Is construction vibration just an annoyance, or does it have the potential to cause aesthetic and structural damage to nearby structures?
Ground vibration waves behave similarly to those that propagate when a stone is dropped into water. Movement through the earth is generated vertically as well as horizontally. As the waves travel away from the source, they encounter an increasingly large amount of material, which causes the energy in the wave to dissipate. Therefore, the larger the distance between the source of the vibration and the object detecting the vibration, the weaker the effect.
The human body is an excellent detector of vibration, but a poor measuring device. Most investigators have determined that the best way to measure the magnitude of vibration and the effect on human and building response is using peak particle velocity (PPV). PPV is measured in inches per second (IPS), with a larger value representing a bigger vibration. Some average measurements for daily activities in a house are: walking - 0.29 IPS, nail hammering - 0.55 IPS, door slamming - 0.59 IPS, and jumping - 2.19 IPS. Research shows that the human body can notice PPV as little as 0.02 IPS, which is far below the activities previously mentioned.
Houses that are poorly maintained, or with brittle plaster walls, can experience aesthetic damage once the PPV approaches 1.0 IPS. Sound residential structures have a damage threshold value of 2.0 IPS, and commercial structures are at 4.0 IPS. These values show that there is quite a big difference between the size at which the human body begins to notice a vibration and the size of a vibration that will cause damage to a building.
Most construction sites that involve the use of explosives are required to do pre-blast surveys to map the existing cracks or other defects in buildings within a certain radius from the blasting activity and to measure the vibrations produced during construction. If the vibrations from the blasting exceed the threshold level and damage is reported by the homeowner or business owner, the contractor can determine what damage existed prior to the blast so a comparison can be made, and any damage caused by the construction can be repaired. Cracks caused by construction vibration, whether from blasting or from large equipment, look very similar to typical settlement cracks or cracks caused by moisture and thermal changes in the structure. Therefore, it is important to know which cracks existed prior to the construction activity.
Construction sites that do not involve blasting typically do not perform preconstruction surveys of the adjacent buildings to map wall cracks and other pre-existing conditions because the likelihood of damage is very small. Devices to measure the vibrations produced by the construction equipment are also not typically used. Claims against a contractor typically occur when vibrations are felt by a home or business owner and they notice cracks in the interior walls, veneer, or foundation of the structure. Vibrations produced from typical construction machinery located approximately 15 feet from the structure are measured at the following PPVs: a small dozer - 0.008 IPS, jack hammer- 0.07 IPS, a large dozer - 0.2 IPS, and a vibratory pile driver - 1.5 IPS. All of these activities except for the pile driver are well below the damage threshold for all structures; however, the vibrations produced by the machines will be noticed by the human body.
While the noise and the vibrations produced by nearby construction activity may be discomforting and disruptive to daily activities, rarely are the vibrations damaging to structures. Contractors should be aware of historical buildings or dwellings that are in disrepair when performing activities in proximity to these structures. If heavy machinery is going to be operated around these structures, consideration should be given to performing a preconstruction survey of the structures to document pre-existing conditions that later may be confused as damage caused by the construction.
DONAN, a family owned company founded in 1947, provides full-service Forensic Engineering and Fire Investigation Services. For over 60 years, Donan Engineering has been providing unbiased answers to their client's complicated questions. Their team of licensed and experienced forensic experts provides investigative services in the fields of engineering investigations, fire and explosion origin & cause, roofing investigations, and component testing. The diversity of their multidisciplinary staff allows them to provide not only a complete service, but a complete service whose conclusions can be successfully and completely supported.
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