SALIENT FEATURES OF IS:13920 - 1993.CODE OF PRACTICE FOR DUCTILE DETAILING OF RC STRUCTURES

SUBJECTED TO SEISMIC FORCES.

BEAM DESIGN:

DESCRIPTION

1 Ductile detailing is a must for structures in Zone IV & V. However it should also

be followed in zone III, when Importance factor is > 1.0 OR Structure is > 5.0 Storey high OR the structure is industrial in nature.

2 Minimum longitudinal reinforcement on any face/section shall be :

0.24 * sqrt (fck)/fy

3 The factored axial stress shall not be > 0.1 fck, else the beam should be designed as column.

4 B/D > 0.30 preferably.

5 B should not be < 200 MM.

6 The maximum steel ratio should not be > 2.5 % per face.

7 Beam should not be a DEEP beam.

8 +ve reinforcement should not be < 50 % of -ve steel at that joint.

9 Minimum steel at any section face shall not be < 25 % of maximum -ve steel at any joint.

10 Re-distribution of support moments are not allowed for seismic moments at

joints.

11 Development length {Ld} = Ld + 10 x at end joints of column/beam.

12 Top & bottom reinforcements shall be continuous at column joints.

13 All links shall be closed type, having a 135 hook with a 10 extension, but

not less than 75 mm at each end.

14 The longitudinal bars shall be spliced, only if links are provided over the entire splice length at spacing not > 150 MM.

15 All splice shall have Ld in tension.

16 Lap splice shall not be at :

Column Joints.2 x d from column face.Within 0.25 x span.

17 Not > 50 % of bars shall be spliced at any section.

18 The Minimum link shall be 6 MM for span < 5.0 M.Use 8 MM links for span > 5.0 M.

19 The Links shall be designed for :Factored SF as per Analysis.

SF due to formation of plastic hinges at both ends + gravity loads as per analysis.

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Page 1 of 2Beam design as per IS-13920-1993 Limitations & INFO:

Spacing of Links within 2 x d from supports shall be minimum of :

d/48 x of smallest longitudinal bar.

21 Spacing of links shall not be < 100 MM.

22 1st link shall start 50 mm away from support.

23 Spacing of links away from 2 x d from support shall not be > d 2.

24 Link spacing shall not be > 300 MM. { As per IS-456-2000 }.

25 The top as well as bottom reinforcement shall atleast have 2 bars continuous throughout the whole member.

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