In CSA O86, there is a distinction between Wood Screws and Lag Screws. The yield modes are more or less the same, however the safety factor is 0.6 for lag screws vs. wood screws. More importantly, Wood Screw provisions account for a higher embedment strength in the point side member (rope effect), while the Lag Screw provisions make a distinction based on the direction of the load vs. grain.
Wood screws larger than #12 are to be analyzed as lag screws because of the shank/thread dimension limits. When reviewing the literature for GRK screws, it seems that they give capacities that are all over the map.
1. The comparison table (PG. G26) shows a value of 366lbs or 466lbs for all diameters
2. The tables on PG G28-G30 show various values for different embedment, but note that Wood Screw provisions have been used
3. Tables on PG G48 seem to suggest an NDS approach, and offer different capacities for parallel and perpendicular loading.
4. When reviewing a similar type of self-drilling screw (ASSY), their documentation makes it clear that Lag Screw provisions are used. And this is reflected in their tables. However, from the naked eye the ASSY screw is quite similar to the GRK screw. Both of which appear to be more refined than a lag screw or wood screw alternative.
How are other designers handling these types of fasteners? Is it sufficient to go off the manufacturer's data, even though the provisions may not be as specified by code? Is it sufficient to use ESR reports and apply a judgement/FOS to the results to get capacities within the threshold between NDS, CSA Wood Screws, and CSA Lag Screws (or sim)? What is the capacity of a GRK?
Wood screws larger than #12 are to be analyzed as lag screws because of the shank/thread dimension limits. When reviewing the literature for GRK screws, it seems that they give capacities that are all over the map.
1. The comparison table (PG. G26) shows a value of 366lbs or 466lbs for all diameters
2. The tables on PG G28-G30 show various values for different embedment, but note that Wood Screw provisions have been used
3. Tables on PG G48 seem to suggest an NDS approach, and offer different capacities for parallel and perpendicular loading.
4. When reviewing a similar type of self-drilling screw (ASSY), their documentation makes it clear that Lag Screw provisions are used. And this is reflected in their tables. However, from the naked eye the ASSY screw is quite similar to the GRK screw. Both of which appear to be more refined than a lag screw or wood screw alternative.
How are other designers handling these types of fasteners? Is it sufficient to go off the manufacturer's data, even though the provisions may not be as specified by code? Is it sufficient to use ESR reports and apply a judgement/FOS to the results to get capacities within the threshold between NDS, CSA Wood Screws, and CSA Lag Screws (or sim)? What is the capacity of a GRK?
