Variations in dynamic properties of a steel arch footbridge : An experimental study

This study separately investigates how temperature as well as two real load-situations affects the modal damping ratio and natural frequencies of a 64.9m span steel arch footbridge. Measurements of acceleration have been completed which covers a temperature span of  to . The natural frequencies of the five investigated modes were observed to decrease 2-6% as the temperature increased. This effect was with the help of beam-theory and finite element modelling deduced to originate mostly from changes in Young’s modulus of the materials, but also geometrical changes in steel because of thermal expansion. Further investigation included a static mass in the form of packed snow that was estimated to weigh 14 tons. The natural frequencies were observed to remain unchanged while the modal damping ratios decreased. The second load-case was an uncontrolled mass-event where a large group of pedestrians travelled over the bridge as two cars stood stationary at the quarter-point of the span. A large increase (146%) of the damping ratio was observed while the natural frequency of the first mode decreased 4%. This change was suggested come from the human structure interaction (HSI) partially because the natural frequency of the human body is close to the first vertical frequency of the bridge thus making humans act like dampers on the bridge when close to resonance, and that the number of pedestrians contribute to the modal mass of the system, thus decreasing the natural frequency.Denna studie undersöker separat hur temperaturen såväl som två verkliga belastningssituationer påverkar de modala dämpnings kvoterna och egenfrekvenserna hos en 64,9 meter lång stål-bågs gångbro. Mätningar av accelerationen i bron har genomförts som täcker en temperatur på -10°C till 10°C. De naturliga frekvenserna hos de fem undersökta moderna observerades minska 2–6% när temperaturen ökade. Denna minskning var med hjälp av balk-teori och finita element-modellering härled att troligen komma från förändringar i Youngs modul av materialen, men även geometriska förändringar i stålet på grund av termisk expansion. Vidare undersökning innefattade en statisk massa i form av packad snö som uppskattades att väga 14 ton. Egenfrekvenserna observerades förbli oförändrade medan de modala dämpnings kvoterna minskade. Det andra lastfallet var ett okontrollerat massevenemang där en stor grupp fotgängare gick över bron medan två bilar var stationära en fjärdedel in på brons längd. En stor ökning (146%) av dämpnings kvoten för den första vertikala moden observerades medan egenfrekvensen minskade 4%. Denna förändring föreslogs komma från interaktionen mellan människan och bron, delvis för att människokroppens egenfrekvens ligger nära brons första vertikala frekvens vilket gör att människan agerar som en dämpare när de är nära resonans med bron, och att antalet fotgängare bidrar till den modala massan av systemet vilket sänker frekvensen

Variations in dynamic properties of a steel arch footbridge : An experimental study

This study separately investigates how temperature as well as two real load-situations affects the modal damping ratio and natural frequencies of a 64.9m span steel arch footbridge. Measurements of acceleration have been completed which covers a temperature span of  to . The natural frequencies of the five investigated modes were observed to decrease 2-6% as the temperature increased. This effect was with the help of beam-theory and finite element modelling deduced to originate mostly from changes in Young’s modulus of the materials, but also geometrical changes in steel because of thermal expansion. Further investigation included a static mass in the form of packed snow that was estimated to weigh 14 tons. The natural frequencies were observed to remain unchanged while the modal damping ratios decreased. The second load-case was an uncontrolled mass-event where a large group of pedestrians travelled over the bridge as two cars stood stationary at the quarter-point of the span. A large increase (146%) of the damping ratio was observed while the natural frequency of the first mode decreased 4%. This change was suggested come from the human structure interaction (HSI) partially because the natural frequency of the human body is close to the first vertical frequency of the bridge thus making humans act like dampers on the bridge when close to resonance, and that the number of pedestrians contribute to the modal mass of the system, thus decreasing the natural frequency.Denna studie undersöker separat hur temperaturen såväl som två verkliga belastningssituationer påverkar de modala dämpnings kvoterna och egenfrekvenserna hos en 64,9 meter lång stål-bågs gångbro. Mätningar av accelerationen i bron har genomförts som täcker en temperatur på -10°C till 10°C. De naturliga frekvenserna hos de fem undersökta moderna observerades minska 2–6% när temperaturen ökade. Denna minskning var med hjälp av balk-teori och finita element-modellering härled att troligen komma från förändringar i Youngs modul av materialen, men även geometriska förändringar i stålet på grund av termisk expansion. Vidare undersökning innefattade en statisk massa i form av packad snö som uppskattades att väga 14 ton. Egenfrekvenserna observerades förbli oförändrade medan de modala dämpnings kvoterna minskade. Det andra lastfallet var ett okontrollerat massevenemang där en stor grupp fotgängare gick över bron medan två bilar var stationära en fjärdedel in på brons längd. En stor ökning (146%) av dämpnings kvoten för den första vertikala moden observerades medan egenfrekvensen minskade 4%. Denna förändring föreslogs komma från interaktionen mellan människan och bron, delvis för att människokroppens egenfrekvens ligger nära brons första vertikala frekvens vilket gör att människan agerar som en dämpare när de är nära resonans med bron, och att antalet fotgängare bidrar till den modala massan av systemet vilket sänker frekvensen

Smart Hydroponics : Conceptual Design of Hydroponic Plant System for Home Environment

Hydroponics is a method of cultivating plants without the use of soil. Soil acts as a growth medium which gives plants stability, provides nutrients and allows roots to be kept wet without drowning. In hydroponics the soil’s functions are replaced by synthesized methods. Stability comes from a substrate (i.e. LECA, rockwool perlite).The 16 essential nutrients are solved in water which are distributed to plants’ roots by different techniques. To generate photosynthesis natural light is replaced by artificial light, especially red light in the proximity of 660 nm. Hydroponics has been used as a cultivation method for at least 2000 years. During the 20th century industrial applications became common since plastics allowed for complex systems engineering. The method also makes it possible to grow the same amount of crops with approximately 10% water usage and 25% of the area compared to conventional cultivation. During the past few years systems for home use has emerged but the product genre is still in its cradle. This master thesis covers a new conceptual design of a hydroponic home system. The project was carried out at Omecon AB in Stockholm as a consulting design project. Omecon AB is an engineering consultant agency within mostly mechanical construction looking to widen the competence base. Using a design process based on Human-Centered Design the project involved the stakeholders users, extreme users, Omecon AB, plant experts, electronics engineering and service as well as plastics design engineering. Additional/supplemental economical–, ecological– and social sustainability aspects has been considered during all phases of the process. By using the Human-Centered Design process the problem range is expanded from its initial state which results in a more complete end result. Common methodology altered with some unorthodox twists has been utilized throughout the project. The final result is a conceptual hydroponic system for home environment which is designed as an interior design product as well as a high-performance cultivation system. By using natural materials such as wood and steel the users expands its life span and thus mitigates the negative environmental impact. Another aspect which prolongs the products life span is the modular usage which lets users vary and choose their preferred settings. All manufactured materials included in the final concept were flow resources and the parts were engineered to be easily separable for future replacement and recycling. A new type of pot was invented along with a new way of adjusting the height-wise position of lamps. The aeroponic technique, which was applied to this concept, is generally considered to generate the largest plants and thus comprises higher performance compared to other home systems. The use of substrate was also eliminated which decreases continous material consumption within hydroponics.Hydroponik är en metod för att odla växter utan jord. Jord i odling agerar som ett växtmedium som ger plantor stabilitet, tillför näringsämnen och tillåter rötter att vara i väta utan att dränka dem. I hydroponik ersätts jordens funktioner med syntetiska metoder. Stabilitet ges av ett substrat (t.ex. LECA-kulor, stenull eller perlit). De 16 essentiella näringsämnena löses i vatten och distribueras till plantors rötter med hjälp av olika tekniker. For att skapa fotosyntes ersätts naturligt ljus med artificiellt ljus. Speciellt rött ljus i närheten av 660 nm. Hydroponik har använts som odlingsmetod i åtminstånde 2000 år. Under 1900-talet blev industiella applikationer vanliga eftersom plast möjliggjorde tillverkling av komplexa system. Metoden tillåter även att odla samma mängd grödor med 10% av vattenmängden och 25% av ytan jämfört med konventionell odling. Under de senaste åren har system avsedda för användning hemma blivit vanligare men produktgenren är fortfarande ung. Det här examensarbetet täcker en ny konceptuell design av ett hydroponiskt system för hemmabruk. Projektet utfördes på Omecon AB i Stockholm som ett konsultarbete inom design. Omecon AB är en konsultfirma som mestadels är verksamma inom mekanikkonstruktion men de vill vidga sin kompetens. Genom användning av en designprocess som har baserats på Human-Centered Design har projektet involverat intressenterna användare, extrema användare, Omecon AB, växtexperter, en elektronikingenjör samt plastkonstruktion. Vidare har aspekter inom ekonomisk–, ekologisk– och social hållbarhet beaktats genom alla faser av processen. Via användning av Human-Centered Design-processen har problemrummet expanderats från den initiala utgångspunkten vilket resulterar i ett mer komplett slutresultat. Vanlig metodik varvat med okonventionella anpassningar har använts genom projektet. Slutresultatet består av ett konceptuellt hydroponiskt system för hemmabruk som är designat som en inredningsprodukt samt ett odlingssystem med hög prestanda. Genom användning av naturliga material som trä och stål förlänger användarna produktens livslängd och på så sätt förmildras den negativa klimatpåverkan. En annan aspekt som förlänger produktens livslängd är moduläriteten som låter användare variera och välja deras föredragna inställningar. Alla tillverkade material inkluderade i slutkonceptet var flödesresurser och delarna konstruerades så att de går lätt att separera för framtida ersättning och återvinning. En ny typ av kruka uppfanns tillsammans med ett nytt sätt att justera höjden av lamporna. Den aeroponiska tekniken, som används is konceptet, är allmänt ansedd att generera de största plantorna och innefattar därför högre prestanda jämfört med andra hydroponiska hemmasystem. Användning av substrat eliminerades också vilket minskar kontinuerlig materialkonsumption inom hydroponik

Syntetiska Slaggbildare för Rostfritt Stål

Currently, at Sandvik Materials Technology, slag from the AOD is primarily utilized in ladle treatment of steel. This project has evaluated three synthetic slag formers for ladle treatment. The evaluation has been conducted by measuring how the total oxygen contents and amount of non-metallic inclusions change when using the three syntethic slag formers. The result from these measurements has then been compared to how the total oxygen content and amount of non-metallic inclusions change when using the slag from the AOD. The amount of slag in the ladle has, furthermore, been measured in two ways. By the use of mass balance, and by physically measuring the slag height in the ladle. The results from these two methods of measuring the slag amount has been compared. Lastly, a correlation between the total oxygen content and detected amount of non-metallic inclusions has been evaluated. The results show that the three synthetic slag formers provides a cleaner steel with regards to total oxygen content and amount of non-metallic inclusions in comparison to the slag from the AOD. There is a good conformance between measuring the amount of slag by mass balance compared to physically measure it. Lastly, it can be determined that there is no correlation between the total oxygen contents and the detected amount of non-metallic inclusions in the steel.Vid Sandvik Materials Technology i Sandviken används i nuläget huvudsakligen AOD-slagg vid skänkugnsbehandling. Detta projekt har utvärderat tre syntetiska slaggbildare för skänkugnen. Utvärderingen har gjorts genom att mäta hur väl de tre syntetiska slaggbildarna renar stålet med avseende på den totala syrehalten och mängden icke-metalliska inneslutningar under skänkugnsbehandling. Resultatet från de tre syntetiska slaggbildarna har därefter jämförts med hur väl AOD-slaggen renar stålet. Vidare har slagghöjden i skänken mätts på två sätt. Både genom massbalans med hjälp av slaggsammansättning och genom att fysiskt mäta slagghöjden. Resultatet från dessa två metoder har jämförts. Dessutom har en korrelation mellan den totala syrehalten och den detekterade mängden icke-metalliska inneslutningar undersökts. Resultaten visar att de tre syntetiska slaggbildarna renar stålet bättre jämfört med AOD-slaggen. Det finns en bra överrensstämmelse mellan att mäta slagghöjden med hjälp av massbalans jämfört med att mäta slagghöjden fysiskt. Slutligen kan det konstateras att det ej finns en korrelation mellan den totala syrehalten och den detekterade mängden icke-metalliska inneslutningar.

Variations in dynamic properties of a steel arch footbridge : An experimental study

This study separately investigates how temperature as well as two real load-situations affects the modal damping ratio and natural frequencies of a 64.9m span steel arch footbridge. Measurements of acceleration have been completed which covers a temperature span of  to . The natural frequencies of the five investigated modes were observed to decrease 2-6% as the temperature increased. This effect was with the help of beam-theory and finite element modelling deduced to originate mostly from changes in Young’s modulus of the materials, but also geometrical changes in steel because of thermal expansion. Further investigation included a static mass in the form of packed snow that was estimated to weigh 14 tons. The natural frequencies were observed to remain unchanged while the modal damping ratios decreased. The second load-case was an uncontrolled mass-event where a large group of pedestrians travelled over the bridge as two cars stood stationary at the quarter-point of the span. A large increase (146%) of the damping ratio was observed while the natural frequency of the first mode decreased 4%. This change was suggested come from the human structure interaction (HSI) partially because the natural frequency of the human body is close to the first vertical frequency of the bridge thus making humans act like dampers on the bridge when close to resonance, and that the number of pedestrians contribute to the modal mass of the system, thus decreasing the natural frequency.Denna studie undersöker separat hur temperaturen såväl som två verkliga belastningssituationer påverkar de modala dämpnings kvoterna och egenfrekvenserna hos en 64,9 meter lång stål-bågs gångbro. Mätningar av accelerationen i bron har genomförts som täcker en temperatur på -10°C till 10°C. De naturliga frekvenserna hos de fem undersökta moderna observerades minska 2–6% när temperaturen ökade. Denna minskning var med hjälp av balk-teori och finita element-modellering härled att troligen komma från förändringar i Youngs modul av materialen, men även geometriska förändringar i stålet på grund av termisk expansion. Vidare undersökning innefattade en statisk massa i form av packad snö som uppskattades att väga 14 ton. Egenfrekvenserna observerades förbli oförändrade medan de modala dämpnings kvoterna minskade. Det andra lastfallet var ett okontrollerat massevenemang där en stor grupp fotgängare gick över bron medan två bilar var stationära en fjärdedel in på brons längd. En stor ökning (146%) av dämpnings kvoten för den första vertikala moden observerades medan egenfrekvensen minskade 4%. Denna förändring föreslogs komma från interaktionen mellan människan och bron, delvis för att människokroppens egenfrekvens ligger nära brons första vertikala frekvens vilket gör att människan agerar som en dämpare när de är nära resonans med bron, och att antalet fotgängare bidrar till den modala massan av systemet vilket sänker frekvensen

Syntetiska Slaggbildare för Rostfritt Stål

Currently, at Sandvik Materials Technology, slag from the AOD is primarily utilized in ladle treatment of steel. This project has evaluated three synthetic slag formers for ladle treatment. The evaluation has been conducted by measuring how the total oxygen contents and amount of non-metallic inclusions change when using the three syntethic slag formers. The result from these measurements has then been compared to how the total oxygen content and amount of non-metallic inclusions change when using the slag from the AOD. The amount of slag in the ladle has, furthermore, been measured in two ways. By the use of mass balance, and by physically measuring the slag height in the ladle. The results from these two methods of measuring the slag amount has been compared. Lastly, a correlation between the total oxygen content and detected amount of non-metallic inclusions has been evaluated. The results show that the three synthetic slag formers provides a cleaner steel with regards to total oxygen content and amount of non-metallic inclusions in comparison to the slag from the AOD. There is a good conformance between measuring the amount of slag by mass balance compared to physically measure it. Lastly, it can be determined that there is no correlation between the total oxygen contents and the detected amount of non-metallic inclusions in the steel.Vid Sandvik Materials Technology i Sandviken används i nuläget huvudsakligen AOD-slagg vid skänkugnsbehandling. Detta projekt har utvärderat tre syntetiska slaggbildare för skänkugnen. Utvärderingen har gjorts genom att mäta hur väl de tre syntetiska slaggbildarna renar stålet med avseende på den totala syrehalten och mängden icke-metalliska inneslutningar under skänkugnsbehandling. Resultatet från de tre syntetiska slaggbildarna har därefter jämförts med hur väl AOD-slaggen renar stålet. Vidare har slagghöjden i skänken mätts på två sätt. Både genom massbalans med hjälp av slaggsammansättning och genom att fysiskt mäta slagghöjden. Resultatet från dessa två metoder har jämförts. Dessutom har en korrelation mellan den totala syrehalten och den detekterade mängden icke-metalliska inneslutningar undersökts. Resultaten visar att de tre syntetiska slaggbildarna renar stålet bättre jämfört med AOD-slaggen. Det finns en bra överrensstämmelse mellan att mäta slagghöjden med hjälp av massbalans jämfört med att mäta slagghöjden fysiskt. Slutligen kan det konstateras att det ej finns en korrelation mellan den totala syrehalten och den detekterade mängden icke-metalliska inneslutningar.

Vibration Analysis on AC Electric Arc Furnace

A computerized Fast Fourier Transform system has been used to analyse vibration measurements sampled from a 100-ton electric arc furnace. It has been the hypothesis that patterns in the vibration data would correlate to specific events in the electric arc furnace during the melting process. The theory was that the vibration patterns would be most powerful in multiples of 50 Hz, as the electric arcs operate with a frequency of 50 Hz. It was concluded that the multiples of 50 Hz were dominant. Investigation was made regarding how the amount of scrap affects the amplitude in the vibrations after a defined amount of energy input. It was confirmed that the intensity of the vibrations decreased with increasing mass and basket volume. Another discovery was the M-shaped pattern at the beginning of the melting process. This pattern was statistically analysed. It was found that 71 % of the 41 charges showed an M-shaped correlation. The appearance of this M-shape was analysed regarding power usage, and steel-type. It was concluded that the steel type affected the appearance of the M-shape. The occurrence of flat-bath was also investigated. The theory was that the vibration data would be fairly constant with the occurrence of flat-bath. It was discovered that the vibration data experienced a somewhat constant behaviour towards the end of the melting process in approximately 57 % of the 41 charges. Difficulties were encountered regarding detection of patterns, and correlating them to specific conditions, due to the many parameters that affect the vibration measurements from charge to charge. It was concluded that vibration analysis are unlikely to be used as an absolute way to foresee every event in the electric arc furnace during each charge. But can rather serve as a statistical tool, upon which decisions of how the melting process should be conducted could be based on

Vibration Analysis on AC Electric Arc Furnace

A computerized Fast Fourier Transform system has been used to analyse vibration measurements sampled from a 100-ton electric arc furnace. It has been the hypothesis that patterns in the vibration data would correlate to specific events in the electric arc furnace during the melting process. The theory was that the vibration patterns would be most powerful in multiples of 50 Hz, as the electric arcs operate with a frequency of 50 Hz. It was concluded that the multiples of 50 Hz were dominant. Investigation was made regarding how the amount of scrap affects the amplitude in the vibrations after a defined amount of energy input. It was confirmed that the intensity of the vibrations decreased with increasing mass and basket volume. Another discovery was the M-shaped pattern at the beginning of the melting process. This pattern was statistically analysed. It was found that 71 % of the 41 charges showed an M-shaped correlation. The appearance of this M-shape was analysed regarding power usage, and steel-type. It was concluded that the steel type affected the appearance of the M-shape. The occurrence of flat-bath was also investigated. The theory was that the vibration data would be fairly constant with the occurrence of flat-bath. It was discovered that the vibration data experienced a somewhat constant behaviour towards the end of the melting process in approximately 57 % of the 41 charges. Difficulties were encountered regarding detection of patterns, and correlating them to specific conditions, due to the many parameters that affect the vibration measurements from charge to charge. It was concluded that vibration analysis are unlikely to be used as an absolute way to foresee every event in the electric arc furnace during each charge. But can rather serve as a statistical tool, upon which decisions of how the melting process should be conducted could be based on

Adequacy of consent in patients with distal radius fractures

Health professionals have a legal and ethical obligation to obtain a valid consent before any procedure. The aim of this study was to assess the adequacy of consent for treatment of distal radius fractures. It also outlines potential improvements that could be made. A study of patients undergoing treatment for distal radius fracture was undertaken. We analysed the risks and complications recorded on the consent form. The common recorded risks were infection (95.6%), vascular injuries (77.8%), nerve injuries (66.7%) and stiffness (42.2%); 31.1% of the consent forms had abbreviations. Junior doctors who consented the patients performed 6.7% of the procedures. The poor documentation of risks or complications indicates that patients are not given appropriate information to ensure that the consent is valid. Proper documentation and refining of consent forms is mandatory to ensure that all major risks are understood by patients. This could go a long way in preventing litigation