Inadequate Embedment - Looking for Ideas
Inadequate Embedment - Looking for Ideas
(OP)
Background:
I'm designing a concrete member (door jamb - 8' tall) to support a flood gate. The concrete door jamb will be oreinted vertically and will be doweled into an adjacent wall. Then, so I could sleep at night, I was also going to notch the top and the bottom of the support (into the floor and ceiling) as well as put a "healthy" amount of reinforcement into the floor and ceiling.
Problem:
The problem that I'm having is that I can't get enough embedment into the adjacent wall to get adquate support for the dowels. I've been trying to epoxy the dowels in.
FYI: Shear=3800 lbs and Pull-out=4100lbs at the critical dowel - 7" spacing, 7/8" dowel, 4" Edge distance (opposite the direction of applied load).
Does anyone have any ideas as to how I could get adequate embedment?? Top and bottom dowels recieve too large a load to be effective on their own....plus the floor and ceiling are inadequate for the forces.
One idea that was suggested at work (not by a structrual engineer), was to thicken the adjacent wall to the point where I would have adequate embedment. Can you do this or does the "slip plane" between the walls significatnly weaken the embemdent?? This idea scares me!!
Any ideas on how to get adequate embedment OR change the design to make the dowels less critical?? All comments welcome!!
I'm designing a concrete member (door jamb - 8' tall) to support a flood gate. The concrete door jamb will be oreinted vertically and will be doweled into an adjacent wall. Then, so I could sleep at night, I was also going to notch the top and the bottom of the support (into the floor and ceiling) as well as put a "healthy" amount of reinforcement into the floor and ceiling.
Problem:
The problem that I'm having is that I can't get enough embedment into the adjacent wall to get adquate support for the dowels. I've been trying to epoxy the dowels in.
FYI: Shear=3800 lbs and Pull-out=4100lbs at the critical dowel - 7" spacing, 7/8" dowel, 4" Edge distance (opposite the direction of applied load).
Does anyone have any ideas as to how I could get adequate embedment?? Top and bottom dowels recieve too large a load to be effective on their own....plus the floor and ceiling are inadequate for the forces.
One idea that was suggested at work (not by a structrual engineer), was to thicken the adjacent wall to the point where I would have adequate embedment. Can you do this or does the "slip plane" between the walls significatnly weaken the embemdent?? This idea scares me!!
Any ideas on how to get adequate embedment OR change the design to make the dowels less critical?? All comments welcome!!
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Andrew






RE: Inadequate Embedment - Looking for Ideas
Smaller dowels should require shorter embedment. To off-set the lower capacity of smaller dowels, just put more of them.
If the current dowel size is heavily loaded and are already close to the minimum spacing, then you might be out of luck.
RE: Inadequate Embedment - Looking for Ideas
Can you cut back the concrete of the existing wall to expose the rebar? Then hook (or weld) the new dowels round the exposed rebar. The dowels should be detailed as links eclosing the new rebar of the door jamb. When casting the new concrete, make sure it is a strong mix with a high proportion of OPC but a very low water content. You may need a superplasticiser to ensure compaction. This will generate a lot of heat and high strength ensuring that shrinkage causes the new jamb to pull back hard onto the old concrete. Good preparation and quality control should ensure a watertight joint.
Good Luck
RE: Inadequate Embedment - Looking for Ideas
You should get proper bond length. If the force required is more, increase the dia of bolts, ut take care as it also require increased bond length and increase spacing.
RE: Inadequate Embedment - Looking for Ideas
RE: Inadequate Embedment - Looking for Ideas
RE: Inadequate Embedment - Looking for Ideas
vmirat,
How do you detail the steel shear plate??
This is something I had not considered but this may work better in this situation!! What are the items one needs to be wary of when using this type of design??
Thanks to all for your advice/ideas so far!!
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Andrew
RE: Inadequate Embedment - Looking for Ideas
If YES, consider how one would extend the rebar. We would look for adequate lap to produce teh required anchorage bond. Edge istance is still an important factor, but is reduced by the links binding the main bars.
Can you apply similar reasoning to your dowels.
RE: Inadequate Embedment - Looking for Ideas
Check the horizontal rebar in the wall. Once you cut the slot for the shear plate, you will develop a weakened plane in the concrete wall and induce a crack through the wall. The existing rebar must be capable of holding the wall together. I would use an angle with one leg epoxied into the wall and the other leg imbedded into your new door jamb. I would also use an epoxy to bond the new concrete to the old wall.
RE: Inadequate Embedment - Looking for Ideas
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Andrew
RE: Inadequate Embedment - Looking for Ideas
RE: Inadequate Embedment - Looking for Ideas
That's interesting!! I hadn't heard this before. Do you know of a source where I can read more about this??
Thanks!
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Andrew
RE: Inadequate Embedment - Looking for Ideas
RE: Inadequate Embedment - Looking for Ideas
RE: Inadequate Embedment - Looking for Ideas
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Andrew
RE: Inadequate Embedment - Looking for Ideas