Practical method for load and resistance factor design (LRFD) of deep foundations at the strength and service limit states

Roberts, Lance A.; Misra, Anil; Levorson, Steven M.

doi:10.3328/ijge.2008.02.04.355-368

Cited by 14 publications

(6 citation statements)

References 9 publications

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“…A t-z model back-computation procedure using load test data is described extensively in Roberts et al (2008). The method is an iterative process where the load-settlement and strain magnitude predicted by the t-z model is matched to the load-settlement and strain magnitudes of the deep foundation using the load test data.…”

Section: Analysis Of Load Test Datamentioning

confidence: 99%

Support of Structures in Expansive Shale Using Recycled Plastic Piles

Roberts

Brandner

2010

DFI Journal - The Journal of the Deep Foundations Institute

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Expansive soil formations can be found throughout the United States. When subjected to wetting, these formations have the potential to swell and exert large uplift forces on buildings and foundations. Lightly loaded structures, such as single family residences founded in areas of expansive soils, can be significantly damaged due to uplift movement from swelling actions. Designing an economical deep foundation that can resist uplift forces is critical to prevent damage to these structures. The current solutions to control uplift due to swelling soils, such as over-excavation and replacement of the expansive material or the use of drilled shafts can be costly. Piles made from recycled polymer materials could provide a solution. Due to a lower coefficient of friction along the interface of the soil-pile interface compared to traditional pile materials, solid recycled plastic piles can allow expansive soils to move nearly independently from the pile when wetted. This results in a much smaller magnitude of uplift force being transferred to the structure, which minimizes the risk of significant structural damage from excessive movements. This paper presents the results of research conducted on the use of recycled plastic piles in an expansive shale environment. The preliminary phase of the project involved the installation of six recycled plastic piles at a test site on the South Dakota School of Mines and Technology campus. Two of the piles were subjected to a full-scale compression load test in order to determine ultimate capacity. The remaining four piles were subjected to long-term monitoring of uplift movement during the course of the project. A concrete anchor was also installed at the test site for uplift monitoring. Data gathered during the field and laboratory testing was utilized in a non-linear soilstructure interaction model to predict the displacement behavior and internal stresses within a plastic pile and concrete anchor subjected to uplift forces from the swelling shale. While more research is needed to further understand the application for recycled plastic piles, the results from this research indicate that their use is a viable alternative for support of lightly loaded structures in expansive soil environments.

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Section: Analysis Of Load Test Datamentioning

confidence: 99%

Support of Structures in Expansive Shale Using Recycled Plastic Piles

Roberts

Brandner

2010

DFI Journal - The Journal of the Deep Foundations Institute

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“…Nonlinear, load-settlement analyses using the t-z model approach have been described extensively by Misra and Roberts (3), Misra et al (4,5), Roberts (6), and Roberts et al (7 ). In a t-z model approach, the resistance of the soil along the side of a deep foundation element and at the tip is represented by a nonlinear spring system.…”

Section: Load-settlement Analysis Using T-z Model Approachmentioning

confidence: 99%

“…The force-displacement behavior of the soil-structure interface springs is often assumed to be hyperbolic, with an initial stiffness, K init , and an ultimate strength, q o , which is the product of the deep foundation perimeter and the ultimate shear strength of the soil-structure interface τ u in drained or undrained conditions. The force-displacement behavior of the tip soil can be similarly represented using the initial tip soil stiffness, K ti , and the ultimate strength of the tip soil, q t , in drained or undrained conditions (3)(4)(5)(6)(7). The soil-structure interface strength and stiffness parameters are related to the deep foundation The axial design of deep foundations has traditionally followed ultimate limit state principles where the ultimate capacity is determined using either static capacity predictions or field load test interpretations.…”

Section: Load-settlement Analysis Using T-z Model Approachmentioning

confidence: 99%

“…In Figures 1a and 1b, head settlement and strain gauge data from a field load test conducted on a drilled displacement (DD) pile are shown as a series of points. Following the backcomputation procedure given in Roberts et al (7), the t-z model is used to match the observed deep foundation field performance using both the head settlement and strain gauge data, and the model prediction is superimposed on the measured points as the solid lines. Thus, the nominal spring parameters determined using a t-z model backcomputation process can be directly verified from field settlement performance of an installed deep foundation at a given site.…”

Section: Load-settlement Analysis Using T-z Model Approachmentioning

confidence: 99%

“…The COV of the PDF in Figure 4 represents the variability of the foundation resistance at the limiting tolerable settlement and is thus equal to Ω R . Because the t-z model was used to obtain the load-settlement performance of the deep foundation in the field, λ R was assumed to be equal to unity (5)(6)(7). Once these values for Ω R and λ R are substituted into Equation 2, the resistance factor for the strength limit state is computed.…”

Section: Performance-based Design For Resistance Factor Calibrationmentioning

confidence: 99%

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Performance-Based Design of Deep Foundation Systems in Load and Resistance Factor Design Framework

Roberts

Misra

2010

Transportation Research Record

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Performance-based design methods are increasingly being used for the design and analysis of structures. For performance-based design of deep foundation systems, limiting tolerable movements are one of the design criteria that can be used in lieu of the usual ultimate load capacity. The limiting tolerable movement is often selected to correspond to a movement that will cause damage to a structure but will not produce a collapsible failure of the structure. Performance-based design principles can be extended to include the axial design of deep foundation systems under strength and service loading conditions. In this extended approach, limiting tolerable settlements can be selected to correspond to a movement that will either cause excessive stresses in the structure or render a structure functionally inoperable because of serviceability limits. A performance-based design approach for axial design of deep foundations under the strength and serviceability limit states was developed. The design approach is integrated with the load and resistance factor design framework to develop an efficient and consistent methodology for satisfying both limit state criteria.

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Probabilistic analysis of site-specific load-displacement behaviour of cement-fly ash-gravel piles

Xin

2019

Soils and Foundations

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Practical method for load and resistance factor design (LRFD) of deep foundations at the strength and service limit states

Cited by 14 publications

References 9 publications

Support of Structures in Expansive Shale Using Recycled Plastic Piles

Support of Structures in Expansive Shale Using Recycled Plastic Piles

Performance-Based Design of Deep Foundation Systems in Load and Resistance Factor Design Framework

Probabilistic analysis of site-specific load-displacement behaviour of cement-fly ash-gravel piles

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