Owner: The City of Longmont 
Client: The City of Longmont 
Completion Date: 2022
Services: Existing Structures, Vibration Testing and Analysis

Summary:

J.R. Harris & Company conducted a floor vibration study at the Longmont Public Library to assess concerns about perceptible vibrations in the main floor office area. The study was initiated in response to ongoing complaints from occupants, with vibrations noted since the building’s addition in 1993. The project involved a detailed structural evaluation, including vibration monitoring, data analysis, and a three-dimensional finite element model to simulate floor behavior under dynamic loading.

Measurements were taken both before and after structural repairs to the concrete floor slab, revealing a significant reduction in vibrations following the repairs. The analysis confirmed that the existing floor system experienced movement due to normal walking activity, with vibrations falling just outside acceptable comfort thresholds. To further mitigate these effects, J.R. Harris & Company developed a conceptual design to structurally interconnect the main and second floors, increasing mass participation and reducing perceptible motion.