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Proceedings of the International Conference on
Advances and New Challenges in Earthquake
Engineering Research, Hong Kong Volume
VISION-BASED SENSORS
FOR MONITORING SEISMIC DEMANDS
Tara C. Hutchinson 1 and Falko Kuester
'Department of Civil & Environmental Engineering
Department of Electrical and Computer Engineering
University of California, Irvine USA 92697
ABSTRACT
A vision-based approach is evaluated for its applicability as a new sensing technology for measuring
earthquake induced motions. Traditional motion sensors used in laboratory and field experiments must
be physically attached to the structure and require cumbersome cabling, configurations and substantial
time for set-up. Moreover, for reduced scale experiments, sensors generally add substantial mass or
change the response characteristics of the system. The approach evaluated in this paper is
advantageous since it requires very limited physical attachment to the structure of interest, is highspeed,
high-resolution and does not introduce additional mass or otherwise modify the properties of the
structure. In this exploratory phase, four digital high-speed, high-resolution cameras outfitted with redlight
emitters are used to track reflective (nearly) mass less spherical elements discretely mounted on a
scale 5-story steel frame structure. The structure is mounted on the University of California, Irvine's
bi-axial shake table and subjected to different earthquake motions. The structure is also instrumented
with a total of eleven conventional (wired) transducers (LVDTs and accelerometers) providing a
unique comparison with the vision-based approach. Results from this exploratory study show that the
non-intrusive vision-based approach is extremely promising in terms of its ability to capture inter-story
drift, floor level velocities and accelerations, provided proper post-processing of the data occurs.
INTRODUCTION
Alternative methods of tracking seismic motions are desirable, particularly in the laboratory setting
where scale models are often used to study earthquake response. Many fields, besides earthquake
engineering, require precise high-speed motion tracking and thus new technologies are rapidly
becoming available. Biomechanics, human gait analysis, robotics, virtual reality (VR), gaming and
even entertainment have successfully employed a variety of new motion tracking techniques. Typically
these applications require accurate six degree-of-freedom tracking, expressed by position (x, y, z) and
orientation (yaw, pitch, roll). In earthquake engineering, generally the three positional degrees-offreedom
are the most important motions to track and often only one of these dominates depending
upon the problem. However, high spatial and temporal resolution (high sampling rates), large working
volumes, limited instrumentation time and low-cost are also required. Depending on the particular