1. Presented by
Khandaker Mehedi Hasan
Student ID:10.01.03.158
Department of Civil Engineering
AUST,Dhaka
2. Course Teachers
Lecturer Mr. Galib Muktadir
Assistant prof. Ms. Sabreena Nasrin
Department of Civil Engineering
Ahsanullah University of science and Technology
3. A T-Beam is
a beam that
supports a
slab and the
slab is built
integrally
with the
beam.
4.
Concrete floor slabs and beams are normally tied
together by means of stirrups and bent-up bars if any and
then are cast form one mass of concrete. Such a
monolithic system will act integrally i.e., it is allowed to
assume that part of the slab acts with the beam and they
form what is known as a flanged beam, Fig. 1.1
The part of the slab acting with the beam is called the
flange, and it is indicated in Fig. 1.2 by the area Bts. The
rest of the section confining the area (t-ts)b is called the
stem or web. As Fig. 1.2 indicates.
Fig:1.1
Fig:1.2
5. Various Possible Geometries of
T-Beams
Single Tee
Twin Tee
Box
6. Square T beam
Tapered T beam
Inverted L(Spandrel) Beams
7. Analysis of Flanged
Section
Floor systems with slabs and beams are placed
in monolithic pour.
Slab acts as a top flange to the beam; Tbeams, and Inverted L(Spandrel) Beams.
8. Analysis of Flanged
Sections
Positive and Negative Moment Regions in a
T-beam
9. Analysis of Flanged
Sections
If the neutral axis
falls within the
slab depth
analyze the beam
as a rectangular
beam, otherwise
as a T-beam.
10. Analysis of Flanged
Sections
Effective Flange Width
Portions near the webs are more highly stressed
than areas away from the web.
11. ACI Code Provisions for
Estimating beff
From ACI 318, Section From ACI 318, Section
8.10.2
8.10
T Beam Flange:
beff
L
4
16hf
bactual
Isolated T-Beams
bw
hf
beff
bw
2
4bw
12. Design of T-Beam
T-Beam may be singly reinforced or doubly reinforced.
When steel is provided only in tensile zone (i.e. below
neutral axis) is called singly reinforced t-beam, but
when steel is provided in tension zone as well as
compression zone is called doubly reinforced t-beam.
The aim of design is:
To decide the size (dimensions) of the member and the
amount of reinforcement required.
To check whether the adopted section will perform
safely and satisfactorily during the life time of the
structure.
13. Methods of Design
Allowable Stress – WSD (ASD)
Examples:
WSD
Actual loads used to determine stress
Allowable stress reduced by factor of safety
Ultimate Strength – (LRFD)
Loads increased depending on type load
Ultimate Strength
Factors: DL=1.4 LL=1.7 WL=1.3
U=1.4DL+1.7LL
Strength reduced depending on type force
Factors: flexure=0.9 shear=0.85 column=0.7
14. Working Stress
Design(WSD) Method
Assumptions:
–
–
–
–
Plane sections remain plane
Hooke’s Law applies
Concrete tensile strength is neglected
Concrete and steel are totally bonded
Allowable Stress Levels
– Concrete = 0.45f’c
– Steel = 20 ksi for gr. 40 or gr. 50
= 24 ksi for gr. 60
Transformed Section
– Steel is converted to equivalent concrete.
15. Procedure for Design of Singly Reinforced
Beam by Working Stress Method
Given :
(i) Span of the
beam (l)
(ii) Loads on the
beam
(iii)Materials
Grade
of
Concrete
and
type of steel.
i.e. f'c & fy
16. Now,
Selecting
the
suitable diameter of bar
calculate the number of
bars required
As
Singly reinforced T-beam
17. Reasons for Providing
Compression Reinforcement
Reduced sustained load deflections.
Creep of concrete in compression zone
transfer load to compression steel
reduced stress in concrete
Architectural design & view
less sustained load deflection
18. Reasons for Providing
Compression Reinforcement
Effective of compression reinforcement on
sustained load deflections
19. Layout of doubly
reinforced T-beam
Doubly reinforced T-beam