No description available.

No description available.

Wooden multi-family residential houses continue to gain in popularity. Compared to concrete, wooden constructions have low mass and are subject to relatively poor sound insulation at low frequencies. In a series of Swedish research projects (AkuLite, Aku20 and AkuTimber), the correlation between the measured sound insulation in lightweight, cross laminated timber (CLT) and concrete buildings, was compared to the self-rated annoyance from the residents. Impact sound insulation, LnT,w and LnT,w+CI,50−2500, showed weak correlation with the self-evaluated annoyance. Particularly residents living in wooden houses were irritated by footstep noise generated by a sound source with significant energy content below 50 Hz. When determining impact sound insulation, reverberation time (RT) is measured and normalized to 0.5 s. Below 50 Hz, the uncertainty of the measured RT has been reported to be an issue. In this thesis, empirical studies of the spatial variation of the RT are performed in two empty bedrooms of different construction, the measurement methods ”interrupted noise” and ”integrated impulse response” are compared. The spatial variation of the RT is studied. The uncertainty, in terms of standard deviation, is not found to be larger for frequencies below 50 Hz compared to higher frequencies. The bedrooms are then furnished and the RT is measured with the integrated impulse response method, found to be favorable below 50 Hz. To what extent furniture contributed to the absorption, and thereby affected the RT, is studied. At frequencies below 50 Hz, no statistically significant difference in the absorption, due to furniture, is found. Consequently, below 50 Hz, there should be no need for the normalization of 0.5 s when impact sound insulation is evaluated. From the scientific literature, there is an evident need to develop and upgrade sound insulation prediction methods of CLT panels. A finite element (FE) model is provided, capable of predicting the airborne sound insulation of typical CLT wall configurations. Single and double CLT panels, with air and mineral wool respectively in the cavity, are studied. A 2D-3D Hybrid FE model is introduced that rotates the panels to capture a diffuse-like sound field with reduced computational time compared to a full 3D model. The purposes are to predict the weighted sound reduction indexes, Rw and Rw + C50–3150, as well as to study the response as the materials and dimensions alter. For single walls, the differences regarding Rw and Rw +C50–3150 are within ±2 dB compared to analytical calculations and laboratory measurements. For double walls, the Hybrid model can provide an indication of the airborne sound insulation and serve as a tool for relative comparisons, but due to the lack of comparative data, the absolute accuracy cannot be stated. Metamaterial, an engineered material with properties not found in naturally occurring materials, may at a later stage be added to the FE model with the aim to improve the sound insulation below 50 Hz of CLT constructions. Passive vibroacoustic metamaterial, designed according to the localized resonance principle where the eigenfrequency of the unit cell (building up the metamaterial) coincides with the wanted wave length to decrease or cancel, is of particular interest. One such example is the Mie resonator which are studied in a pilot study. Two critically coupled Mie resonators, tuned to have monopolar and dipolar resonances in the same frequency region, will produce the highest sound absorption and thereby the highest sound insulation of the CLT construction. The Mie resonator was designed to absorb sound within the 31.5 Hz octave band, the result from the pilot study seems promising.

No description available.

Bostäders uppvärmning står för en stor del utav vår energianvändning. För att minska energianvändningen är det viktigt att minimera värmeutsläppet genom byggnadens konstruktionsdelar. Genom att optimera isoleringen i en byggnad bidrar man till att minimera värmeutflödet, vilket bidrar till minskad energianvändning. Syftet med detta examensarbete är att undersöka möjligheterna att minska värmeutflödet i anslutningen av mellanbjälklag i trästomme genom applicering av vakuumisoleringspaneler. Resultaten ska sedan jämföras med hur mycket mer vanlig mineralull som behövs i resterande del av ytterväggen för att uppnå samma minskning av värmeutflöde.Vakuumisoleringspaneler är ett superisoleringsmaterial som vanligtvis består av pressad kiseloxid som omsluts av ett metallhölje. Innan höljet sluts samman töms materialet på luft och vakuum bildas.Konstruktionsdelen som valts i denna studie är infästningen mellan yttervägg och mellanbjälklag. Både ytterväggen och mellanbjälklaget har träreglar som stomme. Sedan genomfördes simuleringar med hjälp av energiberäkningsprogrammet Comsol Multiphysics. Det gjordes flertalet simuleringar med till exempel olika storlekar och tjocklekar på vakuumisoleringspaneler.Resultatet visar att köldbryggan som uppstår i anslutningen mellan yttervägg och mellanbjälklag av en trästomme kan minskas med 260–460% vid användningen utav vakuumisoleringspaneler, resultatet beror på tjocklek på trästommen och hur stor panel som används. Att resultatet visar en större minskning än 100% betyder att värmeflödet genom anslutningen blir lägre än genom den kontinuerliga ytterväggen när VIP används.Om man inte använder sig utav vakuumisoleringspaneler i denna konstruktionslösning kan man ersätta dess effekt genom att tillämpa extra isolering i yttervägg, mängden isolering som krävs är mellan 25mm och 55mm, beroende på vilken av stomtjocklekarna och vilken storlek på panelen som används.

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Abstract MSD or musculoskeletal disorders and diseases that mainly occur in the joints, back and shoulders, affects a large number of construction workers. An innovation that could possibly prevent MSB is the exoskeleton. The purpose of this study is to address the applicability of the exoskeleton in the construction industry from a work environment perspective. Results from the studies showed that the majority of the participants experienced exoskeleton as a good aid, and they also considered using it continuously in their work, but only in some working steps like, workstep above shoulders. The conclusions that can be drawn from the study are that the majority of the participants had positive perceptions about the applicability of the exoskeleton in the construction industry.

The adsorption of polyelectrolytes, both as monolayers and as multilayers, was investigated as an easy and non-expensive way of producing lignocellulosic fibrous materials with enhanced mechanical properties. In the first part of the work described in this thesis, the adsorption of a polyelectrolyte monolayer onto the surface of unbleached and unbeaten kraft pulp fibres with different kappa numbers was investigated. Adsorption isotherms were obtained in order to determine the amounts of polymer that could be adsorbed by the different pulps. Handsheets were made from the treated fibres and the mechanical properties were studied. The results showed that the use of only 2 mg/g of a polymeric amine such as polyallylamine or polyvinylamine could under certain conditions increase the tensile strength index by up to 50 %. In a second investigation, the Layer-by-Layer deposition technique was used to build up polyelectrolyte multilayers on the surfaces of bleached kraft pulp fibres. Two systems were studied and the presence of added salt in the systems was also investigated. The results showed that the system composed of polyallylamine hydrochloride and hyaluronic acid provided a dramatic increase in both strength (from 20 Nm/g to 70 Nm/g) and strain at break (from 2.0 % to 6.5 %) with only five deposited bilayers. Such a stretchability could make this material very suitable for 3D-forming of packaging materials. The behaviour of this polyallylamine/hyaluronic acid system was then studied from a more fundamental point of view in a third study in order to determine the mechanisms on the nano-scale behind the large improvements observed on the macroscopic paper scale. A quartz crystal microbalance equipment was used to study the adsorption onto model surfaces and show the superlinear trend of the build-up. Atomic force microscopy was also used to study the structural changes occurring upon adsorption of each polymeric layer as well as the adhesive properties of the system. / <p>QC 20121204</p>

For certain bridge types, the influence of soil-structure interaction (SSI) may have an important contribution to the stiffness and damping of the structural system. From a design point of view, this influence may be both conservative and non-conservative and therefore, an increased knowledge within this field could lead to better design assumptions. In terms of maintenance, assessment and upgrading of existing structures, an increased knowledge of the phenomena and parameters which govern the soil-structure interaction, may lead to more realistic models and thereby, to more precise information for the decision makers and railway system owners and administrators. SSI appears to be most important for short and relatively stiff structures such as portal frame bridges. Dynamic analyzes of this bridge type have shown a large sensitivity in the choice of boundary conditions, where applying elastic constraints on the vertical degree of freedom at the support, compared to fixing this degree of freedom, may increase the maximum vertical bridge deck acceleration by as much as a factor of three. In this thesis, numerical analysis procedures for the computation of dynamic stiffness functions describing the frequency dependency of the foundation-soil interface have been explored under the assumption that the analysis can be performed using linear theories alone. The numerical solution of the equations of motion of structural systems, including such frequency dependent parameters, is performed using an integration scheme based on the discrete Fourier transform. Furthermore, preliminary experimental work on a newly built portal frame bridge is described. This portal frame bridge is subject to a case study in which the the computational techniques mentioned above are applied on a two dimensional model of the bridge. Theoretically, the damping of the SSI is shown to give a large contribution to those modes of vibration which excite the foundations much. These structural modal damping ratios may be much larger than those prescribed by the design codes. Those modes of vibration which do not excite the foundations much are similar to those obtained using clamped or constant elastic boundary conditions and in these cases, the contribution to the modal damping ratio of the structure is only a fraction of that prescribed by the design codes. A very rough analysis of measurements taken from the bridge indicate a similar behavior, but the amplitudes of vibration in many of the estimated modes are quite small (in the order of the quantization error of the measurement system) and therefore, the errors in the damping ratio estimates may be substantial. The work with this thesis have raised many questions, the answers to which are believed to substantially improve our understanding of resonance phenomena and also our possibilities to update numerical models of existing railway bridges using dynamic measurements. From the simplified analysis of a portal frame bridge performed within this project, it has been concluded that when the elastic modulus of the soil is increased, the total structural damping ratio when dynamic SSI is included decreases. Furthermore, with respect to vertical bridge deck accelerations, clamped boundary conditions are certainly not conservative as compared with static and dynamic SSI.

<p>QC 20180326</p>