2
-
‫توقف‬
‫عن‬
‫العمل‬
ً‫ا‬‫فور‬
3
-
‫اقطع‬
‫التيار‬
‫الكهربائي‬
‫للمكان‬
‫إن‬
‫أمكن‬
‫ذلك‬
4
-
‫استخدم‬
‫الساللم‬
‫للخروج‬
‫وال‬
‫تستخدم‬
‫المصاعد‬
‫الكهربائية‬
5
-
‫غادر‬
‫المبنى‬
‫عن‬
‫طريق‬
‫مخارج‬
‫الطوارئ‬
6
-
‫توجه‬
‫إلى‬
‫أقرب‬
‫نقطة‬
‫تجمع‬
7
-
‫التنبيه‬
‫على‬
‫الموظفين‬
‫والعاملين‬
‫بعدم‬
‫الركض‬
‫أو‬
‫تجاوز‬
‫زمالئهم‬
‫حتى‬
‫ال‬
‫تقع‬
‫اصابات‬
‫بينهم‬
8
-
‫ال‬
‫تخاطر‬
‫وال‬
‫تجازف‬
‫بحياتك‬
‫وال‬
‫ترجع‬
‫إلى‬
‫المبنى‬
‫مهما‬
‫كانت‬
‫األسباب‬
‫إال‬
‫بعد‬
‫أن‬
‫يأذن‬
‫لك‬
‫بذلك‬
‫من‬
‫السؤولين‬
1- Be calm and don’t be confused
2- Stop the work immediately
3- Cut off the electricity if you can
4- Use the stairs to get out and do not use the elevators
5- Leave the building through the nearest emergency exits
6- Go to the nearest assembly point
7- Alert employees and workers not to run or overrun Colleague; to
avoid having injuries.
8- Do not put your life in risk, and do not return to the building for
any reason until you being authorized by the responsible person

“ ‫أنــــواع‬
‫طفايــــات‬
‫الحـــــــريق‬
Fire Extinguishers Type

“ ‫طريقة‬
‫استخدام‬
‫طفايات‬
‫الحر‬
‫يق‬
How to use Fire Extinguishers
Pull | ‫اسحب‬ Aim | ‫ه‬ّ‫ج‬‫و‬
Squeeze | ‫اضغط‬ Sweep | ‫ك‬ّ‫حر‬
1 2
3 4

‫الجامعي‬ ‫الحرم‬ ‫في‬ ‫المرورية‬ ‫السالمة‬
Traffic safety in university campus
‫االلتزام‬
‫بالسرعة‬
‫المحددة‬
20
‫كم‬
/
‫س‬
Commit to speed limit of 20
km/h
‫الم‬ ‫في‬ ‫عكسيه‬ ‫بطريقة‬ ‫السيارات‬ ‫ايقاف‬
‫واقف‬
Reverse parking
‫المواقدددف‬ ‫فدددي‬ ‫السددديارات‬ ‫ايقددداف‬ ‫عددددم‬
‫الخاصة‬ ‫االحتياجات‬ ‫لذوي‬ ‫المخصصة‬
Do not park vehicles in
parking lots for disables

‫الجامعي‬ ‫الحرم‬ ‫في‬ ‫المرورية‬ ‫السالمة‬
Traffic safety in university campus
‫المداخل‬ ‫عند‬ ‫السيارات‬ ‫ايقاف‬ ‫عدم‬
Do not park vehicles in front
of entries
Compliance with
signboards
‫االرشادية‬ ‫باللوائح‬ ‫االلتزام‬
Permits
‫التصددددار‬
‫يح‬

‫الكهربائ‬ ‫التوصيالت‬ ‫استخدام‬ ‫مخاطر‬
‫ية‬
Electrical Extensions Hazards
‫زيادة‬
‫األحمال‬
‫على‬
‫التوصيالت‬
‫الكهربائية‬
‫تؤدي‬
‫إلى‬
‫وقوع‬
‫حر‬
‫يق‬
Overload on electrical
extensions lead to fire
‫مطا‬ ‫ددر‬‫د‬‫ي‬ ‫ال‬ ‫ددة‬‫د‬‫الكهربائي‬ ‫دديالت‬‫د‬‫التوص‬ ‫ددتخدم‬‫د‬‫تس‬ ‫ال‬
‫ددة‬‫د‬‫بق‬
‫والمقاييس‬ ‫لالشتراطات‬
Be aware, don’t use electrical
extensions that don’t meet with the
specifications and standards.
‫الممددرات‬ ‫فددي‬ ‫كهربائيددة‬ ‫كددابالت‬ ‫ددب‬ ‫و‬ ‫عدددم‬
‫ب‬ ‫الكهربائي‬ ‫التوصيل‬ ‫محوالت‬ ‫واستخدام‬
‫شكل‬
‫الصيانة‬ ‫قسم‬ ‫واعتماد‬ ‫اشراف‬ ‫مب‬ ‫صحيح‬
Do not put electrical cables in the
walkways and use electrical
adapters correctly with
maintenance department
supervision and approval

‫والورش‬ ‫المختبرات‬ ‫في‬ ‫السالمة‬
Safety in Labs & Workshops
‫يمنب‬
‫التدخي‬
‫ن‬
Smoking Is prohibited
ً‫ا‬‫بات‬ ً‫ا‬‫منع‬ ‫والشرب‬ ‫األكل‬ ‫يمنب‬
Food and drinks are
forbidden in labs
‫مستمر‬ ‫تهوية‬ ‫وجود‬ ‫من‬ ‫التأكد‬
‫ة‬
Availability of an
adequate and
continuous
ventilation system
Using proper PPE
‫دددددددددددالمة‬‫د‬‫الس‬ ‫أدوات‬ ‫دددددددددددتخدام‬‫د‬‫اس‬
‫الشخصية‬
‫عدم‬
‫لمس‬
‫أي‬
‫مواد‬
‫اال‬
‫بارشادات‬
‫الشخص‬
‫المختص‬
Do not touch any
materials unless
instructed by the
competent person

‫المختبرات‬ ‫في‬ ‫حريق‬ ‫بطانية‬ ‫وجود‬ ‫من‬ ‫التأكد‬
Availability of fire blanket in
labs
‫ددددلة‬‫د‬‫س‬ ‫م‬ ‫ددددة‬‫د‬‫فاعلي‬ ‫ددددن‬‫د‬‫م‬ ‫ددددد‬‫د‬‫التأك‬
‫العيون‬
Eye wash is working
Follow safety material
data sheet instruction
when using, handling,
and storing of chemicals
‫تخدز‬ ‫فدي‬ ‫السدالمة‬ ‫قواعد‬ ‫تطبيق‬
‫ين‬
‫الكيميائ‬ ‫دواد‬‫د‬‫الم‬ ‫دل‬‫د‬‫ونق‬ ‫واسدتخدام‬
‫دة‬‫د‬‫ي‬
‫المستخدمة‬
‫التأكد‬
‫من‬
‫فاعلية‬
‫أنظمة‬
‫اإلنذا‬
‫ر‬
‫واإلطفاء‬
‫في‬
‫المختبرات‬
‫والورش‬
Fire alarm system and
firefighting system are
working
‫والورش‬ ‫المختبرات‬ ‫في‬ ‫السالمة‬
Safety in Labs & Workshops

ً‫ا‬‫دائم‬
‫احتفظ‬
‫بأرقام‬
‫التواصل‬
‫مب‬
‫قسم‬
‫األمن‬
‫والسالمة‬
Always keep in mind of
HSSE Dept. contact
numbers
‫ومالحظات‬ ‫الحوادث‬ ‫جميب‬ ‫عن‬ ‫اإلبالغ‬
‫الفور‬ ‫على‬ ‫السالمة‬
Report all incidents and
safety observations
immediately
‫لك‬ ‫طوارئ‬ ‫مخرج‬ ‫أقرب‬ ‫على‬ ‫التعرف‬
Identify the nearest
emergency exit
‫السالمـة‬ ‫قواعـد‬
Safety Roles

‫السالمـة‬ ‫قواعـد‬
Safety Roles
‫تعرف‬
‫على‬
‫أقرب‬
‫نقطة‬
‫تجمب‬
‫لك‬
Identify the nearest
assembly point
‫الحريد‬ ‫طفايدات‬ ‫أنواع‬ ‫على‬ ‫التعرف‬
‫ق‬
‫استخدامها‬ ‫وطرق‬
Identify fire extinguisher's
locations and how to use
them
‫ومخدددارج‬ ‫مسدددارات‬ ‫ددو‬‫د‬‫خل‬ ‫مدددن‬ ‫ددد‬‫د‬‫التأك‬
‫دائم‬ ‫بشكل‬ ‫العوائق‬ ‫من‬ ‫الطوارئ‬
Make sure that all routes
and exits are free from
obstacles

‫استخدم‬
‫كلتا‬
‫يديك‬
‫وامسك‬
‫الحمل‬
‫من‬
‫زوايا‬
‫متعاكسة‬
Use both of your hands
and grasp the object
from opposite corners
‫احدى‬ ‫تقديم‬ ‫مب‬ ‫مريحة‬ ‫مساحة‬ ‫خذ‬
ً‫ال‬‫قلي‬ ‫األمام‬ ‫إلى‬ ‫القدمين‬
Take a wide stance, with
one foot slightly forward
ً‫ا‬‫يدوي‬ ‫األدوات‬ ‫لرفب‬ ‫السالمة‬ ‫تعليمات‬
Safe Manual Handling
‫ابدأ‬
‫بالرفب‬
‫باستخدام‬
‫الساقين‬
‫ب‬ ‫وو‬
‫الثقل‬
‫عليهما‬
Start lifting and put the
load on your legs
‫لتحقيق‬ ‫ظهرك‬ ‫عية‬ ‫و‬ ‫على‬ ‫حافظ‬
‫األحمال‬ ‫توازن‬
Don’t change your back
position, to balance the
load

‫المصعد‬ ‫تعطل‬ ‫حالة‬ ‫في‬ ‫الصحيح‬ ‫التصرف‬
Action in the Event of Elevator Failure
‫اإلرتباك‬ ‫وعدم‬ ‫بالهدوء‬ ‫التحلي‬
‫لق‬ ‫المصعد‬ ‫في‬ ‫الموجودة‬ ‫باألرقام‬ ‫االتصال‬
‫سم‬
‫بالتفاصيل‬ ‫وابالغهم‬ ‫الصيانة‬
:
-
‫الموقع‬
-
‫األشخاص‬ ‫عدد‬
-
‫المتحدث‬ ‫اسم‬
+968 – 2685 (2894)
+968 – 2685 (2887)
Be calm and don’t be confused
Contact maintenance team and inform them
of the following details:
- location - no. people - Speaker’s name
+968 – 2685 (2894)
+968 – 2685 (2887)
1
1
2
2

‫الحادث‬ ، ‫الوقوع‬ ‫قرب‬ ‫حادث‬ ، ‫سليم‬ ‫ير‬ ‫ال‬ ‫التصرف‬ ، ‫سليمة‬ ‫ير‬ ‫ال‬ ‫الحالة‬ ‫بـ‬ ‫التعريف‬
Identifying unsafe condition, Unsafe act, Near miss, Accident

‫والحوادث‬ ‫المالحظات‬ ‫عن‬ ‫اإلبالغ‬
Reporting Observations and Incidents
1
2 3

‫اإلصابة‬ ‫حاالت‬ ‫في‬ ‫الصحيح‬ ‫التصرف‬
Correct Action in Case of Injury
‫اإلرتباك‬ ‫وعدم‬ ‫بالهدوء‬ ‫التحلي‬
‫التالية‬ ‫بالتفاصيل‬ ‫وابالغهم‬ ‫بالعيادة‬ ‫االتصال‬
:
-
‫الموقع‬
-
‫االصابة‬ ‫نوع‬
-
‫المتحدث‬ ‫اسم‬
+968 – 2685 (2998)
+968 – 2685 (2923)
‫لذلك‬ ‫رخص‬ُ‫م‬ ‫تكن‬ ‫مالم‬ ‫المريض‬ ‫اسعاف‬ ‫عدم‬
‫العيادة‬ ‫فريق‬ ‫يصل‬ ‫أن‬ ‫إلى‬ ‫معتمد‬ ‫بمسعف‬ ‫واالستعانه‬
Be calm and don’t be confused
Contact the clinic and inform them
of the following details:
- location - injury - Speaker’s name
+968 – 2685 (2998)
+968 – 2685 (2923)
Do not assist the patient unless you have
experience in that, or call an approved
first aider until the clinic team arrives
1
1
2
3
2
3

‫مكروه‬ ‫كل‬ ‫من‬ ‫وإياكـم‬ ‫هللا‬ ‫حمانا‬
May Allah protect us from all hazards
Laith Alfairuz
- HSE Assistant Trainer (Engineering Department – Mechanic Section)
- Chairperson of HSE Committee
Laith.alfairuz@shct.edu.om

C o d e o f e t h i c s t o b e f o l l o w e d b y d e s i g n e n g i n e e r s
1. Use knowledge and skill for the enhancement of human welfare and the environment.
2. Uphold Safety, health and welfare of the public - professional duties.
3. Engineers shall perform services only in areas of theircompetence.
4. Engineers shall issue public statements only in an objective and truthfulmanner.
5. Engineers shall act in professional matters for each employer or clients as faithful agents or trusteesand
shall avoid conflicts of interest.
5. Engineers shall build their professional reputation on the merit of their services and shall notcompete unfairly with others.
6. Engineers shall act in such a manner as to up hold and enhance the honor, integrity and dignity ofthe
engineering profession and shall act with zero tolerance for bribery, fraud andcorruption.
7. Engineers shall continue their professional development throughout their careers and shallprovide
opportunities for the professional development of those engineers under theirsupervision.

Course learning objectives Course learning outcomes
The course learning objectives enable the students to
1. Establish the philosophies and principles of the
structural design.
2. Interpret structural plan to determine loads on
structural members.
3. Demonstrate an understanding of the design code
by the application to design structure.
4. Outline the use of basic approaches and more
unique method to analyze structure by hand.
5. Identify the responsibility of the engineer to be
ethical in dealing with others and in the presentation
of result from analysis and design.
On completion of the course the student will be able to:
1. Identify properties of reinforced concrete and limit
state method. Outline and define characteristic material
strengths.
2. Identify characteristic loads, partial factors of safety
and stress-strain relationship.
3. Establish an illustration of the distribution of strains
and stresses across a section. Interpret bending
parabolic and equivalent rectangular stress block.
4. Determine singly reinforced rectangular sections in
bending and doubly reinforced rectangular sections in
bending.
5. Determine and compute for reinforced flanged
sections in bending.
6. Identify various loads and load combinations on
structures with analysis of beams.
7. Design of different structural elements such as slabs,
beams, columns, foundations and staircases.

Introduction
• Reinforced concrete is a composite material, consisting of steel
reinforcing bars embedded in concrete.
• Concrete has high compressive strength but low tensile strength.
• Steel bars can resist high tensile stresses but will buckle when
subjected to comparatively low compressive stresses.

CONCRETE, REINFORCED CONCRETE, PRESTRESSED
CONCRETE.
• Concrete is a mixture of cement, sand and aggregate, which are
bound chemically by the addition of water.
• Concrete can be given any shape, with any practical dimensions,
without any joints.

• Concrete has a very good compressive strength, concrete -like stone- is
a weak material as far as tensile forces are concerned. Since the
flexural and shear resistance of a material is directly related to its
tensile strength; concrete is not a suitable material for the loading
conditions that generate flexure and shear.
• Weakness of concrete in tension can be overcome by reinforcing it
with steel bars in the tensile regions.

• Steel bars placed in their positions before the concrete is poured can
have a very good bond with concrete, both mechanically and chemically
after the hardening of concrete.
• This means that the reinforcing bars become an integral part of the
material. This new combination of two materials is called “ Reinforced
Concrete ”.
• Because of the bond the deformation of both concrete and steel i.e.
strains and in surrounding concrete are the same. What’s more, the
coefficients of thermal expansion and contraction of steel and concrete
are luckily the same.

• Concrete cracks even under the normal loads. The
cracks may be invisible, hence the term “ hairline
cracks”.
Reinforcement
A
P1 P2
A
n.a
SECTION A-A
FIG. 1.1
Fig.1.1 shows a reinforced concrete beam under the action of bending
moments.

• One important result of the cracking is that, the tensile zone of the beam
can no more contribute to the resistance of the beam. This part of the
beam is there simply ignored during the design process. Resisting forces in
a beam section after the cracking is shown in Fig.1.2.
c
z
FIG. 1.2

• On the other hand, if a beam is compressed before any lateral exterior
load is applied, superposition of flexure stresses and initial
compressive stresses will yield either totally compressive stress on the
whole concrete section or very small tensile stress at a small area.
These are shown in Fig. 1.3.
+ = or
Mex
Nin
comp.
initial
compression
Bending
stresses
comp. comp.
Tension
FIG. 1.3

• The initial compression applied to the beam should be fixed in a way
that it would last through the life span of the beam.
• This process is called “pre-stressed concrete” and during the pre-
stressing process, steel wires or strands are used.

HISTORY OF REINFORCED CONCRETE
• First known reinforced concrete product is not a building but a boat, which was
demonstrated in 1855 Paris World Exhibition. Later, reinforced concrete was used
for manufacturing flowerpots.
• In 1855 Fraucois Coiguet used reinforced concrete for the first time in a building.
• In 1861 Coiguet wrote a book and explained the use of the reinforced concrete.

• In 1861 Coiguet wrote a book and explained the use of the reinforced
concrete.
• First theory of reinforced concrete was published in 1886 by Koennen.
• Hennebique explained the monolithic behavior of the reinforced concrete
in 1892 and he exhibited his works in 1900 Paris World Exhibition.

LOADS
• In a building certain parts are essentially structural members. They form
the skeleton of the building and are known as the “structural system” of
the building. The purpose of the structural system is to make the building
strong and safe, that is all kinds loads acting on the building must be
carried and transferred to the ground safely by this system. Other parts
of the building such as walls, floor fill, plaster etc. do not take a load-
carrying role in the system even if they are fixed to the structural
elements.

Structures must be designed so that they will not fail or deform
excessively under load. Engineers must anticipate probable loads a
structure must carry. Structures be able to carry all the loads that may act
on throughout its economical life. The design loads specified by the codes
are satisfactory in general. However, depending on the nature of the
structure, an engineer may refer to experiments etc. and increase the
minimum loads specified by the code.

•Typical loads acting on structures are:
• Dead Loads
• Live Loads
• Construction Loads (settlement in supports, lack of it of element
temperature changes etc).
• Wind Loads
• Earthquake Loads
• etc.

• Dead Loads
The load associated with the weight of the structure and its permanent
components (floors, ceiling, ducts etc.) is called the dead load. Dead
loads can not be calculated exactly before the design since the
dimensions of the members are not known at the beginning. Therefore,
initially magnitude of the dead load is estimated for preliminary design
and after sizing of the members it is calculated more accurately.

• Distribution of Dead Load to Framed Floor Systems
Floor systems consist of a reinforced concrete slab supported on a
rectangular grid of beams and load of the slab is carried by these
beams. The distribution of load to a floor beam depends on the
geometric configuration of the beams forming the grid. The area of slab
that is supported by a particular beam is termed the beam’s tributary
area (see figure)

Concept of tributary area; a) square slab, all edge beams support a triangular
area; (b) two edge beam divide load equally; (c) load on a 1 ft of slab in (b).

(d) tributary areas for beams B1 and B2 shown shaded, all diagonal lines slope at 45o;
(e) top figure shows most likely load on beam B2 in figure (d); bottom figure shows
simplified load distribution on beam B2; (f) most likely load on beam B1; (g) simplified
load distribution to beam B1.

• Live Loads
Loads that can be moved on or off a structure are classified as live loads.
Live loads include the weight of people, furniture, machinery, and other
equipment. Live loads specified by codes for various types of buildings
represent a conservative estimate of the maximum load likely to be
produced by the intended use of the building. In addition to long term
live load, when sizing members short term construction loads (if these
loads are large) should be considered.

Live loads are also vertical, but their magnitudes and locations are not
certain. They are mainly occupancy loads i.e. the weights of human beings
and furniture etc. Every country has a national standard, which specifies
the minimum magnitudes of the live loads to be used in design. In
ordinary buildings live loads act on floors. A special kind of live load is the
traffic load on bridges, but they are always specified in bridge design
regulations issued by highway or railway officials. Live loads specified by
the standards are well over the actual average values.

• Wind Loads
The magnitude of wind pressure on a structure depends on the wind
velocity, the shape and stiffness of the structure, the roughness and
profile of the surrounding ground, and influence of adjacent structures.
As wind pressure may be computed from wind velocities an alternative is
the equivalent horizontal wind pressure specified by codes

a) variation of wind velocity with distance
above ground surface; (b) variation of wind
pressure specified by typical building codes
for windward side of building
a) uplift pressure on a sloping roof; (b)
Increased velocity creates negative pressure
(suction) on sides and leeward face

• Earthquake Forces
The ground motions created by major earthquake forces cause
buildings to sway back and forth. Assuming the building is fixed at its
base, the displacement of floors will vary from zero at the base to a
maximum at the roof. As the floors move laterally, the lateral bracing
system is stressed as it acts to resist the lateral displacement of the
floors. The forces associated are inertia forces and related with the
weight and stiffness of the structure.

(a) Displacement of floors as building sways;
(b) inertia forces produced by motion of floors

• In reinforced concrete structures, the structural system is monolithic.
That is, slabs, beams, columns and footings constitute a single three-
dimensional structure. This system deforms in three-dimensional space.
However, for the purpose of analysis, structural systems can suitably be
parted to simplify the analysis. For example, slabs of each floor are
analyzed separately. Frames, which are formed by the beams and the
columns in vertical plane, are analyzed separately as plane systems.

Mechanical Properties of Concrete
a) Properties in Compression
• Properties can be investigated best by crashing cylindrical
specimens under axial compression and drawing the stress-strain
diagram.
300mm
150mm

• A typical set of stress-strain curves of
concrete is:
0.001 0.002
( )
0.003
co


• Such a curve has initial elastic part (proportional limit: Fc =
Ec ec)
• At certain strain curve becomes nonlinear
• Reach to the maximum strength (compressive strength of
concrete eco=0.002 (app.)
• After peak point stress-strain diagram has a descending
part which ends by crashing.
• Approximately, strain when concrete crash is ecu=0.003

Classification of Concrete:
Concrete is classified according to compression
strength
TS 500 (Code of practice for reinforced cocrete
structures) indicates compressive strength as
characteristic strength, fck

Table 2.1 Concrete Classes and Strength Values
Concrete
class
Fck,
characteristic
cylindrical
compressive
strength
(N/mm2)
Equivalent
cubic
compressive
strength
(N/mm2)
Fctk,
characteristic
tensile
strength
(N/mm2)
Ec,
modulus of
elasticity
(28-D)
(N/mm2)
BS16 (C16) 16 20 1.4 27 000
BS18 (C18) 18 22 1.5 27 500
BS20 (C20) 20 25 1.6 28 000
BS25 (C25) 25 30 1.8 30 000
BS30 (C30) 30 37 1.9 32 000
BS35 (C35) 35 45 2.1 33 000
BS40 (C40) 40 50 2.2 34 000
BS45 (C45) 45 55 2.3 36 000
BS50 (C50) 50 60 2.5 37 000
C14, C16, C20 and C25 are normal strength concrete and others are
regarded as high strength concrete.

•Elasticity modulus of concrete at the age
of jth day can be calculated as:
)
/
(kg
140000
10270
)
/
(
14000
3250
2
2
cm
f
E
mm
N
f
E
ckj
cj
ckj
cj





(b) Properties in Tension:
Tension strength  in general, neglected in design since it is low
In many cases, tension strength has to be known (uncracked section analysis etc).
Test to get tension strength of concrete:
• Direct tension test
• Indirect tension test
• Plain concrete test of beams  modulus of rupture
• Cylinder splitting test 
P=applied load
d= diameter of the cylinder
l= length of the cylinder
dl
P
fcts

2


• Tensile strength id related to compressive strength.
TS 500 gives empirical formulas for the
characteristic tensile strength:
)
(kg/cm
1
.
1
)
(N/mm
35
.
0
2
2
ck
ctk
ck
ctk
f
f
f
f


From test results:
fctk=(strength obtained from split tests)/1.5
fctk=(Modulus of rupture)/2

Mechanical Properties of Steel
• In TS 500 mainly three grades of steel are specified:
S220 (BC I)
S420 (BC III)
S500 (BC IV)
Reinforcing bars can be grouped in two classes:
a) Hot rolled steel properties depends on chemical
composition. Larger strain capacity
b) Cold worked steel  worked steel in normal
temperature. Larger strength but less strain capacity
(ductility decreases)

• The surface of steel bars are:
• Smooth
• Deformed (generally used to increase the bond strength
between concrete and steel)
• In Europe bars are designated with their sizes
ϕ6, ϕ8, ϕ10, ϕ12, ϕ14, ϕ16, ϕ18, ϕ20, …. ,
ϕ40
Area of a single bar =
There are tables which gives directly area etc. of the
bars. For example see TABLE A-7 of your text book
4
2
D


When a member is subjected to bending crashing of concrete
is associated with the maximum strain reached at the extreme
fibers (not maximum stress). Maximum stress will reach to
adjoint fiber as strain increases.

SERVICEABILITY, STRENGTH AND SAFETY OF THE
STRUCTURE
• Any structure should not fail when subjected to service loads.
Service loads are the loads used in design. They should also be
reasonably safe. Excessive deformations of structural members,
even if they are strong enough may create problems under the
service conditions. Besides, cracks that form in the concrete
should be invisible, in some structures concrete should not crack
at all. For example, cracks are not desirable in water tanks, reactor
buildings etc. All these requirements are known as the
serviceability of the structure.

• There are a number of uncertainties in the analysis, design and
• construction processes. For this reason neither strength nor
• serviceability of a structure can be defined precisely. However
• as it will be explained later, a margin of safety may be provided
• for both strength and serviceability.
• The main reasons of uncertainties are listed below:
• Actual loads may be different than the assumed ones.
• Distribution of loads may be different than that assumed.
• Calculated load effects (stresses etc.) may be different than the actual effects because
of the assumptions and simplifications made in analysis.
• Actual behavior of the structure may not be as assumed.
• Errors may be made in the dimensions of the members during the construction.
• Errors may be made during the placing of reinforcement.
• Actual material strength may be different than the specified strength.
•
• Margin of safety of a structure should be related to the probable
results of a failure.

STATISTICAL APPROCH FOR SAFETY MARGIN
• Maximum load of a structural element during the lifetime of a
structure is not certain. Variation of the load may be
considered random and may be approximated in the form of a
frequency curve, as shown in Fig. 1.5.
Pk
Pm
f(P)
P
FIG. 1.5

Shaded area represents the probability of occurrence
of loads larger than Pk. Pm is mean value of loads. It
common practice to use a conservative value grater
than Pm in design. For example a characteristic value Pk
can be considered for this purpose. If standard
deviation is the following equation can be written as
Pk = Pm + u. (1.1)
u is a factor depending on the shaded area in Fig.1.5.
p

p


• TS 500, which is code of practice for the design of
reinforced concrete members, specifies the
characteristic load Pk as the load given by TS 498.
Therefore, the designer has not to use equation 1.1.
• Actual strength of material also differ from the
specified design strength. Therefore strength of
material is also considered as a random variable.
Variation of material strength may be approximated
by a frequency curve as shown in Fig. 1.6.

• Rk is the characteristic strength value whereas Rm is
the mean value. Shaded area represents the
probability of occurrence of strength values less than
Rk.
Rk Rm
f(R)
R
FIG. 1.6

Similar to equation 1.1 the following equation
can be given for Rk:
Rk = Rm – u. (1.2)
where is standard deviation for R.
depends on the degree of supervision and
inspection of production. u=1.28 in Turkey. For
the safety of structure Rk Pk if Rk and Pk are
selected as design values.
R

R

R



In Fig.1.7 this situation is shown where double shaded
area represents the probability of failure.
Pm Pk Rk Rm
FIG. 1.7

• Statistical calculation shows that the probability of failure is rather high if
Rk and Pk are used as design values. Hundred percent safety is not
possible but probability of failure can be reduced by increasing the
design value of load and decreasing the strength value. This can be
achieved by using appropriate factors. Dividing Rk by a factor greater
than 1 and multiplying Pk by a factor greater than 1 design values are
obtained. Considering economic results of collapses it is tried to achieve
a probability of failure as small as 10-5-10-7.

Reference
“Design of Structural Elements”
Third Edition
By
Chanakya Arya

Reinforced concrete Design-Chapter1.pdf pdf

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