Behaviour of pre-stressed high strength concrete sleepers subjected to dynamic loads

As part of ballasted railway track, pre-stressed concrete sleepers (PCSs) play an essential role in track response, performance and safety. PCSs are subjected to dynamic loads which are often high magnitude and low duration. The characteristics of dynamic loads, the interactions between track components and the dynamic responses of PCSs under dynamic loads have been vastly investigated throughout past decades and continue to be a subject of interest to the railway industry.. Mechanical behaviours of PCSs such as dynamic response and failure mechanisms are important to meet the structural and durability requirements of railway sleepers. However, the influence of high performance concrete (HPC) mechanical properties on behaviour of PCSs is currently lacking. This paper presents a finite element model developed as a part of a broader investigation undertaken at the University of Melbourne. Finite element modelling package LS-DYNA has been used to represent a sleeper in a simulated track condition. The model is validated based on published experimental information. Different grades of high strength concrete (HSC) have been investigated. Mechanical properties such as compressive strength, tensile strengths, fracture energy and elastic modulus are considered.. The results show that the using higher concrete grade in sleeper leads to a larger bending moment under the same dynamic load. This confirms the inadequacy of current design approach for PCSs

Novel assessment test for granular road foundation materials

Drivers for sustainability have made it necessary for the construction industry to adapt its traditional processes to become both more efficient and produce less waste. Performance based design and specification in the UK for motorways and trunk roads permits a very flexible approach to pavement design, material selection and performance related testing aimed at utilising materials to their maximum potential. However, it is clear that within the emerging philosophy of using materials that are ‘fit for purpose’ there are many technical challenges for design and specification. There is a need to develop suitable methods of evaluating materials prior to their being used on site. This project was born out of this requirement, with a particular emphasis on coarse granular materials due to their common role in capping construction and also their unique difficulty for measurement under laboratory conditions due to their large range of particle size. A novel assessment test for coarse capping materials for roads that can be used to indicate their likely short-term in situ performance, under controlled laboratory conditions before construction on site, has been developed during this research programme. Key findings relating to the behaviour of coarse capping materials, the use of stiffness measuring devices and variables that influence the measurement of composite stiffness are discussed in detail. The research highlights the necessity for adequate drainage and protection of foundation materials against increase in water content. When adopting a performance specification the timing of the pavement assessment is critical, both on site and in the laboratory. The performance measured on site should perhaps only be considered as a ‘snapshot’ relating to the stress state in the material at the time of testing

Advanced Testing and Characterization of Bituminous Materials, Two Volume Set

Bituminous materials are used to build durable roads that sustain diverse environmental conditions. However, due to their complexity and a global shortage of these materials, their design and technical development present several challenges. Advanced Testing and Characterisation of Bituminous Materials focuses on fundamental and performance testin

Mine haul road rolling resistance: influences and impacts

Energy efficiency of haulage, in the production of mineral ores, was investigated through measurement of the rolling resistance experienced by haul trucks while traversing unsealed, unbound granular pavements. It appears pavement surface condition influences rolling resistance more significantly than pavement structural capacity. Validation of various modelling methods with in-situ pavement deflection measurements showed that simple methods are able to estimate pavement surface deflection with similar accuracy to more complex techniques, such as Finite Element Analysis

Experimental evaluation of geocell reinforcement behavior using transparent soil techniques

Geocells are a growing type of geosynthetic product used in many applications, including the reinforcement of unbound granular materials for the construction of flexible pavements. Although significant research has been conducted to quantify the performance of geocell-reinforced soil masses, there is no universally accepted design method for these structures. The Mechanistic-Empirical Pavement Design Guide (MEPDG) is a solid framework on which to base a geocell design method. The resilient modulus of a material is constitutive relationship between the imposed stress state and the resilient strain. It is the relevant design parameter that should be modified in the MEPDG for the design of pavement structures using geocells. However, a more robust understanding of the behavior and mechanisms that contribute to the overall performance of geocell-reinforced materials is necessary to develop theoretically-sound model. As such, the materials and equipment necessary to conduct a thorough analysis of geocells were conceived and implemented as part of this study. This equipment is based around the transparent soil concept – transparent soils are two-part media consisting of solid particles and a saturating fluid with matching refractive indices. Fused quartz and mineral oil were selected as appropriate materials to use as a granular soil surrogate. The large-scale equipment consists of a steel-framed tank with cast acrylic sides. Many lessons were learned with regard to the use of transparent soil techniques in large-scale experiments. Preliminary results indicate the equipment is adequate to validate the results of prior geocell experiments. Additional improvements will allow for the full utilization of transparent soil capabilities and the direct observation of geocell reinforcement behavior and mechanisms in-situ.Civil, Architectural, and Environmental Engineerin

Advanced Testing and Characterization of Bituminous Materials, Two Volume Set

Bituminous materials are used to build durable roads that sustain diverse environmental conditions. However, due to their complexity and a global shortage of these materials, their design and technical development present several challenges. Advanced Testing and Characterisation of Bituminous Materials focuses on fundamental and performance testin

SURFACE AND MECHANISTIC PROPERTIES OF RECYCLED BITUMINOUS MIXTURES

EXECUTIVE SUMMARY Problem Often, when the characteristics of a bituminous mixture are analised, there are major differences between in-lab and in-situ results. This is due to the fact that the procedures and techniques implemented during the design phase (in lab) may be different from those used on site. Then, is very important to be able to predict the main properties of a mixture particularly when innovative materials are used. For example, when crumb rubber is used, phisical and volumetric properties of mixes may change over time, in particular due to the swelling phenomenon that it alters different properties of the mixture (e.g., viscosity). This study aims to investigate the main aspects of road pavement design in order to improve the performance of innovative mixes. Objectives and scopes The main objectives of this thesis are: • Ob. 1 – To set up models for the prediction of surface characteristics of conventional and innovative road pavements. • Ob. 2 – To design innovative bituminous mixtures with crumb rubber. • Ob. 3 – To analyse the consequences related to Life Cycle Cost Analysis deriving from the application of different pavement design methods. Description This thesis intends to investigate the superficial and mechanical properties of conventional and innovative road pavements. The thesis contains a collection of experiments related to: i) laboratory-based study of the surface properties of road pavement; ii) laboratory-based study of the mechanical properties of road pavement and; iii) determination of expected life and pay adjustment. Conclusions The main conclusions of this thesis are: • Macro- and microtexture test can be explained and predicted based on simple physical and geometric models. In lab- measures can be related to the corresponding measures on real pavements. • The variation of viscosity over time is linked to the swelling process of the rubber. The order of components in the asphalt plant does not have significant effects on viscosity. • Short-time oven aging (STOA) and interrupted compaction process entail a worse compaction of mixes. • CRT2 mixes are usually easier to compact and are the most resistant to permanent deformation. • STOA effects are more evident than interrupted compaction effects in terms of compactability, workability, stiffness and rutting. • Rubberised mixes are easier to compact, when STOA process is applied. They have higher stiffness and a better resistance to permanent deformation. • Regard to the variables under investigation (e.g., AV), AASHTO, KenPave, MnPAVE and, M-EPDG have a similar trend in terms of expected lives

Design and dynamic testing of a roller coaster running wheel with a passive vibration damping system

This paper presents a design, a numerical analysis, a build-up and dynamic testing of an engineered and fabricated wheel with a passive vibration damping system designed for a roller coaster system. Taking into account the limited amount of space for fixing a wheel to a roller-coaster, this study shows an approach in which a special wheel design and viscoelastic inserts are used to reduce vibrations. A wheel comprises a rim and hub separated by a viscoelastic material and simultaneously connected by using spring steel fasteners with contractions ensuring elasticity. The dynamic tests of the wheel with a passive vibration damping system were completed with an assessment of the vibration reduction ratio in comparison to conventional roller coaster wheel types currently operated at the amusement park Energylandia located in Zator, Poland. Laboratory test results show reduction of vibrations by 36 % in the low frequency range, by 63 % in the medium frequency range and by 45 % in the high frequency range

Performance of surface layer with Asphaltic Concrete (AC) as wearing course and Hot-Rolled Asphalt (HRA) as binder course

Rutting and fatigue cracking are two apparent failure modes in a flexible pavement. They do not only shorten the performance life of a pavement but also require a lot of money and energy on repair works. This study presents a laboratory investigation of combining asphaltic concrete bituminous mix (AC) as wearing course and hot-rolled asphalt (HRA) binder course in road surfacing structure to overcome the problems. Four types of mixtures namely AC with 80 PEN bitumen grade (AC(80)), AC with 50 PEN bitumen grade (AC(50)), HRA with 50 PEN bitumen grade (HRA(50)) and HRA with 80 PEN bitumen grade (HRA(80)) were made as control specimens to compare the performance of the combination of AC wearing course and HRA hinder course, (AC(80)+HRA(50)). Results from dynamic creep test and wheel tracking test confirm that AC is more superior in reducing rutting. The combined mix provides promising findings when it surpasses rutting performance when compared to normal AC. Meanwhile HRA mix shows a longer fatigue life compared to AC. The combined mix (AC(80)+HRA(50)) shows a better resistance towards fatigue compared to AC(80). At low strain level, the former achieved a fatigue life of 1E+8 cycles while a fatigue life for the latter mix is only 9.98E+5 cycles. Thus, the usage of combined mix has potential to improve the road surfacing performance