publications

2026

1. ASME JAM

   

   On Complex Modal Inverse Analysis: The Cautionary Tale of the Single Surviving Mode

   Chrystal Chern and Oliver M. O’Reilly

   ASME Journal of Applied Mechanics (in press, 2026), 2026

   Abs DOI Bib

   The number of modes of a mechanical system is generally assumed to equal its number of degrees of freedom. In this work, a simple non-classically damped system is shown to possess fewer modes than degrees of freedom unless a restrictive condition is met. When this condition is met, while there is a full set of modes, they are not orthogonal. These results hold for vanishingly small non-classical damping, can evade detection by the modal phase collinearity metric, and are relevant to system identification of mechanical systems in which non-classical damping is present.

   @article{chern2026complexmodal,
     title = {On Complex Modal Inverse Analysis: The Cautionary Tale of the Single Surviving Mode},
     author = {Chern, Chrystal and O'Reilly, Oliver M.},
     journal = {ASME Journal of Applied Mechanics (in press, 2026)},
     year = {2026},
     doi = {10.1115/1.4072378},
     url = {https://doi.org/10.1115/1.4072378},
   }

2. Nonlin. Dyn.

   The Symphony of Gyrations Producing Steady Motions of a Hula Hoop: Insights from a Network Analysis

   Chrystal Chern, Theresa E. Honein, and Oliver M. O’Reilly

   Nonlinear Dynamics (submitted May 2026), 2026

   Abs Bib

   Hula hooping is a rhythmic activity where coordinated body movements induce a steady motion of the hoop. While a range of coordinated movements can successfully actuate the hoop, extracting the causal human motions for this multi-harmonic symphony of gyrations and rotations is an open problem that we seek to answer. Our methods use motion tracking of the body and hoop along with a network analysis for a single set of coordinated motions to establish that a specific rotation of the femur enables the tilting motion of the hoop and that specific rotations of the femur, tibia, and metatarsal enable the whirling motion of the hoop. The conclusions from network analysis are shown to be far superior to the results obtained from a principal component analysis and have application to human motion studies involving rehabilitation and assistive devices.

   @article{chern2026hulahoop,
     title = {The Symphony of Gyrations Producing Steady Motions of a Hula Hoop: Insights from a Network Analysis},
     author = {Chern, Chrystal and Honein, Theresa E. and O'Reilly, Oliver M.},
     journal = {Nonlinear Dynamics (submitted May 2026)},
     year = {2026},
   }

3. JEM

   Modal Clustering for Digital Twinning of Civil Infrastructure

   Chrystal Chern and Khalid M. Mosalam

   Journal of Engineering Mechanics (in preparation), 2026

   Bib

   @article{chern2026modalclustering,
     title = {Modal Clustering for Digital Twinning of Civil Infrastructure},
     author = {Chern, Chrystal and Mosalam, Khalid M.},
     journal = {Journal of Engineering Mechanics (in preparation)},
     year = {2026},
   }

4. MSSP

   Detecting Inelasticity in Seismic Data with Time Response System Identification

   Naiqi Guo, Chrystal Chern, and Khalid M. Mosalam

   Mechanical Systems and Signal Processing (in preparation), 2026

   Bib

   @article{guo2026inelasticity,
     title = {Detecting Inelasticity in Seismic Data with Time Response System Identification},
     author = {Guo, Naiqi and Chern, Chrystal and Mosalam, Khalid M.},
     journal = {Mechanical Systems and Signal Processing (in preparation)},
     year = {2026},
   }

2025

1. EVACES

   Structural Response Prediction from Learned System Realization Matrices

   Chrystal Chern, Claudio Perez, and Khalid M. Mosalam

   In 11th International Conference on Experimental Vibration Analysis of Civil Engineering Structures (EVACES), 2025

   DOI Bib

   @inproceedings{chern2025evaces,
     title = {Structural Response Prediction from Learned System Realization Matrices},
     author = {Chern, Chrystal and Perez, Claudio and Mosalam, Khalid M.},
     booktitle = {11th International Conference on Experimental Vibration Analysis of Civil Engineering Structures (EVACES)},
     year = {2025},
     doi = {10.1007/978-3-031-96110-6_72},
     url = {https://doi.org/10.1007/978-3-031-96110-6_72},
   }

2024

1. JBE

   Human-Machine Collaboration Framework for Bridge Health Monitoring

   Sifat Muin, Chrystal Chern, and Khalid M. Mosalam

   Journal of Bridge Engineering, 2024

   DOI Bib

   @article{muin2024humanmachine,
     title = {Human-Machine Collaboration Framework for Bridge Health Monitoring},
     author = {Muin, Sifat and Chern, Chrystal and Mosalam, Khalid M.},
     journal = {Journal of Bridge Engineering},
     volume = {29},
     number = {7},
     pages = {04024041},
     year = {2024},
     publisher = {American Society of Civil Engineers},
     doi = {10.1061/JBENF2.BEENG-6587},
     url = {https://doi.org/10.1061/JBENF2.BEENG-6587},
   }

2. 4IBSW

   Cross-Sectional Study of Physics-Informed Bridge Health Identification

   Chrystal Chern and Khalid M. Mosalam

   In International Association of Bridge Earthquake Engineering (IABEE) Fourth International Bridge Seismic Workshop (4IBSW), 2024

   Bib

   @inproceedings{chern2024physicsinformed,
     title = {Cross-Sectional Study of Physics-Informed Bridge Health Identification},
     author = {Chern, Chrystal and Mosalam, Khalid M.},
     booktitle = {International Association of Bridge Earthquake Engineering (IABEE) Fourth International Bridge Seismic Workshop (4IBSW)},
     year = {2024}
   }

3. Software

   mdof: 0.0.16-alpha

   Chrystal Chern, Claudio Perez, and Khalid M. Mosalam

   2024

   DOI Bib

   @misc{chern2024mdof,
     title = {mdof: 0.0.16-alpha},
     author = {Chern, Chrystal and Perez, Claudio and Mosalam, Khalid M.},
     howpublished = {Open-source Python package for system identification, Zenodo},
     year = {2024},
     doi = {10.5281/zenodo.11660201},
     url = {https://doi.org/10.5281/zenodo.11660201},
   }

4. PhD

   Digital Twin Framework for Vibration-Based Structural Health Monitoring

   Chrystal Chern

   University of California, Berkeley, 2024

   Bib

   @phdthesis{chern2024dissertation,
     title = {Digital Twin Framework for Vibration-Based Structural Health Monitoring},
     author = {Chern, Chrystal},
     school = {University of California, Berkeley},
     year = {2024}
   }

5. Caltrans

   BRACE2: Bridge Rapid Assessment Center for Extreme Events, Phase I Final Report

   Chrystal Chern, Claudio Perez, and Khalid M. Mosalam

   2024

   Bib

   @techreport{chern2024brace2,
     title = {BRACE2: Bridge Rapid Assessment Center for Extreme Events, Phase I Final Report},
     author = {Chern, Chrystal and Perez, Claudio and Mosalam, Khalid M.},
     institution = {State of California Department of Transportation},
     number = {CA24-3703},
     year = {2024}
   }

2020

1. SMIP20

   Human-Machine Collaboration Framework for Bridge Health Monitoring

   Sifat Muin, Chrystal Chern, and Khalid M. Mosalam

   In SMIP20 Seminar on Utilization of Strong-Motion Data Proceedings, 2020

   Bib

   @inproceedings{muin2020humanmachine,
     title = {Human-Machine Collaboration Framework for Bridge Health Monitoring},
     author = {Muin, Sifat and Chern, Chrystal and Mosalam, Khalid M.},
     booktitle = {SMIP20 Seminar on Utilization of Strong-Motion Data Proceedings},
     pages = {100--127},
     year = {2020}
   }

2019

1. MS

   Deep Learning for Transmission Tower Structural Health Monitoring in Small Datasets

   Chrystal Chern

   University of California, Berkeley, 2019

   Bib

   @mastersthesis{chern2019msreport,
     title = {Deep Learning for Transmission Tower Structural Health Monitoring in Small Datasets},
     author = {Chern, Chrystal},
     school = {University of California, Berkeley},
     year = {2019}
   }