Theory and Design of Structures I
Reinforced Concrete Design
Scope
• Rectangular singly and doubly reinforced beams
• Elastic design
• Limit state design concepts; material strength
and loading
• Flexural strength and shear strength of beams;
oneway slabs
References
1. BS8110: 1985, Structural use of concrete – Part 3: Design charts for
singly reinforced beams, doubly reinforced beams and rectangular
columns, BSI, London, 1985.
2. BS8110: 1997, Structural use of concrete – Part 1: Code of practice
for design and construction, BSI, London, 1997.
3. Code of practice for structural use of concrete 2004, second edition,
Buildings Department, Hong Kong, 2008.
4. Design of structural elements: concrete, steelwork, masonry and
timber design to British standards and Eurocodes, 2nd ed., C. Arya,
Spon Press, London, 2003.
5. Reinforced concrete design, 5th ed., W.H. Mosley, J.H. Bungey and
R. Hulse, Macmillan Press, Basingstoke, 1999.
6. Reinforced concrete designer’s handbook, 10th ed., C.E. Reynolds
and J.C. Steedman, E. & F.N. Spon, London, 1988.
7. Reinforced concrete design to BS8110: simply explained, A.H.
Allen, E. & F.N. Spon, London, 1988.
8. Structural design in concrete to BS8110, L.H. Martin, P.C.L.
Croxton and J.A. Purkiss, Edward Arnold, London, 1989.
Introduction
• Steel reinforcement is introduced into a concrete
beam mainly to carry tension, thereby resulting in a
reinforced concrete (RC) beam.
• Components: concrete and reinforcing bars (rebars)
Rectangular
beam
Tbeam
Tension
reinft.
Singly reinforced
beam
Tension
reinft.
Doubly reinforced
beam
Comp.
reinft.
Stirrup carrier or
link hanger
Stirrup or link
Introduction
Figure 1(a)
Plain concrete beam under loading.
f
c
f
c
′
b
d
Z = b d
2
/ 6
*
*
Compressive strength
Compression
Tension
Modulus of rupture
Cracks & collapses
!
Plain concrete beam
(Unreinforced concrete beam)
Introduction
Figure 1(b)
Reinforced concrete beam under loading.
T
Section
(cracked)
C
a
M
=
C
⋅
a
=
T
⋅
a
Compression
Tension
Neutral axis
Load increases
N.A.
Concrete cracks
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document• Distinct yield point
• Linear relationship within elastic range
• Beyond the yield point, plastic deformation
followed by work hardening
Properties of steel
stress
strain
Y.P.
Stressstrain curves for steel.
• No clearly defined yield point
• Portion of the curve below 1/3 of the ultimate
strength is nearly linear
• Beyond that, it becomes elastoplastic
Properties of concrete
strain
Stressstrain curves for concrete
Methods of design
1. Elastic theory (elastic method in CP114 and
previous HK codes)
2. Ultimate load / load factor method (load
factor method in CP114 and previous HK
codes)
3. Limit states design philosophy (BS8110,
CP110 and present HK concrete code)
Elastic design of an RC section
Elastic method
• At working load, the maximum stress in the
concrete is a certain fraction of the cube
strength and the maximum stress in the steel is
a certain fraction of the yield stress
At working load
≤
f
cu
/ (FOS)
conc
≤
f
y
/ (FOS)
steel
Elastic method
Assumptions:
• Plane sections remain plane after bending
• The materials are linearly elastic
• The tensile strength of concrete is ignored
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '10
 profchai
 Strength of materials, Tensile strength, Fst Stress distribution

Click to edit the document details