dynamic response of the civil engineering structures due to microtremor

Introduction

Increasing demands on speed increase, higher axle pressures on transportation, overdimensional and heavy loads cause simultaneous increase of unfavorable traffic effects on the structures of railways, roadways, highways and facilities on them and on structures and buildings in the vicinity of busy roads and railways. The theoretical and experimental investigation of traffic effects on the industrial buildings structure in the KINEX a.s Bearing Processing Building Complex at Byta are described in this paper.

Processing   Buildings Structures

The complex of bearing processing buildings

in the KINEX a.s Byta consist of  9 industrial halls with concrete - steel structures. The processing building M6 used for production bearings is tailored to technological function is the nearest building to new constructed road with busy road traffic

Load bearing structure in processing building M6 creates reinforced concrete columns, trussed girders, prefabricated column bases and roofing slabs. The single-deck structure is divided by modular rectangle parts with module dimensions 12 x 18 m. The most sensitive part of the processing building M6 is dilated and it consists of 5 x 3 modules. The structural height of the processing part is 8 m. (Figure 1)

Figure 1:  The view of processing building M6

Finite element consulting

The two versions of computing model was created as an FE model in computing system IDA Nexis which respects all data assumed in project documentation and design calculation. The first version of the computing model considers roofing slabs as a load bearing members connected with joints to truss girders and the second version considers only the mass of the slabs. The first 10 natural frequencies and modes of natural vibration were calculated for this FE model.

Figure 2: An example of natural modes

Experimental results

The dynamic assessment of the processing building M6 was divided to five parts:

Experimental tests of the structure dynamic response due to production process without any microtremor effects

The dynamic soil parameters evaluation by impact tests

Experimental tests of the structure dynamic response due to construction machines during road under construction

Experimental tests of the structure dynamic response due to road traffic means

Data processing and evaluating

The important areas of these tests were to observe microtremor effects on:

Safety of  the building structure

Sensitivity of the very precision machines vibration.  

The set of accelerometers (BK 8306) were used for measurement of global and local vibrations in the most representing areas and points of M6 structure [1]. The structure vibration amplitudes were recording using A/D converters, filters, portable computer (PC/DX4) with relevant

software

The recorded signals (Figure 3) were analyzed in laboratory of the Department of Structural Mechanics (CEF - University of ilina) using amplitude (Table 1), frequency and amplitude - phase analysis, by method of spectral and correlation analysis using two channel frequency analyzer connected via GPIB with relevant software (DISYS, DAS 16).

Figure 3. Time history of structure vibration due  

to microtremor

Table 1. Comparison max v_RMS velocity vibration amplitude at the nearest structure point to road

Figure 4 shows power spectral spectrum G_v(f) measured at point B 38-x and Figure 5 illustrates the cross power spectrum between points B5 and B6 in horizontal directions. Positions of structure measured points are described in [1].

Figure 4: The power spectral density G_v(f) at point

B599 due to processing + road traffic effect.

Figure 5: Cross power spectrum S_D(f) between points A1/A2 measured dynamic response

Conclusion

The tested structure processing estimation of microtremor effect as a complex of dilated parts is described in several conclusions:

Results from spectral analysis show that the frequencies area due to road traffic does not endanger neither building structures safety nor production process in building M6

Based on amplitude analysis the danger phase of structure vibrations was observed during the road under construction only. During this phase a rather in old part of building M6 were observed increasing of the structure cracks.

It is necessary to strengthen the cracked parts of building M6 structure.

References

Benat, J., et all. Report on Microremor Test Results in the Industrial Processing Buildings Structures in the KINEX a.s Byta. Report No. PC/37/SvF/06, Zilina

Bendat, JS. and Piersol, A.G. EngineeringApplication of Correlation and Spectral Analysis.John Willey and Sons, New York, N.Y. 302. (1980)