Dr. Maureira-Carsalade, Nelson

This paper introduces a system allows for seismic isolation of the pallet from the rack in the down-aisle direction, occupies minimal vertical space (5 cm) and ±7.5 cm of deformation range. A conceptual model of the isolation system is presented, leading to a constitutive equation governing its behavior. A first experimental campaign studying the response of the isolation system's components was conducted to calibrate the parameters of its constitutive equation. A second experimental campaign evaluated the response of the isolation system with mass placed on it, subjected to cyclic loading. The results of this second campaign were compared with the numerical predictions using the pre-calibrated constitutive equation, allowing a double-blind validation of the constitutive equation of the isolation system. Finally, a numerical evaluation of the isolation system subjected to a synthetic earthquake of one component. This evaluation allowed verifying attributes of the proposed isolation system, such as its self-centering capacity and its effectiveness in reducing the absolute acceleration of the isolated mass and the shear load transmitted to the supporting beams of the rack.

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.

This research assesses the feasibility of recycling copper mine tailings (CMT) by analyzing the durability and mechanical characteristics of cement mortar using these tailings as filler additives. CMT are mineral wastes generated during the process of mining. In this work, specimens of cement mortar were incorporated with up to 30 wt.% of a CMT. Bulk density, dynamic modulus of elasticity, apparent density, ultrasonic pulse velocity, flexural and compressive strengths tests were evaluated. Total amount of voids, sorptivity, water absorption and chemical resistance tests were also obtained to evaluate the mortar durability. When10wt.%CMTwasincorporated, overall amount of voids in the mortar was reduced by 20% and mechanical performance was improved by 16% after 28 days. The flexural strength of the mortar was also found to increase, with the 20% wt.% CMT mortar incorporation reaching a flexural strength of 5.89 MPa. Thus represents 16% increase compared to the control 0% CMT strength. The results indicated that there was not a perfect correlation between these results and the mechanical strength results for the 15and 20wt.% CMT mortars. In addition, the CMT acts as a protective barrier against harmful chemicals. The results of this research indicate that reusing CMT by incorporating into cement mortar is a feasible method for their recycling. Mortar made with as much as 15 wt.% CMT presented the same strength and durability as mortar with traditional sand and cement.

The steel-concrete composite column comprises a steel core and surrounding concrete. The purpose of the system is to provide analysis and design techniques for a newly invented class of laced steel-concrete composite short columns for cyclic axial loads. To minimize the increasing density issues associated with nominal strength concrete and in consideration of the depletion of natural resources required to produce concrete, factory-obtained lightweight sintered fly ash aggregates with and without basalt fiber are employed. The normal-weight concrete containing basalt fiber is shown to be more ductile than any other column. The axial deformation of columns LNA and LSA at failure was found to be 3.5 mm, whereas columns LNAF and LSAF reached an axial shortening of 4.5 mm at failure. The column LSAF was found to have 5.3% more energy absorption than the LSA and 11.5% less than the column LNAF. It was observed that the rigidity of these fabricated components had been enhanced. It was found that the section configuration with a lacing system had improved confinement effects and ductility. Comparing the finite element analysis to the experimental data revealed a strong connection with numerical modeling, with a variance of around 8.77%.

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.

Introducción: el haplotipo GA de los polimorfismos rs1554483 y rs4864548 se ha asociado con componentes del síndrome metabólico como la hipertensión arterial y los niveles de triglicéridos. Sus portadores presentan un riesgo de obesidad 1,5 veces mayor que el resto de la población. Metodología: se obtuvieron los SNP rs1554483 y rs4864548 de 2504 individuos desde la base de datos “1000genomes phase 3”. Los datos se agruparon en cinco macropoblaciones (África, Asia Oriental, Asia Meridional, Europa y Latinoamérica) cubriendo un total de 26 poblaciones. Se analizaron las diferencias en la frecuencia del haplotipo entre las macropoblaciones y las poblaciones, para lo cual se utilizó el estadístico F de Fisher. Resultados: la macropoblación de África presentó la menor frecuencia (17,9 %) y la del Este de Asia la mayor (57,4 %). Dentro de las poblaciones existe una relativa homogeneidad en las frecuencias, excepto en el caso de las que componen la macropoblación de Latinoamérica, donde la población peruana de Lima y la puertorriqueña presentan frecuencias mucho mayores que el resto. Conclusiones: el haplotipo GA presenta heterogeneidad entre las macropoblaciones, lo que sugiere procesos microevolutivos altamente dife- renciados entre los continentes. Se propone estudiar la asociación del haplotipo GA con otros polimorfismos, como rs3749474, rs11932595 y rs6859524, que también se han asociado con el riesgo de obesidad y factores asociados al síndrome metabólico.