Zur Prognose der Schalldämmung zweischaliger Membrankonstruktionen

Transmission‐loss prediction for double‐leaf membrane constructions. The sound transmission loss of double‐leaf membrane constructions can be predicted quite well, if the cavity between the membranes contains absorptive material. This is exemplified by a construction with a membrane distance of 20 cm and a 10 cm thick, open‐porous foam plate inside the cavity. The program LAYERS is used for the calculations. A previously applied approximate formula is inappropriate, because it does not correctly account for the incidence‐angle dependency of the sound transmission. In principle, a LAYERS prediction is also possible with an “empty”, only lightly damped cavity. However, the results are less accurate, since information about the absorption within the air or gas space and at the boundaries is scarce. Further uncertainties pertain to the distributions of incidence angles in testing facilities and their influence on the sound transmission loss.     

Einfluss des Verlustfaktors auf die Schalldämmung von Lochsteinmauerwerk

Effect of loss factor on the sound insulation of hollow block masonry. Sound insulation is known to depend on the loss factor. In solid construction elements the loss factor is largely determined by the energy transfer to adjacent construction elements via the edges, so that the installation conditions influence the sound insulation. This effect is taken into account in the calculation models of EN 12354 through the so‐called in‐situ correction, whereby the overall loss factor of a component tested in the laboratory is converted to an expected loss factor in a real building. This paper illustrates how the loss factor correction should be applied for vertically perforated bricks with possible resonance frequencies from around 800 Hz. It was found that the correction can basically be applied in the same way as for homogeneous masonry, but only up the first resonance frequency of the brick. For higher frequencies the sound insulation was found to be independent of the installation conditions, so that in this range no loss factor correction should be applied.     

Verlustfaktor‐Korrektur der Schalldämmung bei gefülltem Ziegelmauerwerk

In einem gemeinsamen Forschungsvorhaben der Hochschule für Technik Stuttgart und des Fraunhofer‐Instituts für Bauphysik wurden die akustischen Eigenschaften von mit Dämmstoffen gefüllten Lochziegeln systematisch untersucht. Hierbei zeigte sich, dass sich die gefüllten Steine in ihrem Verhalten nicht wesentlich von ungefüllten Ziegeln unterscheiden. Der wichtigste Unterschied besteht in einer größeren inneren Dämpfung und als Folge davon einer gegenüber gleichartigen ungefüllten Ziegeln um etwa 1 bis 2 dB erhöhten Schalldämmung. Auf Grundlage der Untersuchungsergebnisse wurde ein modifiziertes Verfahren zur Verlustfaktor‐Korrektur der Schalldämmung von Hochlochziegel‐Mauerwerk entwickelt, das für gefüllte und ungefüllte Steine gleichermaßen anwendbar ist. Loss factor correction for hollow bricks filled with insulation material. The acoustic properties of hollow bricks filled with insulation material were systematically investigated in a joint research project by the University of Applied Sciences in Stuttgart and the Fraunhofer Institute for Building Physics. The findings showed that the acoustic performance of filled bricks differs only slightly from that of non‐filled bricks. The main difference is greater inner damping and a resulting increase in sound insulation of about 1 to 2 dB compared to non‐filled bricks of the same type. Based on the results of the investigation a modified procedure for the loss factor correction of the sound insulation of vertically perforated hollow brick masonry was developed, which applies equally to filled as well as non‐filled bricks.     

Schalldämmung und Schall‐Längsdämmung von Fassadenkonstruktionen im Prüfstand – Erkenntnisse für die bauakustische Beratung in der Praxis

Airborne sound insulation and flanking sound insulation of façade constructions (Curtain wallings) in the test stand – findings for acoustic consulting in practice. Based on serial and single measurements for the determination of the weighted sound reduction index and of the normalized flanking sound insulation in horizontal and in vertical transmission direction of façades effects of the measurement procedure and of constructive façade details onto the measurement result are shown. For the performance of measurements of the weighted sound reduction index of façade constructions the possibility of the utilization of German standards DIN ENISO140‐3 in a test stand for wall constructions or of the in field procedure of DIN ENISO140‐5 in a test stand for the determination of the flanking sound insulation of façades is possible. Because the two measurement procedures lead to measurement results with systematically differences for the same façade construction, next to the formal aspect of the communicability of the two measurement procedures the mounting situation of façade elements in the test stand is taken into account. The influence of constructive details of the façade construction and their detailed effect on the determined weighted sound reduction index and/or the determined normalized flanking level difference is supposed to be shown due to carried out measurements of different façades. To that size, kind and order of the glazing, carrying out of façade molliums and façade transoms as well as construction of the façade connecting element as a single‐element for the determination of the normalized flanking sound insulation of a façade construction are taken into account.     

Wärme‐ und Feuchtetransport in Vakuumisolationspaneelen

Heat and Moisture Transport in Vacuum Insulation Panels. Due to their extremely low thermal conductivity, vacuum insulation panels (VIP) allow for high standard thermal insulation with slim building components. Within few years, this led to widespread use especially in building situations where space is limited. As there are no long‐term experiences concerning the thermal characteristics of VIPs, however, their rated values of thermal conductivity are notably higher than the actual measured values at present, which primarily represents effects of degradation caused by gases infiltrating the panel. Most significant is the influence of water vapour diffusing into the VIP. Whereas the effects of dry gases are well known and can be exactly quantified, water vapour causes different processes of heat and matter transfer which increase thermal conduction within the VIP considerably, but which cannot be separated accurately by means of measuring. Thus a theoretical model was developed which describes heat flux basing on the kinetic theory of gases for molecular diffusion and surface diffusion. It moreover provides information about the diffusion characteristics of the core material.     

Tragverhalten von teilweise vorgefertigten Stahlbetonwänden mit Ortbetonergänzung und integrierter Wärmedämmung

Load carrying behaviour of partially precast concrete panels with additional site‐cast concrete and integrated thermal insulation. For partially precast concrete panels with additional site‐cast concrete and integrated thermal insulation, the connection between the interior and external wall layer currently is made by using stainless steel lattice girders. The lattice girders are leading to a flexible shear connection of both wall layers, which is acting under transversal loads (wind or earth pressure), under temperature changes and different shrinkage of the interior and external concrete cross section. Following the loads acting on the outer wall layer and on the lattice girders will be described, which are significant for dimensioning of these construction elements.     

Messtechnische Analyse flachgeneigter hölzerner Dachkonstruktionen mit Sparrenvolldämmung — Teil 2: Nicht belüftete,extensiv begrünte Dächer mit Zellulose‐ und Mineralwolledämmung

Im gegenständlichen zweiten Teil dieser Aufsatzreihe werden die Messwerte aus zwei Gründachelementen, welche zum einen mit Mineralwolledämmung und feuchteadaptiver Dampfbremse und zum anderen mit Zellulosedämmung und Vliesdampfbremse ausgeführt sind, diskutiert. Dabei zeigt sich, dass die Temperatur auf der Dachabdichtung neben den Witterungsbedingungen auch vom Bewuchsgrad des Gründaches abhängt. Aufgrund der geringen sommerlichen Umkehrdiffusion der Gründächer kommt es zu erhöhten Luftfeuchten im Gefach. Dies führt beim Gründach mit Mineralwolledämmung zu erhöhten Materialfeuchten. Das Gründach mit Zellulosedämmung weist diese erhöhten Materialfeuchten hingegen weniger stark auf. Trotz der teilweise lang andauernden hohen Feuchtelast im Gefach der beiden Gründächer konnten weder Schimmel‐ noch holzzerstörende Pilze in diesen entdeckt werden. Measuring investigations of the hygrothermal behaviour of timber flat roofs — Part 2: Non‐ventilated green roofs with cellulose and mineral wool insulation. In the second part of this article serial the measuring values of two green roof elements made of mineral wool insulation with a moisture adaptive vapour retarder and cellulose insulation with a fibrous vapour redarder are discussed. It is shown that the roof surface temperature, beside the weathering conditions, depends on the level of plant coverage. Because of very low drying potential of green roofs high air humidity occurs in the cavity. This leads to higher material moisture content in the element with mineral wool insulation. The green roof element with cellulose insulation shows this higher material moisture content less pronounced. Despite high moisture loads in the cavities of both green roof elements no mould or rot could be found in the investigated roofs.     

Meßtechnische und rechnerische Untersuchungen an einer mit Vakuum‐Isolations‐Paneelen gedämmten Holztür

Measurement and analytical investigations on wooden door insulated by Vacuum Insulation Panels. Thermal transmittance measurements, IR‐investigations and finite element calculations on a wooden door containing Vacuum Insulation Panels (V.I.P.) were done at EMPA. The results of all these investigations are presented and discussed in this article. The comparison of the different methods and calculations according to the standards shows the differences of the approaches and possible ways for optimization.     

Teil 2: Trittschalldämmung — Flankentrittschallpegel und Trittschallminderung

Sound protection of cavity floors. Part 2: Impact sound insulation — namely impact sound flanking level and impact sound reduction In part 1 [1] of this three‐part report on cavity floor sound protection, the history of the development of cavity floors introduced on the market since the early 1980s, the main design principles of such floors, and the concepts of flanking level reduction and weighted standard flanking level difference were illustrated. This second part examines two aspects of impact sound insulation, namely impact sound flanking level — previously sometimes referred to as horizontal impact sound insulation — and impact sound reduction. The following discussion of these two impact sound insulation parameters is based on approximately 150 measurements in an acoustics laboratory. The bulk of the measurements was carried out according to DIN 52 210 [3], more recent measurements according to DIN EN ISO 140‐12 [4].     

Schraubpfähle: Herstellung,Tragfähigkeit und numerische Modellierung

Screw piles: construction methods, bearing capacity and numerical modeling. In the last years the technology of screw‐piling has been developed to overcome the shortcomings of the non‐displacement piles (e.g. bored or flight auger piles) that are always accompanied by soil disturbance, which affect negatively the pile bearing capacity. On the contrary, the screw piles can be considered more or less as full displacement piles, which are comparable with the conventional displacement driven piles. Due to vibration free installation and minimal noise disturbance of the environment they can be applied in urban areas, where driven piles are not appropriate. The full displacement screw piles offer meaningful advantages in terms of environmental engineering. This relatively new piling technology is used successfully as an efficient foundation system that fulfils both stability and serviceability requirements. The use of standard compact machines with high productivity simplifies site operations and contributes to economical performance of the system at the same time. A general overview of the pile system ‐installation techniques, process and bearing capacity – will be described and discussed. First numerical analyses, calibrated on pile load tests to check the validity of the numerical model were applied.     

Robuste und abstimmbare Schalldämpfer in der Abluft von Fertigungs‐ und Heizungsanlagen

Durable and tunable silencers in the exhaust air of manufacturing and heating systems. The requirements for silencers, which are used as secondary noise control devices in exhaust ducts, are particularly high in industrial plants (e. g. paper and mineral fiber production, painting plants) as well as power stations and combined heat and power stations. This is caused by the load of the exhaust gas flow with residual substances, which clog the surfaces of the silencers and reduce their efficiency. High flow rates, temperatures and humidity are further influences, which may affect the service live of the silencers. Additionally, high attenuation at low frequencies is required, as the sound sources (fans, compressors, turbines and engines) exhibit high contributions in this range. Conventional silencers lead to uneconomic solutions under these conditions. This problem is treated here and silencer developments are presented that are durable and tunable with respect to the specific need and frequency range. The operating principle and the construction of the silencers, which consist of panel, cavity and active resonators, are described. Its space and money saving employment are demonstrated with examples realized already in practice. These include the employment of the so‐called Angular Stack Silencer and Cleanable Reactive Silencer as resonators in plants for the paper production and power stations. The employment of active resonators is demonstrated in heating systems. New developments of resistant absorber materials and durable acoustically reacting covers give a survey of innovative solutions.