Report Part 1: State of Practice State of the...
Transcript of Report Part 1: State of Practice State of the...
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Towards next generation p-y relationships : Part 1
Presenter: Anne Lemnitzer Graduate student contributor: Camilla Favaretti
Report Part 1: State of Practice – State of the Art
University of California, Irvine
Project Overview:
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Presentation Outline
Brief review of project objectives, background & motivation
Content of report to be published / p-y issues Discussion
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Project Members Anne Lemnitzer (UC Irvine, PI, Lead) Pedro Arduino (Univ. of Washington) George Anoyatis (Univ. of the West of England) Scott Brandenberg (UCLA) Tara Hutchinson (UCSD) George Mylonakis (Univ. of Bristol)
Advisory Panel Peter Robertson (Gregg Drilling) Jonathan Stewart (UCLA) Tom Shantz (Caltrans)
Extended Project Members and expert board Diane Fiorelli (Langan) Haze Rodgers (Langan) Kyle Rollins (BYU) Armin Stuedlein (Oregon State Univ.) Ben Turner (Dan Brown & Associates) John Turner (Dan Brown & Associates) Shin-Tower Wang (Ensoft) Silas Nichols (FHWA)
Current Project Team
Academia Industry
Government
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P-Y Curves – what motivates this design tool?
Predicts the full, nonlinear lateral load-deformation response;
Can incorporate multiple layers of soil and/or rock;
Accounts for nonlinear M–EI behavior of reinforced concrete shaft;
Provides structural analysis (shear, moment, rotation, and displacement) of the drilled shaft;
Accounts for the effects of axial compression load on the structural behavior of the shaft;
Can be implemented easily on a desktop computer with available software.
Lack of a strong theoretical basis for p-y curves
Requires back analysis of instrumented load tests to verify and validate p-y curves; such verification is currently lacking or limited to a few cases.
Discontinuity of response results
Advantages
Limitations
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P-Y Models – where are we coming from?
Matlock 1970 – Soft clay with free water Reese et al 1975 – Stiff clay with free water Reese et al 1974 – Sand O’Neill & Murchison (1983) - Sand
API
Matlock (1970)
Reese et al. (1975)
Reese et al. (1974) O’Neill & Murchison
(1983)
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Example: Reese & Cox, 1975 (Stiff Clay Study)
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Screenshot of the p-y formulations available in Lpile.
User defined py curve option is used less than 10% of the time [personal communication with Ensoft, Inc.]
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1 General Introduction to the PY analysis
2 State of the Practice Survey 3 State of the Practice Review 4 State of the Art Review 5 Recommendations for Immediate
and Long Term Future Research
Group Meeting with the Project Team: Report Outline
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Working group meeting: September, 2017
State of the Art Issue to be discussed in the report:
• Diameter studies
• Inertial & kinematic loading effects
• Fixity conditions (at the pile head and pile tip – e.g., rock socketing)
• Pile nonlinearity & structural performance issues
• Influence of loading: cyclic and dynamic loading, torsion
• Effects of batter
• Behavior of pile groups
• Effect of soil layering
• Installation effects
• Py relationships from advanced insitu testing
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P-Y Models – what has been done since the 1960s?
Our initial review showed that since the early studies, we have approximately: - More than 200 analytical studies on py relationships - More than 30 studies in centrifuge - More than 80 studies on large scale experimental pile behavior
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Statistics of > 65 large scale tests reviewed
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Example: Research on Head Fixity
0.6 m Flagpole
0.6 m Fixed-Head pile
Khalili Tehrani et al. (2014) compared test results from RC fixed & free head pile researched by Stewart et al (2007).
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• Fixed-head capacity is 50% greater than flagpole. • The fixed-head pile has 100% larger capacity than API. • Initial stiffness is overestimated by 30% by API.
Experimental curves API curves
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Reese et al. (1974) Reese et al. (1975) Lam & Cheang (1995) Fan (1996) Ashford &Juirnarongrit (2005)
kind
Stevens & Audibert (1979) Wiemann et al. (2004) Sorensen (2010) kdep
Hansen (1961) Broms (1964) Reese et al. (1974) Briaud & Smith (1983) Fleming et al. (1992)
k0=p/y
D^? D^1
pult No recommendation
Experiments:
2ft
6ft Photo: Juirnarongrit, 2005
Stewart et al. 2007, Khalili-Tehrani et al. 2014
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Huang et al. 2001 Roberson et al., 1989
PY Curves from In-Situ Testing: DMT, PMT, CPT
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PY Curves from In-Situ Testing: DMT, PMT, CPT
Robertson et al., 1986
Pressuremeter Concept:
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Brandenberg and Arianna (2017)
- Use of the pySimple3 material model - Computing p-y properties from CPT data (continuous) - Special Focus on Intermediate Soils (2.3 <IC<2.7) - Incorporation of layering effects - Use of small strain stiffness
Courtesy of Brandenberg and Arianna
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Testing with new materials
• Main Concern: Seismic. Increased seismic loads
necessarily require increased steel reinforcement
using current design specifications
• The density of steel in the rebar cage can cause
difficulty during concreting, leading to voids and
loss of cover
• high strength (550 MPa) steel as an alternative to
420 Mpa
• use of permanent steel casing in design for
flexure, lateral load transfer
• Evaluate use of hollow bar as dual purpose
elements (structural, CSL access), compare to
TIP Thermal Wires
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Example: Stuedlein et al. 2017, 2018
ODOT-ADSC WCC Study: Axial and Lateral Response of Drilled Shafts
with High-strength Steel and Steel Casing
PI: A.W. Stuedlein, OSU
HSIR
CNIR CIR
MIR
MIR: mild steel, uncased
HSIR: high strength, uncased
CIR: mild internal steel, cased
CNIR: no internal steel, cased
Slide Courtesy of Prof. Armin Stuedlein
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Lateral Loading Tests: Test Setup
January 29, 2018 20
MIR HSIR
CIR CNIR
(b)
(a)
Slide Courtesy of Prof. Armin Stuedlein
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Stuedlein et al. 2017: Torsional Response of Drilled Shafts
0 50 100 150 200 250 300Torque, Th (kN-m)
0.021°
0.048°
0.092°
0.103°
(b)TDS
0
1
2
3
4
5
0 50 100 150 200
De
pth
(m
)
Torque, Th (kN-m)
0.023°
0.084°
1.07°
1.75°
(a)TDSFB
Head
Rotation,qh
FDM with τult = τm (Solid Lines, typ.)
FDM with τult = τc (Dashed Lines, typ.)
Head
Rotation, qh
0.023 0.084
1.75
1.07
0.021 0.048 0.092
0.103
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Supporting Survey – State of Practice – Preliminary Results (Survey is currently expanded towards east coast and outside CA)
In which Sector do you practice? Which industrial application is your work/design mostly related to (please circle):
Are you structural/geotechnical. Which degree and licenses do you hold?
What type of deep foundations do you design and how often (in % of total amount of deep foundation design)? (e.g., drilled shafts, driven piles, monopiles, auger cast piles, etc.)
Which type of analysis methods (%) do you use for your lateral deep foundation design? Which Software do you typically use? Please indicate the %.
How are the results of your lateral pile analysis used? What type of lateral loading do you primarily use in your analysis? Please circle your answer.
How do you determine your EQ loads:
What are the primary sources of uncertainty during your lateral foundation analysis and design?
What type of site investigation methods do you primarily use? Where do you get your strength parameters from?
Sample questions
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Which industrial application is your work/design mostly related to?
Answers in % of all responders, multiple choice
* Please note: responders were able to select multiple answers (chart will not add up to 100%)
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Which type of analysis methods do you use for your lateral deep foundation design?
* Please note: responders were able to select multiple answers (chart will not add up to 100%)
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If you use the p-y method, to which % of the time to you employ this method?
100% of the time
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Which software do you typically use for Single Pile design?
Lpile
Strain Wedge
FLAC OpenSees
Plaxis MFAD
Ansys Abaqus
Other
* Please note: responders were able to select multiple answers (chart will not add up to 100%)
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How are the results of your lateral pile analysis used?
* Please note: responders were able to select multiple answers (chart will not add up to 100%)
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What type of lateral loading do you primarily use in your analysis?
* Please note: responders were able to select multiple answers (chart will not add up to 100%)
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What are the primary sources of uncertainty during your lateral foundation analysis and design? (open ended question)
(layering, variability, Insufficient data)
* Please note: responders were able to select multiple answers (chart will not add up to 100%)
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Online tool for literature review: Database of lateral load tests