B 60
[Subsidiary]
L.N. 294/76.
L.N. 294/76.
CAP. 123] Building (Construction) Regulations
[1985 Ed.
(4) (a) In no case shall the flexural stresses of a beam or girder of symmetrical section exceed the appropriate stress specified in column 2 of Table XXII.
(b) The percentage increase permitted by paragraph (3) shall not be taken into account in regulation 100.
TABLE XXII
Maximum flexural stresses of a beam or girder of symmetrical section
2
MPa
1.
Steel complying with the appropriate provisions of BS 4360: 1972-
(a) beams or girders, other than plate girders (b) plate girders
150
145
2.
High yield stress structural steel complying with the appropriate provisions of BS 4360: 1972–
(a) beams and girders, other than plate girders---
(i) material not more than 25 mm thick
(ii) material more than 25 mm thick
(b) plate girders-
(i) material not more than 25 mm thick (ii) material more than 25 mm thick
210
190
200
185
(5) Beams and girders with equal flanges may be designed as cased beams provided the following conditions are fulfilled:
(a) the section is of single web and I-form or of double open channel form with the webs not less than 40 mm apart;
(b) the beam is unpainted and is solidly encased in dense concrete not inferior to that designated grade IIIA in regulation 19:
(c) the minimum width of solid concrete encasing is at least equal to (b+100) mm, where b is the width of the steel flange in mm:
(d) the surface and edges of the flanges of the beam have a concrete cover of not less than 50 mm;
(e) the casing is effectively reinforced with wire to BS 4482: 1969 The wire shall be at least 5 mm diameter, and the reinforcement shall be in the form of stirrups or binding at not more than 150 mm pitch, and so arranged as to pass through the centre of the covering to the edges and soffit of the lower flange;
(f) the beam or girder has a depth not exceeding 750 mm (over plating where used) and a width not exceeding 450 mm;
(g) the beam or girder is not of a box section. The least radius of gyration (ky) may be deemed to be equal to 0.2 (b+100) mm and the radius of gyration (kxx) shall be deemed to be equal to that of the uncased section:
Page 60
Page 61