Delayed grape ripening by intermittent shading to counter global warming depends on carry-over effects and water deficit conditions

Grapevine phenology is continuously advancing due to global warming, exposing berry ripening to increasingly drier and hotter episodes that can dramatically affect yield and berry quality. This study aimed to analyse whether intermittent shading produced by panels placed over the plants can delay berry ripening to counter the impact of global warning on phenology. A two-year outdoor trial repeated on two batches of young potted grapevine (cv. Syrah) was conducted in Montpellier (South of France). Shading was created in a row using 2 m-wide horizontal panels placed 2.4 m above the ground. A moderate water deficit was also applied at the start of veraison to half the plants in both full sun (without panels) and shaded conditions to mimic usual field conditions. Variables related to budburst, flowering, veraison and sugar at harvest were analysed in all treatments. Although intermittent shading did not significantly modify air temperature within the canopy when cumulated over the growing season, the panels substantially delayed veraison by up to more than 30 days under well-watered conditions. The most marked phenological shifts were noted in the second year of treatment between flowering and veraison when carbon demand sharply increased during berry formation, suggesting there was a carry-over effect likely due to limited carbon assimilation. This was accompanied by sharp decreases in berry diameter and sugar content per berry at harvest. Higher berry growth and sugar loading were maintained when shading was combined with water deficit. However, the trigger effect of water deficit on veraison almost halved the phenological delay caused by the panels. Overall, a cooler period for ripening could be achieved with panels over the vines but at the expense of berry size and sugar amount in berries. It can be concluded that shading intensity and duration should be adapted to evaporative and soil water conditions to benefit from the phenological delay caused by panels, without altering production in the long term

Stability assessment of masonry retaining walls

Partout où la pierre est facilement disponible, on trouve des constructions en maçonnerie de pierre. Suivant les coutumes et les usages, les blocs de pierres sont assemblés bruts, simplement ébauchés ou parfaitement taillés, avec ou sans l'ajout d'un liant. Supplantée par le béton dans les constructions neuves depuis le milieu du XX} siècle, les ouvrages en maçonnerie demeurent majoritaires dans le patrimoine bâti français, un patrimoine qu'il convient d'entretenir rationnellement. L'objectif de ce travail de thèse est de poursuivre l'élaboration d'un cadre scientifique rigoureux et opérationnel afin de donner aux décideurs et aux gestionnaires les outils nécessaires pour mener à bien leur mission. Nous proposons ici deux outils d'évaluation de la stabilité d'ouvrages de soutènement en maçonnerie basés sur l'utilisation conjointe du calcul à la rupture avec des méthodes d'homogénéisation. Dans un premier temps, nous mettons d'abord au point un outil analytique permettant de dimensionner des ouvrages neufs ou d'évaluer la stabilité d'ouvrages peu déformés. Cet outil permet également de dimensionner des solutions de renforcement par clouage lorsque cela est jugé nécessaire. Dans un deuxième temps, nous implémentons cet outil dans un code numérique afin de lui donner la souplesse nécessaire à l'étude d'ouvrages non-conventionnels, de grandes taille ou fortement pathologique. Enfin, nous mettons en oeuvre plusieurs campagnes expérimentales qui nous fournissent les données nécessaires à la validation de ces modèles de calculWherever stone is readily available, we encounter stone masonry buildings. Depending on customs or dedicated use, the blocks are used raw, lightly faced or perfectly cut, with or without the use of mortar. Althougth concrete has replaced masonry in new construction for some decades, the better part of the French built heritage is made of masonry, an heritage we are responsible for. This works aims at contributing to create a reliable scientific frame for that purpose. This thesis uses the yield design theory alongside with homogenisation techniques to study the stability of stone masonry earth retaining walls. First, we provide an analytical tool suitable for designing new structures or assessing the stability of existing ones that are still in good shape. Should it be needed, this tools allows for the design of a strengthening solution based on soil-nailing. Then, we implement it in a finite element code to give it the versatility required to study unconventionnal structures or structures badly damaged. We then present several experimental campaigns aiming at validating the proposed tool

Evaluation structurale des murs de soutènement en maçonnerie

Wherever stone is readily available, we encounter stone masonry buildings. Depending on customs or dedicated use, the blocks are used raw, lightly faced or perfectly cut, with or without the use of mortar. Althougth concrete has replaced masonry in new construction for some decades, the better part of the French built heritage is made of masonry, an heritage we are responsible for. This works aims at contributing to create a reliable scientific frame for that purpose. This thesis uses the yield design theory alongside with homogenisation techniques to study the stability of stone masonry earth retaining walls. First, we provide an analytical tool suitable for designing new structures or assessing the stability of existing ones that are still in good shape. Should it be needed, this tools allows for the design of a strengthening solution based on soil-nailing. Then, we implement it in a finite element code to give it the versatility required to study unconventionnal structures or structures badly damaged. We then present several experimental campaigns aiming at validating the proposed toolsPartout où la pierre est facilement disponible, on trouve des constructions en maçonnerie de pierre. Suivant les coutumes et les usages, les blocs de pierres sont assemblés bruts, simplement ébauchés ou parfaitement taillés, avec ou sans l'ajout d'un liant. Supplantée par le béton dans les constructions neuves depuis le milieu du XX} siècle, les ouvrages en maçonnerie demeurent majoritaires dans le patrimoine bâti français, un patrimoine qu'il convient d'entretenir rationnellement. L'objectif de ce travail de thèse est de poursuivre l'élaboration d'un cadre scientifique rigoureux et opérationnel afin de donner aux décideurs et aux gestionnaires les outils nécessaires pour mener à bien leur mission. Nous proposons ici deux outils d'évaluation de la stabilité d'ouvrages de soutènement en maçonnerie basés sur l'utilisation conjointe du calcul à la rupture avec des méthodes d'homogénéisation. Dans un premier temps, nous mettons d'abord au point un outil analytique permettant de dimensionner des ouvrages neufs ou d'évaluer la stabilité d'ouvrages peu déformés. Cet outil permet également de dimensionner des solutions de renforcement par clouage lorsque cela est jugé nécessaire. Dans un deuxième temps, nous implémentons cet outil dans un code numérique afin de lui donner la souplesse nécessaire à l'étude d'ouvrages non-conventionnels, de grandes taille ou fortement pathologique. Enfin, nous mettons en oeuvre plusieurs campagnes expérimentales qui nous fournissent les données nécessaires à la validation de ces modèles de calcu

Dynamic shading effects on grapevine development and berry quality

Le réchauffement climatique accélère la phénologie de la vigne, déplaçant la phase de maturation du raisin vers des périodes où les risques de canicule et de sècheresse augmentent. Ces changements ont entraîné une diminution de l'acidité dans les baies alors que leur concentration en sucres a augmenté, menant à des vins aux taux alcooliques élevés et aux propriétés organoleptiques altérées. L'ombrage permet de diminuer la contrainte hydrique et la température de la plante afin de limiter ces différents effets non désirés. Cependant, une réduction trop importante du rayonnement disponible pour la plante peut affecter la photosynthèse et les rendements. La technologie de l'entreprise Sun'Agri®, offre la possibilité de moduler l'ombrage grâce à ses persiennes mobiles sur trackers placées au-dessus des cultures. Il s'agit d'identifier les conditions et les périodes d'ombrage les plus favorables au développement de la vigne. Dans cette thèse, les réponses physiologiques et morphologiques de la vigne à ce type d'ombrage ont été étudiées pour renseigner une approche de modélisation visant à prédire les conséquences des différentes stratégies de pilotage de l'ombrage sur les rendements et sur la qualité du raisin.Une expérimentation basée sur le campus de La Gaillarde de l'Institut Agro Montpellier a permis d'étudier les effets d'un ombrage intermittent fort créé par des panneaux fixes sur de jeunes plantes en pots durant 2 années consécutives. Les résultats ont été confrontés aux réponses de plantes au champ sur un site équipé de panneaux fixes au sein de l'unité expérimentale INRAE de Pech Rouge et sur un site de la chambre d'agriculture du Vaucluse, équipé d'un dispositif agrivoltaïque dynamique installé par Sun'Agri®. Les effets de l'ombrage ont été caractérisés sur un vaste ensemble de réponses impliquées dans l'élaboration du rendement : phénologie, surface foliaire et interception du rayonnement, assimilation et allocation du carbone, composantes du rendement et évolution des caractéristiques principales de la qualité du raisin.Les panneaux fixes de La Gaillarde ont entrainé un retard important de la véraison en particulier en conditions irriguées après deux années d'ombrage mais ceci s'est accompagné d'effets non désirés à la récolte. Le retard était beaucoup moins important lorsque l'ombrage était limité à la période post-véraison ou combiné à un déficit hydrique. Au champ, des retards plus légers ont été observés à partir de la véraison et le chargement en sucre a été ralenti. En revanche, le rendement tendait à diminuer après plusieurs années de traitement. Le syndrome d'évitement de l'ombrage a été observé avec des feuilles plus fines et, en pots, une allocation du carbone déplacée des racines vers les parties aériennes. L'ombrage fort en pots a réduit les capacités photosynthétiques mais au champ, l'ombrage modéré ne les a presque pas affectées. Un avantage de photosynthèse semblait même possible grâce au meilleur état hydrique, mais le rayonnement fortement réduit en phase ombrée en a limité l'importance. Une diminution de biomasse végétative et de niveau des réserves a été observée en pots sous fort ombrage intermittent mais pas au champ avec un ombrage plus modéré. Enfin, l'ombrage intermittent semble avoir permis une certaine préservation de la qualité du raisin en augmentant l'acidité à la récolte.Plusieurs éléments peuvent être considérés pour améliorer le pilotage de l'ombrage tels que l'ombrage pré-véraison qui permet un retard phénologique substantiel, l'amélioration de l'état hydrique de la vigne ou les conséquences sur les capacités photosynthétiques. Il conviendrait à l'avenir de vérifier qu'un taux d'ombrage modéré est à l'origine des résultats intéressants obtenus au champ et d'explorer plus longuement l'évolution pluriannuelle des réserves carbonées qui semblent influencer la production dès la 2ème année de traitement.Global warming is continually accelerating the phenology of grapevine, shifting the ripening phase of the grape to periods of increased risk of heat waves and drought. In recent decades, these changes have led to a decrease in acidity in the berries while their sugar concentration has increased significantly, leading to wines with increasingly high alcohol levels and altered organoleptic properties. Shading reduces water stress and plant temperature in order to limit these various undesired effects. However, excessive reduction in the radiation available to the plant can affect photosynthesis and thus yields. The technology of the company Sun'Agri®, leader in Agrivoltaics, offers the possibility of modulating the shading thanks to its mobile panels on trackers placed above the crops. Optimizing the technology then requires to identify the conditions and periods of shading that are most profitable to vine development and production. In this thesis, the physiological and morphological responses of the vine to this type of shading were studied to inform a modelling approach aimed ultimately at predicting the consequences of different shading control strategies on yields and grape quality.An experiment based on the La Gaillarde campus of the Institut Agro Montpellier studied the effects of strong intermittent shading created by fixed panels on young plants in pots during 2 consecutive years. The results were then compared with the responses of plants in the field on a first site equipped with fixed panels at the INRAE experimental unit of Pech Rouge near Narbonne and on a second site equipped with a dynamic agrivoltaic demonstrator installed by Sun'Agri® near Orange. At each site, the effects of intermittent shading were characterised on a wide range of responses involved in yield development: phenology, leaf area establishment and radiation interception, carbon assimilation and allocation, yield component establishment and changes in key grape quality characteristics.The fixed panels at La Gaillarde caused a significant delay in veraison, particularly under irrigated conditions after two years of shading, but this was accompanied by undesired effects at harvest. The delay was much less important when shading was limited to the post-veraison period or combined with a water deficit. In the field, where the water status of the plants was close to that observed in pots under water deficit, much smaller delays were observed from veraison onwards in response to shading and sugar loading was slowed. On the other hand, yield tended to decrease after several years of treatment. On potted and field-grown vines, the shade avoidance syndrome was observed with thinner leaves and, in pots, a shift in carbon allocation from roots to aerial parts. Strong shading in pots reduced photosynthetic capacity, but in the field more moderate shading hardly affected it. An advantage in photosynthesis even seemed possible due to the better water status under shade, but the strongly reduced radiation during the shaded phases limited its importance. A decrease in vegetative biomass and reserve levels was observed in pots under strong intermittent shade but not in the field under more moderate shade. Finally, intermittent shading seems to have allowed some preservation of grape quality by increasing acidity at harvest.Several elements from this work can be taken into account in the management of shading by panels, such as well-irrigated conditions and pre-veraison shading, which allow a substantial phenological delay, the improvement of the water status of the vine or the quantification of the consequences on photosynthetic capacities. In the future, it would be advisable to verify that a moderate shading rate is indeed at the origin of the more interesting results obtained in the field and to explore in greater detail the multi-year evolution of carbon reserves, which seem to influence production from the 2nd year of treatment

Upper bound limit analysis of masonry retaining walls using PIV velocity fields

Masonry is the building of structures from individual units, with or without the use of mortar as a bonding component. Stone masonry structures are frequent in the regions where stones are ubiquitous. In Europe, it was massively used until the nineteenth century to build earth retaining walls. For instance, they represent 85% of the retaining walls in Great Britain and 60% in France. Most of these masonry walls are currently perfectly safe, showing an average durability of more than a century. The best economic interest is to maintain the stock in good order by identifying and repairing the structures at risk of collapse and to preserve the currently satisfactory structures at the lowest investment level. Unfortunately, there is not sufficient scientific knowledge to do so reliably. This work aims to develop a design method suitable for existing structures. The analytical model is based upon the yield design theory which provides a rigorous framework and has proven to be effective for this kind of structures. The strength domain of stone masonry is determined using the homogenization theory. The modelisation is carried out in 2D. An experimental campaign was carried out in order to verify the proposed model. The experimental setup is in 2D thanks to the use of Schneebeli rods and is considered to be a physical model and is not scaled. The theoretical failing load and the theoretical kinematics of the failure are compared with the experimental failing load and the actual kinematics of the failure. The discrepancies and differences between the two sets are then discussed

Assessing and repairing masonry retaining structures by yield design analysis and experimental modelling

International audienc

Assessing the Three-Dimensional Behaviour of Dry Stone Retaining Walls by Full-Scale Experiments

Dry stone masonry is a widespread building technique, which has been used in Europe and all around the world in both monumental and vernacular architecture. Amongst them, dry stone structures retaining slopes have received growing attention over the past two decades, but only a few studies concentrate on the influence of localised loading upon the backfill. This paper describes an experimental campaign, comprising two tests on full-scale structures, which has been undertaken in France in order to investigate the behaviour of dry stone road retaining walls. The results of these tests are compared with those of a previous experimental campaign, and of a theoretical approach

Experimental and Numerical Investigation on the Strain Response of Distributed Optical Fiber Sensors Bonded to Concrete : Influence of the Adhesive Stiffness on Crack Monitoring Performance

The present study investigated the strain response of a distributed optical fiber sensor (DOFS) sealed in a groove at the surface of a concrete structure using a polymer adhesive and aimed to identify optimal conditions for crack monitoring. A finite element model (FEM) was first proposed to describe the strain transfer process between the host structure and the DOFS core, highlighting the influence of the adhesive stiffness. In a second part, mechanical tests were conducted on concrete specimens instrumented with DOFS bonded/sealed using several adhesives exhibiting a broad stiffness range. Distributed strain profiles were then collected with an interrogation unit based on Rayleigh backscattering. These experiments showed that strain measurements provided by DOFS were consistent with those from conventional sensors and confirmed that bonding DOFS to the concrete structure using soft adhesives allowed to mitigate the amplitude of local strain peaks induced by crack openings, which may prevent the sensor from early breakage. Finally, the FEM was generalized to describe the strain response of bonded DOFS in the presence of crack and an analytical expression relating DOFS peak strain to the crack opening was proposed, which is valid in the domain of elastic behavior of materials and interfaces

20-Years Field Durability Experience of oldest UHPFRC Structural Elements

International audienc