can i increase footing tie beam size by bonding agent only?
can i increase footing tie beam size by bonding agent only?
(OP)
can i increase footing tie beam size by bonding agent only?
or do i need dowels to develop new concrete to existing concrete?
if i need dowels, how do i calculate number of dowels required.
thanks,
or do i need dowels to develop new concrete to existing concrete?
if i need dowels, how do i calculate number of dowels required.
thanks,






RE: can i increase footing tie beam size by bonding agent only?
RE: can i increase footing tie beam size by bonding agent only?
RE: can i increase footing tie beam size by bonding agent only?
I would not rely on any form of "adhesion" of new to the old.
Kinda depends on why the increase in size is necessary. Consider that the existing concrete has probably undergone most of its shrinkage. The new concrete will shrink with respect to the existing, and will compromise the bond that you're looking for.
If you need the additional cross-sectional size for compressive forces, then your encasement method may work. I would roughen the existing surface, use a good bonding agent, and provide shrinkage/temperature reinforcement using more frequent small bars rather than large.
If you need the additional cross-sectional size for tensile forces, I would consider casting an additional beam (or 2) next to the eisting with no attempt to bond to the existing, then concentrate on developing the end anchorage into the footing or cap at each end. Any shrinkage cracks that develop will be distributed over the length of the new beam(s) and should not be of a size for concern.
Ralph
Structures Consulting
Northeast USA
RE: can i increase footing tie beam size by bonding agent only?
The spacing of dowels would be dependent on the shear force to be transferred between new and existing concrete. The capacity of one dowel in shear is determined by shear friction principles if the dowel is adequately anchored each side of the joint. Dowels can be anchored into the existing concrete with epoxy so that they develop their full yield strength.
BA
RE: can i increase footing tie beam size by bonding agent only?
This is why chemical anchors have a factor of safety of 4 and this is just for simply filling a hole with the stuff and shoving in an anchor bolt (much simpler than what you propose).
Glulams undergo a lot of testing to ascertain the effectiveness of their adhesives.
So in summary, I would not recommend the use of adhesives for one off applications that are not backed up by extensive testing.
Is there any reason why the existing beam cannot simply be demolished and replaced with the new larger beam?
RE: can i increase footing tie beam size by bonding agent only?
i'm just checking another person's work, and he increased the size because development length is short on the new tie beam perpendicular to existing.
i guess in this case it may be ok loads are minimal.
RE: can i increase footing tie beam size by bonding agent only?
RE: can i increase footing tie beam size by bonding agent only?
RE: can i increase footing tie beam size by bonding agent only?
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: can i increase footing tie beam size by bonding agent only?
also is it cheaper to demolish the existing beam than to apply bonding agent all over the length of the beam.
RE: can i increase footing tie beam size by bonding agent only?
This is a footing tie beam - I would expect axial load to control more than anything else.
As far as expense - one does not need to be fussy with demolition, except at each end of the existing. Proper surface prep (top & sides) and bonding agent application will be time consuming. I have to believe it would be less expensive to replace rather than enhance, and you get a little more peace of mind that the fix will be reliable.
Ralph
Structures Consulting
Northeast USA
RE: can i increase footing tie beam size by bonding agent only?
i do feel demolish and replace is better than roughening the top and side then applying bonding agent.
i'll discuss with him.
RE: can i increase footing tie beam size by bonding agent only?
RE: can i increase footing tie beam size by bonding agent only?
No need to remove the concrete core inside the existing cage. The new stirrups should be fine.
Pre-wet the existing to saturate surface dry. Cure the new material properly to reduce shrinkage.
RE: can i increase footing tie beam size by bonding agent only?
To solve your shear problem I would dowel into the existing footing and rely on dowel action to transfer the shear. The calculations on the section will be complicated by the fact that there is pre-existing stresses on the cross-section which need to be considered.
Best of luck.
RE: can i increase footing tie beam size by bonding agent only?
From a very pragmatic viewpoint - all of the suggestions offered are worth considering, BUT the best solution is the one that offers the highest assurance that design parameters are met for the least cost.
Add up the total cost of surface prep, form & rebar installation, bonding application, concrete placement & curing, form removal, and close supervision for all of this - I submit that the best solution is demo & replace.
Ralph
Structures Consulting
Northeast USA
RE: can i increase footing tie beam size by bonding agent only?