Jul 26, 2012

Grant Awarded to Study Alternative Design for Large-Diameter Steel Pipe

Two-year research project at UT-Arlington could lead to significant savings on $2.3 billion Integrated Pipeline Project

A major research project conducted at the University of Texas at Arlington could lead to significant advances in the design of large-diameter steel pipe. The two-year study, which is tied to a multi-billion-dollar pipeline project in North Texas, could have major ramifications for the way steel pipe is designed and installed in projects across North America.

The “Three Dimensional Nonlinear Finite Element Analyses” study is being led by Dr. Abolmaali, professor of structural engineering & applied mechanics with the civil engineering department at UT-Arlington. The research is funded by a $603,600 grant developed in conjunction with the Integrated Pipeline (IPL) Project, a massive water delivery system conceived by the Tarrant Regional Water District (TRWD) in partnership with the city of Dallas. The pipeline will travel from Lake Palestine to Lake Benbrook, with connections to Cedar Creek and Richland-Chambers Reservoirs—149 miles in all. The project is budgeted for $2.3 billion and is scheduled for completion in 2040.

“We believe Dr. Abolmaali’s research could lead to substantial cost savings on this project if the study proves that modified backfill can be used in the installation of large-diameter steel pipe,” said David Marshall, engineering services director for TRWD. “If we are able to reuse the materials excavated from the pipeline trench, we could reduce the number of tractor-trailer runs each day from roughly 60 to two.”

The finite element model simulation will examine how excavated soil interacts with the steel pipe system under widely varying conditions, thereby optimizing design based on informed analyses.

Dr. Abolmaali and his team have developed three-dimensional computer models to predict pipe performance under varying backfill and loading conditions. Hundreds of computerized simulations will be performed to predict the pipe’s behavior under multiple variables, by using incremental 3-dimensional finite element models that consider staged construction, material, geometric and contact non-linearities.

Importantly, these simulations will be corroborated by full-scale field tests in which large-diameter steel pipes will be installed and analyzed with varying fill depths, trench widths and backfill materials. Upon verification of the simulation model with field tests, a sensitivity study will be performed by testing the effects of several independent variables on the response of the staged construction soil-pipe interaction analyses.

“Our study will aid the TRWD design team by providing more data on the behavior of the soil-pipe interaction than has previously been available,” said Dr. Abolmaali. “While the current American Water Works Assn. specifications offer important guidance, they don’t take into account detailed nonlinear soil-structure interaction analyses such as those addressed by our research. Our study will allow the IPL team to optimize the backfill used during construction so that the pipe system is neither over- nor under-designed.”

“Current design techniques used for large-diameter steel pipe are rather empirical in nature,” Marshall said. “I am hopeful that this study leads to a more refined and advanced design that not only reduces construction costs but extends the service life of the IPL system.”