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.

The behavior of the web panel zone has a direct effect on the cyclic performance of steel moment connections. While the mechanisms of web panel zone failure are known under cyclic load, little is known about the behavior of the web panel zone under bidirectional loads in bolted connections. Using experimental tests and calibrated numerical models, this research evaluated the web panel zone behavior under unidirectional and bidirectional cyclic loads. The results showed that bidirectional load can modify the stress and strain distribution in the web panel zone. Moreover, the increasing of the width-to-thickness ratio of the column influences the failure mechanism of the joint configuration and increases the plastic incursion in the column. These data demonstrate that bidirectional effects improve the web panel zone performance under cyclic loads.

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.

In this research, the influence of global slenderness and sliding pallets factor on the seismic design of steel storage racks are assessed. Variations in span length, the height of storage levels, live load, and percentage of live load considered in the seismic mass are studied for different levels of seismic zone and soil type. The models were designed according to the Chilean Code NCh2369. Subsequently, a global sensitivity analysis was developed to analyze the influence of each studied parameter in the seismic design response in terms of fundamental period, drift, and base shear from a response spectral analysis approach. A total of 12000 simulations were performed. Two-hundred additional models were performed to evaluate the variation of seismic mass in the structural response. Results indicate a significant influence of live loads and seismic mass on steel racks designed for soft soils and unbrace conditions. The stiffness also modifies the performance of the racks, mainly in models using braces in the down-aisle direction and cross-aisle direction. In these cases, the seismic mass factor does not have a strong influence on structural response in comparison to the global slenderness.

This research evaluates the effectiveness of using a roller-type base isolation device with tensile strength in reducing the dynamic response of industrial steel storage racks. These were subjected to a seismic input acting separately in both directions of the structure. The seismic record obtained from the earthquake that occurred in Llolleo, Chile, on 3 March 1985, was used as input. This earthquake was scaled in the frequency domain, adjusting its response spectrum to coincide with the design spectrum required by NCh2745. In the calculations of this spectrum, the most hazardous seismic zone (zone 3) and soft soil (soil III) that amplifies the effect of the low frequencies of the earthquake were considered. These frequencies are the ones that have the most affect on flexible structures such as high racks and systems with base isolation. Numerical time-history analyses were performed in fixed base racks and base isolation racks. In both cases, the models include semi-rigid connections with capacity for plastic deformation and energy dissipation. Parametric analyses were carried out considering the most relevant variables, using an algorithm programmed in MATLAB software. The maximum relative displacement, maximum basal shear load, and maximum absolute floor acceleration were considered as responses of interest. The results showed the effectiveness of using the base isolation device by reducing the absolute accelerations between approximately 75% and 90%, compared to the same fixed rack at its base. This makes it possible to reduce the vulnerability of the stored load to overturn under the action of a severe earthquake.

The properties of fibre reinforced concrete were studied under monotonic loads according to Japanese, North American and European codes. Two different types of SIKA polypropylene fibre were with different dosages. One hundred and eighty tests were performed, obtaining resistance to compression, tension, bending, toughness, and energy absorption in the hardened state. The results show that the addition of fibres affects the workability of the concrete mix. The increase in fibre dosage does not affect compressive, tensile, or flexural strength. However, the failure changes from brittle to more ductile, allowing it to reach residual strengths of 50% of the maximum reached and 200% deformation. The dissipated energy increased with increasing fibre dosage. The performance achieved by both fibres was similar, although the optimal dosage was 6 kg/m3 for type A fibres and 8 kg /m3 for type B. Therefore, the replacement of flexural reinforcing steel in the foundation slabs of one-story buildings can be performed if adequate dosages are used in compliance with established analytical procedures for industrial floor design.