Research

Bridge Photos-8
Bridge Photos-5
Bridge Photos-2
Bridge Photos-9

My primary research interest is at the interface of geotechnical and structural earthquake engineering, studying the response mechanisms of sub-and superstructure elements and systems. My current and past research projects include the experimental studies and numerical evaluation of deep foundation systems, underground structures and embankment systems, as well as the response of structural components to static and dynamic loading via large scale testing (field/lab), model scale testing (centrifuge/shake table) and analytical-numerical frameworks. I am also interested in the development of innovative instrumentation schemes and sensor technology applicable to soil structure interaction (SSI) studies. My research in deep foundations also includes the exploration of high performance materials that reduce the carbon footprint in conventional foundation design.

I am furthermore interested in studying the influence of SSI on structural components and systems through case and field studies, model/large-scale testing and numerical and parametric simulations.  Studies pertaining to the structural response behavior due to ground excitation include the assessment of building components (e.g., moment resisting frame components and cladding systems), as well as the investigation of retrofit and strengthening mechanisms for structurally damaged components.

Interests

  • Foundation Engineering
  • Soil-structure interaction
  • Infrastructure response under hazard loading
  • Development of sensor instrumentation
  • Large-scale testing
  • Earthquake engineering

Selected Research Projects

  • Reconnaissance Studies of the 2021 Western European Floods

    To be added

  • Performance of Large-Scale Excavations in Los Angeles

    This could be a full decription about the project

  • Installation effects of drilled displacement piles: a case study analysis of ~140 pile foundations

    In recent years, the use of DD piles in the U.S. has increased, and these elements have been used as structural foundations (e.g., support for column loading) and for ground improvement (e.g., column-supported embankments) on commercial and public work projects. Historically, DD piles have been installed with diameters ranging from about 12- to 26-inches (300 to 675 mm) and to a maximum depth of approximately 125 ft (38m), whereby the geometry of the pile (diameter and depth) are directly related to the capability of the drill rig used to construct a DD pile.

    During the advancement and extraction of the tooling, displacement (via radial compaction) of the in-situ soil is required for this technique to be effective. Understandably, a considerable amount of mechanical work (e.g., energy and power) is required by the drill rig to displace the volume of soil necessary to create the desired size of the DD pile.  At the location of the tooling in the ground, the tool itself imparts compactive stresses and shearing stresses to the soil during the construction of the DD pile.  Various contractors and researchers have reported on the different design approaches / assumptions used, equipment and tooling, benefits of DD piles, and QC/QA protocol.

     

    Funding Agency: Deep Foundations Institute (DFI)

    Time Frame of Investigation and Data collection: 10/2016 – 8/2022

    Products and Publications generate through this work:

  • Towards Next Generation P-Y Curves - Part 1: Evaluation of the state of the art and identification of recent research developments

    This research program consists of a well-coordinated literature study of analytical, model-scale and large-scale deep foundation systems under lateral loading with the objective to (i) identify limitations with existing p-y curves & p-y design recommendations, (ii) summarize recent research that can help address these limitations, and (iii) identify additional research needs required to formulate Next Generation P-Y (NGPY) relations. The specific outcome consists of a comprehensive report which will compile foundation studies performed in the last 40 years and help develop a new set of “Next Generation P-Y Curves” in the near future.

    Funded by: Pacific Earthquake Engineering Research Institute (PEER)

     

    Project Info

    http://peer.berkeley.edu/transportation/wp-content/uploads/2010/09/PEER-NGPY1_Lemnitzer-web2016113.pdf

  • Levees and Earthquakes: Averting an Impending Disaster

    This study evaluated the performance of liquefiable and non-liquefiable embankment systems in California’s Delta region. Study objectives included the overall performance behavior of levees under various levels of ground shaking and the investigation of settlement mechanisms pertaining to the soft underlying soils (peat). A full award description, including the final project reports are publicly available: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1208170

    Recognition by ASCE: 2022 ASCE MIDDLEBROOKS AWARD

    The authors’ most recent paper (titled “Settlement Rate Increase in Organic Soils Following Cyclic Loading” ) was published in the ASCE Journal of Geotechnical and Geoenvironmental Engineering was selected for the 2022 Middlebrooks Award by ASCE.  Using a combination of novel testing methods and analysis, the paper shows that settlement rates of levees on peaty organic soil accelerate following severe earthquake shaking. This is an important finding that could threaten levees that are vital infrastructure in California’s complex water distribution system.

    https://www.asce.org/career-growth/awards-and-honors/thomas-a-middlebrooks-award

     

    Selected publications generated through this research study include:

    1. Lemnitzer, A., Yniesta, S., Cappa, R., and Brandenberg, S. (2021). “Settlement Rate Increase in Organic Soils Following Cyclic Loading”. ASCE Journal of Geotechnical and Geoenvironmental Engineering, 147(2), https://doi.org/10.1061/(ASCE)GT.1943-5606.0002432
    2. Cappa, R., Brandenberg, S. and Lemnitzer, A. (2017). “Strains and pore pressures during cyclic loading of embankment structures on soft organic soil”. ASCE Journal of Geotechnical and Geoenvironmental Engineering 143 (9), https://doi.org/10.1061/(ASCE)GT.1943-5606.0001721 
    3. Lemnitzer, A., Cappa, R., Yniesta, S. and Brandenberg, S.J. (2015). “Centrifuge Testing of Model Levees atop Peaty Soils : Experimental Data”. Earthquake Spectra, August 2016, Vol. 32, No. 3, pp. 1903-1924, doi: http://dx.doi.org/10.1193/032715EQS048
    4. Yniesta, S., Lemnitzer, A., Cappa, R., and Brandenberg, S.J. “Vacuum pluviation device for achieving saturated sand without backpressure“ Geotechnical Testing Journal, Manuscript ID GTJ-2014-0173, Volume 3, No.3,  May  2015
    5. Lemnitzer, A., Cappa, R., Yniesta, S., Stewart, J., and Brandenberg, S. (2017). “Post-cyclic settlements of embankments on organic soil”, 3rd Conference for performance based design in earthquake geotechnical engineering – PBD-III, Vancouver, Canada, July 16-19, 2017
    6. Cappa, R., Yniesta, S., Lemnitzer, A., Brandenberg, S. and Shafiee, A. (2015). “Settlement Estimations of Peat during Centrifuge Experiments“. Proceedings International Foundations Congress and Equipment Exposition (IFCEE), San Antonio, TX, March 17-21, 2015, Pages 152-160
    7. Yniesta, S., Cappa, R., Lemnitzer, A. and Brandenberg, S. (2015). “Centrifuge Testing of Levees: Saturation Techniques during Model Construction“. Proceedings International Foundations Congress and Equipment Exposition (IFCEE), San Antonio, TX, March 17-21, 2015, Pages 1197-1206
    8. Cappa, R., Yniesta, S., Lemnitzer, A., Brandenberg, S.J., and Stewart, J.P. (2014). “Centrifuge Experiments to Evaluate the Seismic Performance of Levees on Peaty Soils in the Sacramento-San Joaquin Delta“. Proceedings, Dam Safety Conference, San Diego, CA, September 21-25, 2014 

  • Seismic soil pressures: U.S. Instrumentation and data processing of a large-scale experiment on soil-structure interaction of underground structures on the E-Defense shake table in Miki, Japan

    Sensor instrumentation to capture seismic soil pressures on large scale vertical underground components were developed and installed to gain insight in the nonlinear dynamic response of subsurface elements different from conventional walls or piles. Experimental studies are complements with numerical modeling and the development of simplified design charts for non-rigid subsurface elements.

     

    Selected publications from this research effort include:

    1. Keykhosropour, L. and Lemnitzer, A. (2019). “Experimental studies of seismic soil pressures on vertical flexible, underground structures and analytical comparisons”, Soil Dynamics and Earthquake Engineering, Volume 118, March 2019, Pages 166-178, doi.org/10.1016/j.soildyn.2018.12.012
    2. Lemnitzer, A., Keykhosropour, L., Kawamata, Y., and Towhata, I. (2017). “Soil-Structure-Interaction of Underground Structures during Large Scale Testing at E-Defense: Data”. Earthquake Spectra, February 2017, Vol. 33, No. 1, pp. 347-372, doi: http://dx.doi.org/10.1193/032816EQS048DP

     

  • Evaluation of Interface Shear of Rock-Socketed Piles – Experimental Studies

    Rock socketing of drilled shafts is an attractive anchor- and load-transfer mechanism for axially loaded piles subject to compression or uplift forces. Simultaneously, rock-socketed piles provide stable embedment fixity when lateral loads or rotational moments need to be transferred along the pile length into sufficient depth where fixity can be guaranteed.

    Good understanding has been gained and published for axially loaded shafts; however, uncertainties exist for laterally loaded piles in rock sockets when designed using Winkler based analysis models. Currently no experimental data exist to verify the pile behavior and the development of internal moment and shear forces of rock-socketed piles under lateral loading. Simultaneously only very few numerical studies exist which investigate this particular problem. To address our current, limited knowledge in correctly estimating and designing for the actual shear demand in piles along the rock-soil boundary, the proposed research will consist of a well- coordinated combination of analytical studies, and development of an experimental program and the execution of baseline load tests on 3 pile shafts.

    Publications from this work include:

    1. Farrag, R., and Lemnitzer, A. (2022). „Effect of Rock-Shaft Interface Properties on the Shear Demands of Laterally Loaded Rock-Socketed Drilled Shafts”. 12th National Conference on Earthquake Engineering (12NCEE), Salt Lake City, Utah, June 27th – July 1st, 2022.
    2. Farrag,R., Cox, C., Turner,B., and Lemnitzer, A. (2020). “Shear Demands of Rock-Socketed Piles Subject to Cyclic Lateral Loading”. DFI Journal, Volume 14, Issue 2, DFI Student Paper Award 2020, https://doi.org/10.37308/DFIJnl.20200526.223.
    3. Lemnitzer, A., Cox, C., Farrag, R., Turner, B. (2019). “Laterally loaded pile behavior at soil-rock impedance contrast”, XVI Panamerican Conference on Soil Mechanics and Geotechnical Engineering, Cancun, Mexico, November 17-20th, 2019. (Keynote paper)
    4. Lemnitzer, A., and Turner, B. (2017). “Rock-Socketed Pile Shear”. SuperPile Conference, Coronado, CA, June 14-16,2017 (oral presentation)

     

     

  • Large -scale testing of RC SMRF beams with openings under cyclic loading: Experimental and numerical studies

    This research project investigates the nonlinear response behavior and cyclic performance of moment resisting frame beams with and with out openings. Experimental and numerical studies provide insight into the opportunity and challenge of openings in structural elements that are part of lateral force resisting systems. Failure patterns, hinge development, and interaction mechanisms are studied and complemented by parametric simulations. The behavior of and performance of the specimens strengthened with FRP schemes is also investigated via large scale testing.

    Publications from this work (ongoing):

    1. Herrera, L., Anacleto, S. and Lemnitzer, A. (2017). „Experimental performance of RC moment frame beams with rectangular openings“, Engineering Structures 152 (2017), pp.149 -167  https://doi.org/10.1016/j.engstruct.2017.08.043
    2. Herrera, L. and Lemnitzer, A. (2014). “Cyclic performance of RC Beams with Web Openings”. Proc. 2nd European Conference on Earthquake Engineering and Seismology, Istanbul, Turkey, August 24-29, 2014

  • Cyclic behavior of reinforced concrete cladding panels under multiaxial loading: Experimental and analytical studies

    Information will come shortly

  • Findapile.com - An online collection of large-scale test data of deep foundations under lateral loading

    Findapile.com is the first and most comprehensive online platform that collects and synthesized lateral load test data for large scale pile tests. Over 70 pile load tests are implemented in the searchable database, with general data such as load-deflection, soil properties and p-y formulations. A full reference to the original research work is provided. The database is established, authored and maintained by Prof. Lemnitzer.

    http://www.findapile.com

    Funding Agencies:

    DFI & ADSC National & ADSC West Coast Chapter

     

    Reference Publications:

    1.  Favaretti, C. and Lemnitzer A. (2014). “ Recent advances in p-y formulations based on experimental research work “ Proc. 2nd European Conference on Earthquake Engineering and Seismology, Istanbul, Turkey, August 24-29, 2014

  • Analytical studies on inertial and kinematic soil-structure interaction of pile foundations

    Analytical studies on the inertial and kinematic response behavior of laterally loaded pile foundations include a proposed continuum solution for lateral soil resistance due to pile motion, the development of new and simple formulation for a dynamic Winkler modulus,  closed form expressions for pile stiffness and damping, a study of the effect of pile tip fixities and impedance contrasts, as well as the development of a frequency dependent Winkler modulus for kinematic load applications.

    Publications generated by this analytical research effort include:

    1. Anoyatis, G. and Lemnitzer, A. (2017). “Pile response to kinematic loading”. Soils and Foundations, 57 (2017) pp. 453-471, DOI: 10.1016/j.sandf.2017.05.011
    2. Anoyatis, G., Di Laora, R., and Lemnitzer, A. (2017). “Pile response and stiffness due to lateral harmonic motion – pile with bottom fixity”. Soil Dynamics and Earthquake Engineering, Volume 97, June 2017, Pages 454-467, http://doi.org/10.1016/j.soildyn.2017.03.025
    3. Anoyatis, G. and Lemnitzer, A. (2017). “Dynamic pile impedances for laterally-loaded piles using improved Tajimi and Winkler formulations”. Soil Dynamics and Earthquake Engineering, Volume 92, January 2017, Pages 279-297, http://doi.org/10.1016/j.soildyn.2016.09.020
    4. Anoyatis, G., Mylonakis, G., and Lemnitzer, A. (2016). “Soil resistance to lateral harmonic pile motion”. Soil Dynamics and Earthquake Engineering, Volume 87, August 2016, Pages 164–179, doi:10.1016/j.soildyn.2016.05.004