* It is also permitted to use a diagram in which the resisting tensile force is progressively decreasing on the length lb,net.
Figure 5.11 — Envelop line for the design of flexural members. Anchorage lengths
(3) The anchorage lengths of bent-up bars which contribute to the resistance to shear should be not less than 1.3 lb,net in the tension zone and 0.7 lb,net in the compression zone.
22.214.171.124.4 Anchorage of bottom reinforcement at an end support
(1) Over supports with little or no end fixity it is necessary to retain not less than | one-quarter | of the steel section present in the span;
(2) The anchorage of the reinforcement should be capable of resisting a tensile force of:
where Nsd denotes the design axial tensile force.
(3) The anchorage length is measured from the line of contact between the beam and its support; it should be taken as:
— for a direct support : | 2/3 | lb net (see Figure 5.12 a);
— for an indirect support: lb net (see Figure 5.12 b). with lb,net according to Equation (5.4).
Figure 5.12 — Anchorages of bottom reinforcement at end supports a - direct support b - indirect support
Figure 5.12 — Anchorages of bottom reinforcement at end supports
126.96.36.199.5 Anchorage of bottom reinforcement at intermediate supports
(1) Amount of reinforcement: 188.8.131.52.4(1) applies.
(2) Such anchorage should have a length of not less than 10 0 (for straight bars) or not less than the diameter of the mandrel (for hooks and bends) [see Figure 5.13(a)].
(3) In addition, it is recommended that the reinforcement used should be continuous and able to resist accidental positive moments (settlement of the support, explosion, etc., see Figure 5.13(b).
184.108.40.206 Shear reinforcement
(1) The shear reinforcement should form an angle of 90° to 45° with the mid-plane of the structural element.
(2) The shear reinforcement may consist of a combination of:
— links enclosing the longitudinal tensile reinforcement and the compression zone;
— shear assemblies in the form of cases, ladders, etc. of high bond bars which are cast in without enclosing the longitudinal reinforcement (see Figure 5.14), but should be properly anchored in the compression and tension zones.
(3) Links should be effectively anchored. A lap joint on the leg near the surface of a web is allowed only for high bond bars.
(4) At least | 50 % | of the necessary shear reinforcement should be in the form of links.
(5) The shear ratio is given by Equation (5.16):
is the shear reinforcement ratio is the area of shear reinforcement within length s s is the spacing of the shear reinforcement bw is the breadth of the web of the member a is the angle between the shear reinforcement and the main steel (i.e. for vertical stirrups a = 90° and sin a = 1)
In general, the minimum values for pw are given in Table 5.5 Table 5.5 — Minimum values for pw
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