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.

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.

An improved numerical formulation for a self-centering frictional damper is presented. This was experimentally validated through quasi-static tests carried out on a steel-made prototype of the damper. Its design is ad hoc for implementation in the seismic protection of industrial storage racks. The conceptual model of the device was adjusted to the prototype built. The formulation of the analytical model, a parametric analysis of it, and the validation with experimental results are presented. The improvement of the model presented here explicitly considers elements included in the prototype, such as a system of load transmission rings and the friction between all of the components that slide or rotate relatively. In the experimental validation, the parameters of the improved model were determined. The numerical predictions for the improved model were contrasted with those obtained with the original one and with the experimental results. This demonstrates that the improvement leads to a better adjustment of the numerical predictions concerning the experimental measurements, which is useful for nonlinear analysis. The device withstood forces of considerable magnitude in addition to dissipating enough energy per load–unload cycle to be effective in the seismic protection of industrial storage racks.

A novel energy dissipation device is proposed to protect structures against dynamic loads. A conceptual model of the device is presented, describing the fundamental components of its operation. This model has a linear elastic element and a frictional damper. The equilibrium equations that lead to the relationship that governs its behavior are proposed. A functional model of the device was built on a 3D printer with PLA filament. Experimental trials were carried out to characterize its elastic component and the coefficient of friction of the damping parts. Proofs of concept load-unload tests were also carried out on the device, subjecting it to cyclical movement sequences. The results of the first two types of tests allowed the parameters of the previously developed analytical model to be calibrated. The results of the load-unload tests were compared with the predictions of the analytical model using the calibrated parameters. Consistency was observed between the experimental and analytical results, demonstrating the basic attributes of the device: self-centering capacity, dissipation capacity and force proportional to the displacement demand. It is concluded that the proposed device has the potential to be used effectively in the protection of structures under dynamic loads.