Experimental and numerical investigation of gap K-joints of rectangular hollow section trusses

This paper is concerned with investigating of the plastic behaviour on gap K-joints of truss girders, made from thin-walled rectangular hollow section members. An experimental study was carried out on a full-scale girder under a concentrated load on two central nodes. A numerical analysis was carried out using ABAQUS in order to clearly see the behaviour of this type of joint and to make a comparison with the experimentation. This study will make it possible to examine attentively and to define the analytical model for this type of joint. The results obtained in this paper have shown that the sections with very thin-walled present different behaviours compared to the thin or more or less thick sections. As a result, the tested truss made it possible to observe the failure mode of this type of section, follow-up of a comparative study on the determination of the joint capacity by Eurocode 3 and CIDECT

Numerical investigation of the cold-formed I-beams bending strength with different web shapes

The wide use of cold-formed sections (CFS) in the field of steel constructions, favored by the multiple advantages they offer (lightness, ease of installation, etc.), has led us to reflect on a new process for manufacture of metal beams allowing the design of very large span hangars and a reduction in instability problems. This paper presents a study of the theoretical and numerical behavior of a large span CFS beam with different webs, a solid web, a triangular corrugated web, and a trapezoidal corrugated web. These beams are stressed by a concentrated bending load at mid-span. Numerical modeling was done using the finite element software ABAQUS. The results were validated with those theoretically found, based on the effective width method adopted in standard EN1993-1-3. The load capacity and failure modes of the beams were discussed. According to numerical and analytical analysis, corrugated web beams perform better than all other sections

Flexural behavior of delta and bi-delta cold-formed steel beams: experimental investigation and numerical analysis

Cold-formed steel (CFS) structural members retain their positions in the lightweight construction industry. This is due to the significant advantages of CFS. The optimization of these CFS elements will allow the construction of economical buildings with increased load capacities and solutions for stable and economical construction will be obtained. The main aim of this research was to evaluate the effectiveness of these new CFS sections with the estimation of remarkable instabilities and failure modes. This article deals with an experimental study on the behavior of CFS beams of open delta and bi-delta form stressed by four-point bending loads. These cross section shapes are often used in floors as main and secondary beams. The section properties are based on the effective width method designated by the Eurocode 3 standard. A nonlinear finite element (FE) analysis using the ABAQUS program is performed and the comparison between the experimental, numerical and theoretical results is done. Finally, the results showed above all that the breaking loads of the delta and bi-delta beams corresponded to the modes of local buckling and crushing of the web

Experimental and numerical investigation of gap K-joints of rectangular hollow section trusses

This paper is concerned with investigating of the plastic behaviour on gap K-joints of truss girders, made from thin-walled rectangular hollow section members. An experimental study was carried out on a full-scale girder under a concentrated load on two central nodes. A numerical analysis was carried out using ABAQUS in order to clearly see the behaviour of this type of joint and to make a comparison with the experimentation. This study will make it possible to examine attentively and to define the analytical model for this type of joint. The results obtained in this paper have shown that the sections with very thin-walled present different behaviours compared to the thin or more or less thick sections. As a result, the tested truss made it possible to observe the failure mode of this type of section, follow-up of a comparative study on the determination of the joint capacity by Eurocode 3 and CIDECT

Experimental contribution to the study of the physic-mechanical behavior and durability of high-performance concretes based on ternary binder (cement, silica fume and granulated blast furnace slag)

Le béton à hautes performances (BHP) est un béton innovant largement utilisé dans la construction moderne. De nouvelles techniques de formulation et de conception du HPC ont permis d'obtenir des performances mécaniques et une durabilité remarquables par rapport au béton conventionnel. Les principaux avantages du HPC sont liés à sa faible porosité, sa très haute résistance mécanique et son excellente durabilité. La facilité d'application du HPC est obtenue par l'utilisation combinée de superplastifiant et d'ajout de minéraux, ce qui se traduit par une augmentation significative de la résistance à la compression tout en améliorant la maniabilité et la durabilité. L'utilisation d'un liant ternaire (ciment, fumée de silice et laitier granulé de haut fourneau broyé) dans la fabrication du HPC est une nouvelle avancée dans la construction durable qui offre des avantages économiques, techniques et écologiques. L'objectif de ce travail de recherche était d'améliorer les propriétés physico-mécaniques du HPC à base de liant ternaire en étudiant l'influence du remplacement du ciment par du laitier granulé et des fumées de silice. Les résultats des tests mécaniques montrent que les performances du HPC réalisé avec ces liants ternaires sont similaires au HPC témoin sans laitier granulé. Enfin, il est conclu que l'utilisation de tels liants est très bénéfique pour diminuer les problèmes environnementaux et améliorer la durabilité du HPC

Effect of parent concrete strength on recycled concrete performance

The reuse of concrete waste as a secondary aggregate could be an efficient solution for sustainable development and long-term environmental protection. However, the variable quality of waste concrete, especially with various compressive strengths, can have a negative effect on the final compressive strength of recycled concrete. In this approach, the major goal of this research is to study the effect of parent concrete qualities on the performance of recycled concrete. To accomplish this task, three grades of different compressive strengths (10 to 15) MPa, (20 to 25) MPa, and (30 to 40) MPa have been analyzed in an experimental test program, in which an unknown compressive strength is introduced as well. The experimental mix use 40% of secondary aggregates (both course and fine) and 60% of natural aggregates. This led to the decreasing of the compressive strength of the test concrete between 14% and 23.7% compared to the normal concrete. This loss was improved by adding an amount of cement equivalent to 4% of the weight of the recycled aggregate used. The achieved results prove that the strength properties of the parent concrete have a limited effect on the compressive strength of the recycled concrete. Additionally, low compressive strength parent concrete, when crushed, generates a high amount of fine aggregate and large percentage of recycled coarse aggregates with less attached mortar, and presents the same compressive strength as an excellent parent concrete

A machine learning assessment of the two states model for lipid bilayer phase transitions

We have adapted a set of classification algorithms, also known as Machine Learning, to the identification of fluid and gel domains close to the main transition of dipalmitoyl-phosphatidylcholine (DPPC) bilayers. Using atomistic molecular dynamics conformations in the low and high temperature phases as learning sets, the algorithm was trained to categorize individual lipid configurations as fluid or gel, in relation with the usual two-states phenomenological description of the lipid melting transition. We demonstrate that our machine can learn and sort lipids according to their most likely state without prior assumption regarding the nature of the order parameter of the transition. Results from our machine learning approach provides strong support in favor of a two-states model approach of membrane fluidity

Valorization and recycling of packaging belts and post-consumer PET bottles in the manufacture of sand concrete

The valorization of local by-products in the manufacture of a new range of sand concrete and the improvement of their properties, will lead to seek an arrangement between performance and cost in order to achieve a resistant material. Waste recycling affects two very important affect namely the environmental impact and the economic impact. The main objective of our work is to contribute to optimize the formulation of sand concrete as part of the recovery of waste, which is harmful to the environment given its bulky and unattractive nature, it is waste plastic. Most PET bottles become waste after use, causing environmental problems. To solve this problem, a method for recycling PET bottles as fibers to strengthen concrete is proposed. Two types of plastic waste are added to sand concrete; the first concerns the recycling of post-consumer bottles in PET, in the form of polyester fiber supplied by the company RET-PLAST and the second type concerns the packaging belts made of polyethylene terephthalate (PET). The properties in the fresh state (workability and density) and in the hardened state (compressive strength, tensile strength and water absorption) of the various produced concretes are analyzed and compared against their respective controls. From the experimental results, it can be concluded that the reinforcement of the cement matrix with PET fibers with a rate of 1% improves the mechanical properties of sand concrete as well as a remarkable decrease in its water absorption capacity

Evolution of the macromolecular structure of sporopollenin during thermal degradation

AbstractReconstructing the original biogeochemistry of organic microfossils requires quantifying the extent of the chemical transformations they experienced during burial and maturation processes. In the present study, fossilization experiments have been performed using modern sporopollenin chosen as an analogue for the resistant biocompounds possibly constituting the wall of many organic microfossils. Sporopollenin powder has been processed thermally under argon atmosphere at different temperatures (up to 1000 °C) for varying durations (up to 900 min). Solid residues of each experiment have been characterized using infrared, Raman and synchrotron-based XANES spectroscopies. Results indicate that significant defunctionalisation and aromatization affect the molecular structure of sporopollenin with increasing temperature. Two distinct stages of evolution with temperature are observed: in a first stage, sporopollenin experiences dehydrogenation and deoxygenation simultaneously (below 500 °C); in a second stage (above 500 °C) an increasing concentration in aromatic groups and a lateral growth of aromatic layers are observed. With increasing heating duration (up to 900 min) at a constant temperature (360 °C), oxygen is progressively lost and conjugated carbon–carbon chains or domains grow progressively, following a log-linear kinetic behavior. Based on the comparison with natural spores fossilized within metasediments which experienced intense metamorphism, we show that the present experimental simulations may not perfectly mimic natural diagenesis and metamorphism. Yet, performing such laboratory experiments provides key insights on the processes transforming biogenic molecules into molecular fossils