Vibrations in buildings in the mid frequency range

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Hilary Bennett
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1 ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari 2011 Vibrations in buildings in the mid frequency range Hans Verbraken, Geert Degrande, Geert Lombaert bwk.kuleuven.be/bwm Structural Mechanics, Department of Civil Engineering K.U.Leuven

2 Ground vibration in the built environment Railway traffic (train, tram, subway) Road traffic Construction works Industrial activities Seismic sources ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

3 Ground vibration in the built environment Railway traffic (train, tram, subway) Excitation mechanisms: wheel/rail roughness, rail joints... Vehicle-track interaction: dynamic axle loads. Dynamic interaction between the track/tunnel and the soil: transfer functions Wave propagation in the soil: dynamic reciprocity theorem. Dynamic soil structure interaction. ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

4 Ground vibration in the built environment Malfunctioning of sensitive equipment Discomfort to people Low frequent vibration (1 80 Hz) Re-radiated noise ( Hz) Damage to buildings ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

5 Prediction methods Numerical [Lombaert et al., JSV, 2009][François et al., CMAME, 2010] + Great variety in numerical models Need for accurate parameter characterization + Soil characteristics inherently taken into account Accurate input data is not always available Hybrid Experimental transfer function (red) and 95% confidence region (blue) between 2 points in the free field [Schevenels, OPTEC, 2009] x x Displacement [m/n] Prior model Frequency [Hz] Displacement [m/n] Posterior model Frequency [Hz] ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

6 prediction methods The empirical FRA procedure Prediction of the vibration velocity level in one-third octave bands [Hanson et al., 2005]: L v = L F + TM L + C build (1) Vibration velocity level L v = 20 log 10 (v RMS ) [db ref 10 8 m/s] Force density L F [db ref N/ m ] Transfer mobility TM L [db ref 10 8 Coupling loss factor C build [db] m/s N/ m ] (a) Time history, (b) frequency content and (c) one-third octave band spectrum of the vibration velocity at the foundation of a building. (a) v(t) [m/s] 1 x Time [s] (b) v(f) [m/s/hz] 4 x Frequency [Hz] (c) L v [db ref 10 8 m/s] ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

7 prediction methods Line transfer mobility TM L Characterization of the wave propagation in the soil TM L = 10 log 10 (h n k=1 10 TM Pk 10 ) (2) Impact locations z x y Rail alignment Measurement line Impact locations z y x Measurement line Rail alignment ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

8 prediction methods Force density L F Determination of the force density L F = (L v C build ) TM L L v C build TM L ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

9 prediction methods Coupling loss factor C build Determination of the coupling loss factor C build = L v (L F + TM L ) L v L F + TM L ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

10 Numerical simulation of the FRA procedure Case Ballasted track with monoblock sleepers and UIC 60 rails Thalys train with 26 axles Soil: homogeneous halfspace Soft soil:c s = 100 m/s Medium soil:c s = 150 m/s Stiff soil:c s = 300 m/s Two story masonry building with 4 interior walls 30 m ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

11 prediction methods Prediction of L v on site with existing track and new building L F and TM L are detemined on site C build is determined at other site with similar conditions for building and soil ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

12 Numerical simulation of the FRA procedure Influence of the soil characteristics Coupling loss factor determined at (a) 30 m and (b) 42 m on a soft, medium and stiff soil for a two story masonry building C build [db] 0 10 C build [db] 0 10 (a) 20 (b) 20 Prediction of the vibration velocity level (a) 30 m and (b) 42 m with a coupling loss factor determined on a soft, medium and stiff soil. L v [db ref 10 8 m/s] Az L v [db ref 10 8 m/s] Bz (a) 40 (b) 40 ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

13 prediction methods Prediction of L v on site with existing building and new track TM L and C build are determined on site L F is determined at other site with similar conditions for train, track and soil ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

14 Numerical simulation of the FRA procedure Influence of the soil characteristics Force density determined at (a) 8 m and (b) 32 m on a soft, medium and stiff soil (impacts on soil) for the passage of a Thalys train at 288 km/h. (a) L F [db ref 1 N/m 0.5 ] (b) L F [db ref 1 N/m 0.5 ] Prediction of the vibration velocity level (a) 8 m and (b) 32 m with a force density determined at 8 m on a soft, medium and stiff soil (a) L v [db ref 1 N/m 0.5 ] (b) L v [db ref 1 N/m 0.5 ] ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

15 Appropriate input data are important for accurate experimental Hybrid combine advantages of numerical and experimental Further research Experimental verification Verification of the accuracy of a hybrid prediction Efficient prediction of vibration velocity levels in mid frequency range ABAV Studiedag Wie-doet-wat in het Belgisch akoestisch onderzoek? 23 februari /15

interaction and ground borne vibration Excitation mechanisms of train/track Structural Mechanics, Department of Civil Engineering, KU Leuven

RIVAS Training Workshop 9//23, Hotel Bloom, Brussels, Belgium "Reducing railway induced ground vibration by controlling the source" Excitation mechanisms of train/track interaction and ground borne vibration