(b)For floors with only nominal percentage of reinforcement (smaller than
the minimum specified) the concrete floor should be cast in panels with
sides not more than 4.5m.
(c) In concrete walls, the movement joints should normally be placed at a
maximum spacing of 7.5m. in reinforced walls and 6m in unreinforced
walls. The maximum length desirable between vertical movement joints
will depend upon the tensile strength of the walls, and may be increased
by suitable reinforcement. When a sliding layer is placed at the
foundation of a wall, the length of the wall that can be kept free of cracks
depends on the capacity of wall section to resist the friction induced at
the plane of sliding. Approximately the wall has to stand the effect of a
force at the place of sliding equal to weight of half the length of wall
multiplied by the co-efficient of friction.
(d)Amongst the movement joints in floors and walls as mentioned above
expansion joints should normally be provided at a spacing of not more
than 30m between successive expansion joints or between the end of the
structure and the next expansion joint; all other joints being of the
construction type.
(e)When, however, the temperature changes to be accommodated are
abnormal or occur more frequently than usual as in the case of storage of
warm liquids or in uninsulated roof slabs, a smaller spacing than 30m
should be adopted that is greater proportion of movement joints should be
of the expansion type). When the range of temperature is small, for
example, in certain covered structures, or where restraint is small, for
example, in certain elevated structures none of the movement joints
provided in small structures up to 45mlength need be of the expansion
type. Where sliding joints are provided between the walls and either the
floor or roof, the provision of movement joints in each element can be
considered independently.