Firstly it is true to say that people do not normally experience vibration in
their homes; therefore, when there is a new source of vibration, occupants are
disturbed and assume that damage is being caused. Occupants tend to examine the
property for signs of damage and will probably find cracking which they had not noticed
previously; it seems natural to attribute the "new" cracking to the new vibration
source; however, given that occupants donít normally look for cracks, it may
simply be that the cracks preceded the new vibration source.
Buildings are fairly resilient to ground-borne vibration; therefore real damage to buildings is rare, although possible; cosmetic damage such as cracking is much more likely than damage to load bearing elements.
BS 7385: Part 2: 1993 "Evaluation and measurement for vibration in buildings" gives guidance on the levels of vibration above which building structures could be damaged. The standard states that there is a major difference between the sensitivity of people in feeling vibration and the onset of levels of vibration which damage the structure. Furthermore it states that cracking commonly occurs in buildings whether they are exposed to vibration or not.
For residential buildings, the standard states that for cosmetic damage (cracking in plaster work etc.) to occur, a peak particle velocity of some 15 mm/s is necessary at a vibration frequency of 4 Hz; this rises to 20 mm/sec at 15 Hz, and thereafter the limit rises to 50 mm/s at 40 Hz and above. The ANC's document "Measurement and Assessment of Groundborne Noise and Vibration" states that these limits apply to the maximum of the vibration levels in the three mutually perpendicular axes and that minor structural damage can occur at levels around twice the above limits and major damage can occur at levels around four times the above limits.
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