As the saying goes, you have to crack a few eggs to make an omelet. On some construction projects, heavy equipment and machinery can crack more than just eggs. Complaints and lawsuits related to damages in adjacent buildings, equipment malfunction, noise, and uncomfortable vibrations, are becoming common in our industry.
As early as practical during a construction project, the location and sensitivity of nearby properties should be identified. Threshold noise and vibration levels should be established in the planning phase of construction, which helps all project team members to plan and phase their work. Evaluating the condition of structures adjacent and nearby to the planned construction is critical to minimizing future damage claims and setting an appropriate threshold for anticipated construction-related noise and vibrations.
Once a vibration monitoring program is developed, it is highly recommended to establish a baseline of conditions in the areas of construction. The baseline involves pre-construction condition of the structures using visual surveys and baseline monitoring of the vibrations prior to active construction. Depending on the type of structure to be surveyed, Terracon uses a combination of techniques such as unmanned aerial vehicles (UAV), high-resolution infrared camera survey, observations using suspended scaffold or rope access, foundation floor profile survey, photogrammetry, and light detection and ranging (LiDAR) 3D imaging. Pre- and post-construction condition surveys are critical to identifying possible damage causing conditions within the structure(s) that may need immediate attention, sometimes prior to construction start.
Vibration monitoring is often performed to directly measure the vibrations present at a given site in almost real time. Depending on the amount of construction activity, sensitivity of monitored structures, and often times project budget, a remote monitoring system or a combination of remote monitoring with stationed staff monitoring the vibrations is used. Terracon uses wireless monitoring instruments to notify construction team members using alert messages in almost real time of the detection of excessive vibrations or noise. Various guidelines defining different permissible levels of vibrations have been published; however, the response of existing buildings to vibrations is often site-specific and unique to that structure. Terracon often assists the project team in determining a site-specific threshold level of vibration considering the age of the building, proximity to vibration causing activities, the consequences of excessive vibration, and the risk tolerance of the owner and project team.
Medical facilities and laboratory equipment are typically much more sensitive to vibration, which can be extremely problematic when construction activities and equipment operations are located nearby. Operating rooms and MRI equipment are often considered critical facilities which cannot be closed for construction and have very strict vibration limitations. Newer facilities may have vibration isolation equipment in place, however, older facilities were likely not designed with vibration in mind. Coordination needs to occur between the construction team and the medical team when planning construction or demolition activities near an existing medical facility.
Additionally, Terracon can perform in-depth statistical and structural analysis to assist clients in evaluating the performance of structure and the risks of excessive vibration. This analysis can be useful in determining the source of vibrations. It can also can be used for predicting the response of existing fragile structures to nearby vibrations.
Upon completion of construction, a post-construction survey of each adjacent building should be performed to compare their condition to the condition (baseline) documented in the pre-construction survey. The intent of this is to determine if existing conditions have worsened and to determine if new damage has occurred.
Implementing a vibration monitoring program can protect project teams from unreasonable claims of alleged construction-induced damage. Terracon has worked for clients on projects involving residential buildings, commercial buildings, hospitals, and research facilities. With the up-to-date testing system and experienced engineers, Terracon delivers reliable and resourceful services in a cost-efficient and time-saving manner.
Zhengqi (Jason) Li, Ph.D., P.E., is a project engineer in Terracon’s Houston office. He specializes in diagnostics and evaluation on concrete materials and structures.
Scott Lefton, P.E., SECB, is a structural engineer based in Terracon’s San Antonio office.
Jigar Desai, Ph.D., P.E., is an office manager on Terracon’s Facilities Services team in our Philadelphia office. He serves as a technical leader for structural and materials