Professor Abolmaali has received a one-year $117,635 research grant to conduct Nonlinear Three Dimensional Finite Element Analyses for the Integrated Pipeline Project (IPL) from the Tarrant Regional Water District and Dallas Water Utility. The IPL project includes 150 miles pressure pipelines from Lake Palestine to Dallas Fort Worth.

The research will develop a high fidelity and highly robust nonlinear three-dimensional (3D) Finite Element Model (FEM) for steel pipe and American Water Works Association Specifications C-301 pre-stressed concrete cylinder pipe (PCCP) that can be used to predict pipe performance under varying backfill and loading conditions to be identified by the IPL design team. The FEM analyses algorithm will consider material, geometric, and contact nonlinearities. The material non-linearity will consist of elasto-plastic and tension-stiffening constitutive law for steel and PCCP, respectively. For soil, both short-term and long-term material properties will be considered. Material models such as Drucker-Prager, Mohr-Coulomb, Selig Hyperbolic, and others will be considered for optimum performance. The geometric non-linearity will include the large deformation analysis for soil and steel pipe materials which will be based on the Almansi (Eulerian) strain that yields to the Cauchy stress tensor from which the total Lagrangian algorithm will be employed. The implementation of large deformation algorithm will ensure that the deformation of the soil and pipe are accurately simulated. Finally, the contact nonlinearity will include the contact elements at the interface between the pipe and soil and different soil layers during sequential layered construction. Several different contact algorithms such as surface-to-surface and node-to-surface will be implemented for model optimization. Displacement-control analysis algorithm will be employed to eliminate potential errors resulting from discontinuities in material constitutive law such as C0 type curves resulting from elasto-plastic response of steel materials or bilinear response of concrete and steel cylinder in tension stiffening model.