‘Development length’ on each side of any section is the length over which the force in the reinforcement at that section will be developed without bond failure between these two materials. Sometimes a reinforcing bar is extended and/or bent at its ends to satisfy development length requirement. Such extension and/or bending of a bar at its ends is called anchorage. A bent bar provides a greater safety against bond failure as during a pull-out the whole concrete is to be crushed.
Fig: Development length of reinforcement in concrete
Reinforcing
bars have limited lengths for ease of handling and transporting; hence
in case of a continuous member or a member of large span it is necessary
for continuity to join two bars by overlapping the ends at the joint.
The overlapping portion are joined together either by concrete itself by
providing proper development length or by welding in case of limitation
of length for overlapping. Such jointing of two bars for continuity of
reinforcing bar at any section is called splicing.
Fig: Detailing of Reinforcement in continuous beam
Reinforcements
are round bars. They are provided as straight or shaped appropriately
to suit the requirements. These reinforcements are placed at certain
spacing to meet the design requirements. But these spacing must be
within a range of the minimum spacing and the maximum spacing for ease
of casting, compaction, control of cracking, etc. as laid down in the
Standard Code of Practice.All types of reinforcements must have sufficient concrete cover to protect them from environmental exposure conditions and also against fire. Such cover is called Nominal Cover.
Other requirements of detailing are the minimum and the maximum amount of reinforcement, side face reinforcement, distribution of reinforcement, etc.
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