Dr. Maureira-Carsalade, Nelson

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.

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.

This study examined the relations between permeability of the concrete due to addition of new cracks. The different concrete types analyzed were standard concrete, reinforced steel fiber concrete, and reinforced concrete polypropylene fiber. In consideration of the improved polypropylene content of polypropylene fiber reinforced concrete, the crack diameter was decreased by 72-93% for up to 0.25% fiber and cracks were eliminated with 0.3% fiber inclusion. In terms of steel fiberreinforced concrete, the results showed that steel reinforcing macro fibers decrease the permeability of cracked concrete at wider crack widths. While the permeability of unreinforced concrete was the highest, 0.5% steel content resulted in lower permeability while a higher steel content concrete with 1% steel had the lowest permeability. Crack stitching phenomenon and the effect of multiple cracks may be attributed to the decrease in the permeability. With respect to normal concrete, the findings showed the crack opening displacement at the highest tension is less than 20 microns. At this loading stage, after unloading, around 80% of the displacement is restored and the residual crack opening is notably small, indicating the low impact of cracking on concrete permeability (CP) and showing that CP was increased with crack width. As a result, adding polypropylene aggregate to concrete could significantly reduce the width of crack, while adding steel fiber to concrete reduces the permeability of cracked concrete compared to normal concrete which may result in a minor crack on CP.

A proposal of a semi-rigid self-centering connection for the seismic protection of wooden structures is studied. An analytical model for the characterization of the response of the connection is developed. Quasi-static tests of a wooden column with the proposed connection allowed to validate the model and calibrate its parameters, obtaining errors smaller than 6% between analytical prediction and experimental results. The self-centering capacity and the effectiveness of the connection to limit the loads transmitted to the connected elements were evidenced. Damped free vibration tests evidenced the capacity of the connection to reduce structural vibrations. It was verified that the resistance and dissipation capacity of the connection can be modified by two design parameters that can be adjusted at the assembly. The proposed connection has desirable characteristics for its use in the protection of structural wooden frames, is versatile, and its design is simple, with explicit physical parameters.