Question

A T-beam roof section has the following particulars:

Thickness of slab : 100mm
Width of rib : 300mm
Depth of beam : 500mm
Centre to centre distance of beams : 3.0 m
Effective span of beams : 6.0m
Distance between points of contraflexur :3.60m

The effective width of flange of the beam is

• A. 3000mm
• B. 1900mm
• C. 1600mm
• D. 1500mm

Answer 1

The correct option is D 1500mm

Effective width

(i) For T-beams $b_f=\frac{L_0}{6}+b_w+6D_f\ngtr b$

(ii) For inverted L-beam

$b_f=\frac{L_0}{12}+b_w+3D_f\ngtr b$

(iii) For isolated T-beam

$b_f=\frac{L_0}{\left(\frac{L_0}{b}\right)+4}{b}_w$

(iv) For isolated L-beam

$b_f=\frac{0.5L_0}{\left(\frac{L_0}{b}\right)+4}{b}_w$

$b_f\to$ effective width of flange

$L_0\to$ distance between points of zero moments (points of constaflexure) which may be taken as 0.7 times the effective span for continuous beams and for beams in frames

$b_w\to$ breadth of web

​​​​​​​$D_f\to$ thickness of flange

​​​​​​​$b\to$ actual width of flange which is equal to breadth of web plus half the sum of the clear distance between the beams on the either side.

$b=300+2700=3000mm$

$L_0=3600mm$

$b_w=300mm$

$D_f=100mm$

$\therefore b_f=\frac{3600}{6}+300+6\times 100=1500mm$