Dr. Maureira-Carsalade, Nelson

Cold-formed steel (CFS) members offer significant advantages over hot-rolled sections, primarily due to their high strength-to-weight ratio and versatility in forming various cross-sectional shapes. These attributes make CFS an efficient choice for design and construction. This paper reviews current design methods for CFS, focusing on the impact of initial imperfections. It also examines various techniques for measuring residual stress in CFS sections, including analytical, experimental, and numerical approaches. The study concludes that while analytical methods are effective, they become complex when accounting for material anisotropy. Laboratory techniques provide reliable measurements but are limited in detecting through-thickness residual stresses. Numerical approaches offer comprehensive insights but require further validation across different material and geometric configurations. The paper highlights the need for advanced analytical models, improved laboratory methods, and expanded numerical techniques to address existing knowledge gaps in residual stress assessment for CFS structures.

This study evaluates bentonite clay (BNC) as a sustainable supplementary cementitious material for enhancing the structural performance of rigid pavement systems, with a dual focus on durability and eco-efficiency. Using Response Surface Methodology (RSM), the effects of varying BNC content on concrete properties were systematically analyzed. Results indicate that increasing BNC reduces workability, with slump values declining from 10.21 to 62.55 % due to its high-water absorption and decreases density (2355 kg/m³ for control vs. 2293 kg/m³ for 20 % BNC) owing to its lower specific gravity. While early-age strength diminishes at higher BNC levels, an optimal replacement of 12–16 % enhances long-term compressive strength via pozzolanic reactions, achieving 37.55 MPa at 91 days for the 16 % BNC mix. Flexural strength improvements are attributed to BNC’s crack and shrinkage mitigation. However, excessive BNC content (>16 %), compromises durability, evidenced by reduced ultrasonic pulse velocity (UPV) and increased porosity. BNC enhances sulfate resistance and thermal stability, demonstrating suitability for hot climates. Cement substitution with BNC reduces the carbon footprint by 31.91 %, aligning with sustainability goals. RSM-derived empirical models exhibit strong predictive accuracy (F-values: 67.07 for compressive strength, 36.92 for flexural strength; non-significant lack-of-fit, p > 0.04). The optimized mix (16 % BNC, 82-day curing) balances strength, durability, and environmental benefits. This work advances sustainable pavement design, addressing performance trade-offs and promoting low-carbon construction practices.

Background/Objectives: Fibromyalgia (FM) is a chronic syndrome characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, and mental health issues. It affects approximately 1.78% of the general population; an estimated 4:1 ratio between women and men is observed. It significantly impacts quality of life and carries both clinical and social stigma. This study aims to evaluate the relationship between drug use and mental health in female patients with fibromyalgia. Methods: This study is prospective, observational, and cross-sectional. A questionnaire was administered to 544 subjects, achieving a representative sample size from a population of 800,000 subjects by using an algorithm for proportion estimation with a known sampling frame. The selection was non-random, making the sampling non-probabilistic. Logistic regression models were applied to assess the effect of drug use on perception of mental health; presence of symptoms such as comprehension and memory problems, insomnia, depression, and anxiety; and severity of cognitive symptoms and non-restorative sleep. To quantify the impact, odds ratios and confidence intervals have been observed. Results: The findings indicate the non-recommended use of medications and reveal the ineffectiveness and adverse effects of drug interactions on mental health. The use of benzodiazepines and sedative-hypnotics is significantly associated with a negative perception of mental health. Benzodiazepines do not improve symptoms or significantly reduce their severity. SSRI antidepressants do not enhance mental health perception; however, when used exclusively, they are effective in reducing the severity, but not the prevalence, of cognitive symptoms. Conclusions: The results highlight the complexity of pharmacological management in FM and raise concerns about the inappropriate use of ineffective or counterproductive drug interactions affecting patients’ mental health. They underscore the need for multidisciplinary and personalized strategies that include close and careful monitoring, as well as the simultaneous use of non-pharmacological treatments that have demonstrated evidence in improving quality of life without negatively affecting mental health, such as patient education, psychological therapy, physiotherapy, and mindfulness.

Introducción: el contacto con la naturaleza es fundamental para la salud física y mental de las personas, especialmente en estudiantes universitarios. Sin embargo, este vínculo se ha ido perdiendo en las últimas décadas debido al crecimiento de las ciudades. El objetivo de este estudio fue comparar el nivel de contacto directo con el medio natural en estudiantes universitarios chilenos según la zona geográfica donde habitan. Métodos: se realizó una investigación cuantitativa con un diseño descriptivo analítico. Participaron 272 estudiantes de 6 universidades chilenas ubicadas en diferentes zonas geográficas (norte, centro y sur). Se aplicó la escala de contacto con la naturaleza de manera online. Se utilizó la prueba de Kruskal-Wallis para determinar diferencias significativas entre las distribuciones de respuesta según zona geográfica. Resultados: los estudiantes de la zona central reportaron mayor contacto con la naturaleza en su vida cotidiana (45,40 % en niveles 4-5). En excursiones, los del sur lideraron (45,16 % en niveles 4-5). En actividad física, los del sur también presentaron los mayores porcentajes (58,06 % en niveles 4-5). Se encontraron diferencias significativas entre zonas en todas las dimensiones (p<0,05). Conclusiones: en general, los estudiantes presentan un bajo contacto con entornos naturales, siendo los de la zona norte quienes reportan los niveles más bajos. Esto evidencia la necesidad de incluir más áreas verdes en las instituciones educativas, especialmente en el norte y grandes ciudades, para fomentar el vínculo con la naturaleza y sus beneficios en la salud y desarrollo de los estudiantes.

Se presentan resultados de ensayos de conexiones de momento viga-columna de racks de almacenamiento. Se realizaron ensayos cuasi-estáticos usando un actuador electromecánico controlado por desplazamiento a conexiones con dos diferentes torques de apriete de pernos. El montaje experimental contempla una columna 1.48 m de largo, rotulada en sus dos extremos, y una viga de largo 1.72 m. El actuador cuenta con una celda de carga de 900 kg de capacidad en su extremo de conexión con la viga y registra ladeformación aplicada mediante un sensor de desplazamiento de recorrido de 300 mm. La viga fue instrumentada con sensores de giro, disponiendo uno justo antes del apoyo, y dos en el perfil L que la conecta con la columna. El forzante corresponde a secuencias de desplazamiento cíclico tipo serrucho con amplitudes crecientes, adaptada del AISC341 (2022) sección K. Los resultados mostraronque, al incrementar el torque de 54.2 Nm a 108.5 Nm, la rigidez elástica se incrementó en un 45%. Un mayor torque de apriete generó reducción en el pinching y aumento en la energía disipada de la conexión, en comparación al caso con menor torque. En general, las conexiones fueron capaces de resistir rotaciones de hasta 0.07 rad.

Today, new materials based on natural fibres have been emerging day by day to completely eradicate plastics to favour our environmental nature. In this view, the present work is based on the extraction and characterisation of the novel root fibres of the Zea mays (Zm) plant, grown by the hydroponic method. Both the dried untreated and alkali treated root fibres are investigated using a variety of structural, morphological, thermal, elemental and mechanical tests by subjecting both the samples to p-XRD, FT-IR, SEM-EDAX, TGA-DTA, CHNS and tensile strength analyses. Thermal conductivity of the untreated and treated fibres is found using Lee’s disc experiment. From p-XRD analysis, the Crystallinity Index, Percentage Crystallinity and Crystallite size of the samples are found. FT-IR studies clarify the different vibrational groups associated with the fibre samples. SEM images show that the surface roughness increases for the chemically treated samples, such that it may be effectively utilised as reinforcement for polymeric composites. The diameter of the fibre samples is found using SEM analysis. According to the EDAX spectrum, Zm fibres in both their raw and processed forms have high levels of Carbon (C) and Oxygen (O). The TGA-DTA tests revealed that the samples of natural fibre have good thermal characteristics. CHNS studies show that Carbon content is high for these samples, which is the characteristic of many natural fibres. Chemical analysis is used to ascertain the prepared samples’ chemical makeup. It reveals that both samples have significant amounts of cellulose. The density of the fibres is found to be in the range 0.3–0.6 g/cc, which is much less than any other natural fibre. Therefore, it can be used in light weight applications. From the tensile strength analysis, physical properties such as Young’s modulus and micro-fibril angle are determined. The fibres in the roots exhibit a lower tensile strength. Thus, these fibres can be used in powdered form as reinforcement for natural rubber or epoxy composites. After examining all of its properties, it could be reasonably speculated that Zea mays root fibres can be considered as an efficient reinforcement for various matrices to produce attractive bio-composites.

There have been efforts to use building demolition waste as an alternative aggregate in concrete to decrease the use of natural resources for construction. The World Green Building Council estimates that the construction industry is responsible for more than 50% of all material extracted globally and that construction and demolition waste makes up 35% of global landfills. As a result, incorporating recycled aggregate (RA) in concrete production is a prudent course of action to reduce the environmental impact. This study reviews prior research on using recycled aggregate instead of conventional ingredients in concrete. The composition and morphology of different types of RA, the behavior of RA in fresh and hardened states, keyword co-occurrence and evolution analysis, and the various additives used to enhance the inferior properties of RA are discussed. The RA showed different physical properties when compared with natural aggregate. However, the addition of pozzolanic materials and various pretreatment techniques is desirable for improving the inferior properties of RA. While building waste has been utilized as a substitute for fine and coarse aggregate, prior research has demonstrated that a modified mixing approach, an adequate mixing proportion, and the optimum replacement of cementitious materials are necessary. Based on the review, the recommendation is to use RA at a replacement level of up to 30% and the addition of precoated and pozzolanic materials as a treatment to provide concrete with adequate workability, strength, and durability for structural applications.