Help with lifting hooks for slab

[CBS12]

I've never actually designed lifting hooks for a concrete slab before and would like to double check what I've come up with and my reasoning. Here is the situation. We have a slab design 2.4m x 1.9m and 200mm thick with a 600mm square opening and cover in the middle. The concrete will be 40MPa, has recinforcing in both directions, top and bottom and will rest over an existing hole (supported on all 4 sides). It is going to be precast off site so we want to include 4 reinforcement bars (one at each corner) cast into the concrete for lifting and placement of the slab. The bars will be bent into a hook shape at midlength and recessed into the top of the slab. What size bars should be used and long should they run in each direction from load point? Cheers.

 

[apsix]

I only specify proprietary lifting eyes or pins with rated capacities.

By the time you design, detail, fabricate and galvanise (assuming it's outside) your lifting hooks they won't be much cheaper.

 

[csd72]

CBS12,

You have not said what country you are working in but in Australia using bent reinforcing bars was banned by the Health and Safety Authorities in several states.

There is a potential ductility problem caused by the bending.

 

[cntw1953]

Check with your local "precast concrete association", in the US, go pci.org to get a copy of precast concrete manual, you will find it is quite useful.

Agree with csd72, I have witnessed failure of bent reinforcing lifting ring before.