<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.</p><p>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.</p><p>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.</p><p>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>

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<p>Wood-stud shear walls are commonly used to provide lateral stability against horizontal forces in wood houses. Therefore, accurate predictions of the deformation properties of shear walls are necessary in order to improve the design of wood frame houses against earthquake loading. The aim of this thesis is to increase damping capacity of wood-stud shear walls and hence improve wood frame houses resistance against earthquake.</p><p>The starting point has been the laboratory experiments of nail joint’s deformation properties. Purpose of the experiments was to determine material properties of a nail joint. The material properties have later been used as material input data in the finite element (FE) model of wood-stud shear wall elements under alternating lateral loading.  FE results have shown that wood-stud shear wall element’s damping capacity is mainly dependent on nail joints properties, number of nail joints, wall dimension and the use of middle studs.</p> / <p>Skjuvväggar av trä används ofta för att ge stabilitet åt horisontalbelastade träshustommar. Därför är kunskaper om skjuvväggars deformationsegenskaper nödvändiga för att kunna förbättra utformningen av trästommar utsatta för jordbävningslaster. Syftet med detta examenarbete är att visa på olika sätt som ökar skjuvväggars absorberande energi eller dämpningskapacitet och som därigenom ger möjligheter att förbättra trästommars motstånd mot jordbävningslaster.</p><p> </p><p>Utgångspunkten har varit laboratorieexperimenten avseende spikförbandens deformationsegenskaper. Syftet med experimenten var att bestämma materialegenskaper för två olika spikförband. Materialsambanden användes därefter som indata i finita element (FE) modeller av skjuvväggselement utsatta för växlande sidobelastning. FE resultaten har visat att skjuvväggars totala dämpningskapacitet beror i huvudsak på spikförbandets materialegenskaper, antal spikförband, väggdimensionen och användningen av mellanreglar.<strong> </strong></p>

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<p><p>Byggbranschen är en olycksdrabbad bransch. År 2007 skedde 3114 olyckor och 16 dödsfall. Många teorier och förklaringar har gjorts i olika publikationer som visar på problemet. En oro finns inom branschen som riktas mot den höga olycksstatistiken. Det kan vara svårt att lokalisera de brister som orsakar olyckor och ibland kanske man blundar för viktiga faktorer. Därmed uppstår svårigheter att uppnå den nollvision man har som mål för arbetsplatserna.</p><p>Denna studies syfte är att lokalisera problem och brister på NCC Construction hus Jönköpings byggarbetsplatser genom intervjuer, enkäter och arbetsplatsbesök. En analys av resultatet kommer att ge förslag till företagets fortsatta arbete att utveckla en säker och trygg arbetsmiljö. Studien fokuserar på hur människans attityder och psykologiska reaktioner leder till brister i säkerheten. Utifrån kontakten med de anställda kan vi sätta oss in i hur personerna påverkas och påverkar situationen på NCC arbetsplatser genom sin attityd och inställning. Olyckorna är i regel påverkade av hur den existerande arbetsmiljön ser ut på arbetsplatsen. En välmående arbetsplats med en stressfaktor som ligger på en acceptabel nivå för alla individer ger grund till en arbetsplats som är säker. Vid en lagom låg stressnivå är alla fokuserade och engagerade i vad som händer. En bra planering och bra ledning kan göra detta möjligt. Stress orsakas inte bara av tidsbrist utan även av en individs personliga välmående på arbetet. Informationen till de anställda är i hög grad betydelsefullt då en delaktighet och uppskattning för det man gör påverkar individer positivt.</p><p>NCC Construction hus i Jönköpings anställda har en bra attityd gentemot säkerheten och tycker att företagets engagemang och driv i sin utveckling av arbetsmiljön är god.</p><p>Slutsatsen av studien är att många olyckor beror på slarv eller okoncentration. Trots bra attityder till säkerheten begås många ”farliga” misstag som kan orsaka olyckor. Ämnet är aktuellt och viktigt att bearbeta. Mycket kan göras och många frågeställningar behöver ges svar på. Denna bransch som har så hög utsatthet och många riskmoment borde fundera på om priset den just nu betalar är värt det.</p></p>

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The problem of unwanted noise in buildings has grown continuously over the last twenty years and impact noise through separating floors has been identified as a particularly important problem. One accepted method for improving impact sound insulation is to use floating floors in which the walking surfaces are isolated from the supporting structure by a resilient layer. Traditionally the resilient layers comprise mineral or glass fibre quilts but other materials such as flooring grade polystyrene are increasingly used. Recently, shallow profile floating floors comprising flexible open cell polyurethane foam resilient layers have been developed. These systems are attractive for refurbishment projects since they can simply be placed on existing floors in order to improve their impact sound insulation whilst raising the existing floor level less than systems comprising fibre quilts. Shallow profile floating floors with thin layers of flexible open cell polyurethane foam are the subject of investigation as part of this research work. This thesis reviews the previous research on polyurethane foams and evaluates the usefulness of the Standard Tests on these materials for assisting in the selection of foam for use as resilient layers under lightweight floors. Both the static and dynamic behaviour of flexible open cell polyurethane foam are investigated and recycled polyurethane foam is shown to be particularly useful for use under floating floors Its characteristic behaviour under compressive strain is described for the first time. This thesis shows that by modifying the Standard Method for the determinaf on of the dynamic stiffness of resilient layers under floating floors (BS EN 29052-1), the effect of the air contained in the open cell foam specimens can be included in the Standard laboratory test. The modification makes it possible to evaluate the dynamic stiffness of low airflow resistivity resilient polyurethane resilient layers using the apparatus described in BS EN 29052-1 for the first time. Field measurements of impact sound pressure level conducted using sections of lightweight shallow profile floating floor on a concrete supporting floor are described. The measured improvements in impact sound insulation achieved by using the sections of floating floor are compared with the improvements predicted using the results from the modified Standard laboratory tests on the foams used as resilient layers. It is shown that by compensating for the mass impedance of the Standard tapping machine hammers good correlation between predicted and measured data is achieved. A simple method for predicting the weighted standardised impact sound pressure level (L'nT,w) in the receiving room is proposed which shows excellent correlation with L'nT,w obtained from the measured data. The work shows that BS EN 29052-1 is more widely applicable than the Standard itself states and for the first time identifies a method of predicting the performance of lightweight shallow profile floating floors with polyurethane foam resilient layers. Finally the use of the ISO tapping machine for assessing the impact sound insulation of the very lightweight floating floors of interest to this research is considered. Different methods of correlating perceived and measured the impact sound insulation of floors are reviewed. Experimental results conducted in this research programme, along with searches of the literature confirm that the tapping machine is a suitable source for measuring the impact sound insulation of these floors.