Sylvie Yotte

Development of a two-stage inspection process for the assessment of deteriorating infrastructure

Inspection-based maintenance strategies can provide an efficient tool for the management of ageing infrastructure subjected to deterioration. Many of these methods rely on quantitative data from inspections, rather than qualitative and subjective data. The focus of this paper is on the development of an inspection-based decision scheme, incorporating analysis on the effect of the cost and quality of NDT tools to assess the condition of infrastructure elements/networks during their lifetime. For the first time the two aspects of an inspection are considered, i.e. detection and sizing. Since each stage of an inspection is carried out for a distinct purpose, different parameters are used to represent each procedure and both have been incorporated into a maintenance management model. The separation of these procedures allows the interaction between the two inspection techniques to be studied. The inspection for detection process acts as a screening exercise to determine which defects require further inspection for sizing. A decision tool is developed that allows the owner/manager of the infrastructural element/network to choose the most cost-efficient maintenance management plan based on his/her specific requirements.

Cluster characterisation in a metal matrix composite

Abstract Inhomogeneities in the reinforcement of particulate metal matrix composites (PMMC) change their post elastic behaviour. Thus it is important to qualify and quantify particle clustering. Images of an Al–Si/SiC PMMC are analysed here in order to calculate interparticle distance, intercluster distance, and distance from isolated particles to clusters. This is done on six images at ×100 magnification, two images at ×200 magnification and one image at ×50 magnification. The analysis is done through increasing size dilatations. This is applied to the nine images but also to random images, allowing thus a comparison of the nine images and random ones. This gives four characteristic distances, and also the cluster size and the link between clustering and cracking. The particle and cluster alignment in the extrusion direction is also shown.

Fatigue life modelling of asphalt pavements under multiple-axle loadings

The fatigue damage caused by multiple-axle configurations is a key issue for pavement design. The standard fatigue test consists of the application of a continuous sinusoidal signal on a specimen, which enables the fatigue life to be described as a function of the strain level. For more complex loading signals, additional parameters were found to have an influence on the fatigue life of bituminous mixtures. In the French design method, the effect of multiple-axle loadings is simplified and taken into account via load equivalency factors using Miners Law. In this article, we present a method for the computation of the fatigue life of bituminous mixtures under multiple-axle configurations that couples a structural approach and a material-based approach. The structural approach consists of a parametric study of real loading signals that enables the computation of the independent shape parameters characterising a loading signal. An experimental plan whose variables are the independent shape parameters was then defined and the synthetic loading signals constructed (material-based approach). The results of the laboratory fatigue tests enabled the computation of a multi-linear fatigue model that writes the fatigue life as a function of the independent shape parameters characterising the loading signal.

Better Assessment of Bituminous Materials Lifetime Accounting for the Influence of Rest Periods

ABSTRACT Fatigue life of bituminous mixes is analyzed through two-points bending fatigue tests, the experimental protocol having been modified such as to manage rest periods. Fatigue sequences and rest sequences are analyzed and the parameters enabling to quantify the variation of stiffness with time (during rest) or loading (during fatigue) are defined and modeled. It is shown that the re-damaging rate is a good indicator of non-recoverable damage. Varying the experimental parameters that drive damage evolution, the respective weights of fatigue and healing are addressed.

Accounting for variability and uncertainties in NDT condition assessment of corroded RC-structures

ABSTRACT The quantitative forecasting of corrosion development remains difficult, limiting the development of validated preventive maintenance strategies. Difficulties come from the spatial variability of material properties, the temporal variability of the environment and the sensitivity of non destructive measurements to changing environmental conditions. The reinforced concrete Barra Bridge, Portugal, has been thoroughly investigated, and on site data have been used for modelling the development of corrosion and its variability. A model has been derived from additional laboratory experiments, which enables to account for the influence of environment and to support the decision process regarding the corrosion state and the forecasting of its evolution.

Laboratory evaluation of pavement macrotexture durability

ABSTRACT The aim of this paper is to present a study concerning the evaluation of the durability of the asphalt concrete macrotexture in laboratory. An experimental procedure was developed. This experimental procedure consists in a mechanical test which aims to alter the upper face macrotexture of a cylindrical specimen through the application of a sinusoidal repeated load on its surface. In order to quantify the macrotexture evolution produced we use a laser texture evaluation system. This system allows the scanning of surface specimen before and after mechanical solicitation. In this paper, we first present the materials and the experimental procedure. Then, we expose the various surface indicators analysis and finally we discuss the experimental results.

Multiple axle loadings: Shape parameters and their effect on the fatigue life of asphalt mixtures

ABSTRACT The effect of multiple axle loads on the fatigue life of asphalt pavements is a key issue dealing with the effect of heavy trucks on pavement distresses. Equivalent Single Axle loads are currently calculated with simplified hypotheses. This is an important stake for the ecological transportation: increasing the load per truck results in decreasing the emission of toxic gases per ton of transported goods. To study the effect of multiple axles, real displacement signals in the pavement are needed. The LCPCs accelerated testing facility (Nantes, France) enables the measurement of real loading signals in an experimental pavement. Parameters describing the pavement strain curves were computed for this database. A factorial analysis gives four independent parameters that define an experimental plan of a campaign of fatigue tests whose aim is to identify how the fatigue life is affected by the shape parameters.

A multi-linear fatigue life model of flexible pavements under multiple axle loadings

The fatigue damage of a pavement under repeated traffic loadings is a key issue for pavement design. At the material scale, the fatigue performance of asphalt mixtures can be assessed with laboratory tests. The standard fatigue test consists of the application of a continuous sinusoidal signal on the specimens and enables to write the fatigue life as a function of the strain level. Real loadings are more complex. Additional parameters may therefore have an influence on the fatigue life of bituminous mixtures. A methodology for a better calculation of the fatigue life of asphalt pavements is developed. It couples a structural approach and a material-based approach. This paper presents the material-based approach of the methodology. A database of laboratory fatigue tests with complex loadings has been built. An experimental plan whose variables are the independent shape parameters characterising a loading signal is defined and the synthetic complex loading signals constructed. The results of the fatigue tests enabled the calibration of a multi-linear fatigue model where the fatigue life is a function of the independent shape parameters characterizing the loading signal. Coupling the multi-linear fatigue model with a pavement model enables the calculation of the fatigue life of a pavement under different loading conditions.

An Original Evaluation of the Wearing Course Macrotexture Evolution using the Abbot Curve

ABSTRACT The wearing course is the top surface layer of the road. The road surface has multiple functions the main one being traffic safety, which is conditioned by skid resistance. This skid resistance is conditioned by pavement texture. This paper presents an experimental procedure allowing to evaluate surface macrotexture evolution of an asphalt concrete specimen by laboratory testing. Specimen surface changes through the application of a sinusoidal repeated load at high temperature. The studied surface is scanned before and after mechanical testing using a laser profiler. Texture maps are analysed using Abbott curve which is also called bearing ratio curve. The 3D analysis enables to quantify macrotexture evolution under repeated traffic conditions and to analyze the influence of both temperature and binder.

Recommendations for Recycling, Processing and Reuse of Concrete

Some countries started to recycle concrete materials for reuse in structural or other issues. Some of them, like Germany, Australia and Canada have established their own recommendation guide for recycling concrete [1,2]. The recycling consists of crushing old concrete into aggregates, and then processing it into new mixture using recycled aggregates with specified sizes [3,4]. The aim of this recycling is to save nature from deforestation and dryness, by reducing the need to gravel and so the quarries work, and also to economize the waste management [5,6]. The present research work consists of an experimental study assessing the impact of using recycled aggregates on the concrete behavior and on the country’s economy. We are especially interested in determining the best composition for the new mixture of concrete resulting from reusing different types of recycled aggregates. Different types of tests have been done depending on the aggregates sizes, their origin and their state (burned or safe). The analysis is based on the comparison between compressive strength, water-cement ratio, slump, porosity and durability. Otherwise, the impact on economy is analyzed, a priori, by studying the effect of reducing the cost of the resulting concrete on construction spending. The resulted recommendations indicate the sizes of aggregates which may constitute the best composition for recycling and processing concrete, and the best use for each type of concrete depending on behavior and economy effect.© 2007 ASME