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Research Activities: 2008
MTI/MoDOT Transportation Geotechnical Research Program - Tasks 2 & 4
Matching Research Agency
Missouri Department of Transportation (MoDOT) and University of Missouri
Two graduate students
The general objective of the load test program, Task 2, is to develop methods and procedures that will allow MoDOT to design the lowest cost bridge foundations in different geologic conditions, to improve foundation selection so that the most appropriate foundation type is selected, and to decide when design and/or construction phase field load tests will produce lower cost structures. The primary means for achieving this objective will be to quantify the bias and variability introduced into the foundation design process by relevant design methods. This approach is similar to what will be undertaken for Task 1 of the broader program except that the load test program will quantify variability and bias in foundation design procedures themselves (many of which are empirically based) while the site characterization program will quantify the variability and bias in the input parameters that will be used in those design methods. The combined effects due to input parameters and due to design procedures will be integrated in the LRFD specifications to be developed as part of Task 4.
The objective of Task 4 is to develop new, MoDOT specific load and resistance factors based on the results of other activities within this research program and to develop new design specifications that will produce substantial cost savings made possible by the entire research program. Specifically, this project will serve to establish MoDOT specific load and resistance factors for design of earth slopes and foundations and to develop recommended LRFD design specifications for adoption by MoDOT to implement the results of this research program. The developed specifications will allow MoDOT to achieve appropriate target risk levels and to account for the variability and conservatism established for relevant design soil parameters and design methods in other tasks.
This project includes two components of a comprehensive research program to develop new and improved LRFD specifications, and associated commentary documents, for design of bridge foundations and earth slopes. Task 2 involves a program of full-scale load testing of foundation elements to evaluate and quantify variability and bias in relevant design methods for deep foundations. Task 4 focuses on performing analyses to establish improved load and resistance factors for design of bridge foundations and earth slopes and development of a new design specification to allow implementation of these improvements. This task will integrate the results of lab and field investigations performed as part of this research program to produce substantial and recurring cost savings for MoDOT.
Results of this task will serve as the primary means for implementing the results of the entire research program and for reaping cost savings associated with more effective design. The new design specifications will allow MoDOT to realize cost savings associated with designing for consistent and appropriate risk, without requiring formal risk and reliability analyses for individual projects. We expect the design process will remain familiar to those using current LRFD design methods, but with slight modifications to account for the improved knowledge to be developed from this research program.
We also expect the new design specification to provide MoDOT designers with the practical information necessary to make effective design decisions for bridge foundations. This information is expected to result in better choices for bridge foundations (e.g. drilled shafts vs. driven piles vs. spread footings), more appropriately sized foundations, and better decisions regarding the value and appropriateness of various site investigation activities and design or construction phase load tests.
Relationship to other Research/Projects
This project is one component of a comprehensive research program to develop new and improved LRFD specifications for design of bridge foundations and earth slopes. Funding for this program is to be provided by the Missouri Department of Transportation, NUTC, and the University of Missouri – Columbia and Missouri University of Science and Technology. The program includes four broad tasks that, when integrated, will allow MoDOT to realize substantial and continuing cost savings for design of bridges and earth slopes. Task 1 includes activities to improve site characterization practices through a comprehensive laboratory and field investigation to quantify variability and bias in relevant design parameters. Task 2 includes a program of field load testing for bridge foundations and assessment of current and improved methods for design of bridge foundations. Task 3 involves assessment and evaluation of risks for bridge foundations and earth slopes and development of appropriate target risks for bridge foundations and earth slopes. In Task 4, the results of Tasks 1 through 3 will be integrated with analyses to develop new and improved LRFD methods for design of foundations and earth slopes. The principal deliverables from this program will be two new design specifications (one for Bridge Foundations and one for earth slopes), and three commentary documents to accompany the specifications. The commentary documents will detail the results of research produced in Tasks 1 through 3, provide justification for the new specifications, and provide guidance for implementation of the new specifications in MoDOT practice.
Technology Transfer Activities
Technology transfer for this portion of the research program will be achieved through publication of one or more papers at technical conferences or in refereed journals.
Transportation Research Board Keywords
Bridge foundations, design, embankments, risk management