Laserfiche WebLink
• <br />reference purposes. <br />A discussion of recommended vibration limits follows. Some of this <br />information does not pertain to this job but was included for <br />RECOMMENDED VIBRATION LIMITS <br />• <br />Seismological research by the U.S. Bureau of Mines, foreign <br />investigative groups, and individual seismologists has established <br />criteria relating the occurrence of structural damage to certain <br />frequencies and levels of ground motion. <br />USBM Report of Investigations 8507, by David Siskind, 1980, states <br />that residential structures are most prone to damage as a result of <br />vibration energy within the frequency range of 4-12 hertz. Within <br />this range, a 0.5 inch 'per second maximum particle velocity is <br />recommended to preclude 'threshold' damage to the plaster-on-wood <br />lathe interior portions of older structures. <br />Threshold damage is defined by the USBM as the loosening of paint, <br />small plaster cracks at joints between construction elements or the <br />lengthening of old plaster cracks. A maximum of 0.75 inch per <br />second is recommended for the protection of modern drywall interior <br />construction. The damage threshold is normally considerably higher <br />for load-bearing or other structural portions of a house. <br />representations at the end of this report. <br />Above 12 hertz, the allowable vibration increases as the frequency <br />increases, up to 40 hertz. Above 40 hertz, a constant 2.0 inches <br />per second level is recommended to protect the interior walls and <br />ceilings of structures regardless of construction material. A <br />graphic representation of the USBM recommended criteria is shown in <br />the velocity versus frequency curve on the following page, and the <br />vibration, analysis of the recordings are plotted on graphic <br />It should be noted, however, that <br />practice to visually determine if <br />typical seismogram is actually <br />range. This is because ground <br />mixture of many frequencies which <br />visual analysis of a seismogram. <br />it is almost impossible in actual <br />the recorded peak vibration on a <br />within the Bureau's 4-12 hertz <br />vibration is usually a complex <br />cannot'be accurately separated by <br />Proper implementation of the Bureau's limit can only be <br />accomplished by a computerized technique which analyzes the <br />seismograph data in terms of both peak particle velocity and <br />frequency. <br />Therefore, in order to best determine the potential effects of <br />ground vibrations recorded in this study, a computerized response <br />• versus frequency technique known as RSVP was used in the <br />preparation. of this report. <br />5 <br />