Forklifts to be used in the building impart 8,000 pounds of force at the wheel, which has a 6-inch by 10-inch tire footprint on the slab. Take the case of a warehouse with a 6-inch-thick, 2,500-psi concrete slab on 2 inches of EPS insulation with a rated stiffness of 360 psi for one inch. u = Poisson’s ratio for concrete (0.15)Īn example illustrates the significant difference in the calculated results.h = Thickness of concrete slab in inches.f ‘ c = specified concrete compressive strength in pounds per square inch.E = Modulus of elasticity of concrete in pounds per square inch (57000√ f ‘ c).k = Stiffness of one inch of EPS insulation in pounds per square inch.K = Subgrade reaction modulus of total EPS insulation in pounds per cubic inch (k/t).P = concentrated load on concrete slab in pounds.The pressure beneath a given slab under a load can be determined using the following formula, found in the Theory of Plates on Elastic Foundations, as described by Timoshenko and Woinowsky-Krieger: A more accurate approach to this problem is to use the Modulus of Subgrade Reaction (K) to determine the slab’s deflection and the resultant stress applied to the elastic insulation subgrade. This assumption, while not necessarily incorrect, can be very conservative.Ĭoncrete slabs distribute loads in a more even fashion, which means that the insulation does not need as high a compressive resistance compared to the typical simplified approach. Many designers assume that a concentrated load applied to the slab transfers to the rigid foam subgrade through a triangular load path. The problem is that designers often do not adequately account for how the concrete slab and underlying subgrade interact. Such insulation helps reduce heat loss to the ground in residences, cold storage units, warehouses and other commercial, institutional and industrial structures. Rigid foam insulations, such as expanded polystyrene (EPS), have been used successfully under concrete slabs for more than 40 years. EPS insulation in an under-slab application.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |