FEM vs Empirical PTI Methods
FEM vs Empirical PTI Methods
(OP)
All,
First time facing this issue. Usually FEM analysis yeilds a thinner slab in practice for us so this issue hasn't arisen. We recently designed a PT SOG uniform thickness slab for a large apartment complex (6-8 units per building). The soils have large edgelift conditions andcomplex geometry. We designed the slab using a FEM program and came up with 14" thick slabs that barely work. The owner has hired another engineer for a second opinion and he (using the empirical PTI method) comes up with 10" slabs. I understood the PTI method to be conservative compared to FEM analysis. I do not know how to justify our thicker slab except to say that we have designed to the exact site conditions while the other engineer is using less exact solutions. Have any of you had this happen? What did you do or recomend doing?
akastud
First time facing this issue. Usually FEM analysis yeilds a thinner slab in practice for us so this issue hasn't arisen. We recently designed a PT SOG uniform thickness slab for a large apartment complex (6-8 units per building). The soils have large edgelift conditions andcomplex geometry. We designed the slab using a FEM program and came up with 14" thick slabs that barely work. The owner has hired another engineer for a second opinion and he (using the empirical PTI method) comes up with 10" slabs. I understood the PTI method to be conservative compared to FEM analysis. I do not know how to justify our thicker slab except to say that we have designed to the exact site conditions while the other engineer is using less exact solutions. Have any of you had this happen? What did you do or recomend doing?
akastud





RE: FEM vs Empirical PTI Methods
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.