Contents Page 1 5. Effects on buried pipework 5. Principles of evaluating the offects of vibration on structures General Determining stresses by analysis. Permissible stresses Evaluating serviceability Effects of vibration on soil 5 Evaluating effects of short-term vibration 5.
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For analytical purposes, the character of the signal shall also be taken into consideration, for instance by means of suitable data windows cf. Appendix D. For civil engineering structures e.
In the case of buildings as in line 3 of table 1, it may be necessary to lower this value to prevent minor damage. It is assumed that the pipes have been manufactured and laid using current technology; if this is not the case, special considerations will have to be made. Additional considerations need also be made where mechanical processes in the ground could have deleterious effects on pipes, or where there are different stress conditions at junctions e.
The values given in table 1 for foundations also apply to the first two metres nearest the building of gas and water service pipes. Drain pipes shall be evaluated using the values given in line 3 of table 2.
To measure vibration in foundations, the pick-ups for the three directions of measurement shall be placed close together on the ground floor of the building to be investigated, either at the foundation of the outer wall, on the outer wall itself, or in a recess in that wall. Measurement points shall preferably be on the side of the structure that faces the source of excitation. The time history of the vertical vibration z-axls and horizontal vibration x- and y-axes, at right angles to each other shall be recorded, with one of the directions of measurement running parallel to a side wall of the building.
For structures with a large ground floor area, simultaneous measurements shall be made at several locations. In addition to the measurements made on the foundation and the highest floor, a measurement in the vertical direction may also have to be made on the floors on which the strongest vibration is expected; in this case, the point of measurement should be in the centre of the floor cf. Pick-ups for measurements in the highest floor shall be placed on or immediately next to structural masonry so that the two horizontal directions of measurement, x and y, are at right angles to each other, with one direction running parallel to a side wall.
When carrying out measurements on pipework, pick-ups shall be placed directly on the pipes whenever possible. As an alternative, the pick-up may be placed on the ground surface directly above the pipe, although in this case, it is only possible to make estimates see Appendix 0. A test report as in Appendix A shall be drawn up for each measurement.
Experience has shown that if these values are complied with, damage will not occur. Exceeding the values in table 3 slightly does not necessarily lead to damage. Should they be considerably exceeded, the stresses may be determined as described in subclauses 4. If a building is subjected to harmonic vibration, then the maximum values can also occur in floors other than the top floor, or in the foundation.
The values given in table 3 also apply in these cases. When other points of reference are used, separate analysis is required. In the case of flexural vibration close to resonance, which often occurs when floors vibrate at high magnitudes, the additional dynamic stress can be approximated using the method mentioned in subclause 4.
For beams and one-way spanning solid slabs of rectangular cross section l. The eigenmode coefficient is dependent on the boundary conditions and the degree of the mode.
Both of these have only a slight influence; however, in practice, the value for kn lies between 1 and 1 ,3. For two-way spanning slabs, the bending stress so calculated is also to be considered a maximum. Such vibration is very clearly perceptible. For structures as in line 3 of table 3, no guideline value can be given for vertical vibration. Minor damage cf. The restrictions given in subclause 5. For vibration having the lowest natural mode, it is normally Page 7 DIN : sufficient to take measurements on the top floor.
When evaluating horizontal vibration in the structure as a whole, it may be necessary in special cases to take into account possible rotational movements in the floor plane and any rigid rotation.
The natural frequency of floors is normally greater than 10Hz, and in most cases, only vertical movements are significant. The vertical vibration shall thus be measured at the point of maximum velocity, which is usually at the centre of the floor.
Appendix A The test report shall include the information listed below. Table A.