F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

Problems 329
Problems
8.1 In yield-line analysis, where a slab is reinforced with both top and
bottom reinforcements, the assumption is made that the sagging yield
moment m may be calculated from the bottom steel A. by ignoring the
existence of the top steel; similarly, it is assumed that the hogging yield
moment may be calculated from the top steel A~ by ignoring the existence
of the bottom steel. Comment critically on the error introduced by this
assumption, which amounts to ignoring completely any interaction
between the top and bottom reinforcement bars.
Ans.
See Example 8.4-4 if necessary.
8.2 An isotropically reinforced slab is simply supported along two edges
and carries a uniformly distributed load. For a collapse mode consisting of
a single yield line from the vertex to the free edge, verify that the worst
layout is when the yield line bisects the angle between the two supported
edges, i.e. when a = f/J/2. (See Example 8.5-2: Comment (a) at the end
of the solution.)
Problem8.2
8.3 A rectangular slab, simply supported along all four edges, is
isotropicaly reinforced to give a yield moment of 27 kNm per metre width
I·
am
T
~~~LLLL~~~~~i/
6111
1~~
·I
Problem8.3