239,724 research outputs found
Capacity and traffic safety analysis of two crossings at the strada Nuova per Opicina (SR58), municipality of Trieste, Opicina
No full textV sklopu diplomske naloge smo predstavili prometno varnostno in kapacitetno analizo dveh križišč, ki se nahajata v občini Trst, in sicer na območju deželne ceste (SR58) Nova cesta za Opčine/(SR58) Strada Nuova per Opicina, in dveh stranskih cest, ceste za Ferluge/Salita a Conconello in Ulice Della Bellavista. V prvem delu diplomske naloge smo predstavili varnostno analizo s pomočjo programov Microsoft Access in ArcMap, s katerima smo tudi grafično prikazali vse lokacije nezgod. S pomočjo urada za infrastrukturo, logistiko in transportne storitve Avtonomne Dežele Furlanije Julijske Krajine in tržaške občinske policije smo na analiziranem odseku zbrali podatke 10 letnih nezgod, in sicer od leta 2010 do 2019. V nadaljevanju so navedene in opisane rešitve, ki bi zmanjšale cestne nesreče.
V drugem delu diplomske naloge smo predstavili kapacitetno analizo obravnavanih križišč. Izvedli smo analizo obstoječega in planskega stanja, ki ga predvidevamo čez 20 let. Ugotovili smo, da je današnji nivo uslug nezadosten glede na sodobni pravilnik. Zato smo zasnovali nove rešitve, s katerimi bi izboljšali prometni tok na odseku. S programom SIDRA INTERSECTION 9 smo izdelali variante obstoječega stanja in ga primerjali z dvemi variantami (križišči s sistemom semaforizacije in krožno križišče). Na podlagi rezulatov lahko sklepamo najboljšo rešitev: krožno križišče.My graduation thesis focuses on the safety and traffic analysis of two intersections, located in the municipality of Trieste, namely in the area where the regional road Strada nuova per Opicina intersects with the roads Salita a Conconello and Via della Bellavista.
The first part of the examines the safety of the area. The safety analysis was conducted by using the programs Microsoft Access and ArcMap, to graphically display all the locations where the accidents occurred. The collaboration with the Office for Infrastructure, Logistics and Transport Services of the Region Friuli Venezia Giulia and the municipal police made possible the collection of information regarding the annual accidents from 2010 to 2019. The results based upon the collected data confirmed the presence of critical points, where the numbers of road accidents peaked. In the final part of the research possible solutions to reduce road accidents are presented.
The second part of the thesis consists in the analysis of the traffic load during the peak hours. The current load of traffic was the starting point for the research. Statistical tools and calculations were applied to the current data in order to show the traffic conditions in the next 20 years. The results reveal how the road intersections are characterized by heavy traffic and therefore, are not flow. The latter part of the analysis shows some potential solutions to the problem. In this case, the program SIDRA INTERSECTION 9 was used. Models of the area were created both reproducing the current and the future state of the intersections. The two models were compared with a solution where a traffic light system and a roundabout were installed. The final results indicate how the best solution to diminish the traffic congestion and increase the safety is the creation of a roundabout
Whittemore Strain Gauge
No full textThis strain gauge was invented around 1926 at the National Bureau of Standards by mechanical engineer Herbert L. Whittemore. This instrument was designed for the Committee on Arch Dam Investigations at the request of the Engineering Foundation. It was used for measuring the elongation of a 10-inch gage length in large structural pieces such as bridge trusses and was designed for use under adverse conditions in the field. It was also used to measure the reinforcement for the dome of the Natural History building of the Smithsonian Institution, built during the period from 1904 to 1911. Whittemore’s design was produced commercially and was commonly used when structural strains were measured at intervals over long periods of time. Another Whittemore gauge from around 1926 is 1998.0036.001. In 1938, Whittemore developed a second strain gauge design (1998.0607.001, 1998.0607.002).[H] 9 cm [W] 14 cm [L] 31 cmWhittemore Strain Gage / Patent No 1638425 / No. 13
Application of optical measurement techniques to high strain rate deformations in composite materials
No full textTraditionally high strain rate material characterisations have been conducted using strain gauges and/or cross head displacements in servo-hydraulic test machines, and force transducers in split Hopkinson bar experiments. Non-contact full-field techniques for experimental stress/strain analysis have been available for many years and used extensively for structural analysis under static or quasi static loading. These techniques have the advantage that they are non-contact and high resolution, so damage initiation can be captured within the field of view and the material behaviour is not modified by the sensor. In the paper, one such technique known as Digital Image Correlation (DIC) is used to assess the material behaviour by using high-speed digital cameras to capture images from material subject to high strain rate events. The high strain rate loading is achieved using an Instron VHS high speed tensile test machine that allows the applied strain rates to vary from 12.5 s–1 to 125 s–1. Although the strain rates that can be achieved are low in comparison to those achieved with the Hopkinson bar, the test machine provides better optical access and opportunities for illumination of the specimen necessary for the DIC. In the paper, a review of the literature associated with high strain rate testing using servo-hydraulic machines is first provided. Then, an experimental study of the high strain rate behaviour of the both composite material and the resin alone is described. The results from both the DIC and strain gauges are compared and discussed
Epidermal Passive RFID Strain Sensor for Assisted Technologies
No full textAn epidermal passive wireless strain sensor using RFID tags is presented. The tag is intended to detect eyebrow or neck skin stretch where paraplegic patients have the capability to tweak facial muscles. The tag is designed on a Barium Titanate loaded PDMS substrate and is assessed to demonstrate the strain gauge sensitivity and repeatability as a function of skin stretch
Whittemore Strain Gage
No full textThis gauge was invented around 1938 at the National Bureau of Standards by mechanical engineer Herbert L. Whittemore. It was used to measure the elongation or contraction of a length on the surface of a structure such as a wall, column, or beam, thereby indirectly measuring the stress on that structure. The purpose of Whittemore’s invention was to 1) provide a portable gauge, which could be used to measure minute changes in length; 2) design a gauge so as to minimize, if not completely eliminate, inaccuracies in gauge readings due to the handling of the instrument; and 3) provide a simple, rugged, and accurate gauge in which readings could be obtained quickly and easily. Whittemore designed this gauge around the time that he was carrying out a program of mechanical tests of component parts for prefabricated houses from 1938 to 1943. Another Whittemore gauge from around 1938 is 1998.0607.001. An earlier design of a strain gauge was developed by Whittemore around 1926 (1998.0036.001, 1998.0036.002).[H] 16.5 cm [W] 4.7 cm [D] 10 cmWHITTEMORE STRAIN GAGE // PATENT NUMBERS // 1.638.425 and 2.177.605 // SERIAL NO. 615; NBS - 1170
Whittemore Strain Gauge
No full textThis gauge was invented around 1938 at the National Bureau of Standards by mechanical engineer Herbert L. Whittemore. It was used to measure the elongation or contraction of a length on the surface of a structure such as a wall, column, or beam, thereby indirectly measuring the stress on that structure. The purpose of Whittemore’s invention was to 1) provide a portable gauge, which could be used to measure minute changes in length; 2) design a gauge so as to minimize, if not completely eliminate, inaccuracies in gauge readings due to the handling of the instrument; and 3) provide a simple, rugged, and accurate gauge in which readings could be obtained quickly and easily. Whittemore designed this gauge around the time that he was carrying out a program of mechanical tests of component parts for prefabricated houses from 1938 to 1943. Another Whittemore gauge from around 1938 is 1998.0607.002. An earlier design of a strain gauge was developed by Whittemore around 1926 (1998.0036.001, 1998.0036.002).[H] 7 cm [W] 38.1 cm [D] 9.5 cmWHITTEMORE STRAIN GAGE // PATENT NUMBERS // 1.638.425 2.177.605 // SERIAL NO. 627; NBS-11707 _MUSEUM NO. 607
Discontinuous modelling of strain localisation and failure
No full textThe computational simulation of failure in solids poses many challenges. A proper understanding of how structures respond under loading, both before and past the peak load, is important for safe and economical constructions. This requires numerical models for failure which are both faithful to the physical reality and mathematically well founded. A serious computational issue is that of objectivity with respect to the spatial discretisation of a problem. This requires that upon refinement of the spatial discretisation of a problem, a unique, physically meaningful result is approached. One approach to ensure objectivity with respect to spatial discretisation when simulating failure in solids is to allow displacement discontinuities in the solution. In this work, different techniques, of varying complexity, are developed to simulate displacement discontinuities which are independent of the spatial discretisation using finite elements. The different techniques are then critically evaluated. The first model examined involves adding only the effect of a displacement discontinuity to a finite element as an incompatible strain mode. This allows a traction–separation relationship to be applied at an interface and can be implemented simply in a standard finite element code. It is however shown that this type of model can be cast in an equivalent continuum format, a form which is known to be sensitive to the spatial discretisation. The second approach developed involves the addition of the Heaviside function to the underlying finite element interpolation basis. This method is based on the partition of unity concept, and allows the Heaviside function to be added locally to a finite element mesh to simulate a propagating displacement discontinuity. The approach is formulated for geometrically linear, geometrically nonlinear, quasi-static and dynamic problems. It is shown to be completely independent of the spatial discretisation. The partition of unity-based model is used also to simulate failure using a regularised strain softening model. When a critical level of inelastic deformation is reached, a displacement discontinuity is inserted. This model is better suited to modelling the entire failure process than a continuum or discontinuous model alone. Through numerical examples, it is shown that the inclusion of a displacement discontinuity during the failure process can lead to a different failure mode than for a continuum-only model
Intermediate strain rate testing methodologies and full-field optical strain measurement techniques for composite materials characterisation
No full textTwo optical full-field strain measurement techniques, Digital Image Correlation and the Grid Method, are applied to characterise the strain-rate dependent constitutive behaviour of composite materials. Optical strain measurement techniques based on full-field images are well established for material characterisation in the quasi-static strain rate region, however in this work they are developed to study the material behaviour at intermediate strain rates, which is relatively unexplored. For this purpose a testing methodology that combines high speed imaging and the use of a high speed test machine is devised. The overall goal is to extract composite materials constitutive parameters to be used in the modelling of strain rate dependent behaviour. Particularly the strain rate dependence of the stiffness of glass and carbon fibre reinforced epoxy materials is investigated. A characterisation procedure based on off-axis specimens with oblique end-tabs is developed and applied to the study of the shear behaviour of a carbon/epoxy composite material.The research in the PhD programme constitutes an essential first step for more profitable applications of full-field measurement techniques to high speed testing. Full-field data acquired with the experimental methodology devised here can be used to investigate non linear material behaviours. Furthermore this experimental methodology, applied to specimens that generate non uniform strain fields, can produce strain maps useful for the application of the Virtual Fields Method. This will lead to a reduction of the experiments needed to characterise materials
A continuous/discontinuous Galerkin formulation for a strain gradient-dependent damage model
No full textThe numerical solution of strain gradient-dependent continuum problems has been hindered by continuity demands on the basis functions. The presence of terms in constitutive models that involve gradients of the strain field means that the continuity of standard finite element shape functions is insufficient. Despite a resurgence of research interest in strain gradient continuum models to represent micro-mechanical effects, a sound, effective and simple framework for the numerical solution of strain gradient-dependent problems is lacking. Here, a formulation is presented which allows the use of finite element shape functions for the solution of a prototype strain gradient-dependent damage model. The formulation is examined in two dimensions for the simulation of crack propagation. Particular attention is paid to the application of non-standard boundary conditions
Simultaneous, independent measurement of temperature and strain using a tilted fibre Bragg grating
No full textA single fibre Bragg grating is used to discriminate between temperature and
strain by exploiting the core-cladding mode coupling of a tilted fibre Bragg
grating (TFBG). The core and cladding modes exhibit different thermal
sensivities, while the strain sensivities are approximately equal. Monitoring
the core-core mode coupling resonance and the core-cladding mode coupling
resonance within the spectrum of a single TFBG allows the separation of the
temperature and strain induced wavelength shifts
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