VIBRATION OF BUILDINGS LOCATED IN RAILWAY STATION AREA

Transcription

1 3 rd International Conference on Experiments/Process/System Modeling/Simulation & Optimization 3 rd IC-EpsMsO Athens, 8-11 July, 2009 IC-EpsMsO VIBRATION OF BUILDINGS LOCATED IN RAILWAY STATION AREA Jan Rozowicz 1 1 Warsaw University of Technology, Faculty of Transport Koszykowa Str. 75, Warsaw, Poland jr1950@o2.pl, web page: Keywords: Vibration, buildings, people under vibration Abstract. This paper presents results of the tests carried out within the area of railway station in Warsaw. Presented studies concern new investment and modernization in station area. This area covers the railway station area, in addition heavy traffic of streetcars, bus service and passenger cars as well. In surrounding of this station there are new-designed objects located. The paper presents a simulation study of the dynamic effect of railway transport on public building, before start of railway line modernization. Characteristics of building included data on its dimensions, structural design, materials and foundation. Mathematical model of the building was worked out in the FEM environment, and sample results of simulation study of the effect of railway traffic induced vibration on the building are presented. Specified in the standards are the maximum acceptable accelerations generated in the building structure. In simulation tests - simulator of vibrations was used. For each node of building model structure - acceleration were obtained. The results were presented in 1/3 octave bands. After completion of the investment verification of simulation studies and experimental measurements of vibration were accomplished. 1 INTRODUCTION On Warsaw University of Technology there is a multidisciplinary team taking up studying dynamic influences on environment caused by the vehicles. The team gathers specialists of transportation, civil engineering, architecture and environmental protection. The essential research problems carried out by the team is the problem of pollutions caused by transport influence, in particular pollution of the environment with noise and vibrations. The main problem, which the team is involved in is the influence of vibrations generated by the means of transport on engineering objects and peoples. Under mentioned article there was presented a proof of research performing methodology elaboration of dynamic influences as well as using of uniform methodology was proposed. It will allow to uniform presented results of studies and to compare them in case of performing analogous studies by various scientifically institutions. There were presented the results of simulation studies about the influence of planned railway line and station modernization on the planned public building [5]. In consequence of railway junction modernization it became necessary to evaluate dynamic effect of the railway line on houses and public buildings in the vicinity. The analyzed building is affected by the nearest underground trains, trams, light and heavy motor traffic as well as multiple railway tracks. Therefore, reorganization of traffic in this area calls for simulation of the response of building structures to increased vibration caused by the traffic. 2 INVESTIGATION 2.1 Method of estimation In connection with modernization of the railway station area a forecast about dynamic impact of the traffic on this building was worked out. Aim of this forecast is to demonstrate the way the traffic induced vibration will affect the building [1,3]. Depending on vibration acceleration value as a function of frequency - five standard zones have been assumed [6] : Zone I vibration imperceptible to the building structure, Zone II vibration sensible to the building, however, harmless to its structure, Zone III vibration harmful to the building resulting in local scratches and fractures, Zone IV vibration considerably harmful to the building posing a threat to safety of the humans, Zone V vibration resulting in damage to the building the walls are breaking down.

2 The Zones are set according to the standards and defined by acceleration values for each frequency within a band (1/3 octave bands) from 1 Hz to 100 Hz. Performing of dynamic influences prognosis, influences generated by the transport on the environment is related with the realization of main tasks mentioned below: to define the zone of transport investment influences on the environment, to define dynamic background in the zone of the investment influence, to work out the dynamic models of engineer objects, to perform simulation studies, to perform the prognosis, to perform the verifying studies, estimation of the prognosis accuracy. 2.2 Object localization The following is a documentation of the location of the planned object. The geographic location of the object describes coordinates: 52 15,5 N, 20 59,5 E. Figure 1. Location of the planned building on the ground (top view, by GoogleMaps) [5]. Figure 2. Location of the object according to plan [5].

3 2.3 Experimental tests The sources of vibrations caused by vehicles are among other factors the impacts caused by the contact of vehicle wheels with the surface. The vibrations are carried by the ground to building, and then are taken by the building in the ground level and carried by the construction of the building to particular rooms, where people are staying and working. There are presented in this paper the results of some selected experiments of the vibrations effects on building structure and people staying in buildings. Vibration acceleration values were checked to see if they did not exceed the limit values acceptable for building structure and people during daytime and night hours. A computer based vibration analyzer and a vibration converter system were used to carry out the measurements. The analyzer consisted of: Sensors, which convert mechanical magnitudes into electric signals; in this case these were three axes accelerometers - DYTRAN, Measuring amplifiers, which match electric signals reaching the sensors with the AC converter board, PCMCIA standard sixteen channel, twelve bit AC converter board, IBM class notebook with PCMCIA input (including suitable software). Batteries supplying the system were capable to provide necessary power for several hours of operation in the field without recharging. Analyzer specification: Number of measurement channels 16 Samples per channel Sampling frequency Hz Measurement time intervals s Recording style binary and open text Measuring boards: Voltage boards ± 10V Typical sensors measurement ranges of the sensors: Accelerations: 0-70 m/s2 (RMS) Vibration velocities: 0-70 *10-3 m/s (RMS) Vibration amplitudes * 10-6 m (RMS) Relative vibrations: *10-3 m Used for the tests were piezzo-electric vibration converters DYTRAN 3143 M1 to the following specification: Frequency range: Hz Sensitivity: 100 mv/g Acceleration values of the vibrations were measured under no-rain weather conditions, with use of the above mentioned instruments. Accelerations occurring in cross sections were measured in three directions (x,y,z): x along the long side of the building plan, parallel to the traffic lane centre line; y along the short side of the building plan, square with the traffic lane centre line; z vertical. Two of measuring points were at ground level, and accelerometers were fixed in special holders to perform vibration measurements of longitudinal and transverse surface wave. The third measurement point is placed on the platform. The choice of the location of the proposed measure reflects the severity of the building after modernization of the train station. Measurements were taken by means of the multi-channel recording of the vibration acceleration time signals to the requirements of Polish Standard specification PN 85/B Basic magnitude obtained from the tests was vibration acceleration in 1/3 octave middle frequency bands in the range from 1 Hz to 100 Hz. Tests were carried out in described below measurement points: Point I - reference point in soil, at the ground surface level, distance approx. 1m, Point II - reference point in soil, at the ground surface level, distance approx. 5m, Point III - on the platform, between the tracks, planned location of object.

4 Figure 3. Reference point N o Results of experimental tests Acceleration of vibration in the selected measurement points are presented below. Acceleration of vibration Acceleration, ay[m/s 2 ] Acceleration, ax[m/s 2 ] Acceleration, az[m/s 2 ] Time, [s] Figure 4. Acceleration of vibration in 3 directions: x, y, z. Then, from recorded in time domain courses, a representative pass were analyzed as the test object. The Fast Fourier Transform (FFT) were used to the second step of numerical analysis. 3 PROGNOSIS 3.1 Simulation of building reaction The building elements were imported to specialist simulation software using the Finite Element Method [8]. In the next step, a model of the building was constructed using imported components by defining constrains existing between them [2]. Below, here are the results of the analysis in frequency bands (1/3-octave bands)

5 passenger trains from the platform started with reference to the suggested limit by the Polish Standard. Figure 5. Acceleration of vibration generated by passenger train from the platform started, and comparison to the lower scale of dynamic influences on building (SWD-I). 3.2 Simulation of vibration influence on people Obtained model (FEM-structure) is three-dimensional and gives the frequency responses in any chosen places and points of the building. Analysis of the effect of vibration on people was carried out according to the Polish Standard PN-88/B [7]. vibration feeling limit accept. level of vibration in day-time X direction Y direction Z - direction Acceleration, axyz[m/s 2 ] Frequency, [Hz] Figure 6. Acceleration recorded during the train leaving platform generated vibration, and comparision to the value of the human vibration perception level and limit values for human presence on the area of public, utility and housing buildings during the day-time.

6 4 CONCLUSIONS Simulation analysis, in FEM-based method, provides a response to the input function for each node of the grid in x, y, z directions. While analyzing the effect of vibration on buildings, maximum values of vibration acceleration in x, y (horizontal) directions were taken into consideration. Analysis of the effect of traffic generated vibration on buildings was carried out according to the Polish Standard PN-85/B [6]. The results were presented as 1/3 octave bands and compared with the values set in the criteria for the division into zones of harmfulness scale. As can be seen in Fig. 5, permissible acceleration values were not exceeded for any frequency band. This means that the planned building under study is not exposed to substantial dynamic impact caused by the railway line, and additional sources of vibration in analyzed area. Presented exemplary building is a part of rail infrastructure. People are regularly present in this building, which is located inside the area of the railway station, it has been required to check whether it is not exposed to excessive dynamic impact. It can be seen from the analysis, that the urban traffic dynamic impact on the building is small, in contrast to passing trains. For few frequencies there are the limit of vibration perception exceeding. Presented above rules of prognostication are mainly based on simulation studies within vibrations and noise influence on humans as well as influence of vibrations on the building. It is necessary to remember that part and parcel of these studies are measurements. Correctly carried out measurements of dynamic background are the base used not only for generation of impacts, but also the platform for simulation studies. Described above method uses the 3-D model which allows to precise modeling of the structure as well as materials used for building of the object. Advantage of this model is the possibility of receiving the response on forces in any point of the building what facilitates not only prognostication of influences on the building, but also on humans staying in them. Model is very suitable to calculations used for buildings with low rate of wear and tear. It may be necessary to perform periodical measurements of vibrations affecting humans inside the buildings in order to counteract the vibration-related hazards. REFERENCES [1] Ciesielski R., Maciąg E.: Road-borne vibration and its influence on buildings (Drgania drogowe i ich wpływ na budynki). Publishing House WKiŁ, Warsaw pages 248. [2] Chmielewski T., Zembaty Z.: Podstawy dynamiki budowli (in Polish) (The rudiments of the dynamics of structures), published by Arkady, Warszawa, [3] ISO 4866: Mechanical vibration and shock Vibration of buildings Guidelines for the measurement of vibrations and evaluation of their effects on buildings. [4] ISO , Mechanical vibration Ground borne noise and vibration arising from rail systems. Part 1: General guidance. [5] Joint publication edited by M. Nader (in Polish): Prognosis of dynamical influences arising from trains passing Warszawa Gdańska station on projected public building. A study ordered by the TOMASZEWSKI Investment Service Office, Warsaw 2008, p. 24. [6] Polish Standard PN-85/B Ocena szkodliwości drgań przekazywanych przez podłoŝe na budynki (in Polish) Estimation of harmfulness of vibration transmitted by the subsoil to the buildings, published by Alfa, Warszawa, [7] Polish Standard PN-88/B Ocena wpływu drgań na ludzi w budynkach (Evaluation of the effect of vibration on the humans inside buildings) [8] Rakowski G., Kacprzyk Z.: (in Polish) FEM in mechanical construction. Publishing house: WPW, 2005.