Benchmarking Traditional PTI Design Against Advanced Finite Element Method on a Ribbed 40×70 Slab-on-Ground and Design of a Wafflemat Using FEM Approach
Post-tensioned, slab-on-ground foundation designs are a practical and affordable foundation option for many single-family, multi-family, and light commercial buildings. The current industry standards in use that offer design guidance include: ACI 318 and PTI 3rd Edition (2008). In 2012, the PTI Slab-On-Ground Alternative Design Committee (DC-15) published an article in the PTI Journal expressing the need for an alternate, analytical design approach to the current methodology.
This report reviews the results of a parametric study that was conducted to determine the calculated performance variations between the traditional PTI method of a slab-on-ground foundation design vs a 3D finite element analysis (FEA) approach implementing the latest computer software. We will review and discuss the variations between a traditional ribbed slab foundation based on the PTI Method, a traditional ribbed slab based on a FEA model, a modified permanent, plastic void form foundation using the traditional PTI method and the modified permanent, plastic void form foundation using a FEA model. Additionally, each one of these methods will be modeled with a 2” PVR soil design parameter and a 4.5” PVR soil design parameter to review the effects of the soil recommendations provided by the geotechnical engineer on a given project. We will further review how geotechnical design vales impact the structural design of the foundation.
Anna Olveda, MSCE
VP of Engineering