We had several consequential failures of epoxy anchors in tension applications. I think taking into account the performance (or lack thereof) of a product in the field when considering it for design, is very practical. Sometimes as engineers we need to come out of our protective shells and be a little more practical. RE: Relying on construction adhesive for structural capacity Eng16080 (Structural) 6 Mar 24 23:15 This is true for the span tables in the IBC/IRC as well, but is found to be acceptable practice. What does this mean? Well, if you're concerned that the span tables are non-conservative, be aware that 50% of the joists (whether that be sawn lumber, mechanically graded, or engineered wood) have lower stiffness than the published value used for design. This is similar to the adjustments used for Emin, which is a strength critical design value rather than serviceability based design value. Appendix F gives methods of adjusting MOE for critical applications. In addition, because MOE is based on the median value, each piece has a 50% chance of having a lower stiffness than what was designed. Per Appendix F, you'll see that the coefficient of variation for MOE of visually graded sawn lumber is 0.25, this is a large COV value, and means there is significant variability on stiffness of members within the population. If you have a copy of AWC's National Design Specification, check out Appendix F. Published MOE value for all wood products are based upon the median design value of a normally distributed population, without any adjustments. ![]() Because MOE is a serviceability related design value, it's design value is not controlled very tightly. Not sure how familiar you are with structural wood products including sawn lumber, but wood is inherently an inconsistent structural material, there is significant variability from one piece to another in any binned product, whether that be visually graded, mechanically graded, or an engineered wood product. So then, the span lengths would be non-conservative in the event that the field crew doesn't glue the subfloor or doesn't glue it per the specs of the I-joist supplier. RE: Relying on construction adhesive for structural capacity JoshPlumSE (Structural) 6 Mar 24 20:46 They ended up going back and screwing the crap out of the floor due to squeaks before the hardwood was installed. Go on a job site in the winter and watch The Framers struggle to squeeze that cold adhesive out of a giant caulk gun and then get back to me. I don't think I would count on it for deflection as you have no control in the field how much and how well it is applied. ![]() deflection, in that you develop partial composite action between the wood members and sheathing, which is reflected in deflection calculations. ![]() However, we do rely on construction adhesive for non-strength based checks, i.e. In the wood industry, we do not rely on construction adhesive for any strength based calculation (moment, shear, etc.), too many things on a jobsite prevent a consistent and reliable bond, dirt, dust, and adhesive skinning/curing before placement are key factors.
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