B 102
CAP. 123]
Building (Construction) Regulations
[1985 Ed.
[Subsidiary]
Negative moments
Positive moments
1
TABLE XXXVII
Distribution expressed as percentage of total negative or positive moments
2
3
Column strip
Middle strip
75
55
23
45
Empirical design of flat slabs.
Note: Provision need not be made for greater negative moments than those at the critical sections for shear immediately adjacent to the column as defined in regulation 149 (1)(g):
Provided that the sum of the maximum positive bending moment and the average of the maximum negative bending moments for the whole panel width used in the design of any 1 span shall be not less than:
2D
W42 [21 - 20]2
10
Li
3
(i) where w is the total load per unit area on the panel; (i) where the diameters of the columns or column heads supporting the panel are not equal, D shall be taken as the average of the 2 diameters;
(h) columns shall be designed to resist the combination of bending moment and direct load consistent therewith which produces the greatest stresses in the column.
156. (1) Flat slabs designed by the empirical method shall comply with the provisions of this regulation.
(2) The slabs shall comprise rectangular panels and there shall be at least 3 continuous panels in both directions.
(3) The ratio of the length of a slab to its width shall not exceed 4:3.
(4) The length or width of any 2 adjacent panels shall not differ by more than 10 per cent of the greater length or width. End spans may be shorter but not longer than adjacent interior panels.
(5) Where adjacent spans differ the length of the longer span shall be used in calculating the negative bending moments between the 2 panels.
(6) For fully continuous interior panels the critical sections for bending moment are--
(a) for positive moment, along the centre lines of the panels;
1