Solid Wood Products 



2621 



ST/FFNESS INDEX 



Figure 22-32. — Stiffness index of 48- by 40-inch nailed hardwood pallets suspended at 

 the corners and subjected to a 2,000-pound concentrated center load for 2 minutes. 

 The index is derived from the cumulative average deflection measured at five loca- 

 tions on each of five pallets of each species. White oak pallets had an index of 100, 

 average for the 22 pine-site hardwood species evaluated. See table 22-14 for deflec- 

 tion values. (Drawing after Stern 1978.) 



After six drops, average distortion of the pallet diagonals was 1.8 percent with 

 a range from 1 .3 percent for green ash to 2.7 percent for laurel oak. Even after 12 

 drops, none had more than 4 percent distortion of pallet diagonal length; the 

 average was 2.2 percent with range from 1 .6 percent for green ash to 4.0 percent 

 for laurel oak (table 22-14). 



The change in lengths of pallet diagonals had a straight line relationship (R^ = 

 0.77) to the specific gravity — hence weight — of deckboards and stringers; the 

 greater the specific gravity, the greater the distortion. 



