Composite Section
Composite Section
(OP)
Has anyone used an adhesive to attach steel strap to dimensioned lumber wood joists to improve the load carrying capacity? I'm thinking of gluing 1/8" x 1-1/2" straps on existing 2x10 joists and maybe pre-flexing the floor joists to offset some of the present dead loading.
Dik
Dik






RE: Composite Section
I'm not sure what your application is, but I would have concern about deterioration of adhesives if exposed to moisture etc. (although this could be overcome with correct specification of the adhesive).
RE: Composite Section
My guess is that because the strapping is so thin, you would have SERIOUS problems with buckling of the strapping unless you space them at something ridiculous, say 2" or 3" o.c.
dik,
Can you use adhesive just as good practice and to help with using fasteners at a reasonable spacing? That strap seems awfully small, could you just use a 2x12 with a better grading?
RE: Composite Section
I think Dik is proposing to use the strapping as a tension member applied to the bottom face of the joists, in which case buckling should not be a concern.
This type of strap (38x3mm) is commonly used in the UK as tension members to aid resistance to wind uplift for timber roofs.
RE: Composite Section
RE: Composite Section
I've a query in to 3M regarding one of their contact adhesives.
Looking at treating the steel and wood as an elastic composite section using an equivalent n value for Ew/Es. Existing electrical/mechanical issues make 'sistering' of floor joists impractical.
Dik
RE: Composite Section
I think your approach sounds reasonable. But I just never felt comfortable using glue for structural applications within a load path.
RE: Composite Section
m looking for an adhesive to reinforce existing wood floor joists with steel straps to increase the load capacity and was wondering if 3M™ Scotch-Weld™ Neoprene High Performance Contact Adhesive 1357 would be suitable.
The glueline must be capable of supporting long term shear stresses. If the above is suitable, can you provide an indication of the ultimate shear capacity and if a safety factor of 4 would be adequate? or a reasonable safe working load? Does the adhesive maintain its strength over an extended period of time when subject to repetitive loading?
Are there any other adhesives that would be better suited?
thanks, Dik
I'll check with them about moisture issues... I didn't think this would be an issue with a neoprene based adhesive, but will check.
One reply that I hadn't considered, but would have if the application works is the attachment of the ceiling... have to scab something on the side or glue a nailer to the bottom.
Dik
RE: Composite Section
RE: Composite Section
Dik
RE: Composite Section
I'd make sure to watch out for the bending stress on the compression side also. You've added steel to the tension side doubling Sbot, but Stop only increases 30%.
And don't forget about shear!
RE: Composite Section
Dik