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[kirtesh_gandhi at hotm...]

Dear all,

Following are some of the interpretations of proposed draft of IS 13920.

1.     IS 13920 supersedes IS 456.
2.     Ductile detailing is applicable to all the RC structures located
in zones 2,3,4,& 5 but certain relaxation is given for zone 2 & 3.
However in the draft code two different clauses give contradictory
statements regarding application of code in zone 2.
3.     New clauses for intermediate moment resisting frame (IMRF) and
gravity columns have been added.
4.     IMRF is applicable to buildings in zone 2 & 3 whereas Special
Moment Resisting Frame (SMRF) is applicable for zone 4 & 5.
5.     Lower value of "R" from IS 1893 is to be used for IMRF for the
calculation of earthquake forces.
6.     Positive steel at the joint face for IMRF is 1/3 of negative
steel whereas for SMRF it is 1/2.
7.     Steel provided at each section of member either top or bottom is
1/5 of maximum negative moment for IMRF whereas for SMRF it is 1/4.
8.     Requirements of hoops for columns are lower for IMRF than SMRF.
9.     For cross ties and hoops extension length is reduced to 6 times
bar diameter from 10 times bar diameter and minimum distance is 65mm
instead of 75mm.
10.     Minimum grade of concrete shall be M25 for all the buildings
located in zones 4 & 5 with more than 4 stories height.
11.     For beams, minimum top and bottom reinforcement shall at least
consist of two bars of 12mm dia. throughout the length of member.
12.     Minimum dimension of column shall not be less than 300 mm or 15
times largest bar dia of beam.
13.     In columns if more than 50% bars are spliced at one section, the
lap length can be increased to 1.3Ld.  Only tension splices are allowed
in columns.
14.     Rectangular columns shall have minimum eight numbers of bars in
lateral load resisting frame.
15.     The sum of moment of resistance of columns shall be 1.1 times
the sum of moment of resistance of beams along each principal plane of
the joint.  Columns not satisfying these requirements shall have special
confining reinforcement over the full height instead of their critical
end regions only.
16.     In case of wide beam, transverse reinforcement is to be provided
through the beam column joint to provide confinement for longitudinal
beam reinforcement outside the column core.
17.     In exterior and corner joints all the 135 degrees hook of cross
ties should be along outer face of column.

Regards,

Kirtesh Gandhi

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