Building in densely-populated urban areas is always a challenge due to the disruption in the quality of life for occupants of nearby buildings. Nobody wants to live next to a construction site. Add to that the possibility of structurally damaging nearby buildings from excessive vibration due to construction activities like demolition and pile driving. To minimize the risk of damaging structures during construction and for occupant comfort, monitoring of vibration should be a part of any urban project. Read on to learn more about how vibration can be monitored and managed.
In downtown areas, a new building will either be an infill into an empty lot or a replacement of an existing structure. In either condition, there will be some form of demolition that needs to take place first. To demolish a structure, equipment such as demolition excavators, backhoes, wrecking balls, and even dynamite are used to take the building down. All of this equipment can introduce significant vibration into the ground. After demolition is complete, site preparation and foundation work for the new building requires activities such as pile driving, soil compaction, and foundation excavation, which also create substantial levels of vibration.
One of the most common methods to ensure that nearby buildings are not being overly stressed by ground-borne vibrations is continuous monitoring of vibration levels. Vibration monitoring has been around for several decades, but due to advances in technology, it is now possible to monitor levels remotely and in real time using accelerometers mounted directly to building facades and gateways on site that send data to a cloud. This allows the on-site personnel to respond almost immediately to excessive vibration.
So, how much is too much vibration in a building? Organizations like ASHRAE have literature stating vibration levels in buildings for human comfort but there is little information on how much vibration a building can incur before becoming a problem. The best method to establish thresholds is to measure baseline vibration levels in the potentially affected buildings before demolition commences. By obtaining this data first, the consultant is cognizant of current levels and can predict tolerances based on the construction of the building. These tolerances serve as the alert level; when exceeded, alerts can be sent to managers on site to halt construction and adjust their activities
By installing a real-time vibration monitoring system, the risk of damage to nearby buildings is significantly reduced. Additionally, monitoring vibration throughout the construction process provides the contractor with a record of the impact on nearby structures, which may be useful down the road.
In addition to monitoring of nearby structures, vibration can also be monitored in the interior of building under construction. Having a monitoring system installed while construction is occurring reassures the occupants that someone is aware of their well-being, and can confirm that the results from sensitive equipment (such as MRIs or lab equipment) are not skewed due to excessive vibration.
There was an earthquake recently in Delaware that we felt in our Philadelphia office while sitting at our desks. While there’s no one you can call to put a stop to Mother Nature’s unexpected vibrations, if the disturbances are of the man-made variety, professional vibration monitoring is a good way to make sure there’s not a “Whole lotta shakin’ goin’ on”!