Dr. Abolmaali Receives Two-Year $486,600 Research Grant from Tarrant Regional Water District
Posted: Mon May 7 08:02:10 2012
Dr. Abolmaali received a two-year $486,600 research grant to conduct Three Dimensional Nonlinear Finite Element Analyses for the Integrated Pipeline Project from the Tarrant Regional Water District. This brings Dr. Abolmaali's funding level, as PI, for the 2011-2012 academic year to $775,235.
The objective of this research is to develop a high fidelity, 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 Pipeline Design Teams. The FEM analysis 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. The material non-linearity for soil will be the time-dependent properties for implementation in the FEM to predict the long term response of the pipe. The geometric non-linearity will include total and or updated Lagrangian large deformation analysis for soil and steel pipe materials. Finally, the contact nonlinearity will include the contact elements used at the interface between the pipe and soil and different soil layers during sequential layered construction. The FEM will use temperature dependent material properties to simulate the effect of compaction on the pipe deflection for each layer. Special algorithm is written to adjust the deformed shape of each subsequent soil layer for pipe shape changes due to the compaction of the current level.
Full scale filed tests will be conducted on large diameter steel pipes by using the CLSM fill depths and varying trench widths. Thus, Field Instrumentation and monitoring of test pipes embedded with native soil CLSM will be conducted. All tests will be held at IPL JB-4 Site in Grand Prairie, TX. The instrumentation will consist of Linear Displacement Variable Transducers (LVDTs) and strain gauges. Horizontal and vertical LVDTs will be installed at two locations along each test pipe length to obtain horizontal and vertical deformation readings, respectively. Strain gauges will be placed at crown, springlines, and invert at multiple locations such that adequate number of readings for hoop and bending strains are obtained.
A nonlinear regression-based parametric study will be conducted to develop design equations for dependent variables as functions of independent variables. A sensitivity study will be conducted by testing the equations for the effects of each independent variable on the response of the dependent variables. This will be done by varying one variable at a time, from its low-to-medium-to-high values while keeping other variables at their intermediate values. The sensitivity plots will identify the effect of each independent variable on the behavior of the dependent variable. For example, a steep slope on such a graph indicates that the effect of that independent variable is significant. On the other hand, if the effect of variation of the independent variable is insignificant, the graph would have a flat slope.