| Popis: |
In smart building infrastructure, the mounting of dynamic measurement devices must be carefully determined to obtain meaningful data and accurately record the dynamics within a building. Specifically, it is important to develop a sensor mounting method so that the highest frequency band of interest can be accurately obtained. This is especially crucial in safety applications such as footstep localization, fall detection, and gunshot detection since high frequencies could possess useful information. Currently, it is common practice in structural health monitoring of building infrastructure for sensors to be mounted either temporarily on the surface of a floor with wax or permanently on the underside of the structural steel floor joists. Using either of these methods causes limitations in either the permanence of the setup or in the placement of sensors. This paper explores several typical mounting locations and a novel accelerometer mounting method designed to overcome these limitations by mounting accelerometers on the underside of a concrete floor structure’s corrugated steel floor tray. The novel mounting method consists of a mounting plate fastened to a concrete floor with concrete anchors and a tapped hole for accelerometer mounting. This method will be evaluated through experimental testing and analysis on two developed floor section mockups mimicking the floor structure in Tennessee Technological University’s newly constructed Lab Science Commons building and the floor currently being constructed in the new Ashraf Islam Engineering Building. Testing is carried out by impacting the floor section in 11 locations with a modal hammer while measuring the response of accelerometers mounted at various locations. The frequency response of the concrete anchored accelerometers is assessed in two scenarios so results can be compared to results for beam mounted accelerometers. From testing, it is found that signals obtained from the bottom center and bottom flange beam mounting locations are attenuated within specific frequency bands. The bottom center beam mounting location experiences signal attenuation in the frequency range of 500 to 1500 Hz. Meanwhile, the bottom flange beam location experiences attenuation from 2800 to 3200 Hz, the topmost evaluated frequency. Mounting positions on the I-beam’s upper flange and the bottom of the concrete floor section, both with and without the beam present, do not display signal attenuation characteristics. Furthermore, a significant amount of system dynamics is seen in signals obtained for mounting locations residing on the I-beam compared to those mounted on the floor section. This increase is suspected to be a result from both the dynamics of the beam itself and the boundary conditions between the beam and floor section. These characteristics are also seen in mounting locations on the concrete floor section with an I-beam present but are not seen with the same intensity as mounting locations existing directly on the I-beam. |
