T Beam USD

AHSANULLAH UNIVERSITY OF SCIENCE & TECHNOLOGY

DEPARTMENT OF CIVIL ENGINEERING

CE-416PRE-STRESSED CONCRETE LAB

SESSIONAL

PRESENTED BY:S. M. RAHAT RAHMAN

ID NO:10.01.03.044

COURSE TEACHERS:MUNSHI GALIB MUKTADIR

SABREENA NASRIN

T BEAM DESIGN : SINGLY & DOUBLY : USD

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

CONTENTS

ULTIMATE STRENGTH DESIGN(USD)

Assuming tensile failure condition

Additional strength of steel after yielding

ACI code emphasizes this method.

T-BEAM

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 .

T-BEAM

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.

SINGLY REINFORCED BEAM

Tension Zone

Compression Zone

Figure : Singly Reinforced Beam for positive moment condition

DOUBLY REINFORCED BEAM

Figure : Doubly Reinforced Beam for positive moment condition

Compression Zone

Tension Zone

T BEAM BEHAVES AS SINGLY REINFORCED BEAM

CONTINUOUS T-BEAM

T-Action

Rectangular

CONTINUOUS T-BEAM

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 T-section.

EFFECTIVE FLANGE WIDTHFrom 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

EFFECTIVE FLANGE WIDTHFrom 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

EFFECTIVE FLANGE WIDTHFrom ACI 318, Section 8.10.2

Effective Flange Width :Condition 3

Isolated T Beam

a) beff ≤ 4 bw

b) hf ≥ bw/2

T - SECTION (STRENGTH ANALYSIS)

Strength Analysis :

1st case : (N.A. is with in the flange)

Analyseas a rectangular beam of width

=

T-SECTION (STRENGTH ANALYSIS)

Case 1 : (N. A. is with in Flange)

hf

Strain Diagram Stress Diagram

T-SECTION (STRENGTH ANALYSIS)

Case 2 : (N. A. is with in Web)

ANALYSIS OF T-BEAM

18

Analysis of T-Beams - ( a > hf)

Consider the total section in two parts:

1) Flange overhangs and corresponding steel;2) Stem and corresponding steel;

εc=0.003

d

c

0.85fc’

a/2

d-a/2

C

T

Strain Diagram Stress Diagram

As

hf

n n1 n2

n1 s sf y

fn2 sf y

2

2

M M M

aM A A f d

hM A f d

T BEAM MOMENT CALCULATION

For : fha

T BEAM MOMENT CALCULATION

Part-1

0.85 fc’ bw a = As1 fy

Part-2

0.85 fc’ (b-bw) hf = As2 fy

0.85 fc’ bw a + 0.85 fc’ (b-bw) hf = As fy

Where,

As1 = As – Asf

As2 = Asf

Thank you

ANY QUESTION ?