Noises and Vibrations in Complex Constructions
Study of Noise and Vibration Propagation in Complex Structures and Engineering Systems (Service Lines) of Buildings and Constructions
Tech Area / Field
- INF-SOF/Software/Information and Communications
3 Approved without Funding
VNIIEF, Russia, N. Novgorod reg., Sarov
- St Petersburg State Polytechnical University, Russia, St Petersburg
- Technische Universitat Braunschweig / Institute of Applied Mechanics, Germany, Braunschweig\nInstitut für Fertigteiltechnik und Fertigbau Weimar e.V., Germany, Weimar\nPhysikalisch-Technische Bundesanstalt, Germany, Braunschweig
Project summaryThe problem of noise prevention is the most important environmental problem. According to some data, over 60% citizens inhabiting large cities are living under excessive noise conditions. For example, the average values of the equivalent sound levels in Peking, Moscow and Hong-Kong are 60–65 dBÀ, in Mexico City they are 70 dBÀ. These are very high levels. Based on the subjective loudness perception, the noise in cities is very often 2 – 4 times as much as the permitted values. A wide use of numerous high-speed overland, air and water means of transport, application of perse and powerful household and sanitary equipment (audio systems, refrigerating units, ventilation, jañuzzi, etc.) have led to the following: a man is subjected to multiple harmful noise effects, the so-called acoustic expansion, whether at a working place, in everyday life, at rest or while traveling. In the recent years serious changes in construction of buildings and structures have taken place: complex structures (complex-shaped structural elements, monolithic and panel buildings, etc.) made of various materials (metal structures, foam concrete, various artificial materials, etc.) are used. All this requires application of optimum acoustic design methods in construction practice. The currently applied methods for calculation of noise and vibration in buildings including standardized methods (see, for example, SNiP 23-03-2003, SNiP II-12-77) have a number of disadvantages the main of which is the impossibility to provide comprehensive consideration of all the vibrational energy propagation ways and their interaction. The initial cause of the drawbacks is the fact that the informative scientific basis for the techniques was developed over thirty years ago and has remained unchanged in relatively new wordings. No opportunities opened up by application of high-performance computing facilities are used in the calculation approaches. There are no reasonably substantiated methods for calculating some components of vibration/noise in buildings (for example, propagating through heating and water supply systems). All this leads to great errors in the calculation of vibration/noise in complex structures and service lines and communications of buildings and as a result to their non-optimal acoustic design. At the same time, the existing world practice of calculating vibration and sound in complex engineering constructions (i.e. constructions comprised of many elements) makes wide use of the finite element method (FEM) and the energy method (EM) that may serve as the basis for the techniques to be used for calculating noise and vibration in complex structures and engineering systems (service lines and communications) of buildings and constructions. The methods have different fields of application: the FEM method is used at low frequencies, the EM method is used at medium and high frequencies; FEM is a more accurate method, EM is an approximate engineering method.
The basic advantage of EM is a comprehensive consideration of all the vibrational energy propagation ways and their interaction. This makes it possible to estimate correctly the efficiency of vibration and noise reduction means, i.e. including all the energy propagation bypasses usually decreasing the nominal efficiency of the means. The method provides a possibility for a simple and fast estimation of the contributions made by independent sources and their components (supporting, non-supporting, aerial) to vibration or noise levels and the role played by some vibrational energy propagation ways in formation of vibrational and sound fields at the reference point. An important advantage of EM is a relative simplicity of calculation formalization, i.e. development of the calculation programs that are a compulsory component of a modern approach to calculations. Thus, the method may be considered a powerful tool of acoustic design. Today, there are actually no other methods for calculating vibration and noise in complex constructions over the sound frequency range that would be so thoroughly developed and officially accepted as the EM method. The examples of successful practical application of EM in various fields of engineering, mainly in automobile construction, shipbuilding and machine-building, are known.
One of the proposed activity objectives is elaboration of the methods for determining the above initial data (using the appropriate software) and obtaining their numerical values, as applied to standard buildings, their service lines and communications, as well as development of the regulations breaking down a complex construction into subsystems. The ILC of subsystems may be only found experimentally. The ILC of standard elements of buildings, service lines and communications will be measured within this work. In some cases the introduced power may be measured, but calculations are a more general way of its determination. This work will look into the possibility of determining the introduced power by applying the FEM method to the complex structure loaded fragment. One of the greatest EM problems is determination of ECC (sound insulation and vibration insulation). The ECC coefficients of subsystems may be determined analytically, experimentally or numerically. The ECC coefficients are calculated analytically from the coefficients of energy penetration through subsystem joints. However, such coefficients are known from analytical solutions only for some elementary types of joints (rigid Ã-, Ò-, cross-shaped joints of semi-infinite beams or plates and some others). This information is usually not enough for practical calculations. The experimental method of ECC determination requires organization of a sophisticated and labor-intensive physical experiment. Therefore, a universal method of ECC determination based on numerical simulation of the subsystems entering the joint will be also studied using the finite element method.
In the last few years new sound-insulating materials such as foam concrete and others, new types of building structures (monolithic, etc.) have appeared, which requires that the sound insulation of new materials and structures should be experimentally determined. These efforts will be partially made within the framework of this project and a database (ECC) on both noise and vibration attenuation in various standard structures, service lines and communications of buildings will be created. The data on vibration penetration through various building structure joints are less available (see, for example, “Noise prevention at a plant”. M.: Mashinostroenie, 1985). In addition, these data were obtained under full-scale or model conditions because there are no test units and standard measurement methods for such measurements. For many types of structures and especially for service lines and communications the experimental data on vibration passing through joints are not available. Such experimental data on vibration insulation of some standard service lines, communications and structures will be generated within the project.
This work will result in proposals on some methods and means to be applied to reduce vibration and noise in complex-shaped buildings and constructions. With the project completed, a plan of using the developed technologies in construction practice will be made. The project participants have some publications in this field (see section 12 “Supporting Information”). In the course of the project implementation the participants are going to file applications for technical decisions on the methods of experimental ILC and ECC determination, and the methods and means of reducing vibration and noise in complex-shaped buildings and constructions.
To obtain the expected results, the VNIIEF available scientific and technical expertise in the field of acoustic and vibration studies (including development of the instrumentation for these studies) as well as the experience gained in acoustics of buildings and creation of methods and means protecting from violent vibrations and noise will be used. The department of distributed intelligence systems in SPSPU applies modern methods of diagnosing structural and aerial sounds propagating from various types of noise and vibration sources in different-purpose structures and constructions. The analytical methods used for signal processing enable detecting the prevailing harmonics of the vibration signal propagating in structures with a fair degree of probability, which gives a more comprehensive idea for further reduction of noise and vibration on the way of propagation and thus makes it possible: 1) to reduce noise in the inhabited rooms and 2) to predict and prevent the vibration failure of structures. The applied methods and the proposed project studies will serve to develop calculation and experimental models of estimating noise in different-purpose rooms at the stage of research and development of new buildings and constructions and at the stage of updating (or reequipping) the existing buildings and constructions. The structural complexity of modern buildings and constructions, application of metalware and various artificial materials in construction point to the analogy of the problems solved in construction of buildings and in shipbuilding. Therefore, a rightful question arises as to whether the advanced methodology of acoustic design of ships could be used in acoustic design of complex-shaped buildings and constructions, which is what is suggested in this proposal. That is the reason why the primary personnel include such specialists from the academician A.N. Krylov Central Scientific Research Institute (St. Petersburg) as I.V. Grushetsky, V.I. Kirpichnikov and À.V. Smolnikov, who have dealt with acoustic design of ships for many years.
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