A Simple, Effective Method for a "Detailed" Building Vibration Analysis

The National Institute of Health's (NIH) building on the campus of Johns Hopkins University will be approximately 300 feet from a newly proposed at-grade, light-rail transit (LRT) system called the Baltimore Red Line. However, research and experiments being conducted inside the building are extremely sensitive to vibration; involving such things as electron microscopes, MRI machines and animal experiments. Consequently, a comprehensive vibration assessment was performed in May 2012 to ensure the proposed Red Line will not adversely affect NIH's operations. This article describes the vibration study, which is particularly noteworthy in that it utilized a simpler and less expensive method to obtain results consistent with the "Detailed" method described in the Federal Transit Administration's (FTA) Transit Noise and Vibration Impact Assessment Manual. The study made use of a 200-pound drop weight apparatus and multiple accelerometers along the ground and inside the building to develop an empirical model of the building's potential response to future Red Line vibration. The results were compared against existing vibration levels and evaluated for acceptability in accordance with FTA's vibration criteria for sensitive devices.