Masonry Magazine December 2016 Page. 20
percent of its maximum allowable strength before reaching To further substantiate the above points, when engineers the threshold, or when it will begin to fail. Simultaneously, calculate and develop span tables for particular plank prod�product C tests at 64 percent of its allowable strength ucts, they have to observe both the modulus ofelasticity and under the same test criteria, meaning there is a 22 percent the fiber bending value and must do so for each plank size, performance difference between products A and C. Both type and quality. Ofcourse, they must also observe the de�products have the same MOE, yet testing shows there is a flection limit of L/60 (length ofspan divided by 60), stipu�substantial difference in ultimate strength performance of lated in the OSHA standards. the two products. This further exemplifies that both design The next time you are doing research to purchase values, Fb and MOE, should be reviewed when selecting a more scaffold plank, do not be fooled if you're told, "The product
For further clarification/experimen�tal purposes, take, for example, two different kinds of EPS foam board in�sulation products ofthe same thickness
SOUTHWEST
and width (one being white bead board commonly referred to as Styrofoam, the
SCAFFOLDING
other being rigid EPS insulation, often referred to as Blue Board). Span both products over two supports the same distance apart, then apply light pressure downward on each (by using your hands
SOUTHWEST SCAFFOLDING
simultaneously). You will find they both have a similar stiffness. The resistance OFFERS THE MOST COMPETITIVE PRICES ON will seem comparable. This is the Mod�
SCAFFOLDING RENTALS AND SALES
ulus ofElasticity. Now follow the same test procedure, but apply even more pressure continuously. Both boards will slowly flex, but eventually the Styrofoam will abruptly snap, while the Blue Board The lesson to be learned is this: if for you. these were scaffold plank beneath your feet instead of insulated foam board, CB We generally can while the MOE value of the product is beat competitor important to your comfort level, it's the pric ing. fiber bendi.ng strength that weighs more on your safety.
There is yet another aspect to be considered as well. Plank thickness governs plank performance, and the design values influence the ultimate performance to a greater extent. The masonry industry is accustomed to using 2 x 10 (1 1/2 x 9 1/4-inch nominal size) plank. Therefore, if you www.scaffoldlngrentalandsales.com are considering a thicker manufactured plank, keep in mind that if it has low design properties, it will likelybe heavier and therefore more difficult to handle. At the very least, it could pose a tripping hazard ifmixed in a scaffold system with other plank types.
www.masonrymagazine.com December 2016 � MASONRY I 17