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Heat exposure of a population is often estimated by applying temperatures from outdoor monitoring stations. However, this can lead to exposure misclassification if residents do not live close to the monitoring station and temperature varies over small spatial scales due to land use/built environment variability, or if residents generally spend more time indoors than outdoors. Here, we compare summertime temperatures measured inside 145 homes in low-income households in Baltimore city with temperatures from the National Weather Service weather station in Baltimore. There is a large variation in indoor temperatures, with daily-mean indoor temperatures varying from 10 °C lower to 10 °C higher than outdoor temperatures. Furthermore, there is only a weak association between the indoor and outdoor temperatures across all houses, indicating that the outdoor temperature is not a good predictor of the indoor temperature for the residences sampled. It is shown that much of the variation is due to differences in the availability of air conditioning (AC). Houses with central AC are generally cooler than outdoors (median difference of − 3.4 °C) while those with no AC are generally warmer (median difference of 1.4 °C). For the collection of houses with central or room AC, there is essentially no relationship between indoor and outdoor temperatures, but for the subset of houses with no AC, there is a weak relationship (correlation coefficient of 0.36). The results presented here suggest future epidemiological studies of indoor exposure to heat would benefit from information on the availability of AC within the population.

Strength assessment of concrete in existing structures is a key issue. Many non destructive techniques (NDT) are available which can provide information about the material condition and several approaches can be used to derive strength estimates from NDT test results. However, common practice suffers from many drawbacks: (a) it is difficult to ascertain the level of accuracy/confidence of concrete strength estimates, (b) one lacks established guidelines for estimating the concrete strength variability, (c) the best way to combine NDT methods and coring remains an open issue. The RILEM TC 249 “Non destructive in situ strength assessment of concrete” is addressing these problems. A benchmark was carried out in order to compare (a) how experts define and can carry out an NDT investigation program and (b) how experts derive strength values from the NDT measurements. The benchmark was based on synthetic simulations which reproduced a synthetic data set corresponding to a grid of twenty 3 m-high columns defining a single-storey building structure. The comparison of the various strategies and the analysis of results enabled identification of the most influential parameters that define an investigation approach and influence its efficiency and accuracy. A special emphasis was placed on the magnitude of the measurement error. A model of the investigation strategy is proposed, that will be detailed in future guidelines. The reader is invited to refer to a companion paper (Alwash et al. in Mater Struct, 1 . doi: 10.1617/s11527-016-0962-x ), based on more extensive Monte-Carlo simulations of the same case-study, which analyzes and quantifies the efficiency of the investigation strategies with respect to both average strength and strength variability assessment, in order to draw conclusions based on rational analyses rather than on the element of chance.

This book provides answers to the following problems: how to identify the most probable critical failures; how to describe and use data-concerning materials that are either heterogeneous, time-variant, or space-variant; how to quantify the reliability and lifetime of a system; how to use feedback information to actualize reliability results; and how to optimize an inspection politic or a maintenance strategy. Numerous authors from public research centers and firms propose a synthesis of methods, both new and well-known, and offer numerous examples concerning dams, geotechnical study, and structures from nuclear and civil engineering.

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 Miner's 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.

In this study, an experimental investigation into the effects of adding a limited proportion of silica sand and cement on crushing properties of simulated carbonate sand is presented. Silica sand in the proportion of 20, 30 and 50% and cement in the proportion of 2 and 4% by dry weight were the fractions added to the base soil. Cemented samples with different dry density 14 and 16 kN/m 3 have been considered. Predictive models for the crushing parameter (C r ) are elaborated using the design of experiment method, considering silica sand fraction, cement fraction and effective normal stresses parameters. A good correlation between the values given by the experimental tests and those given by the model was observed. The main effects of the addition of silica sand and cement are reduction of particles crushing, leading to a soil exhibiting less contraction during shearing. Addition of a fraction of silica sand and/or cement enhances the resistance of the particles to crushing occurring during shear. The greatest resistance in crushing is produced when both a fraction of cement and silica sand are added to the soil and mixed at a denser state.

L'emploi d'additions minérales en cobroyage avec le clinker peut permettre d'améliorer les performances des bétons de sable et de réduire la quantité consommée de ciment. Un sable dunaire est mélangé, en proportions variables, avec un clinker pour obtenir des liants cobroyés utilisés pour composer le béton de sable. Afin de séparer les effets de la finesse du liant de ceux du dosage, un plan d'expériences en deux phases a été suivi. Dans un premier temps, on quantifie la finesse de mouture du liant cobroyé, puis on étudie l'influence des différents paramètres sur les caractéristiques mécaniques des bétons de sable. On caractérise en particulier le degré d'activité des ajouts sableux qui peut se révéler significatif et conduire à l'économie d'une certaine quantité de ciment. Mineral additions can be mixed with the clinker before the grinding process. Thus, one obtains a 'coground' binder which can allow some reduction in the cement ratio. Some dune sand is added, in variable proportions, to the clinker, such as to obtain a coground binder from which different sandcrete mixes are defined. To distinguish the effects of the binder fineness from those of the addition ratio, a two-stage experimental design process has been followed. In a first stage, the fineness of the coground binder has been quantified. Thereafter, the influence of several parameters (fineness, addition ratio, water/binder ratio) on the mechanical properties has been evaluated and modelled. The degree of activity of the mineral additions has been confirmed. It can lead to some gain in the cement content.[PUBLICATION ABSTRACT]

This paper aims to identify the technological proximity between tropical timber species from the Congo Basin. The analysed properties were correlated with mechanical performances and physical behaviour of glulam and glue joints. Deterministic clustering defines six homogeneous clusters. The fuzzy clustering provides a more refined picture where proximity between species can be quantified as a progressive concept. The results of this analysis may help the development of engineered tropical wood products, namely, glulam while preserving endangered timber species.

All people in developed countries benefit from running water in their homes. Providing this service calls for a significant quantity of pipes. To preserve water resources and ensure good network performance, it is important that pipes are renewed at the optimum time. This article presents the two main approaches currently used to plan pipe renewal, one using ‘short-term’ models (1-3 years), and the other employing ‘long-term’ models (more than 30 years). The majority of short-term models are fairly robust, whereas most long-term models currently in use are of questionable quality. The aim of this paper is to design a long-term model in compliance with short-term decisions and future goals. The method was tested using data from the largest water utility in Europe. This paper first estimates the past survival curve for water pipes, based on their age at removal from service. It is then used to make predictions about when pipes will require replacement. A number of performance indicators are then created, such as future renewal length, renewal rate, and future investment need. The proposed approach is different from existing long-term models because it is based on actual historical survival function.

Le contrôle non destructif des ouvrages de génie civil en béton et béton armé représente un intérêt majeur pour la gestion du patrimoine bâti. Les méthodes géophysiques, régulièrement employées en géologie, restent encore mal maîtrisées dans ce cadre. Nous donnons les premiers résultats d'études de mesures électriques menées sur des bétons et des bétons armés. Nous décrivons dans un premier temps le matiel utilisé, notamment un quadripôle carré dévloppé à ces fins. Puis, l'utilisation de la technique sur des ouvrages in situ est envisagé. Pour cela les résultats de modélisations numériques sur l'influence des armatures ou de fissures de surface sont présentés. Ces résultats confirment l'analyse des mesures réalisées sur des corps d'épreuves ou des ouvrages existants. Nous montrons, en particulier, la complémentarité des mesures électriques réalisées pour deux directions d'injection du courant, qui permettent de détecter et de localiser des fissures condutrices ou résistantes électriquement et des armatures. Non destructive testing on concrete and reinforced concrete civil engineering structures represent a great interest in the management of built heritage. Geophysics methods, currently used in geology, are still insufficiently validated for this purpose. This article deals with results of electrical measurement on plain and reinforced concrete. First, the equipment is described, particularly a square configuration quadripole specially developed. The applications on real components and structures are thus considered. Numerical computations help us to quantify the influence of existing cracks or rebars. These results are confirmed through in situ investigations. We show the complementarity of electrical measurements for two directions of current injections, this allowing the detection, location, and characterisation of cracks and rebars.[PUBLICATION ABSTRACT]

Cet article présente les résultats d'essais sur des poutres d'épicéa en dimensions commerciales. La campagne d'essais est divisée en deux étapes: chaque pièce est soumise à des mesures non destructives permettant de quantifier ses caractéristiques, puis dans un second temps à un essai de flexion 4 points jusqu'à la rupture. Cette campagne met en évidence d'une part les corrélations existant entre certains des paramètres non destructifs et d'autre part les relations entre ces paramètres et les propriétés mécaniques. La formalisation de ces relations permettra d'optimiser le tri sélectif des sciages. This paper presents the results of an experimental, program on spruce wood timber. The experiments are divided into two parts: at first, each plank has been examined through various non destructive techniques to quantify its biological properties, in a second stage, it has been loaded under four-point bending until failure. The analysis focusses on one hand on the statistical correlations between several biological measurements and, on the other hand, on the relations existing between these data and structural strength. Using these relations will improve the non destructive evaluation and grading of wood timber.[PUBLICATION ABSTRACT]