Fatigue behavior of damaged concrete beams repaired with composite material

By the present paper, an analytical model was developed to study the cracked FRP-strengthened reinforced concrete beams subjected to fatigue loading. In order to follow the distribution of interfacial shear stresses causing the debonding phenomenon, a new analytical model based on the cohesive zone (CZ) approach was developed. The present model has the possibility to describe the evolution of the shear stress in the three zones (elastic, microcrack and debonding) and the bearing capacity of the repaired structure. Interface damage scenarios were evaluated for a fatigue load estimated to 90% of the elastic load and another at 60% of the ultimate load Pu.  Results obtained are in good agreement with those given by the literature. The results showed that the shear strength developed by the repaired beam is sensitive to the variation of the mechanical properties (Concrete, FRP and Adhesive layer), the fatigue load ratio and the number of cycles. These parameters can be considered as indicators of damage affecting the health status of the structure repaired during fatigue. The debonding at the FRP-concrete interface noticeably reduced the strength and lifespan of the repaired structure.&nbsp

Locally recurrent subcutaneous and muscular hydatid cysts of the leg: an unusual case report

We report a rare case of 50-year-old Moroccan woman with local recurrence of a subcutaneous hydatid cyst in proximity to the medial surface of the tibia and another cyst at the tibialis posterior muscle in the absence of liver, lung und spleen involvement. The first surgery was done in another hospital three years ago; no adjuvant treatment was performed after surgery. Recurrence was diagnosed according to the MRI appearance, serological and pathological findings. The patient underwent complete excision of the subcutaneous cyst with two centimeters of the medial gastrocnemius muscle; the tibialis posterior muscle cyst was intraoperatively drained and irrigated with scolicidal agent as it was next to the posterior tibial pedicle. A periopertive anthelmintic chemotherapy was administered. Two years after the patient showed no recurrence. This case report and literature review describe an approach to the diagnosis and management of this pathological entity

Direct Observation of Propagating Gigahertz Coherent Guided Acoustic Phonons in Free Standing Single Copper Nanowires

We report on gigahertz acoustic phonon waveguiding in free-standing single copper nanowires studied by femtosecond transient reflectivity measurements. The results are discussed on the basis of the semianalytical resolution of the Pochhammer and Chree equation. The spreading of the generated Gaussian wave packet of two different modes is derived analytically and compared with the observed oscillations of the sample reflectivity. These experiments provide a unique way to independently obtain geometrical and material characterization. This direct observation of coherent guided acoustic phonons in a single nano-object is also the first step toward nanolateral size acoustic transducer and comprehensive studies of the thermal properties of nanowires

The Influence of the Type of Lime on the Hygric Behaviour and Bio-Receptivity of Hemp Lime Composites Used for Rendering Applications in Sustainable New Construction and Repair Works

The benefits of using sustainable building materials are linked not only to the adoption of manufacturing processes that entail reduced pollution, CO2 emissions and energy consumption, but also to the onset of improved performance in the building. In particular, hemp-lime composite shows low shrinkage and high thermal and acoustic insulating properties. However, this material also shows a great ability to absorb water, an aspect that can turn out to be negative for the long-term durability of the building. For this reason, the hygric properties of hemp-based composites need to be studied to ensure the correct use of this material in construction and repair works. The water absorption, drying and transpirability of hemp composites made with aerial (in the form of dry powder and putty) and hydraulic limes were investigated here and related to the microbial growth induced by the water movements within the material. Results show that hemp-natural hydraulic lime mixes exhibit the highest transpirability and drying rate, the lowest water absorption by immersion and capillary uptake and the least intense microbial attack and chromatic change. A microscopical study of the hemp shives also related their great ability to absorb water to the near-irreversible swelling of their structure under dry-wet conditions.The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 326983 (NaturALiMe), and the Spanish project MAT-2012-34473 of the Ministerio de Ciencia y Competitividad. Author MB, owner of the CANNABRIC company, had some role in the design and preparation of mortar samples and in the preparation of this manuscript, but did not have any additional role in data collection and analysis

MULTICRITERIA ANALYSIS OF HEMP PARTICLES' IMPACT ON PHYSICAL AND THERMO-MECHANICAL PERFORMANCES OF HEMP CONCRETE

International audienceThe hemp concrete is considered as an eco-material due to its environmental assets. Its constituents are mainly the hemp particles, binder and water to which admixtures are added eventually. The quality of hemp particles is very sensitive to the nature of soil where it is produced and also to its transformation process, which results in properties variability of hemp particles. And this may be a barrier to development of hemp concrete industry. The herein study aims to evaluate scientifically the impact of this variability on hemp concrete performances. This study is carried out through two main steps: (1) predicting the impact of hemp particles on the hemp concrete, (2) hemp concrete characterization. In the first step, a multicriteria analysis (particle size distributions, etc.) highlights the significant variability of the hemp particles and allowed to classify them into three groups. In the second step, the tests carried out on hemp concrete resulted in low, medium and high mechanical performances as predicted. A factor close to 10 is observed between the minimum and maximum compressive strengths. However, the density and the thermal conductivity are of low variability. The performed analysis show that the interaction between the hemp particles and the binder is likely to contribute to the mechanical response