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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Stabilitly analysis of large structures founded on rock : an introductory study

Johansson, Fredrik January 2005 (has links)
<p>Previous investigations of Swedish and international dams have shown difficultiesto assess the safety against failure in rock foundations. The problem was alsogiven additional interest in connection to the recent construction of the newbridge at Traneberg in Stockholm. This project was created in order to increasethe knowledge in the subject of stability analysis of large structures founded onrock, and how they should be performed in order to describe the safety in areliable way.</p><p>This thesis covers the first half of this project. The objectives of the thesis were todescribe the knowledge and current state of practice in the subject with a literaturestudy, and with a case study of the arch dam at Krokströmmen show the problemsfor stability analyses where foundation and structure interact. The objective wasalso to produce a foundation for future work.</p><p>At Krokströmmen arch dam, previous three dimensional finite element analyseshave been performed (Johansson and Palmgren 1996). In these analyses, thestiffness of the foundation was not considered. Based on the results from theseanalyses, stability was analytically analyzed for each monolith by Stille et al.(2002). The results indicated low factors of safety for the central monoliths. As aconsequence, a reinforcement slab was constructed to increase stability.</p><p>In order to show how varying stiffness and non-linear resistance of the foundationaffects stability, a quasi three dimensional finite element analyses were carriedout. In these analyses, five of the central monoliths were first analyzed separately.Thereafter, the reaction forces were adjusted to fit the results from the analyses byJohansson and Palmgren (1996). The monoliths were thereafter coupled togetherwith assumptions of equal deformations and constant total reaction forces for thefive monoliths. Through an iterative procedure, constant deformation and newredistributed reaction forces were obtained. These forces were used to discuss thestability for one of the monoliths in detail.</p><p>This thesis shows that the problem is more complex than described in the Swedishdam safety guidelines, RIDAS (Svensk Energi 2002), and the Swedish bridgedesign code, BRO 2004 (Vägverket 2004). An accurate analysis of the stability ina rock foundation under large structures demands a more refined approach, whichconsiders the specific features associated with rock mechanical problems. Thecase study showed that the interaction between foundation and structure can beconsiderable; deformations and reaction forces acting on the foundation wereredistributed when the stiffness of the foundation was considered. Furthermore,the resistance is a function of deformation. These aspects are necessaryconsidering if stability should be determined with high confidence.</p><p>An additional question which was identified and brought up for discussion wasthe possibility of time-dependent deformation in the foundation at Krokströmmendue to creep and cyclic loading, which in turn can affect the long term stability.</p>
2

Slipforming of Vertical Concrete Structures. Friction between Concrete and Slipform Panel

Fosså, Kjell Tore January 2001 (has links)
<p>Slipforming is a construction method that has been used in several decades for production of concrete structures. It is a wide range of different structures that are slipformed, but typical are vertical structures such as towers, bridge columns and offshore platforms. Slipforming are not only used for straight vertical concrete structures, but also on structures where the geometry of the structure and the wall thickness is changed. Slipforming is normally a continuous working operation (24 hours a day), which require a well-planned supply of materials. Problems that occur during this process needs to be solved instantly. Slipforming is a rather complicated operation compared to other construction techniques. The requirements to the materials, personnel and the execution of the work are therefore accordingly higher.</p><p>Slipforming of concrete structures has in most cases been carried out successfully with no or only minor supplementary work. However, in some cases, surface damages have occurred during slipforming. Typical surface damages are lifting cracks and vertical lined damages caused by lumps formed on the slipform panel. These problems have during recent years caused discussion and partly also scepticism to slipforming as a reliable construction technique. The Norwegian Public Roads Administration has recommended in Publication 77 that some concrete structures should not be slipformed depending on the environmental impact at the location, geometric degree of difficulties of the concrete structure and the type of concrete. Also in other countries there are scepticism to slipforming as a construction technique.</p><p>The prime objective of the research program is to improve the understanding of the slipform technique as a construction method in order to ensure high quality concrete structures. The objective is to identify the parameters affecting the net lifting stress (friction) that occur during lifting of the slipform panel. Focus is given to the importance of the concrete properties that will influence the forces that occur between the slipform panel and the concrete. Also any connection between the friction level and the surface damages is investigated. Based on the result it should be possible to define requirements for materials, mix composition and method of execution to ensure that the specified quality in the structure is obtained.</p><p>The lifting stress can be divided in static lifting stress and sliding lifting stress, where the static lifting stress represents the friction that has to be overcome in order to start sliding and the sliding lifting stress is the minimum friction that occurs during sliding. The difference between the static and sliding lifting stress is caused by the decreasing effective pressure during lifting at the sliding zone and the adhesion that occurs because of no movement of the slipform panel between two lifts. Both static and sliding lifting stress are closely related, but the static lifting stress can be extremely large compared to the sliding lifting stress.</p><p>The friction law can be used to describe the correlation between the net lifting stress and the effective pressure. This correlation is almost linear and applicable for both the net static and sliding lifting stress. The effective pressure, which represents the pressure between the solid particles and the slipform panel, is the difference between the normal pressure (concrete pressure against the slipform panel) and the pore water pressure. It is primarily the pressure in the pore water that is responsible for most of the variation in the effective pressure during the plastic phase and the transition period, which means that it is mainly the variation in the pore water pressure that controls the level of the lifting stress. The pore water pressure is decreasing slightly in early phase because of the settlement in the concrete. During the elastic phase, the pore water pressure start to decrease faster as an effect of the chemical shrinkage that occurs because of the cement reaction.</p><p>The pore water pressure development can be characterised by the decrease rate of the pore water pressure and the minimum pore water pressure. The minimum pore water pressure is defined as the pore water pressure at the time of maximum lifting stress. The minimum pore water pressure occurs just before the pressure is increasing at the sliding zone close to the slipform panel. It is primarily the level of the minimum pore water pressure that will decide the maximum level of the static and sliding lifting stress. The pore water pressure decrease rate and the minimum pore water pressure depends on the particle concentration and particle size distribution for the finer particles and also the air content in the concrete. Higher particle concentration and finer particle size distribution will both result in a faster pore water pressure decrease rate and a lower minimum pore water pressure. A higher air content will reduce the effect from the chemical shrinkage because the existing air volume will act as a pressure release volume, resulting in a lower pore water pressure decrease rate and a higher minimum pore water pressure.</p><p>Also the compaction method will have an impact on the decrease rate of the pore water pressure and the minimum pore water pressure, because the air content will be reduced with prolonged vibration time. Prolonged vibration will in general result in a higher lifting stress, depending on the response on the concrete during vibration. When lightweight aggregate is used in the concrete, the entrapped air in the lightweight aggregate will increase the pore water pressure and result in a lower lifting stress. Porous lightweight aggregate will have larger impact on the pore water pressure than denser lightweight aggregate.</p><p>Pressure gradients that occur between two concrete layers will affect the decrease rate of the pore water pressure. Water will “flow” from layers with younger concrete without any negative pressure to concrete layers with lower pore water pressure. This will reduce the decrease rate in the concrete layer that receives the water. In later stage the same concrete that supplied the concrete layer below with water will receive water from the concrete layer above. The pressure gradient at the joint (between two concrete layers) will be more even as a result of the water communications between the concrete layers. Evaporation of water from a fresh concrete surface will result in a faster decrease rate and a lower minimum pore water pressure because of the drying process will form menisci near the surface. The water communication is in general good in the concrete in this phase.</p><p>The time at which the minimum pore water pressure occurs will also have an impact on the minimum pressure level. A shorter period of time from the minimum pore water pressure occur to the time of initial set will result in a relatively higher minimum pore water pressure and a lower lifting stress. The minimum pore water pressure has occurred earlier when water has evaporated from an exposed concrete surface. Also when very rough slipform panel is used, the incipient vacuum between the slipform panel and the concrete is punctured early (collapse of the capillary system at the sliding zone) because of the rough panel surface and will result in a relative low lifting stress.</p><p>Both the lifting frequency and the lifting height has a considerable effect on the static lifting stress. Lower lifting height or decreased lifting frequency will both result in a lower pore water pressure and a higher static lifting stress. This is probably because the interface zone is disturbed each time the slipform panel is lifted. Less disturbance of the interface will result in a lower minimum pore water pressure. The lifting stress is decreasing during lifting as an effect of the decreasing effective pressure at the sliding zone and the reduced adhesion. The effective pressure at the sliding zone is probably at minimum and the adhesion is completely broken when the lifting stress is stabilized on a minimum level. The sliding lifting stress is also affected of the lifting frequency and the lifting height if not the minimum level is reached during the lift.</p><p>Surface damages caused by high lifting stress are not demonstrated in the vertical slipform rig. However, similar concrete mix design that has been used in a field project, where surface damages occurred, has been tested in the vertical slipform rig. The concrete mix in this field project was replaced with a new concrete mix, where no or only minor surface damages occurred after the replacement. Both concrete mixes is tested in the vertical slipform rig and the result show a considerable higher static and sliding lifting stress for the concrete mix that was used when surface damages occurred. This indicates that there are a connection between high lifting stress and risk for surface damages. This means also that concrete mixes that obtains high lifting stress in the vertical slipform rig is more exposed to surface damages than concrete mixes that has obtained lower lifting stress.</p>
3

Improvement Fatigue Performance of Threaded Drillstring Connections by Cold Rolling

Kristoffersen, Steinar January 2002 (has links)
<p>The research work presented in this thesis is concerned with analytical, numerical and experimental studies of the effect of cold rolling on the fatigue behaviour of threaded drillstring connections.</p><p>A comprehensive literature study is made of the various effects on the fatigue behaviour of residual stresses introduced by mechanical deformation of notched components. Some of the effects studied are cyclic hardening behaviour after prestraining, cyclic creep, fatigue initiation in prestrained materials, short cracks and crack growth models including crack closure. </p><p>Residual stresses were introduced in the surface of a smooth pipe by a rolling device to simulate a cold rolling process and verify the calculated residual stresses by measurements. Strain hardening and contact algorithm of the two bodies were incorporated in the FE analyses. Two significant errors were found in the commercial software package for residual stress evaluation, Restan v. 3.3.2a also called SINT, when using the Schajer method. The Schajer algorithm is the only hole-drilling algorithm without theoretical shortcomings, and is recommended when measuring large residual stress gradients in the depth directions. Using the Schajer method solved by in-house Matlab-routines good agreement between measured residual stress gradients and residual stress gradients from FE analyses was found.</p><p>Full scale fatigue tests were performed on pipes cut used drillstrings with notches of similar geometry as threads used in drillstring connections. The simulated threads consisted of four full depth helix notches with runouts at the surface. The pipe threads were cold rolled and fatigue tested in a full-scale four-point rotating bending fatigue testing rig. The test results showed that cold rolling had an effect on the crack initiating period. A major part of the fatigue life was with cracks observed at the notch root, but due to the increased fatigue crack propagation resistance the final fracture initiated at pits inside the pipe. Therefor, an optimisation of the roll geometry and rolling parameters was not possible. However, a significant fatigue life improvement was achieved. Based on experiments, a roller with similar profile as the thread root is recommended. A rolling force of maximum 20 KN is recommended to minimise the possibility of damaging the thread profile. Shallow cracks were observed typically when 5% of the fatigue life had expired. Re-rolling after 50% of expected improved fatigue life, when also short cracks were observed in the notch roots further increased the fatigue improvements. </p><p>Pretensioned small steel specimens with a notch were used to simulate cold rolled threats. The specimens were fatigue tested in tension with minimum load close to zero. Pretensioning increased the fatigue life form approximately 50 000 cycles to an infinite number of cycles. In these test non-propagating cracks of typically 0.4 mm length were found. The benefit from pretensioning gradually disappeared with increasing mean stress. FE analyses indicated that an almost instant relaxation of residual stresses to a level with no monotonic strain hardening from preloading would take place when cycled to moderate mean stress. Cycled at low mean stress, an instant relaxation of the surface layer was found in analysis. All observations from notched pretensioned fatigue specimens were in good agreement with the available literature. However, preloading was found to be strain rate dependent in tests where a pretension load held for 2 minutes gave a longer fatigue life than a sinusoidal loading-unloading cycle performed over a one minute interval.</p><p>Strain hardening was found not contributing to the fatigue life improvement, whereas the polishing effect from improved surface quality after cold rolling increased the fatigue initiation period. However, residual stress and subsequent early crack closure was the dominating effect at moderate cyclic mean loads. </p><p>The material data required to perform FE fatigue simulation studies of a full threaded cold rolled coupling incorporating make-up torque, include cyclic stress strain behaviour at various amplitudes and mean stress caused by various degrees of prestraining. Such data are not readily available today, and are only possible to obtain in carefully planned and executed experiments. Also, 3D FE model required for cold rolling analysis is extremely CPU time consuming. Consequently, cold rolling simulations could not be successfully implemented in this work.</p><p>One of the main conclusions from this work is that drillstring connections will respond differently to thread rolling at the pin or box. A significant improvement in the fatigue life of box threads from residual stresses is expected mainly from increased resistance to crack propagation. However, the compressive residual stress is sensitive to overloading in compression, and the improvement from residual stress depends strongly on the mean stress (or R-ratio). At values of R of approximately 0.6 or higher the beneficial of rolling therefore tends to disappear. At the critical locations of the pin, which are the last engaged thread or the stress relief groove, the effect of residual stresses introduced by rolling is therefore likely to be severely reduced by the high mean stress imposed during make-up of the connection. However, a beneficial effect of rolling is expected to remain due to improved surface condition and due to a possible effect of strain hardening. The net results of these factors on the fatigue performance of actual drillstrings can only be determined in full scale rotating bending tests. </p>
4

Bil- och järnvägstrafikens inverkan på inomhusmiljön med avseende på ljud och luft : - I planerade bostäder på Haga / Car- and railway traffics influence on indoor environment directed towards noise and air : In planned buildings in Haga

Jansson, Lillemor, Modin, Victoria January 2006 (has links)
<p>NCC has given us a commission to investigate a planned housing area in Haga, Karlstad, situated close to the traffic route Hagaleden and the railway. The housing area consists of one hundred apartments in five different houses. The houses are linked to each other by balconies with glass panels. A long carport is situated between Hagaleden and the housing area to absorb part of the noise from the road. The design of the housing area is creating a silent backyard. The idea of building houses in this place is to create an attractive living in central town and close to the river.</p><p>The air and sound level inside of the planned houses were studied. The major problem is that the noise from the railway traffic and the car traffic are of different kind. The railway traffic creates high maximum sound levels and the car traffic creates high equivalent sound levels. The different kinds of sound levels consist of high and low frequency which means that different measures have to be taken to reduce both types. The emission from the car traffic is the major problem for the air quality, but it is uncertain how much of the emissions that passes to the inside of the houses.</p><p>The result shows that the noise is the main problem. Despite the suggested noise reduction measures, the noise exceeds the limits of the building regulations on the facade of the houses. If the houses are to be built, they will not fulfill the regulations on this point. The noise is the major problem but there are many other factors that influence the air and the sound in the buildings. This essay describes different factors and every part of it ends with a checklist that can be used to create a good indoor environment. It is important for the quality of the air in the apartments that the ventilation system is correctly dimensioned for the building and is well dimensioned. It is recommended that the ventilation system should be complemented with an air treatment unit.</p><p>The purpose of this checklist is to find an easy way to ensure that the demands and regulations of the norms are fulfilled. The items are all listed in an appendix in the work, but they need to be developed to be used easily.</p><p>In the conclusion a suggestion on measures that could make the environment in the apartments better is presented. For example, the design of the balconies has been changed to prevent the noise from getting into the backyard. Suggestions on measures on the outside of the buildings are also presented; an example of this is silent asphalt, an extended carport and noise barriers.</p> / <p>Vi har fått i uppdrag av NCC att studera ett planerat bostadsområde beläget på Haga, Karlstad nära Hagaleden och järnvägen. Bostadsområdet är tänkt att bestå av fem stycken sammankopplade huskroppar innehållande cirka hundra lägenheter. Husen är ihoplänkade med hjälp av inglasade balkonger. Mellan Hagaleden och bostadsområdet är en lång carport placerad för att ta upp en del av bullret. Utformningen av bostadsområdet skapar tysta innergårdar som vetter mot Klarälven. Tanken med att bygga bostäder på denna plats är att skapa ett attraktivt boende som är beläget centralt och vattennära.</p><p>Med hjälp av litteraturstudie studeras hur innemiljön i de planerade bostäderna påverkas av Hagaleden och järnvägen med avseende på luft och ljud. Det största problemet med ljudet är att järnvägstrafiken och biltrafiken skapar olika typer av buller. Järnvägstrafiken skapar höga maximala ljudnivåer medan biltrafiken skapar höga ekvivalenta ljudnivåer. Det innebär att både höga och låga ljudfrekvenser skapas vilket medför att olika bullerdämpande åtgärder krävs för att uppnå en behaglig boendemiljö. När det gäller luften är det biltrafikens avgaser som skapar de största problemen, men det är svårt att veta vilka förorenade partiklar som slutligen tar sig in i lägenheterna.</p><p>Resultatet visar att det är bullret som är det största problemet för trots de åtgärder som tagits fram uppfylls ändå inte bullerkravet vid fasaden. Detta innebär att avsteg från normerna måste göras för att en byggstart ska bli aktuell. Bullret är det största problemet men det finns många andra faktorer som påverkar luften och ljudet i bostäderna. De olika faktorerna är beskrivna i arbetet och varje del avslutas med ”Kontrollera att” -punkter för att ingen viktig ingående del ska glömmas bort. När det gäller luften i lägenheterna är det viktigt att ventilationssystemet är väl fungerande och rätt dimensionerat för byggnaden. Det är lämpligt att ventilationssystemet i detta fall kompletteras med ett luftbehandlingsaggregat.</p><p>Tanken med att skapa dessa punkter är att det på ett enkelt sätt ska gå att kontrollera att de olika krav och normer som finns för respektive del är uppfyllda. Det finns en sammanställning, bifogad som bilaga i arbetet, över alla punkter som tagits fram men dessa behöver utvecklas för att smidigt kunna användas.</p><p>I slutsatser har förslag på åtgärder som skulle kunna förbättra inomhusmiljön arbetats fram. Bland annat föreslås ändrad utformning på de inglasade balkongerna som länkar samman husen för att minska den andel buller som kan ta sig in till innergårdarna. Även förslag på yttre åtgärder som sänker ljudnivåerna har presenterats, exempel på detta är tyst asfalt, ändrad utformning på carporten samt bullerplank.</p>
5

Slipforming of Vertical Concrete Structures. Friction between Concrete and Slipform Panel

Fosså, Kjell Tore January 2001 (has links)
Slipforming is a construction method that has been used in several decades for production of concrete structures. It is a wide range of different structures that are slipformed, but typical are vertical structures such as towers, bridge columns and offshore platforms. Slipforming are not only used for straight vertical concrete structures, but also on structures where the geometry of the structure and the wall thickness is changed. Slipforming is normally a continuous working operation (24 hours a day), which require a well-planned supply of materials. Problems that occur during this process needs to be solved instantly. Slipforming is a rather complicated operation compared to other construction techniques. The requirements to the materials, personnel and the execution of the work are therefore accordingly higher. Slipforming of concrete structures has in most cases been carried out successfully with no or only minor supplementary work. However, in some cases, surface damages have occurred during slipforming. Typical surface damages are lifting cracks and vertical lined damages caused by lumps formed on the slipform panel. These problems have during recent years caused discussion and partly also scepticism to slipforming as a reliable construction technique. The Norwegian Public Roads Administration has recommended in Publication 77 that some concrete structures should not be slipformed depending on the environmental impact at the location, geometric degree of difficulties of the concrete structure and the type of concrete. Also in other countries there are scepticism to slipforming as a construction technique. The prime objective of the research program is to improve the understanding of the slipform technique as a construction method in order to ensure high quality concrete structures. The objective is to identify the parameters affecting the net lifting stress (friction) that occur during lifting of the slipform panel. Focus is given to the importance of the concrete properties that will influence the forces that occur between the slipform panel and the concrete. Also any connection between the friction level and the surface damages is investigated. Based on the result it should be possible to define requirements for materials, mix composition and method of execution to ensure that the specified quality in the structure is obtained. The lifting stress can be divided in static lifting stress and sliding lifting stress, where the static lifting stress represents the friction that has to be overcome in order to start sliding and the sliding lifting stress is the minimum friction that occurs during sliding. The difference between the static and sliding lifting stress is caused by the decreasing effective pressure during lifting at the sliding zone and the adhesion that occurs because of no movement of the slipform panel between two lifts. Both static and sliding lifting stress are closely related, but the static lifting stress can be extremely large compared to the sliding lifting stress. The friction law can be used to describe the correlation between the net lifting stress and the effective pressure. This correlation is almost linear and applicable for both the net static and sliding lifting stress. The effective pressure, which represents the pressure between the solid particles and the slipform panel, is the difference between the normal pressure (concrete pressure against the slipform panel) and the pore water pressure. It is primarily the pressure in the pore water that is responsible for most of the variation in the effective pressure during the plastic phase and the transition period, which means that it is mainly the variation in the pore water pressure that controls the level of the lifting stress. The pore water pressure is decreasing slightly in early phase because of the settlement in the concrete. During the elastic phase, the pore water pressure start to decrease faster as an effect of the chemical shrinkage that occurs because of the cement reaction. The pore water pressure development can be characterised by the decrease rate of the pore water pressure and the minimum pore water pressure. The minimum pore water pressure is defined as the pore water pressure at the time of maximum lifting stress. The minimum pore water pressure occurs just before the pressure is increasing at the sliding zone close to the slipform panel. It is primarily the level of the minimum pore water pressure that will decide the maximum level of the static and sliding lifting stress. The pore water pressure decrease rate and the minimum pore water pressure depends on the particle concentration and particle size distribution for the finer particles and also the air content in the concrete. Higher particle concentration and finer particle size distribution will both result in a faster pore water pressure decrease rate and a lower minimum pore water pressure. A higher air content will reduce the effect from the chemical shrinkage because the existing air volume will act as a pressure release volume, resulting in a lower pore water pressure decrease rate and a higher minimum pore water pressure. Also the compaction method will have an impact on the decrease rate of the pore water pressure and the minimum pore water pressure, because the air content will be reduced with prolonged vibration time. Prolonged vibration will in general result in a higher lifting stress, depending on the response on the concrete during vibration. When lightweight aggregate is used in the concrete, the entrapped air in the lightweight aggregate will increase the pore water pressure and result in a lower lifting stress. Porous lightweight aggregate will have larger impact on the pore water pressure than denser lightweight aggregate. Pressure gradients that occur between two concrete layers will affect the decrease rate of the pore water pressure. Water will “flow” from layers with younger concrete without any negative pressure to concrete layers with lower pore water pressure. This will reduce the decrease rate in the concrete layer that receives the water. In later stage the same concrete that supplied the concrete layer below with water will receive water from the concrete layer above. The pressure gradient at the joint (between two concrete layers) will be more even as a result of the water communications between the concrete layers. Evaporation of water from a fresh concrete surface will result in a faster decrease rate and a lower minimum pore water pressure because of the drying process will form menisci near the surface. The water communication is in general good in the concrete in this phase. The time at which the minimum pore water pressure occurs will also have an impact on the minimum pressure level. A shorter period of time from the minimum pore water pressure occur to the time of initial set will result in a relatively higher minimum pore water pressure and a lower lifting stress. The minimum pore water pressure has occurred earlier when water has evaporated from an exposed concrete surface. Also when very rough slipform panel is used, the incipient vacuum between the slipform panel and the concrete is punctured early (collapse of the capillary system at the sliding zone) because of the rough panel surface and will result in a relative low lifting stress. Both the lifting frequency and the lifting height has a considerable effect on the static lifting stress. Lower lifting height or decreased lifting frequency will both result in a lower pore water pressure and a higher static lifting stress. This is probably because the interface zone is disturbed each time the slipform panel is lifted. Less disturbance of the interface will result in a lower minimum pore water pressure. The lifting stress is decreasing during lifting as an effect of the decreasing effective pressure at the sliding zone and the reduced adhesion. The effective pressure at the sliding zone is probably at minimum and the adhesion is completely broken when the lifting stress is stabilized on a minimum level. The sliding lifting stress is also affected of the lifting frequency and the lifting height if not the minimum level is reached during the lift. Surface damages caused by high lifting stress are not demonstrated in the vertical slipform rig. However, similar concrete mix design that has been used in a field project, where surface damages occurred, has been tested in the vertical slipform rig. The concrete mix in this field project was replaced with a new concrete mix, where no or only minor surface damages occurred after the replacement. Both concrete mixes is tested in the vertical slipform rig and the result show a considerable higher static and sliding lifting stress for the concrete mix that was used when surface damages occurred. This indicates that there are a connection between high lifting stress and risk for surface damages. This means also that concrete mixes that obtains high lifting stress in the vertical slipform rig is more exposed to surface damages than concrete mixes that has obtained lower lifting stress.
6

Improvement Fatigue Performance of Threaded Drillstring Connections by Cold Rolling

Kristoffersen, Steinar January 2002 (has links)
The research work presented in this thesis is concerned with analytical, numerical and experimental studies of the effect of cold rolling on the fatigue behaviour of threaded drillstring connections. A comprehensive literature study is made of the various effects on the fatigue behaviour of residual stresses introduced by mechanical deformation of notched components. Some of the effects studied are cyclic hardening behaviour after prestraining, cyclic creep, fatigue initiation in prestrained materials, short cracks and crack growth models including crack closure. Residual stresses were introduced in the surface of a smooth pipe by a rolling device to simulate a cold rolling process and verify the calculated residual stresses by measurements. Strain hardening and contact algorithm of the two bodies were incorporated in the FE analyses. Two significant errors were found in the commercial software package for residual stress evaluation, Restan v. 3.3.2a also called SINT, when using the Schajer method. The Schajer algorithm is the only hole-drilling algorithm without theoretical shortcomings, and is recommended when measuring large residual stress gradients in the depth directions. Using the Schajer method solved by in-house Matlab-routines good agreement between measured residual stress gradients and residual stress gradients from FE analyses was found. Full scale fatigue tests were performed on pipes cut used drillstrings with notches of similar geometry as threads used in drillstring connections. The simulated threads consisted of four full depth helix notches with runouts at the surface. The pipe threads were cold rolled and fatigue tested in a full-scale four-point rotating bending fatigue testing rig. The test results showed that cold rolling had an effect on the crack initiating period. A major part of the fatigue life was with cracks observed at the notch root, but due to the increased fatigue crack propagation resistance the final fracture initiated at pits inside the pipe. Therefor, an optimisation of the roll geometry and rolling parameters was not possible. However, a significant fatigue life improvement was achieved. Based on experiments, a roller with similar profile as the thread root is recommended. A rolling force of maximum 20 KN is recommended to minimise the possibility of damaging the thread profile. Shallow cracks were observed typically when 5% of the fatigue life had expired. Re-rolling after 50% of expected improved fatigue life, when also short cracks were observed in the notch roots further increased the fatigue improvements. Pretensioned small steel specimens with a notch were used to simulate cold rolled threats. The specimens were fatigue tested in tension with minimum load close to zero. Pretensioning increased the fatigue life form approximately 50 000 cycles to an infinite number of cycles. In these test non-propagating cracks of typically 0.4 mm length were found. The benefit from pretensioning gradually disappeared with increasing mean stress. FE analyses indicated that an almost instant relaxation of residual stresses to a level with no monotonic strain hardening from preloading would take place when cycled to moderate mean stress. Cycled at low mean stress, an instant relaxation of the surface layer was found in analysis. All observations from notched pretensioned fatigue specimens were in good agreement with the available literature. However, preloading was found to be strain rate dependent in tests where a pretension load held for 2 minutes gave a longer fatigue life than a sinusoidal loading-unloading cycle performed over a one minute interval. Strain hardening was found not contributing to the fatigue life improvement, whereas the polishing effect from improved surface quality after cold rolling increased the fatigue initiation period. However, residual stress and subsequent early crack closure was the dominating effect at moderate cyclic mean loads. The material data required to perform FE fatigue simulation studies of a full threaded cold rolled coupling incorporating make-up torque, include cyclic stress strain behaviour at various amplitudes and mean stress caused by various degrees of prestraining. Such data are not readily available today, and are only possible to obtain in carefully planned and executed experiments. Also, 3D FE model required for cold rolling analysis is extremely CPU time consuming. Consequently, cold rolling simulations could not be successfully implemented in this work. One of the main conclusions from this work is that drillstring connections will respond differently to thread rolling at the pin or box. A significant improvement in the fatigue life of box threads from residual stresses is expected mainly from increased resistance to crack propagation. However, the compressive residual stress is sensitive to overloading in compression, and the improvement from residual stress depends strongly on the mean stress (or R-ratio). At values of R of approximately 0.6 or higher the beneficial of rolling therefore tends to disappear. At the critical locations of the pin, which are the last engaged thread or the stress relief groove, the effect of residual stresses introduced by rolling is therefore likely to be severely reduced by the high mean stress imposed during make-up of the connection. However, a beneficial effect of rolling is expected to remain due to improved surface condition and due to a possible effect of strain hardening. The net results of these factors on the fatigue performance of actual drillstrings can only be determined in full scale rotating bending tests.
7

Bil- och järnvägstrafikens inverkan på inomhusmiljön med avseende på ljud och luft : - I planerade bostäder på Haga / Car- and railway traffics influence on indoor environment directed towards noise and air : In planned buildings in Haga

Jansson, Lillemor, Modin, Victoria January 2006 (has links)
NCC has given us a commission to investigate a planned housing area in Haga, Karlstad, situated close to the traffic route Hagaleden and the railway. The housing area consists of one hundred apartments in five different houses. The houses are linked to each other by balconies with glass panels. A long carport is situated between Hagaleden and the housing area to absorb part of the noise from the road. The design of the housing area is creating a silent backyard. The idea of building houses in this place is to create an attractive living in central town and close to the river. The air and sound level inside of the planned houses were studied. The major problem is that the noise from the railway traffic and the car traffic are of different kind. The railway traffic creates high maximum sound levels and the car traffic creates high equivalent sound levels. The different kinds of sound levels consist of high and low frequency which means that different measures have to be taken to reduce both types. The emission from the car traffic is the major problem for the air quality, but it is uncertain how much of the emissions that passes to the inside of the houses. The result shows that the noise is the main problem. Despite the suggested noise reduction measures, the noise exceeds the limits of the building regulations on the facade of the houses. If the houses are to be built, they will not fulfill the regulations on this point. The noise is the major problem but there are many other factors that influence the air and the sound in the buildings. This essay describes different factors and every part of it ends with a checklist that can be used to create a good indoor environment. It is important for the quality of the air in the apartments that the ventilation system is correctly dimensioned for the building and is well dimensioned. It is recommended that the ventilation system should be complemented with an air treatment unit. The purpose of this checklist is to find an easy way to ensure that the demands and regulations of the norms are fulfilled. The items are all listed in an appendix in the work, but they need to be developed to be used easily. In the conclusion a suggestion on measures that could make the environment in the apartments better is presented. For example, the design of the balconies has been changed to prevent the noise from getting into the backyard. Suggestions on measures on the outside of the buildings are also presented; an example of this is silent asphalt, an extended carport and noise barriers. / Vi har fått i uppdrag av NCC att studera ett planerat bostadsområde beläget på Haga, Karlstad nära Hagaleden och järnvägen. Bostadsområdet är tänkt att bestå av fem stycken sammankopplade huskroppar innehållande cirka hundra lägenheter. Husen är ihoplänkade med hjälp av inglasade balkonger. Mellan Hagaleden och bostadsområdet är en lång carport placerad för att ta upp en del av bullret. Utformningen av bostadsområdet skapar tysta innergårdar som vetter mot Klarälven. Tanken med att bygga bostäder på denna plats är att skapa ett attraktivt boende som är beläget centralt och vattennära. Med hjälp av litteraturstudie studeras hur innemiljön i de planerade bostäderna påverkas av Hagaleden och järnvägen med avseende på luft och ljud. Det största problemet med ljudet är att järnvägstrafiken och biltrafiken skapar olika typer av buller. Järnvägstrafiken skapar höga maximala ljudnivåer medan biltrafiken skapar höga ekvivalenta ljudnivåer. Det innebär att både höga och låga ljudfrekvenser skapas vilket medför att olika bullerdämpande åtgärder krävs för att uppnå en behaglig boendemiljö. När det gäller luften är det biltrafikens avgaser som skapar de största problemen, men det är svårt att veta vilka förorenade partiklar som slutligen tar sig in i lägenheterna. Resultatet visar att det är bullret som är det största problemet för trots de åtgärder som tagits fram uppfylls ändå inte bullerkravet vid fasaden. Detta innebär att avsteg från normerna måste göras för att en byggstart ska bli aktuell. Bullret är det största problemet men det finns många andra faktorer som påverkar luften och ljudet i bostäderna. De olika faktorerna är beskrivna i arbetet och varje del avslutas med ”Kontrollera att” -punkter för att ingen viktig ingående del ska glömmas bort. När det gäller luften i lägenheterna är det viktigt att ventilationssystemet är väl fungerande och rätt dimensionerat för byggnaden. Det är lämpligt att ventilationssystemet i detta fall kompletteras med ett luftbehandlingsaggregat. Tanken med att skapa dessa punkter är att det på ett enkelt sätt ska gå att kontrollera att de olika krav och normer som finns för respektive del är uppfyllda. Det finns en sammanställning, bifogad som bilaga i arbetet, över alla punkter som tagits fram men dessa behöver utvecklas för att smidigt kunna användas. I slutsatser har förslag på åtgärder som skulle kunna förbättra inomhusmiljön arbetats fram. Bland annat föreslås ändrad utformning på de inglasade balkongerna som länkar samman husen för att minska den andel buller som kan ta sig in till innergårdarna. Även förslag på yttre åtgärder som sänker ljudnivåerna har presenterats, exempel på detta är tyst asfalt, ändrad utformning på carporten samt bullerplank.
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Miljöklassning av byggnader : <em>kontorshuset Novartis</em>

Westling, Rickard, Ericson, Mattias January 2009 (has links)
<p>För att skapa en utveckling mot en hållbar bygg- och fastighetssektor i Sverigeinleddes ett samarbete mellan företag, kommuner och regeringen som kallas förBygga-bo-dialogen. Ett av dennas mål är att alla nybyggda hus och 30 procent avbefintliga byggnader ska klassificeras senast år 2009.</p><p>Arbetet inleddes med möten, mellan handledare och examensarbetarna, angåendearbetets fortlöpande och ett besök hos AP fastigheter fastställdes, som ägerbyggnaden Novartis. Mötet blev en presentation från AP Fastigheters sida och en genomgång om vadvi skall göra, enkätundersökningen beslutades att de först önskade föra en dialogmed Novartis om den. Här beslutades om ett nytt besök vid själva byggnadenNovartis som skulle klassas. Vid nästa besök utfördes av examensarbetarna mätningar på ventilationsflödet vidbyggnadens tilluftsfläkt och en del stickprov på frånluftsdonen ikontorslandskapet med en luftflödesmätare. De utförde även mätningar avvattentemperaturen vid handfatet på tre våningar, samt bedömde ljudmiljön enligtmiljöklassningssystemets instruktioner. Därefter utfördes klassningen av byggnaden Novartis baserat på insamladeuppgifter. Resultatet innefattar en redovisning av utförda beräkningar ochresultatet av enkätundersökningen i EcoEffect.</p><p>Miljöklassningen kan användas vid projekteringen av byggnader för att få en brabalans mellan dess funktioner, men EcoEffect har en fördel då den viktar hurallvarliga olika problem är i byggnaden. Novartis har goda kvaliteter för inne- och utemiljö men den har problem med atthålla god kvalité för det termiska klimatet. Ventilationssystemet fungerar väldigt bra då den håller låg energiförbrukningtrotts hög solvärmelast, som kräver kylning, och då byggnaden inte har specielltlåga transmissionsförluster. Ventilationssystemet borde kunna användas för atthålla låg energiförbrukning i andra kontorshus.</p>
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Miljöklassning av byggnader : kontorshuset Novartis

Westling, Rickard, Ericson, Mattias January 2009 (has links)
För att skapa en utveckling mot en hållbar bygg- och fastighetssektor i Sverigeinleddes ett samarbete mellan företag, kommuner och regeringen som kallas förBygga-bo-dialogen. Ett av dennas mål är att alla nybyggda hus och 30 procent avbefintliga byggnader ska klassificeras senast år 2009. Arbetet inleddes med möten, mellan handledare och examensarbetarna, angåendearbetets fortlöpande och ett besök hos AP fastigheter fastställdes, som ägerbyggnaden Novartis. Mötet blev en presentation från AP Fastigheters sida och en genomgång om vadvi skall göra, enkätundersökningen beslutades att de först önskade föra en dialogmed Novartis om den. Här beslutades om ett nytt besök vid själva byggnadenNovartis som skulle klassas. Vid nästa besök utfördes av examensarbetarna mätningar på ventilationsflödet vidbyggnadens tilluftsfläkt och en del stickprov på frånluftsdonen ikontorslandskapet med en luftflödesmätare. De utförde även mätningar avvattentemperaturen vid handfatet på tre våningar, samt bedömde ljudmiljön enligtmiljöklassningssystemets instruktioner. Därefter utfördes klassningen av byggnaden Novartis baserat på insamladeuppgifter. Resultatet innefattar en redovisning av utförda beräkningar ochresultatet av enkätundersökningen i EcoEffect. Miljöklassningen kan användas vid projekteringen av byggnader för att få en brabalans mellan dess funktioner, men EcoEffect har en fördel då den viktar hurallvarliga olika problem är i byggnaden. Novartis har goda kvaliteter för inne- och utemiljö men den har problem med atthålla god kvalité för det termiska klimatet. Ventilationssystemet fungerar väldigt bra då den håller låg energiförbrukningtrotts hög solvärmelast, som kräver kylning, och då byggnaden inte har specielltlåga transmissionsförluster. Ventilationssystemet borde kunna användas för atthålla låg energiförbrukning i andra kontorshus.
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En jämförelse mellan mineralull och cellulosafiber : Hur valet påverkar energianvändning, miljö, arbetsmiljö, kostnad och tidsanvändning

Pettersson, Frida January 2010 (has links)
No description available.

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