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Development of High-Quality Databases of Deep Foundations Load Tests

Description:

Data at foundation load test sites can be used to verify and optimize the geotechnical design of foundations in the projects in which they are used. In addition, if complete and high-quality data at load test sites are obtained and compiled in databases, they can be used in the future by: a) designers to improve the geotechnical design for production foundations and, more important, b) by researchers in the reliability calibration to develop more accurate and economical foundation LRFD (Load and Resistance Factor Design) geotechnical design methods.

Reliability calibration is the best option to develop resistance factors for the geotechnical design methods of foundation and thus for implementation of LRFD. As geotechnical practice moved towards LRFD, a vast majority of the current LRFD foundation geotechnical design methods were developed based on past experience and judgement. There are only a very small number of reliability-based resistance factors for foundations adopted by the American Association of State Highway and Transportation Officials (AASHTO) or State Departments of Transportation (DOTs) due to lack of quality and complete foundation load test databases. The current highway engineering practices emphasize the use of load test results for individual projects, not for future reliability calibration. This could lead to two main problems in the load test data obtained in these projects: a) data is not complete or of the quality (accuracy) needed for use in the reliability calibration; and b) not reported or compiled for future use. There are variations in the type of data collected at load test sites and the procedures followed for obtaining these data by various State DOTs. There are still issues with the quality of the reported data at load test sites (e.g., clarity, accuracy and completeness), even in some developed foundation load test databases.

Although there have been some noble efforts in the development of databases for deep foundation load tests, there is still urgent need to address the issues listed above and develop high-quality national, regional, and local deep foundation load tests in the USA.

Objective:

Develop and share a national high-quality database of deep foundation load test data, and develop recommendations to help highway agencies use this national database to develop and share their quality databases of deep foundation load tests.

Benefits:

This research study will help to move the geotechnical design of deep foundations to true reliability-based design, which is the best option for LRFD implementation. It will lead to the development of more accurate and economical foundation geotechnical methods. These advantages will increase the confidence in design methods for foundations and reduce significantly the cost for construction of foundations. Reliability calibration requires development of quality foundation load test databases. It is a crucial need at this time since the vast majority of the current LRFD foundation geotechnical design methods are developed based on past experience and judgement, not reliability calibration. Finally, the local foundation load test databases also would allow for reliability calibration of local design methods not covered in AASHTO LRFD, and the development of more accurate and economical design methods than those developed based on the national databases.

Related Research:

Toward developing quality foundation load test databases, recommendations to develop and share quality foundation load test databases were published in TRR 2511 (Abu-Hejleh et al., 2015), and recently FHWA released its Deep Foundation Load Test Database (DFLTD) - Version 2.0 (Petek et al., 2017). The DFLTD v.2 includes an updated framework and 150 new load test data for large size diameter open end driven piles. The database is relational where records can be queried in numerous ways to include foundation type and size, subsurface soil information, and location. The DFLTD v.2 can be used by Federal and State agencies, universities, consultants and contractors, design engineers and planners, and research and development professionals.

In addition, several State DOTs and researchers developed their own foundation load test databases (e.g., Florida, Iowa, Louisiana, and Illinois). Even so, significant work is still needed to develop high-quality national and local databases of deep foundation load tests that include a complete and adequate number of high-quality and complete records of data at load test sites that cover all common foundation design and construction conditions encountered in the United States.

Tasks:
  • Develop/finalize a national protocol to obtain and report quality, complete, and consistent data at new load test sites, and to identify and compile existing quality load test data that are not reported in load test databases.
  • Develop/finalize the framework for a quality foundation load test database to store the data collected at load test sites and provide the information needed by designers and researchers for the two applications discussed above. This database should be made available online, in line with the developed national protocol, flexible so that it can be easily updated, changed and expanded, and have a user-friendly interface.
  • Develop a national quality database for deep foundation load tests using available data. It should include the reported quality and complete load test data, for example in the existing load test databases, such as DFLTD, v.2 (review these databases), and the available quality load test data that are not documented.

  • Develop recommendations to help State DOTs develop their foundation load test databases using the 3 products described above.

  • Develop guidance and examples for applications and limitations of foundation load tests databases.
  • Develop recommendations for sharing, updating, and maintaining of the national and local foundation load test databases.
Implementation:

Implementation of the results of this research study can be immediate. State DOTs, consultants, and researchers would have access to use the data in the national database. The State DOTs may need to sponsor research studies to benefit from the work performed in this study and develop their own foundation load test database. The study recommendations should be discussed and implemented through collaboration between national and state transportation agencies (AASHOT, FHWA, State DOTs, ASCE, DFI, ADSC, and PDCA).This collaboration can happen at conferences, such as the TRB Annual Meeting, and led by AASHTO and/or FHWA. One of the outcomes of this collaboration is to address how to maintain and update the national database for foundation load test databases

Relevance:

Supported and relevant to: • Ohio DOT
• Alabama DOT • New Mexico • Indiana DOT • Louisiana DOTD • Louisiana Transportation Research Center • North Carolina DOT

Sponsoring Committee:AKG20, Soil and Rock Properties and Site Characterization
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Mr. Mohammed Mulla; Dr. Naser Abu-Hejleh, and Dr. Jennifer E. Nicks
Date Posted:03/20/2017
Date Modified:03/22/2017
Index Terms:Geotechnical engineering, Load tests, Foundations, Load and resistance factor design, Reliability, Databases, Calibration, State departments of transportation,
Cosponsoring Committees:AKG70, Foundations of Bridges and Other Structures; AKG10, Engineering Geology
 
Subjects    
Highways
Data and Information Technology
Design
Geotechnology
Bridges and other structures

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