1964_BUILDING_(CONSTRUCTION)_REGULATIONS — Page 80

B 80

[Subsidiary]

CAP. 123]

Building (Construction) Regulations

[1985 Ed.

Stiffness of members.

L.N. 294/76.

(a) both steel and concrete are elastic within the range of the permissible stresses and the modular ratio is equal to 15;

(b) at any cross-section plane sections remain plane; and

(c) all tensile stresses are taken by the reinforcement except that the concrete may be assumed to resist diagonal tension within the limits of shear stress specified for concrete in regulation 116.

132. (1) Reinforced concrete members shall possess adequate stiffness to prevent such deflexion or deformation as might impair the strength or efficiency of the structure or produce cracks in finishes or in partitions.

(2) For all normal cases it shall be assumed that the stiffness will be satisfactory if

(a) in the case of members with steel stresses not more than 125 MPa, the ratio of span to overall depth does not exceed the values given in Table XXXII; and

(b) in the case of members with steel stresses greater than 125 MPa, the ratio of span to overall depth does not exceed 90 per cent of the values given in Table XXXII.

Simply supported

Continuous

Cantilever

TABLE XXXII

Permissible values of ratio of span to depth of beams and slabs

(1)

(2)

BEAMS--

Ratio of span to overall depth

20

25

10

SLABS-

30

35

Spanning in 1 direction

(i) simply supported

(ii) continuous

Spanning in 2 directions

(i) simply supported

(ii) continuous

Cantilever

30

35

40

12

(3) (a) For the purposes of calculating bending moments in continuous structures, the moment of inertia shall be estimated by considering--

Page 80

Page 81