Identify the CORRECT definition of clear span among the given options.

a) The distance between the two inside surfaces of the span supports for beams

b) The distance between top surface of a column to its centre of gravity

c) The distance between top flange to neutral axis of beams

Concept

Effective span

A. Simply supported beams and slabs (leff)

\({{\rm{l}}_{{\rm{eff}}}} = {\rm{minimum}}\left\{ {\begin{array}{*{20}{c}} {{l_o} + w}\\ {{l_o} + d\;} \end{array}} \right.\)

Here, lo = clear span = distance between the inside surfaces of the span supports for beam (see figure below )

w = width of the support

d = depth of beam or slab

B. For continuous beam

i) If the width of support \( < \frac{1}{{12}}\) of clear span

\({{\rm{l}}_{{\rm{eff}}}} = {\rm{minimum}}\left\{ {\begin{array}{*{20}{c}} {{l_o} + w}\\ {{l_o} + d\;} \end{array}} \right.{\rm{\;}}\)

ii) If the width of support \(> \frac{1}{{12}}\) of clear span

a) When one end fixed other end continuous or both end continuous.

\({{\rm{l}}_{{\rm{eff}}}} = {{\rm{l}}_{\rm{o}}}\)

b) When one end continuous and another end simply supported.

\({{\rm{l}}_{{\rm{eff}}}} = {\rm{minimum}}\left\{ {\begin{array}{*{20}{c}} {{l_o} + \frac{w}{2}}\\ {{l_o} + \frac{d}{2}\;} \end{array}} \right.{\rm{\;}}\)

C. Cantilever

i)

\({l_{eff}} = {l_o} + \frac{d}{2}\)

ii)

\({l_{eff}} = \left( {{l_o} + \frac{w}{2}} \right)\)

The effective span for a cantilever slab at the end of a continuous slab is equal to the length up to the centre of the support or the length up to face of support plus half of the effective width.