A FRAMEWORK AND ANALYTICAL APPROACH TO EVALUATE ALTERNATIVE VEHICLE MILES TRAVELED (VMT) FEE SYSTEMS

Since the fuel tax is a dwindling source of revenue, states need to find alternative funding sources. A vehicle miles traveled (VMT) fee has received serious consideration from a number of states and the federal government. What is missing from the VMT fee consideration is a framework for developing VMT fee systems and an analytical approach with which to study how well a proposed system conforms to the policies promulgated in the framework. This research strives to fill that void. The framework developed presents five areas of importance in VMT fee systems: 1. Revenue sufficiency; 2. Revenue stability; 3. Environmental Justice; 4. Low implementation cost; and 5. Security and privacy preservation. The analytical approach consists of two methods: 1. Use of NPV in order to evaluate the cost/benefit position of a proposed VMT fee system with respect to monetary and non-monetary but monetizable aspects; and 2. Use of an Index to evaluate all other aspects. To demonstrate the application of the framework and analytical approach, four VMT system designs were formulated, analyzed, and then compared to each other and to the fuel tax. The four VMT fee system designs are: 1. Alternative A where the total annual VMT is determined at the state inspection and charged for those miles; 2. Alternative B where the out-of-state VMT is deducted from the total annual VMT as determined at the annual state inspection and the fee charged for in-state VMT only; 3. Alternative C where a fee matrix is applied to GPS reported trip data so that fees may vary based on time and locale; and 4. Alternative D where there is a strategic implementation of Alternatives A, B, and C in that order and with two years separating the implementations. If added revenue is the main goal, then Alternative A is the best choice by being the lowest cost. If added revenue and the provision of a better strategy for alleviating such conditions as congestion, noise or air pollution or charging for higher quality roadways, then Alternatives C or D is the best fit. Alternative B performs best as a stepping-stone in Alternative D. All alternatives have better revenue sufficiency and stability than the fuel tax. The fuel tax exceeds all alternatives with respect to security and privacy preservation since no data, personal or otherwise, is recorded. Since security and privacy preservation are considered the weakest aspects of most VMT fee collection systems, added attention must be applied to incorporating design elements that cover aspects where breaches are possible such as in any data transmission, any computational and database processing, and billing/payment functions. The next step beyond this work is to study the construction of the fee matrix and exercise its use either in simulation or with actual data as collected by a state’s department of transportation

Fracture process in cortical bone: X-FEM analysis of microstructured models

This article was published in the serial International Journal of Fracture [© Springer Science and Business Media]. The definitive version is available at: http://dx.doi.org/10.1007/s10704-013-9814-7Bones tissues are heterogeneous materials that consist of various microstructural features at different length scales. The fracture process in cortical bone is affected significantly by the microstructural constituents and their heterogeneous distribution. Understanding mechanics of bone fracture is necessary for reduction and prevention of risks related to bone fracture. The aim of this study is to develop a finite-element approach to evaluate the fracture process in cortical bone at micro-scale. In this study, three microstructural models with various random distributions based on statistical realizations were constructed using the global model's framework together with a submodelling technique to investigate the effect of microstructural features on macroscopic fracture toughness and microscopic crack-propagation behaviour. Analysis of processes of crack initiation and propagation utilized the extended finite-element method using energy-based cohesive-segment scheme. The obtained results were compared with our experimental data and observations and demonstrated good agreement. Additionally, the microstructured cortical bone models adequately captured various damage and toughening mechanisms observed in experiments. The studies of crack length and fracture propagation elucidated the effect of microstructural constituents and their mechanical properties on the microscopic fracture propagation process. © 2013 Springer Science+Business Media Dordrecht

Fracture of cortical bone tissue

This book chapter is closed access.In this chapter, mechanical behaviours of a unique type of composite material – cortical bone tissue – are considered for different length scales. Both experimental and computational approaches are discussed in this study to evaluate the effects of mechanical anisotropy and structural heterogeneity on the fracture process of cor-tical bone. First, variability and anisotropic mechanical behaviour of cortical bone tissue are characterised and analysed experimentally for different loading condi-tions and orientations. Then, results from the experimental studies are used to de-velop finite-element models across different length-scales to elucidate mechanical and structural mechanisms underpinning the anisotropic and non-linear fracture processes of cortical bone

Nanomechanics insights into the performance of healthy and osteoporotic bones

10.1021/nl402719qNano Letters13115247-5254NALE

Post-yield and failure properties of cortical bone

Ageing and associated skeletal diseases pose a significant challenge for health care systems worldwide. Age-related fractures have a serious impact on personal, social and economic wellbeing. A significant proportion of physiological loading is carried by the cortical shell. Its role in the fracture resistance and strength of whole bones in the ageing skeleton is of utmost importance. Even though a large body of knowledge has been accumulated on this topic on the macroscale, the underlying micromechanical material behaviour and the scale transition of bone's mechanical properties are yet to be uncovered. Therefore, this review aims at providing an overview of the state-of-the-art of the post-yield and failure properties of cortical bone at the extracellular matrix and the tissue level