Association
of
Engineers
,
Gaza Governorates
,
Palestine
ADVANCES IN STRUCTURAL CONCRETE
Mohamed Ziara
Assoc. Prof.
Civil Eng. Dept.,
IUG
Consultant
Center for Engineering and Planning
(CEP)
2
7
March 200
5
2
1.
HISTORICAL DEVELOPMENT
OF STRUCTURA
L CONCRETE
O
ldest
concrete
from the Stone Age around
7000 B.C.
was discovered
in 1985
in
the
Southern Galilee, Palestine.
About
2000 B.C., lime mortar
was used in Crete.
In
third century B.C
., Romans
used
a fine
sandy volcanic ash
mixed with
lime
.
In
A.
D. 126
Romans built the
Pantheon concrete dome
of span
≥
40m.
In
1801
, Coignet published his statement of
principles of concrete construction
.
In
1848,
Lambot constructed a
boat of concrete reinforced with wire.
In
1854,
Wilkinson obtained a patent for a
reinforced concrete floor system
.
In
1861,
Coignet published a
book
illustrating
uses of reinforced concrete.
In
1867,
Monier patented
concrete containers reinforced with
metal frames.
In
1886,
Koenen published the
theory and design of concrete structures
.
In
1906,
Turner developed the first
slab without beams.
T
he
extensive use
of
structural
concrete
began at
the turn of the
twentieth century
where
lot of developments has occurred in the theory, design and construction
.
In
1904,
the first
set of buildin
g regulations
for
reinforced concrete
were
drafted
by
Professor M
ö
rsch of the University of Stuttgart.
Between
1907
and
19
10
,
design regulations for reinforced concrete
were
issued in Britain, Franc, Austria
,
Switzerland
, USA
.
By the year
1910
the
German
C
ommittee for Reinforced Concrete, the
American
Concrete Institute, the
British
Concrete Institute and the
Austrian
Concrete Committee were already established.
By
1920
many
reinforced
concrete structures
were already constructed.
As early as
1920,
the era
of
prestressed
concrete has
beg
u
n
with the pioneer
work Freyssinet.
From
1900
to
1950
the
working stress
method was used universally.
In
1938
u
ltimate strength
design method
was
codified in the
USSR
.
In
1956
u
ltimate strength
design methods were codified
in the
USA
and
UK.
Currently, Limit States Method
is used in most countries in the world.
New
constituent
materials
and
composites
of concrete have been used in the
construction industry for sometimes
(
high

strength concrete
exceeding
200MPa, high streng
th steel bars
and
welded wire fabric
(
exceeding
700
MPa
)
and
prestressing steel
of ultimate strength exceeding
2000MPa
)
.
3
2.
USE OF CONCRETE
Concrete is the dominant construction material in the world because of its
advantages characteristics that include:
E
conomy
(availability of its constituent materials)
.
Easy of
c
onstruction
(can be cast in
various
shape
s
, require simple skills)
.
Rigidity
(at working load conditions)
.
Fire
r
esistance.
etc.
C
oncrete posses some adverse characteristics such as
:
Weak tens
ile strength
(use reinforcing steel)
.
Low strength/weight ratio
(use high strength and light weight concrete)
.
Brittleness
(use confinement
).
Time

dependant volume change
(use expansion joints, non

expansive cement).
etc.
4
3.
MECHANICS OF REINFORCED CONCRET
E
Concrete
is strong in compression and
weak in tension
.
C
racks
develop
when
tension stresses
exceed
tensile strength of concrete
“
f
t
”
Tensile stresses may result from
loading, shrinkage or temperature changes.
Fig. 1 demo
nstrates the mechanics of reinforced concrete beams
.
Use of
longitudinal
and
shear reinforcement
to prevent the failure
. The
resulting
composite material
is called reinforced concrete.
F
ailure
may also be prevented
by
using
“prestressing tendons”
.
The re
sulting
composite material
is called
prestressed
concrete.
Different applications require
different
configuration of
steel reinforcement.
f
t
f
c
f
t
f
c
f
s
f
t
Fig. 1 Mechanics of reinforced concrete beams.
Brittle flexural failure of
Plain concrete beam.
Brittle
shear
failure of Plain
concrete beam.
Prevention of failure in
reinforced concrete beam
Prevention of failure in
prestressed concrete beam
Prestressing
fo
rce
5
4.
DESIGN OBJECTIVES
The structural design should satisfy structural and nonstructural requirements
in Fig.
2
.
Design Requirements
Structural Requirements
Non

Structural Requirements
Strength
Stability
Rigidity
Suitability
Economy
Maintainability
Fig. 2 Requirements of structural design.
6
5.
LIMI
T STATES DESIGN METHOD
T
he design requirements are satisfied using t
hree limit states
in Fig. 3.
A structure reaches its
limit state
when it becomes
unfit
for its use.
Ultimate limit state
is very important since it involv
es
structure
collapse
.
Thus, this limit state should have
low
probability of occurrenc
e.
The
design
is
carried out for the
ultimate limit state
.
T
hen the
serviceability
limit
state is
checked
.
The
special limit state
is considered in case of
abnormal
con
ditions.
Limit States
Serviceability
Limit State
Special Limit
State
Excessive
d
eflection
Excessive
c
rack
w
idth
Excessive
v
ibration
Ultimate
Limit State
Rapture
Progressive
c
ollapse
Instability
/
Loss
of
e
quilibrium
Fatigue
Plastic
m
echanism
Severe
e
arthquake
Explosion,
f
ire, etc.
Environmental
d
eterioration
Chemical
d
eterioration
Fig. 3 Limi
t States Design Method.
7
6.
UNIFIED DESIGN APPROACH FOR
STRUCTURAL CONCRETE
S
tructural concrete
is a unifying name for concrete used for structural
purposes including
plain, reinforced
and
prestressed
concrete.
Previous
research and developments
on structural concrete
h
a
ve
resulted in a
variety of design approaches and codes of practice.
T
he design approach for all types of concrete
(structural concret
e)
should be
consistent
and
unified
, i.e.
t
he unified approach to the design of structural
concrete
.
THE UNIFIED DESIGN
APPROACH
(UDA)
A
ll
regional and national
codes
should be
unified
.
Member
design should
replace
section
design.
More consideration
be given to
:
O
verall structural behavior
.
L
ogical structural systems
.
L
oad paths and flow of forces
.
D
esign concepts
.
Rigor
ous design models and detailing.
Deformation restraints
.
Multi

axial
state of
stress/strain
.
8
7.
BUILDING CODES
To ensure
public’s health and safety
the
design and construction
of buildings
is regulated using
municipal bylaws
called
“Building Codes”
.
Each c
ountry
should
have
or
adopt
its own building codes which then become
legal
documents.
Writing
of a code involves a
complex process
.
A number of
building codes
exist for
various applications
including fire
resistance, heat insulation, occupancy, formwork,
design of structural concrete,
etc.
For example
,
ACI
318
code or
BS 8110
are used for t
he design and construction
of
structural concrete.
The
se
codes give
specific requirements
for
material
,
structural analysis
,
member proportioning
,
construction practic
e
, etc.
O
fficial building codes
do
not
exist in the USA
for structural
concrete
.
A
number of
non

government
institutions
are responsible for developing and
producing the codes. The
ACI
takes the main role in producing the code
.
The
ACI code is regarded as
an
authoritative statement
of current good practice in
the field of reinforced concrete. It has been
incorporated
in a number of
municipal and regional building codes
that have
legal status
and thus the
ACI
code itself
attain a legal standing
. The
ACI
cod
e has also served as
a model
code for many countries in the
world.
Codes do
not substitute
for
sound engineering
judgment.
In many applications
,
codes serve as a guide
and
judgment
is made based on
full understanding
of
the
theory of reinforced concrete
a
nd
structural behavior of members at
material level.
However, this doe
s
not
mean that
E
ngineers
can
violate the code
requirements.
9
8.
STRUCTURAL SAFETY
Uncertainties in Resistance
V
ariability in
material strength
,
member
dimensions
and inaccuracy of
design
methods
.
Uncertainties in Load
By nature
actual loads can not be predicted accurately
. In addition,
mathematical
models
do not adequately represent
actual physical models
.
.
Consequence of Failure
The
level of safety
depends on
subjective factors
such as p
otential
loss of life, cost
of failure
and
type of failure
where sudden
brittle
failures need to be prevented
and alternative
load paths
and
load redistribution
need to be allowed.
The
safety
factors
are calculated following
a
probabilistic
approach
in Fig. 4.
In accordance with the
probabilistic
approach
absolute
safety
can
never
be
achieved
even if a large factor of safety was used in the
deterministic
design
approaches. The
probability
of
failure
can however be
reduced
by
increasing
the
resistance
or by
reducing
the
dispersion
of
resistance
.
f
x
(
X
)
Value (
X
)
Resistance (R)
Load (L)
Failure Area
L>R
Fig. 4 Possible combinations of load and resistance
10
9.
LOAD TYPES
Lo
ads can be classified as shown in Fig.
5
.
The following remarks are related to the type of loads:
C
reep
results from
permanent
loads plus
sustain
part of
variable
load
.
I
nfluence of
dynamic loads
can be considered by
multiplying
the
live load
by
impact factors or
by carrying out
dynamic analysis
.
In the
Ultimate Limit State
the
mean value
of the
maximum live
or
wind
load on the structure in its
lifetime
is considered.
In the
Serviceability Limit State
50%
to
60%
of the
mean
value
of the
maximum live
or
wind
load is considered.
For calculating the
sustained
load
deflection
20%
to
30%
of
specified live
load is considered (
ACI code considers the entire specified
live
load
which
result
s
in overestimating creep deflection of slender columns
).
Load
Permanent
(e.g. own wt.)
Accidental
(e.g. explosion)
Variable
(e.g. occupancy)
Sustain
(e.
g. furniture)
Short duration
(e.g. people)
Free
(e.g. traffic)
Fixed
(e.g. crane)
Fig.
5
Classification of loads.
Dynamic
(produce acceleration)
Static
(do not cause acceleration)
11
10.
LOADING SPECIFICATIONS
L
oads
may be
estimated based on the
ASCE Minimum Design Loads for
Buildings and Other Structures (ASCE 7)
formerly known as
ANSI A58.1.
ASCE 7 specifies dead loads
, live loads due to occupancy, snow loads (depend on
the
use categories
), roof loads, construction loads, wind loads (depend on the
use
categories
), earthquake loads (depend on the
use categories
) and other loads (e.g.
floods, soil loads, etc.).
The
Use C
ategories Are As Follows:
I.
Buildings and other structures that represent a low hazard to human life
at failure, e.g., warehouses and agricultural facilities.
II.
Buildings and other structures that do not fall into categories I, III or IV.
III.
Buildings and other s
tructures that represent a substantial hazard to
human life at failure, e.g., schools, buildings host chemical or explosive
materials.
IV.
Buildings and other structures designated as essential facilities, e.g.,
hospital, police stations, power

generating stat
ions, communication
centers, etc.
12
11.
STRENGTH DESIGN METHOD
IN ACI
“ACI 318

02/318R

02: Building Code Requirements for Structural Concrete
Commentary”.
Working
Load
s
>
Factored
Loads
Reduced
Strength
≥
Required
Strength
Design
Strength
≥
Or
Nominal
Strength
Fig.
6
Strength Design Method
.
13
12.
ADVANCES IN LOAD AND RESISTING FACTORS
IN ACI 318

02
Design Strength (Redu
ced Strength)
Design Strength =
Nmi湡l⁓瑲敮e瑨
S
trength reduction factors
“
´
ACI
9.3
):
㴠=⸹.
for
tension

controlled
sections
.
= 0.70
for
compression

controlled
sections with
spiral
reinforcement
= 0.65
for other
compression

controlled
s
ections
= 0.75
for
shear
and
torsion
= 0.65
for
bearing
on concrete
= 0.75
for
strut
–
and

tie
models
shall be
modified
for
earthquake
resisting
elements
(
ACI 9.3.4
)
.
Required Strength (U)
Load
factors
(
ACI
9.2
)
:
U = 1.4(D + F)
(ACI 9

1)
U = 1.2(D + F + T) + 1.6(L + H) + 0.5(L
r
or S or R)
(ACI 9

2)
U = 1.2D + 1.6(L
r
or S or R) + (1.0L or 0.8 W)
(ACI 9

3)
U = 1.2D + 1.6W + 1.0L + 0.5(L
r
or S or R)
(ACI 9

4)
U = 1.2D + 1.0E + 1.0L + 0.2S
(ACI 9

5)
U = 0.9D + 1.6W + 1.6H
(ACI 9

6)
U = 0.9D + 1.0E + 1.6H
(ACI 9

7)
M
odifications
to the
se
factors are
given in Code
for various loading conditions.
Example
:
U
for L and D
loading case
:
U = 1.2D + 1.6 L
(ACI 9

2)
14
13.
LOAD AND RESISTING FACTORS
IN ACI 318

02
APPENDIX
“C”
A
lternative
S
trength reduction factors
“
´
ACI
C
.3
)
:
㴠=⸹.
for
tension

controlled
sections
.
= 0.7
5
for
compression

controlled
sections with
spiral
reinforcement
= 0.
7
for other
compression

controlled
sections
= 0.
8
5
for
shear
and
tors
ion
= 0.
7
5
for
bearing
on concrete
= 0.
8
5
for
strut
–
and

tie
models
shall be
modified
for
earthquake
resisting
elements
(ACI
C
.3.4)
.
Alternat
!Unexpected End of Formula
Strength
“
U
”
(
ACI C.2
)
U = 1.4D + 1.7L
(C

1)
U = 0
.75(1.4D + 1.7L) + (1.6W or 1.0E)
(C

2)
U = 0.9D + (1.6W or 1.0E)
(C

3)
U = 1.4D + 1.7L + 1.7H
(C

4)
U = 0.75(1.4D + 1.4T + 1.7L)
(C

5)
U = 1.4(D + T)
(C

6)
U = 0.9D + 1.7H
(
In case
L
and
D
reduce effect of
H
)
U = 0.9D + 1.4
F)
(in case
L
and
D
reduce effect of
F
)
F
is
multiplied by
1.4
in
all
load combinations that include
L
.
Notation
D:
Dead load
E:
Seismic Load
F:
Fluid pressure load
H:
Earth pressure load
L:
Live load
L
r
:
Roof live load
R:
Rain load
S:
Snow load
T:
Cum
ulative effects of differential settlement, creep, shrinkage,
expansion or temperature change
U:
Required strength
W:
Wind load
15
14.
ADVANCES IN FLEXURAL THEORY IN ACI 318(02)
Types of Sections
ε
y
≈
0.002
0.002<
ε
s
<0.00
5
ε
s
≥
0.00
5
ε
s
=0.004
ε
s
<0.002
ε
s
=0.004
Over

reinforced brittle sections
ε
s
<0.00
4
ε
s
≥
0.00
4
Under

reinforced
ductile sections
ε
c
=
0.00
3
ε
c
=
0.00
3
ε
c
=
0.00
3
ε
c
=
0.00
3
ε
c
=
0.00
3
Compression

controlled
section
Tension

controlled
section
Balanced
section
Transition
section
Transition
section
Fig.
7
Types of sections
.
16
15.
STRENGTH REDUCTION FACTOR “
´
0.65
0.9
0.002
0.00
5
ε
s
0.004
Beams
Fig.
8
Strength reduction factor
.
17
16.
LONGITUDINAL REINFORCEMENT RATIOS
y
y
c
b
f
f
f
y
s
600
600
85
.
0
1
)
(
y
c
f
f
s
1
)
004
.
0
(
max
364
.
0
y
c
f
f
s
1
)
005
.
0
(
319
.
0
For:
=
b
balanced section
㸠
b
compression

controlled section
≤
)
005
.
0
s
(
tension

controlled section
b
<
<
)
005
.
0
(
s
transition
section
㸠
max
b
rittle behavior
For design of beams:
≤
max
ductile behavior
≥
y
y
c
f
f
f
4
.
1
4
min
ductile behavior
18
17.
EXAMPLE
Find
M
u
for the shown section
Assume tension

controlled s
ection
*
From Equilibrium
C
=
T
b
f
.
f
A
a
c
y
s
85
0
=
73.4
mm
c = a/
1
= 86.4 mm
From strain diagram
ε
s
=
0.01
> 0.005
assumption is ok.
f
s
= f
y
and
㴠=⸹
*
Or
:
Check for
≤
(ε
s
=0.005)
0069
.
0
440
*
200
201
*
3
0131
0
414
20
85
0
319
0
005
0
.
.
*
.
ρ
)
.
(
ε
s
≤
(ε
s
=0.005)
tension

controlled section
)
2
(
a
d
T
M
M
n
u
kN.m
5
.
90
)10
2
73.4
414(440
*
201
*
3
*
0.9
Μ
6
υ
Check
y
y
c
f
f
f
4
.
1
4
min
ρ = 0.0069 > ρ
min
= 0.0034
ok
ε
s
ε
c
=0.003
f
s
0.85
c
f
C
T
200mm
440
c
a
a/2
c
f
=20 MPa
f
y
=414 MPa
3
16
19
18.
ULTRA HIGH STRENGTH CONCRETE
General Properties of the
UHPC
Ultra High Performance concrete
(
UHPC
)
is
a high strength, low porosity
and ductile material.
UHPC is made with
Portland cement, silica fume, quartz flour, fine silica
sand,
high range
water reducer
and
steel or organic
fibres
with very
low
w/c
ratio
.
The
absence of coarse aggregate
is a key asp
ect to
reduce
the
heterogeneity
between the cement matrix and the aggregate.
The
cement content
is more than
1000
kg/m3.
The
density
is high more than
260
0 kg/m3.
The
ductility
is improved by using steel micro
fibres
.
The
compressive strength
is more th
an
200
MPa.
The flexural strength is more than
50
MPa.
It is possible to produce concrete with a strength as high as
700 MPa
in the
laboratory
.
The use of
UHPC
may allow the
elimination
of the
reinforcing steel
.
UHPC
meets all
eight performance criteria
for high performance concrete:
freeze

thaw durability, scaling resistance, abrasion resistance, chloride
penetration, compressive strength, modulus of elasticity, shrinkage, and
creep
.
UHPC
is a milestone on the way towards
no

maintenance
constructions.
T
he
material
itself is
av
ail
abl
e
and the problem is the ease of
application
and the
price
.
Typical Composition of UHPC
Material
Percent by Weight
Portland
Cement
28.7
Fine Sand
41.1
Silica Fume
9.3
Ground Quartz
8.5
Superplasticize
r
0.5
St
eel Fibres
6.4
Water
5.5
20
Design Properties of UHPC
Valid design
rules
for UHPC
do not
yet
exit
.
A work group of the
German Commission on Reinforced Concrete
has
presented a state of the art report on UHPC. Some of the
main aspects
are:
The Modulus
of elasticity “E
c
” for UHPC
or
E
c
= 16.364 Ln (
f
c
)
–
34.828 (10
3
N/mm
2
)
Behaviour Under Compression
UHPC shows a
linear
elastic behavior Until about 70 to
80 %
of
f
c
.
The
failure
of UHPC
without fibres
is of
explosive
nature.
No descending
branch in
the stress

strain

diagram does exist.
Behavior in Tension
Tensile
strength values may reach
15
MPa.
The
slope
of the
descending
branch depends on the fibre
orientation
,
content
and
type
.
21
Shear Resistance of UHPC Structural Elements
Tests proved th
at it is very
effective
to use steel
fibres as a shear
reinforcement
instead of stirrups
.
Shear failure pattern of the test specimens
A model for the
shear
force capacity of HPC

beams
without shear reinforcement
(stirrups) has been proposed by Zink su
ch as:
22
Flexural Design of UHPC Beams
Compressive stress distribution
for UHPC is
trapezoidal
.
ACI
Block
can be used
for strength up to
80
MPa.
Limiting compressive strain
The constant value of strain at extreme concre
te compression fiber of
0.003
prescribed by
ACI 318
represent
s
satisfactorily
the experimental results for
high

strength
as well as lower

strength concrete, although it is
not as
conservative
for
high

strength concrete.
k
3
f
c
c
c
d
T
=A
s
f
y
C=
k
1
k
2
f
c
bc
k
2
c
α
f
c
c
T
=A
s
f
y
T
=A
s
f
y
C=
0.85
f
c
bc
γ
C=
(1
+
)/2
f
c
bc)
Actual for NSC
Block for
NSC
Trapezoidal for
UHPC
23
19.
STRUT

AND

TIE MODELS
Background
The
strut

and

tie
method
is based on the
truss analogy
used
for
shear design of
B

r
egions
shown in Fig.
9
.
The
strut

and

tie
model
is
used to idealize the
flow of force
in a
cracked
concrete
beam.
Marti
and
Schlaich
et al. promoted the use of
t
he strut

and

ti
e method
for
design of
D

Regions
.
V
s
V
s
V
s
V
s
Actual beam
Truss analogy
Fig. 9 Tr
uss analogy for shear.
24
20.
B

AND D

REGIONS
B

(Beam or Bernoulli)
Regions
B

Regions are parts of a structure in which
B
ernoulli's hypothesis of
straight

line
strain
profiles applies.
D

(Disturbed or Discontinuity)
R
egions
D

Regions
are parts of a structure with a
complex variation
in
strain
.
D

Regions include portions near
abrupt
changes in
geometry
(geometrical
d
iscontinuities) or
con
centr
ated forces
(statical
d
iscontinuities).
St. Venant's
P
rinciple
T
he extent of
a
D

Region
spans about
one section depth
of the region on
either
side
of the discontinuity
as shown in Fig. 10
.
Fig. 10 B

and D

regions.
25
21.
GENERAL NOTES ON STM
B

Regions
are
adequately
designed
based on
conventional
models, e.g.
design
for
flexure
is based on conventional
beam theory
and
the design for
shear
is
based on the
truss analogy
.
Previous c
ode
provisions provide
d
little guidance
for design of most types of
D

Regions
such as
deep beams, corbels, beam

column
joints,
and pile
caps
.
D

Regions
were
designed by
empirical approaches
or by using
common
detailing practices
.
The
STM
is emerging as a
code

worthy methodology
for the design of all types
of
D

Regions
in
structural concrete
.
A
lthough the
STM
is equally
a
pplicable
to both
B

and
D

Region problems, it
is
not practical
to apply the
STM
method to
B

Region problems.
,
26
22.
STM DESIGN CONCEPT
STM
is
a
truss model
of a member that is made of
struts
,
ties
and connected at
nodes
capable of transmitting the loads to
supports.
Simple STM is shown in Fig. 11.
Types of Nodes
Types of Struts
C
C
C
C
C
C
T
T
T
T
T
T
CCC Node
TTT Node
CCT Node
CTT Node
Strut
Tie
Node
Prismatic
Bottle
Fan
Fig. 11 Strut and Tie Model (STM).
27
23.
DESIGN PRO
CESS
The design process using STM involves five major steps
that are illustrated for
dapped

ended beam in Fig. 12.
1.
Define the
boundarie
s
of the
D

Region
and determine the
boundary forces
.
2.
Sketch the
truss
and
solve
for the truss member
forces
.
3.
Select
steel
reinforc
ement
that is
properly
anchored
in
to
the
nodes
to provide
the necessary
tie
capacity
.
4.
Evaluate the
dimensions
of the
struts
a
nd
nodes
to carry the forces.
5.
Provide
distributed reinforcement
to ensure
ductile
behavior of the
D

Region
.
Fig. 12 Design steps of STM.
28
24.
STRENGTH OF MODEL MEMBERS
(
ACI 318

02 Appendix A
)
Strength of Struts
F
u
≤
F
n
s
F
ns
= f
cu
A
c
Where
= 0.75
s
= 1
.0
for prismatic struts in
uncracked
compression zones.
= 0.4
for struts in
tension
member
s.
= 0.
75
for
bottle shaped struts
with
crack control reinforcement
*
.
= 0.6
for all other cases.
*
C
rack control reinforcement
=
= steel ratio of reinforcement crossing the strut under review
.
= angle between the axis of the strut and the bars.
Strength of
Node
s
F
u
≤
F
nn
F
nn
= f
cu
A
n
Where
= 0.75
n
= 1
.0
for
nodes bounded by struts and/or bearing areas.
= 0.
8
for
nodes
anchor only one tie
.
= 0.6
for nodes
anchor
more than
one tie
.
Strength of
Ties
F
u
≤
F
nt
F
nt
= f
y
A
s
Where
= 0.75
29
25.
DESIGN EXAMP
LE: DEEP BEAM
and
Check Bearing Strength
Bearing strength at points of loading
=
= 0.75(0.85)(25)(1.0)(450)(500)/1000
= 3586 kN > 1600 kN
OK
B
earing strength at s
upports
=
= 0.75(0.85)(25)(0.80)(450)(500)/1000
= 2868 kN > 1600 kN
OK
Strut

and

Tie Model
30
Member Forces and Dimensions
Note that t
he entire
deep beam
is a
disturbed
D

re
gion
.
F
BC
=
F
AD
=
1850
kN
,
F
BC
=
2444
kN
Check capacity of
“
prismatic
”
strut
BC
:
= 0.75(0.85)(1.0)(25)(500)(240
#
)/1000
=
= 1912 kN
OK
#
width of strut
.
Check Capacity of
bo
ttled

shape
strut AB:
= 0.75(0.85)(0.75)(25)(500)(476)/1000
= 2885 kN > 2444 kN
OK
Use crossing vertical and horizontal
(
1 #13 on each face at
s
h
= 300 mm) and
vertical (
1 #16 on each face at
s
v
= 300 mm)
reinforcement in this strut (
s
= 0.75
).
= 0.00312 > 0.003
OK
Tie
AD
:
Use
2 layers of 5 #29 bars = 6450 mm
2
@ 80 mm and 220 mm from bottom
.
31
26.
SPECIAL ADVANCES IN STRUCTURAL CONCRETE
1.
Mohamed Ziara,
“
Structural Reha
bilitation of Reinforced Concrete Water
Tanks
,”
The Ninth Arab Structural Engineering Conference (9ASEC),
November 29

December 1, 2003, Abu Dhabi, United Arab Emirates, pp 479
–
486.
2.
Mohamed Arafa and Mohamed Ziara,
“Non

Linear Finite Element Analysis
of R
C Beams With Special Detailing of Stirrups,”
Proceedings of the
International Conference on Engineering and City Development, the Islamic
University, 22

23 September 2003, Gaza, Palestine, pp C

038

C050.
3.
Mohamed M. Ziara, Hasan S. Dweik and Mohammed S.
Hadidoun,
“Engineering Properties of Concrete made with Ground Melamine

Formaldehyde Thermosetting Plastics as Sand Replacement,”
The Sixth
International Conference on Concrete Technology for Developing Countries,
Amman, Jordan,
21

23 October 2002
.
4.
Moham
ed M. Ziara and David Haldane,
“Flexure

Shear Model for
Prevention of Diagonal Failures in Beams Made with High Strength
Concrete,”
The Eighth East Asia

Pacific Conference on Structural
Engineering and Construction: Challenges in the 21
st
Century, Singapor
e,
5

7
December 2001
.
5.
Mohamed M. Ziara,
“Structural Upgrading of RC Beams Using Composite
Overlays,”
Journal of Construction and Building Materials, UK, Vol. 14, No.
8,
December 2000,
pp. 397

406.
6.
Mohamed M. Ziara, David Haldane and Stuart Hood,
“Proposed
Changes to
flexural Design in BS 8110 to Allow Over

Reinforced Sections to Fail in a
Ductile Manner,”
Magazine of Concrete Research (London), UK, Vol. 52,
No. 6,
December 2000,
pp. 443

454
.
7.
Mohamed M. Ziara,
“The Use of Under, Over and Highly

Over Reinforc
ed
Flexural Members Made With Normal And High Strength Concrete,”
The
4
th
Technical Congress, Advances in Civil Engineering, Gazimagusa, TRNC,
1

3 November 2000.
8.
D. Haldane and Mohamed M. Ziara,
“Strengthening of Reinforced Concrete
Girders with
"
Π
"
and
"T"
Cross Sections,”
The Institute of Civil
Engineering, Structures and Building Journal, UK,
Vol. 140,
Feb. 2000,
pp.
61

72.
9.
Mohamed M. Ziara, David Haldane and A. S. Kuttab,
“Prevention of
Diagonal Tension Failures in Beams Using a Flexural

Shear
Interaction
Approach,”
Magazine of Concrete Research (London),
UK,
Vol. 51, No. 4,
August 1999
, pp. 275

289.
32
10.
S. Jada and Mohamed M. Ziara
“Repair and Strengthening of Slabs Using
Bonded Concrete Overlays,”
IABSE Symposium, Long

Span and High

Rise
Structure
s, Kobe, Japan,
September 2

4, 1998
, pp. 373

375.
11.
Mohamed M. Ziara, R. Rustom, M. El

Bayya and A. Amer,
“Codes,
Standards and Regulations in Palestine,”
The Reconstruction of Palestine:
Issues, Options, and Strategies, edited by A. B. Zahlan, Published by
Kegan
Paul International, London and New York,
1997,
pp. 71

79.
12.
Mohamed M. Ziara,
“The Strength and Ductility of Structural Concrete
Members in Earthquake Regions,”
First Palestinian Symposium for
Earthquake Hazard Mitigation, An

Najah National University,
Nablus,
Palestine,
18

20 June 1996
.
13.
Mohamed M. Ziara, D. Haldane and A. Kuttab,
“Flexural Behavior of Beams
with Confinement,”
American Concrete Institute ACI, Structural Journal,
USA,
Vol. 92, No. 1,
January

February 1995
, pp. 103

114.
14.
Mohamed M. Ziara,
D. Haldane and A. Kuttab,
“Shear and Flexural
Strengths Resulting from Confinement of the Compression Region in
Circular Section Structural Concrete Beams,”
Magazine of Concrete
Research
(London), UK, Vol. 45 (No. 164),
September 1993
, pp. 211

219.
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