B 84
CAP. 123]
Building (Construction) Regulations
[1985 Ed.
[Subsidiary]
TABLE XXXIV
Bending moment coefficients for slabs spanning in 2 directions at right angles simply supported on 4 sides
2 3 5 7 8 9 10 11 lly 1.0 1.2 1.3 1.4 1.5 1.75 2.0 2.5 3.0 Xx 0.062 * 0.074 0.084 0.093 0.099 0.104 0.113 0.118 0.122 0.124 0.062 0.061 0.059 0.055 0.051 0.046 0.037 0.029 0.020 0.014(4) In the case of slabs restrained on 4 sides-
(a) where the corners of a slab are prevented from lifting and adequate provision for torsion in accordance with sub-paragraph (e) is made, the bending moments shall be assumed to have the values given in sub-paragraph (c);
(b) slabs are considered as being divided in each direction into middle strips and edge strips as shown in Diagram 1, the middle strip having a width of 3/4 of the width of the slab and each edge strip having a width of 1/8 of the width of the slab, except that, for slabs for which the ratio of the sides l/ly exceeds 4.0, the middle strip in the short direction shall be taken to have a width of ly-lx, and each edge strip a width of 1/2(lx-(ly-lx)).
DIAGRAM 1
Division of slabs into middle and edge strips
FOR SPAN lx
ly
FOR SPAN ly
ly
EDGE STRIP
EDGE STRIP
MIDDLE STRIP
EDGE STRIP
MIDDLE STRIP
EDGE STRIP
(c) the maximum bending moments per unit width in the middle strip of a slab shall be calculated by the following equations:
Ms = Bx wlx2
My = By wlx2
where-
Mx and My are the maximum bending moment on strips of unit width in the direction of spans lx and ly, respectively;
w is the total load per unit area;
lx is the length of the shorter side;
ly is the length of the longer side;
Bx and By are coefficients given in Table XXXV.
TABLE XXXV
Bending moment coefficients for rectangular panels supported on 4 sides with provision for torsion at corners
Short span coefficients Bx