Maria I. Todorovska

Bio: Maria I. Todorovska is an academic researcher from Tianjin University. The author has contributed to research in topics: Soil structure interaction & Strong ground motion. The author has an hindex of 40, co-authored 143 publications receiving 4577 citations. Previous affiliations of Maria I. Todorovska include University of Southern California & University of Montenegro.

Introduction to the Special Issue on Rotational Seismology and Engineering Applications

Abstract: Rotational seismology is an emerging field for studying all aspects of ro- tational ground motions induced by earthquakes, explosions, and ambient vibrations. It is of interest to a wide range of geophysical disciplines, including strong-motion seismology, broadband seismology, earthquake engineering, earthquake physics, seis- mic instrumentation, seismic hazards, seismotectonics, and geodesy, as well as to physicists using Earth-based observatories for detecting gravitational waves generated by astronomical sources (predicted by Einstein in 1916). In this introduction to the BSSA special issue on rotational seismology and engineering applications, we will include (1) some background information, (2) a summary of the recent events that led to this special issue, and (3) an overview of its 51 papers—27 articles, 11 short notes, 4 reviews, 6 tutorials, and 3 supplementary articles. Our comments on these 51 papers are very brief and give just a hint of what the papers are about. Papers in this special issue demonstrate that earthquake monitoring cannot be limited to measuring only the three components of translational motion. We also need to simultaneously measure the three components of rotational motion and the many components of strains. A golden opportunity to improve our understanding of earth- quakes lies in the near field of large earthquakes (within about 25 km of the earthquake ruptures), where nonlinear rock and soil response influences ground motions in a com- plicated way.

Apparent Periods of a Building. II: Time-Frequency Analysis

Abstract: In this, the second of a two-part paper, the analysis of the apparent frequency of a seven-story reinforced-concrete hotel building in Van Nuys, Calif., is extended to consider its time-dependent changes, both short and long term. The instantaneous apparent frequency is measured by two methods: windowed Fourier analysis and zero-crossings analysis. The results show that it changes from earthquake to earthquake and during a particular earthquake. The results also suggest ''self healing'' believed to result from settlement of the soil with time and dynamic compaction from aftershock shaking. Implications of such high variability of the system frequency on structural health monitoring, control of response, as well as on the design codes are discussed. Nonlinear response of the foundation soil acts as a sink of the incident seismic wave energy. It is suggested that it could be exploited in future designs to serve as a powerful and inexpensive energy-dissipation mechanism. reinforced-concrete hotel in Van Nuys, Calif. (VN7SH) by Fourier analysis. We also described an approximate model in which the soil-structure interaction phenomena are viewed in the simplest possible form, via a rigid foundation model. Be- cause the Fourier transform of the response is evaluated from the entire time history of response, the results in Part I gave an insight only into the overall changes of the apparent system frequency from one earthquake to another. The trend that emerged from the results of the Fourier analysis is a reduction of the apparent system frequency with increasing levels of shaking at the site. In this part, we study the time and ampli- tude-dependent changes of by time-frequency analysis. The ˜ f description of the building, recorded strong motion data, earth- quake damage, and full-scale ambient vibration tests con- ducted following the Northridge earthquake of 1994 were pre- sented in Part I and will not be repeated here.

Apparent Periods of a Building. I: Fourier Analysis

Abstract: This and the companion paper present an analysis of the amplitude and time-dependent changes of the apparent frequency of a seven-story reinforced-concrete hotel building in Van Nuys, Calif. Data of recorded response to 12 earthquakes are used, representing very small, intermediate, and large excitations (peak ground velocity, vmax = 0.6 2 11, 23, and 57 cm/s, causing no minor and major damage). This paper presents a description of the building structure, foundation, and surrounding soil, the strong motion data used in the analysis, the soil-structure interaction model assumed, and results of Fourier analysis of the recorded response. The results show that the apparent frequency changes form one earthquake to another. The general trend is a reduction with increasing amplitudes of motion. The smallest values (measured during the damaging motions) are 0.4 and 0.5 Hz for the longitudinal and transverse directions. The largest values are 1.1 and 1.4 Hz, respec- tively, determined from response to ambient noise after the damage occurred. This implies 64% reduction of the system frequency, or a factor '3 change, from small to large response amplitudes, and is interpreted to be caused by nonlinearities in the soil.

Fundamentals of earthquake engineering

Abstract: PART 1 DEALS WITH THE DYNAMIC ASPECTS OF THE SUBJECT: MATHEMATICAL ANALYSIS OF SYSTEMS SUBJECTED TO INDEPENDENT VIBRATIONS BY MEANS OF MATHEMATICAL MODELS. THE ANALYTICAL SYSTEMS USED ARE NON-LINEAR SYSTEMS, HYDRODYNAMICS AND NUMERICAL METHODS. PART 2 EXAMINES SEISMIC MOVEMENTS, THE DYNAMIC BEHAVIOUR OF STRUCTURES AND THE BASIC CONCEPTS OF THE SEISMIC DESIGN OF STRUCTURES.

Guided wave based structural health monitoring: A review

Abstract: The paper provides a state of the art review of guided wave based structural health monitoring (SHM). First, the fundamental concepts of guided wave propagation and its implementation for SHM is explained. Following sections present the different modeling schemes adopted, developments in the area of transducers for generation, and sensing of wave, signal processing and imaging technique, statistical and machine learning schemes for feature extraction. Next, a section is presented on the recent advancements in nonlinear guided wave for SHM. This is followed by section on Rayleigh and SH waves. Next is a section on real-life implementation of guided wave for industrial problems. The paper, though briefly talks about the early development for completeness,. is primarily focussed on the recent progress made in the last decade. The paper ends by discussing and highlighting the future directions and open areas of research in guided wave based SHM.

A New Frontier of Printed Electronics: Flexible Hybrid Electronics.

Abstract: The performance and integration density of silicon integrated circuits (ICs) have progressed at an unprecedented pace in the past 60 years. While silicon ICs thrive at low-power high-performance computing, creating flexible and large-area electronics using silicon remains a challenge. On the other hand, flexible and printed electronics use intrinsically flexible materials and printing techniques to manufacture compliant and large-area electronics. Nonetheless, flexible electronics are not as efficient as silicon ICs for computation and signal communication. Flexible hybrid electronics (FHE) leverages the strengths of these two dissimilar technologies. It uses flexible and printed electronics where flexibility and scalability are required, i.e., for sensing and actuating, and silicon ICs for computation and communication purposes. Combining flexible electronics and silicon ICs yields a very powerful and versatile technology with a vast range of applications. Here, the fundamental building blocks of an FHE system, printed sensors and circuits, thinned silicon ICs, printed antennas, printed energy harvesting and storage modules, and printed displays, are discussed. Emerging application areas of FHE in wearable health, structural health, industrial, environmental, and agricultural sensing are reviewed. Overall, the recent progress, fabrication, application, and challenges, and an outlook, related to FHE are presented.