Modelling of bond between three-wire strands and concrete

The bond between strands and concrete is of importance for prestressed concrete. The research presented in the current paper aims at a better understanding of the bond mechanism, and of how different detailings of the strand interface affect the behaviour. A bond model for three-wire strands was established and calibrated by use of pull-through tests. The results from finite element (FE) analyses with the bond model and the tests were used in parallel. It was found that adhesion, friction and the ability to develop normal stresses determine the bond response of the strand; consequently, they were used as input parameters in the bond model. How different detailing of the strand surface affects these parameters, and the influence on the bond mechanism, are shown. For example, adhesion has the strongest influence on the initial bond response in the cases of smooth and indented strands. Regarding indented strands, the maximum bond capacity is determined by the strand indentation. The knowledge gained can be used to design the strands for a certain bond behaviour. \ua9 2006 Thomas Telford Ltd

Cracks in turnout sleepers -- Conclusions from a questionnaire to the UIC Track Expert Group

To investigate the occurrence of cracks in turnout sleepers, how these were assessed and handled, a questionnaire was sent out to 15 members of the UIC Track expert group in December 2020. By February 20, 2021, eleven responses have been received. The responses are summarised and commented below

Simulation of vertical dynamic vehicle–track interaction using a two-dimensional slab track model

The vertical dynamic interaction between a railway vehicle anda slab track is simulated in the time domain using an extendedstate-space vector approach in combination with a complex-valuedmodal superposition technique for the linear, time-invariant andtwo-dimensional track model. Wheel–rail contact forces, bendingmoments in the concrete panel and load distributions on the supportingfoundation are evaluated. Two generic slab track modelsincluding one or two layers of concrete slabs are presented.The upper layer containing the discrete slab panels is describedby decoupled beams of finite length, while the lower layer isa continuous beam. Both the rail and concrete layers are modelledusing Rayleigh–Timoshenko beam theory. Rail receptances forthe two slab track models are compared with the receptance ofa traditional ballasted track. The described procedure is demonstratedby two application examples involving: (i) the periodicresponse due to the rail seat passing frequency as influenced bythe vehicle speed and a foundation stiffness gradient and (ii) thetransient response due to a local rail irregularity (dipped weldedjoint)

Discreet element modeling of under sleeper pads using a box test

It has recently been reported that under sleeper pads (USPs) could improve ballasted rail track by decreasing the sleeper settlement and reducing particle breakage. In order to find out what happens at the particle-pad interface, discrete element modelling (DEM) is used to provide micro mechanical insight. The same positive effects of USP are found in the DEM simulations. The evidence provided by DEM shows that application of a USP allows more particles to be in contact with the pad, and causes these particles to transfer a larger lateral load to the adjacent ballast but a smaller vertical load beneath the sleeper. This could be used to explain why the USP helps to reduce the track settlement. In terms of particle breakage, it is found that most breakage occurs at the particle-sleeper interface and along the main contact force chains between particles under the sleeper. The use of USPs could effectively reduce particle abrasion that occurs in both of these regions

VIBRATIONER OCH STOMBURET LJUD I TRÄKONSTRUKTIONER : Experimentell modalanalys och finit elementmodellering

This doctoral thesis concerns flanking transmission in light weight, wooden multi-storey buildings within the low frequency, primarily 20-120 Hz. The overall aim is to investigate how the finite element method can contribute in the design phase to evaluate different junctions regarding flanking transmission. Two field measurements of accelerations in light weight wooden buildings have been evaluated. In these, two sources; a stepping machine, and an electrodynamic shaker, were used. The shaker was shown to give more detailed information. However, since a light weight structure in field exhibit energy losses to surrounding building parts, reliable damping estimates were difficult to obtain. In addition, two laboratory measurements were made. These were evaluated using experimental modal analysis, giving the eigenmodes and the damping of the structures. The damping for these particular structures varies significantly with frequency, especially when an elastomer is used in the floor-wall junction. The overall damping is also higher when elastomers are used in the floor-wall junction in comparison to a screwed junction. By analysing the eigenmodes, using the modal assurance criterion, of the same structure with two types of junctions it was concluded that the modes become significantly different. Thereby the overall behavior differs. Several finite element models representing both the field and laboratory test setups have been made. The junctions between the building blocks in the models have been modeled using tie or springs and dashpots. Visual observation and the modal assurance criterion show that there is more rotational stiffness in the test structures than in the models. The findings in this doctoral thesis add understanding to how modern joints in wooden constructions can be represented by FE modelling. They will contribute in developing FE models that can be used to see the acoustic effects prior to building an entire house. However, further research is still needed.Denna doktorsavhandling behandlar flanktransmission i flervåningshus med trästomme, inom det lågfrekventa området, främst 20-120 Hz. Det övergripande målet är att undersöka hur finita elementmetoden kan bidra i konstruktionsfasen för att utvärdera olika knutpunkters inverkan på flanktransmissionen. Två fältmätningar av accelerationer i trähus har utvärderats. I dessa har två olika lastkällor använts, i den första en stegljudsapparat och i den andra en elektrodynamisk vibrator (shaker). Det visades att shakern kan ge mer detaljerad information, men eftersom vibrationerna även sprider sig till omgivande byggnadsdelar vid fältmätningarna var det svårt att estimera tillförlitliga dämpningsdata även då shaker användes. Fältmätningarna följdes av två mätningar i laborationsmiljö. Dessa två experiment utvärderades med experimentell modalanalys, vilket ger egenmoder och dämpning hos strukturerna. Dämpningen för dessa trähuskonstruktioner varierar kraftigt med frekvens. Extra stora variationer registreras då en elastomer användes i knutpunkten mellan golv och vägg. Den totala dämpningen är generellt högre när elastomerer används i knutpunkten mellan golv och vägg i jämförelse med då knutpunkten är skruvad. Genom att analysera egenmoder och deras korrelationer (MAC), för samma trästruktur men med olika typer av knutpunkter, drogs slutsatsen att knutpunkten drastiskt förändrar strukturens dynamiska beteende. Flera finita elementmodeller av både fält- och laboratorieuppställningar har gjorts. I dessa har knutpunkterna mellan byggnadsdelar modellerats helt styvt eller med hjälp av fjädrar och dämpare. Visuella observationer av egenmoder och korrelationen dem emellan visar att det finns mer rotationsstyvhet i försöken än i finita elementmodellerna. Resultaten i denna doktorsavhandling har gett förståelse för hur knutpunkter i träkonstruktioner beter sig och kan simuleras med finit elementmodellering. Vidare kan resultaten bidra till utvecklingen av FE-modeller som kan användas för att kunna se de akustiska effekterna redan under konstruktionsstadiet. Dock behövs ytterligare forskning inom området

VIBRATIONER OCH STOMBURET LJUD I TRÄKONSTRUKTIONER : Experimentell modalanalys och finit elementmodellering

This doctoral thesis concerns flanking transmission in light weight, wooden multi-storey buildings within the low frequency, primarily 20-120 Hz. The overall aim is to investigate how the finite element method can contribute in the design phase to evaluate different junctions regarding flanking transmission. Two field measurements of accelerations in light weight wooden buildings have been evaluated. In these, two sources; a stepping machine, and an electrodynamic shaker, were used. The shaker was shown to give more detailed information. However, since a light weight structure in field exhibit energy losses to surrounding building parts, reliable damping estimates were difficult to obtain. In addition, two laboratory measurements were made. These were evaluated using experimental modal analysis, giving the eigenmodes and the damping of the structures. The damping for these particular structures varies significantly with frequency, especially when an elastomer is used in the floor-wall junction. The overall damping is also higher when elastomers are used in the floor-wall junction in comparison to a screwed junction. By analysing the eigenmodes, using the modal assurance criterion, of the same structure with two types of junctions it was concluded that the modes become significantly different. Thereby the overall behavior differs. Several finite element models representing both the field and laboratory test setups have been made. The junctions between the building blocks in the models have been modeled using tie or springs and dashpots. Visual observation and the modal assurance criterion show that there is more rotational stiffness in the test structures than in the models. The findings in this doctoral thesis add understanding to how modern joints in wooden constructions can be represented by FE modelling. They will contribute in developing FE models that can be used to see the acoustic effects prior to building an entire house. However, further research is still needed.Denna doktorsavhandling behandlar flanktransmission i flervåningshus med trästomme, inom det lågfrekventa området, främst 20-120 Hz. Det övergripande målet är att undersöka hur finita elementmetoden kan bidra i konstruktionsfasen för att utvärdera olika knutpunkters inverkan på flanktransmissionen. Två fältmätningar av accelerationer i trähus har utvärderats. I dessa har två olika lastkällor använts, i den första en stegljudsapparat och i den andra en elektrodynamisk vibrator (shaker). Det visades att shakern kan ge mer detaljerad information, men eftersom vibrationerna även sprider sig till omgivande byggnadsdelar vid fältmätningarna var det svårt att estimera tillförlitliga dämpningsdata även då shaker användes. Fältmätningarna följdes av två mätningar i laborationsmiljö. Dessa två experiment utvärderades med experimentell modalanalys, vilket ger egenmoder och dämpning hos strukturerna. Dämpningen för dessa trähuskonstruktioner varierar kraftigt med frekvens. Extra stora variationer registreras då en elastomer användes i knutpunkten mellan golv och vägg. Den totala dämpningen är generellt högre när elastomerer används i knutpunkten mellan golv och vägg i jämförelse med då knutpunkten är skruvad. Genom att analysera egenmoder och deras korrelationer (MAC), för samma trästruktur men med olika typer av knutpunkter, drogs slutsatsen att knutpunkten drastiskt förändrar strukturens dynamiska beteende. Flera finita elementmodeller av både fält- och laboratorieuppställningar har gjorts. I dessa har knutpunkterna mellan byggnadsdelar modellerats helt styvt eller med hjälp av fjädrar och dämpare. Visuella observationer av egenmoder och korrelationen dem emellan visar att det finns mer rotationsstyvhet i försöken än i finita elementmodellerna. Resultaten i denna doktorsavhandling har gett förståelse för hur knutpunkter i träkonstruktioner beter sig och kan simuleras med finit elementmodellering. Vidare kan resultaten bidra till utvecklingen av FE-modeller som kan användas för att kunna se de akustiska effekterna redan under konstruktionsstadiet. Dock behövs ytterligare forskning inom området

Structural Vibrations of Wooden House Walls

The flanking transmission between apartments due to a structure borne source is studied. The apartments studied were two-storey houses with a wooden framework. Acoustic measurements are often made in new built apartments to make sure that they fulfil the building regulations. Traditional measurements give no information about the contribution of the surrounding walls to the sound transmission. This paper describes a method of measuring flanking transmission. The acceleration levels on the receiving parts in the apartment below the source are studied. Thereby the contribution to the sound pressure in the room from each flanking part can be distinguished

FE modeling of wooden building assemblies

Residential timber framed buildings have in some cases received complaints from inhabitants due to structure-borne sound at low frequencies, even if the building meets the regulations with respect to impact sound quality. This paper describes FE-analyses to evaluate the test setups of a building assembly and to prepare for the full-scale experimental modal analysis planned. By modal analysis, the dynamic properties of a structure, such as eigen modes and damping characteristics, can be extracted.   The test assembly consists of prefabricated wall and floor/roof timber elements. Different assembly and joining methods as well as building element are used. The eigen modes and damping differs between the assemblies investigated which influence the dynamic response in the lower frequencies. The results are carefully evaluated and planned measurements are discussed

FE modeling of wooden building assemblies

Residential timber framed buildings have in some cases received complaints from inhabitants due to structure-borne sound at low frequencies, even if the building meets the regulations with respect to impact sound quality. This paper describes FE-analyses to evaluate the test setups of a building assembly and to prepare for the full-scale experimental modal analysis planned. By modal analysis, the dynamic properties of a structure, such as eigen modes and damping characteristics, can be extracted.   The test assembly consists of prefabricated wall and floor/roof timber elements. Different assembly and joining methods as well as building element are used. The eigen modes and damping differs between the assemblies investigated which influence the dynamic response in the lower frequencies. The results are carefully evaluated and planned measurements are discussed

Static and dynamic properties of connections in timber-frame structures : BOOST + FBBB project

Connections play an important role in timber frame structures, especially when approaching the market of multi-story buildings. Two questions faced by practitioners were studied: for the first is the deformation behavior of such structures, where connections between wall and floor elements play an important role for the global stability of the timber structure. For the second is the sound transmission within elements of high importance, particularly timber building systems face challenges. For that reason, the static and dynamic behavior of such connections was studied in a joined experimental program. Two different building systems were investigated in 13 different test setups of how a floor and wall elements were connected to each other. By adjusting connection elements, the influence of various parameters on the dynamic and static behavior was studied. Sound/vibration transmission over the wall-floor connection was the special interest of the dynamic study. The floor element was excited by a shaker, and the response of floor and wall element was measured by accelerometers. This allowed to identify eigenfrequencies and eigenmodes as well as the damping of the structure and the insertion loss over the connection, respectively. Distinct differences between the building systems of the different producers were seen, while adjustments within building systems influenced only slightly the dynamic behavior. For the static part of the study, the moment-rotation behavior of the wall-floor connection was investigated. Variations of connection designs and layouts were tested to better understand the load-transfer and the mechanical interaction using different connectors and connector arrangements. The nailed connection between vertical studs and the bottom rail of the wall element was identified as a soft point when loaded by a horizontal force perpendicular to the plane of the wall element. Using screws this connection showed a substantial improvement of the connection strength. Further adjustments on the connector arrangements showed only partly influence on connection stiffness and strength.FBBB Framtidens biobaserade byggande och boendeBOOST - Boende- och bostadsutveckling för stärkt tillväx