As-salamu alaykum
Welcome to the presentation on “T Beam Design: Singly & Doubly by USD method” Presented By -
S. M. Rahat Rahman
ID: 10.01.03.104
1.Contents :
USD (Ultimate Strength Design Method)
T-beam
T - Beam acts Like Singly Reinforced Beam
T – Action vs rectangular Action
Effective Flange width of t-beam
Strength analysis
Nominal moment for t section
2. USD : Based on the ultimate strength of the structure member assuming a failure condition , due to concrete crushing or yielding of steel. Although there is additional strength of steel after yielding (strain hardening zone) which will not be considered in the design.
Actual loads are multiplied by load factor to obtain the ultimate design loads. ACI code emphasizes this method.
3. T Beam : For monolithically casted slabs, a part of a slab act as a part of beam to resist longitudinal compressive force in the moment zone and form a T-Section. This section form the shape of a "T“ . It can resist the longitudinal compression
4. Occurrence and Configuration of T-Beams
• Common construction type
• The slab forms the beam flange, while the part of the beam projecting below the slab forms is what is called web or stem.
5. Singly Reinforced Reinforcement is provided in tension zone only
6. Doubly Reinforced > Concrete can not develop the required compressive force to resist the maximum bending moment
> Reinforcement is provided in both compression and tension zone.
7. T-Beam Act As a Singly Reinforced Beam
8. Continuous T Beam :
When T-shaped sections are subjected to negative bending moments, the flange is located in the tension zone. Since concrete strength in tension is usually neglected in strength design, the sections are treated as rectangular sections.
On the other hand, when sections are subjected to positive bending moments, the flange is located in the compression zone and the section is treated as a T-section.
9. Effective Flange Width
10. Strength analysis of T beam
11. Analysis of T beam
12. T Beam moment calculation
1. AHSANULLAH UNIVERSITY OF
SCIENCE & TECHNOLOGY
DEPARTMENT OF CIVIL ENGINEERING
CE-416
PRE-STRESSED CONCRETE LAB
SESSIONAL
PRESENTED BY:
S. M. RAHAT RAHMAN
ID NO:10.01.03.044
COURSE TEACHERS:
MUNSHI GALIB MUKTADIR
SABREENA NASRIN
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4. Assuming tensile failure condition
Additional strength of steel after yielding
ACI code emphasizes this method.
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5. Concrete beams are often casted integrally with the slab and
formed a “T” – shaped beam.
These beams are very efficient .
Here slab portion carries the compressive load and web portion
carries the tension .
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6. Occurrence and Configuration of T-Beams
• Common construction type
• The slab forms the beam flange, while the part of the beam projecting
below the slab forms is what is called web or stem.
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11. T Versus Rectangular Sections
When T-shaped sections are subjected to negative
bending moments, the flange is located in the tension
zone. Since concrete strength in tension is usually
neglected in strength design, the sections are treated
as rectangular sections.
On the other hand, when sections are subjected to
positive bending moments, the flange is located in the
compression zone and the section is treated as a Tsection.
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12. From ACI 318, Section 8.10.2
Effective Flange Width :
Condition 1
For symmetrical T-Beam or having slab on both sides
a) 16 hf + bw
b) Span/4
c) c/c distance
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13. From ACI 318, Section 8.10.2
Effective Flange Width :
Condition 2
Beams having slabs on one side only
a) bw + span/12
b) bw + 6hf
c) bw + 1/2 * beam clear distance
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14. From ACI 318, Section 8.10.2
Effective Flange Width :
Condition 3
Isolated T Beam
a) beff ≤ 4 bw
b) hf ≥ bw/2
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18. ANALYSIS OF T-BEAM
Analysis of T-Beams - ( a > hf)
Consider the total section in two parts:
1) Flange overhangs and corresponding steel;
2) Stem and corresponding steel;
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19. T BEAM MOMENT CALCULATION
εc=0.003
0.85fc’
a/2
hf
C
c
For :
a
hf
d
d-a/2
As
T
Strain Diagram
Mn
M n1
M n2
Stress Diagram
M n1 M n2
As
Asf f y d
Asf f y d
hf
2
a
2
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20. T BEAM MOMENT CALCULATION
Part-1
0.85 fc’ bw a = As1 fy
Where,
As1 = As – Asf
As2 = Asf
Part-2
0.85 fc’ (b-bw) hf = As2 fy
0.85 fc’ bw a + 0.85 fc’ (b-bw) hf = As fy
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Based on the ultimate strength of the structure member assuming a failure condition , due to concrete crushing or yielding of steel. Although there is additional strength of steel after yielding (strain hardening zone) which will not be considered in the design.Actual loads are multiplied by load factor to obtain the ultimate design loads. ACI code emphasizes this method.
DefinitionFor monolithically casted slabs, a part of a slab act as a part of beam to resist longitudinal compressive force in the moment zone and form a T-Section. This section form the shape of a "T“ Concrete beams are often poured integrally with the slab, forming a much stronger “T” – shaped beam. These beams are very efficient because the slab portion carries the compressive loads and the reinforcing bars placed at the bottom of the stem carry the tension. A T-beam typically has a narrower stem than an ordinary rectangular beam. These stems are typically spaced from 4’-0” apart to more than 12’-0”. The slab portion above the stem is designed as a one-way slab spanning between stems.
Occurrence and Configuration of T-Beams• Common construction type.- used in conjunction with either on-way or two-way slabs.• Sections consists of the flange and web or stem; the slab forms the beam flange, whilethe part of the beam projecting below the slab forms is what is called web or stem.
A singly reinforced beam is one in which the concrete element is only reinforced near the tensile face and the reinforcement, called tension steel, is designed to resist the tension.
A doubly reinforced beam is one in which besides the tensile reinforcement the concrete element is also reinforced near the compressive face to help the concrete resist compression. The latter reinforcement is called compression steel. When the compression zone of a concrete is inadequate to resist the compressive moment (positive moment), extra reinforcement has to be provided if the architect limits the dimensions of the section.
T- versus Rectangular SectionsWhen T-shaped sections are subjected to negative bending moments, the flange is located in the tension zone. Since concrete strength in tension is usually neglected in strength design, the sections are treated as rectangular sections of width w b . On the other hand, when sections are subjected to positive bending moments, the flange is located in the compression zone and the section is treated as a T-section.
T- versus Rectangular SectionsWhen T-shaped sections are subjected to negative bending moments, the flange is located in the tension zone. Since concrete strength in tension is usually neglected in strength design, the sections are treated as rectangular sections. On the other hand, when sections are subjected to positive bending moments, the flange is located in the compression zone and the section is treated as a T-section.
For symmetrical T-Beam or having slab on both sides a) 16 hf + bw b) Span/4 c) c/c distance (smallest value should be taken)
Beams having slabs on one side only a) bw + span/12 b) bw+ 6hf c) bw+ 1/2 * beam clear distance (smallest value should be taken)
Isolated T Beam a) beff ≤ 4 bw b) hf ≥ bw/2 (smallest value should be taken)
Analyse as a rectangular beam of width𝑏=𝑏𝑒𝑓𝑓𝑀𝑛= 𝐴𝑠 𝑓𝑦 (𝑑− 𝑎2)Analyse as a rectangular beam of width 𝑏=𝑏𝑒𝑓𝑀𝑛= 𝐴𝑠 𝑓𝑦 (𝑑− 𝑎/2)
T beam may be treated as a rectangular if stress block depth a ≤ hfand as a T beam If a >hf .Nominal moment , Mn = 𝐴𝑠 𝑓𝑦 (𝑑 − 𝑎2)T beam may be treated as a rectangular if stress block depth a ≤ hfand as a T beam If a >hf .Nominal moment , Mn = 〖 𝐴〗_𝑠 𝑓_(𝑦 )(𝑑 − 𝑎/2)
T beam may be treated as a rectangular if stress block depth a ≤ hfand as a T beam If a >hf .Nominal moment , Mn = 𝐴𝑠 𝑓𝑦 (𝑑 − 𝑎2)T beam may be treated as a rectangular if stress block depth a ≤ hfand as a T beam If a >hf .Nominal moment , Mn = 〖 𝐴〗_𝑠 𝑓_(𝑦 )(𝑑 − 𝑎/2)