Reinforced Concrete Design
SIMPLIFIED SUMMARY OF MAJOR TOPICS
(NSCP 2015)
Prepared by:
Engr. Ken Lua, MSCE
REINFORCED CONCRETE DESIGN
Major Topics:
Introduction to Reinforced Concrete Design Week 1
Structural Elements
Week 2, 3
Loads on Structures
Module 1
Beam Flexure
Singly Reinforced Beams
Week 4
Doubly Reinforced Beams
Beam Shear Week 5
Slab Design Week 6 Module 2
Monolithic Beams or T-Beams Week 7
Compression Members Week 8
Reinforced Concrete Detailing Week 9 Module 3
REINFORCED CONCRETE DESIGN
Quiz = Objectives
Course Requirements: HW = Problem solving
Introduction to Reinforced Concrete Design Week 1 Activity 1: Current knowledge and expectations
Structural Elements
Week 2 Quiz 1 - Introduction
Loads on Structures
Beam Flexure
Singly Reinforced Beams Week 3
Doubly Reinforced Beams Week 4 HW1 – Beam Flexure – Actual Design/Analysis
Beam Shear Week 5 Quiz 2 - Beams
Slab Design Week 6 HW2 – Beam Shear, Slab Design
Monolithic Beams or T-Beams Week 7
Compression Members Week 8 Quiz 3 – Columns
Reinforced Concrete Detailing Week 9
Week 10/11 Submission of Notes
PART 1: INTRODUCTION
Introduction to Reinforced Concrete Design
Structural Elements
Loads on Structures
INTRODUCTION
Concrete:
A mixture of sand, gravel, crushed rock,
or other aggregates held together in a
rocklike mass with a paste of cement
and water. Sometimes one or more
admixtures are added to change certain
characteristics of the concrete such as
its workability, durability, and time of
hardening.
INTRODUCTION
Reinforced Concrete:
A combination of concrete and steel
wherein the steel reinforcement
provides the tensile strength
lacking in the concrete.
Red – Main reinforcements (resists flexural
forces)
Silver – Stirrups / Shear reinforcements (resists
shear, used to hold main reinforcements
ADVANTAGES/DISADVANTAGES
Advantages Disadvantages
Good compressive strength per unit cost Low tensile strength
Great resistance to fire and water Low strength per unit weight leads to
heavy members
Low-maintenance
Low strength per unit volume leads to
Can be cast into variety of shapes larger members
Inexpensive local materials Large variance in concrete property
because of variations in its proportioning
Lower grade of skilled labor is required and mixing
OTHER TERMINOLOGIES Sand = fine aggregate
Gravel = coarse aggregate
Cement and Water
Used in binding aggregates (sand and gravel)
Water/cement ratio greatly affects the strength of concrete
Curing of Concrete
Curing is performed by submerging the specimen
underwater. This is done in order to prevent moisture loss.
Rapid moisture loss leads to cracking and loss of strength of
the concrete specimen
Ideally, the maximum strength of concrete is attained at the
28 th day of curing.
OTHER TERMINOLOGIES
Creep
Additional deformation because of the load applied
for a very long time.
Shrinkage of Concrete
Contracting of a hardened concrete mixture due to
the loss of water/moisture. Shrinkage or temperature
bars are used.
STRESS-STRAIN RELATIONSHIP
REINFORCED CONCRETE
STRESS-STRAIN RELATIONSHIP
STEEL REINFORCEMENT
ELASTIC MODULUS OF CONCRETE
fc’ : concrete strength, in MPa
ULTIMATE COMPRESSIVE
STRENGTH OF CONCRETE, f’c
- the load-carrying capacity of the uncracked portions of the concrete reaches a maximum value
Commercial Available fc’ of Concrete
17 MPa - Lowest value according to NSCP 2015
21 MPa - 3 ksi
28 MPa - 4 ksi
34 MPa - 5 ksi
CONVERSION : 1 ksi = 6.895 MPa
TYPES OF STEEL REINFORCEMENTS
STEEL REINFORCEMENTS
DESIGN APPROACH
WORKING STRESS DESIGN (WSD) METHOD
fy
The behavior of concrete is LINEAR ELASTIC.
fs
The consideration is up to the proportionality limit
ULTIMATE STRENGTH DESIGN (USD) METHOD
The behavior of concrete is NON-LINEAR ELASTIC.
The consideration is up to the ultimate strength.
DESIGN CODES
DESIGN CODES
Design codes provide detailed technical
standards and are used to establish the
requirements for the structure. It should be
realized, however, that codes provide only a
general guide for design.
DESIGN CODES
A code is a set of rules and specifications or systematic
procedures for design, fabrication, installation and
inspection methods prepared in such a manner that it can
be adopted by legal jurisdiction. Codes can be approved
by local, state or federal governments and can carry the
force of law.
Design codes provide detailed technical standards and are
used to establish the requirements for the actual structural
design. It should be realized, however, that codes provide
only a general guide for design.
“The ultimate responsibility for the design lies with
the structural engineer.”
National Structural Code of the Philippines 2015
PART 1: INTRODUCTION
Introduction to Reinforced Concrete Design
Structural Elements
Loads on Structures
STRUCTURAL ELEMENTS
A structure refers to a system
of connected parts used to
support a load. Important
examples related to civil
engineering include buildings,
bridges, and towers;
When designing a structure to
serve a specified function for
public use, the engineer must
account for its:
1. Safety – Stability, Strength
2. Serviceability
3. Economic Factors
4. Environmental Constraints
5. Aesthetics
SLABS
Slabs are flat horizontal panels that
support the floor. It can be supported by
beams/girders on edges or directly by
columns. They carry gravity loads and
transfer them to the vertical components
(columns and/or walls), and also act as
horizontal diaphragms by transferring the
lateral load to the vertical components of
a structure.
TYPES
1. One – way Floor System
2. Two – way Floor System
ONE-WAY SLABS
One-way floor system is a slab or deck that is
supported such that it delivers its load to the
supporting members by one-way action. It is
often referred to as a one-way slab.
One-way slab bends in only one direction along
the short span
TWO-WAY SLABS
Two-way floor system is a slab or deck that is
supported such that it delivers its load to the
supporting members by two-way action. It is
often referred to as a two-way slab.
Load is assumed to be delivered to the
supporting beams and girders in two directions
BEAMS AND GIRDERS
Beams are usually straight horizontal
members used primarily to carry vertical
loads. Quite often they are classified
according to the way they are supported, as
indicated the figure.
Beams are primarily designed to resist
bending moment; however, if they are short
and carry large loads, the internal shear force
may become quite large and this force may
govern their design.
BEAMS AND GIRDERS
BEAMS AND GIRDERS
Tension at the bottom Tension at the top
BEAMS – FAILURE TYPES
FLEXURE CRACKS
Originates in maximum moment region
because the flexural capacity of the
beam is inadequate
SHEAR CRACKS
Originates near supports because the
shear capacity of the beam is
inadequate
BEAMS – REINFORCEMENTS
BEAMS – REINFORCEMENTS
BEAMS – REINFORCEMENTS
BEAMS – MINIMUM DEPTH
COLUMNS
Members that are generally vertical and resist
axial compressive loads are referred to as
columns.
PART 1: INTRODUCTION
Introduction to Reinforced Concrete Design
Structural Elements
Loads on Structures
REVIEW OF LOADS AND LOAD PATH
LOAD DISTRIBUTION
P = pressure load
w = P*(s/2)
w = P*(s/2 + s/2)
Bea
ms
pac
ing
,S
LOAD DISTRIBUTION
One-way Slab (s/l ≤ 0.5)
ps/2
E F
psl/4 psl/4
LOAD DISTRIBUTION
Two-way Slab (s/l > 0.5)
W= PS/2
S
LOAD DISTRIBUTION
Two-way Slab
W=PS/2
S
W=PS/2
LOAD DISTRIBUTION
LOAD DISTRIBUTION
P = pressure load
s/2
Bea
mo
r Jo
s
ist
spa
cing
,S
LOAD DISTRIBUTION
s/2
w=P
Ps
w=
LOAD DISTRIBUTION
w
w
LOAD DISTRIBUTION
p = 5 kPa or kN/m2
300mm
150mm
S = 2m s s s l
s s
L = 3m BEAM 1
BEAM 2
w1
w1 = ps = 5(kN/m2) * 2(m) = 10kN/m
w2
w2 = ps/2 = 5(kN/m2) * 2(m) / 2 = 5 kN/m
BEAM FORMULAS WITH SHEAR AND MOM (linsgroup.com)
LOAD DISTRIBUTION
p = 5 kPa or kN/m2
s s s l
s s
BEAM 1
BEAM 2
