F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

236 Shear, bond and tors ion
fyy = the characteristic strength of the links (but not to be taken
as exceeding 460 N/mm 2 );
fy = the characteristic strength of the longitudinal reinforcement
(but not to be taken as exceeding 460 N/mm 2 );
Sy = the spacing of the Iinks;
XI = the smaller centre-to-centre dimension of the links;
YI = the larger centre-to-centre dimension of the links.
Step 8 Detailing requirements
The detailing of torsion reinforcement should satisfy the following
requirements:
(a) The links should be of a c10sed type similar to Code 74 of BS 4466
(see Fig. 6.11-1).
(b) The Iink spacing Sy should not exceed the least of X h Y I 12 or
200 mm, where symbols are as defined in Step 7.
(c) The longitudinal torsion reinforcement required by eqn (6.11-6)
should be distributed evenly round the inside perimeter of the
links. The c1ear distance between these bars should not exceed
300 mm and at least four bars, one in each corner of the links,
should be used.
(d) Longitudinal torsion bars required at the level of the ten sion or
compression reinforcement may be provided by using larger bars
than those required for bending alone.
(e) AII longitudinal torsion bars should extend a distance at least equal
to the largest dimension of the cross-section beyond where it ceases
to be required.
(f) In the component rectangles of T-, L- or I-sections, the reinforcement
cages should be detailed so that they interlock and tie the
component rectangles of the section together (see Fig. 6.11-2).
Where the torsional shear stress VI in a minor component rectangle
is less than Vlmin' no torsion reinforcement need be provided in that
rectangle.
Comments on Step 1
The relation G = 0.42E c may be derived from the elastic relationship
G = E12(1 + v) by taking Poisson's ratio v as 0.19 (see Section 2.S(d) on
• 4
Fig. 6.11-1 Closed link for torsion
Fig.6.11-2 Torsion reinforcement
for flanged beam