Strong Motion Structural Monitoring in Practice

Thousands of buildings, bridges, and structures worldwide have been instrumented with systems (including vibration accelerometers, strong-motion sensors, strain gauges, etc.) for the sole purpose of recording structural response data. Researchers, structural engineers, and seismologists use these data to further our understanding of actual building dynamic behavior, validate theories, and ultimately lead to building code improvements. However, these structural health monitoring and instrumentation systems are rarely implemented directly on real-world building projects. The objective of this paper is to present the following case studies on how structural instrumentation has been implemented and how these technologies have been executed. The case studies are intended to show the potential usefulness of leveraging measured data and stimulate further use of structural instrumentation technology in practice: 1. California Hospital with Seismic Movements: Each seismically separated hospital wing of the Naval Medical Center San Diego (NMCSD) is a pre-Northridge steel moment frame. The entire medical facility encompasses over 1 million square feet of space. One seismically separated wing of this building, the nursing tower, has some structural irregularities and some unique building properties. Additionally, recent structural analysis has been conducted on this building for the purposes of conducting seismic upgrades in addition to strong-motion accelerometers being installed in the building in 2015. The M5.2 Borrego Springs earthquake that occurred on June 10, 2016 was measured by the building’s strong motion accelerometers and some of the measurement data is compared with other structural analysis calculations. 2. Washington Hospital with Seismic Movements: The hospital and clinic at Naval Hospital Bremerton (NHB) are pre-Northridge steel moment frame structures that represent 249,000 square feet of space used for essential medical services. In 1980, the building was instrumented with 12 channels of strong-motion accelerometers with an analog data recorder. After the 2001 M6.8 Nisqually Earthquake event, the data from this recording was digitized and allowed the nonlinear dynamic time-history analysis required for a seismic evaluation and upgrades design to be tuned to the actual dynamic characteristics of the building rather than the generalized assumptions provided by building standards.