stirrup hook at the bottom of a cantilever beam
stirrup hook at the bottom of a cantilever beam
(OP)
hi guys,
during an inspection on site, i saw that for all the cantilever beams, the hook for the stirrup was at the bottom of the beam not at the top. When i discussed why it was done that way with the foreman, he told me that is because a cantilever beam. I couldn't find anything in the ACI regarding this subject.
Any thoughts whether he is right ?
during an inspection on site, i saw that for all the cantilever beams, the hook for the stirrup was at the bottom of the beam not at the top. When i discussed why it was done that way with the foreman, he told me that is because a cantilever beam. I couldn't find anything in the ACI regarding this subject.
Any thoughts whether he is right ?






RE: stirrup hook at the bottom of a cantilever beam
2. Bottom of the cantilever beam should also have reinforcements, but its mainly due to formwork (scaffolds and the sorts)
Item 2 is further clarified with the following diagram.
RE: stirrup hook at the bottom of a cantilever beam
any reason for the hook to be at the bottom of the beam not at the top ?
RE: stirrup hook at the bottom of a cantilever beam
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: stirrup hook at the bottom of a cantilever beam
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RE: stirrup hook at the bottom of a cantilever beam
Kootk, closed stirrups but the hook (the one required to be 6 db) is at the bottom face of the cantilever beam.
RE: stirrup hook at the bottom of a cantilever beam
Anchorage of hooks is best achieved on the compression side, but this would include all negative moment regions, not just cantilevers. There was at one time a clause in the Australian code recommending this, but as it was not followed, I think the clause has been removed. Just not practical, and without evidence of actual adverse performance, the requirement is unnecessary. It is still important for designers to consider how stirrups are anchored, especially in shallow beams.
RE: stirrup hook at the bottom of a cantilever beam
8.2.12.4 End anchorage of bar
Bars used as shear reinforcement shall be anchored to develop the yield strength of the bar,
at any point in the legs, transverse to the longitudinal flexural reinforcement.
This requirement for the anchorage of stirrups and ties shall be deemed to be met provided
the following requirements are met:
...
(b) A fitment hook should be located preferably in the compression zone of the structural
member, where anchorage conditions are most favourable. Such an anchorage is
considered satisfactory, if the hook consists of a 135° or 180° bend with a nominal
internal diameter of 4db plus a straight extension of 10db or 100 mm, whichever is the
greater.
(c) Where a fitment hook is located in the tension zone, the anchorage described in
Item (b) is deemed to be satisfactory provided the stirrup spacing calculated using
Clause 8.2.10 is multiplied by 0.8 and the maximum spacing specified in
Clause 8.2.12.2 is also multiplied by 0.8.
Cracking in a tension zone runs perpendicular to the main steel, therefore it runs in the same plane as the stirrups and may reduce the strength if the stirrups are lapped as opposed to hooked. I assume this is why it is good practice to lap in the compression zone. But the clause was removed in 2009...
RE: stirrup hook at the bottom of a cantilever beam