Numerical Study on Seismic Response of Steel Storage Racks with Roller Type Isolator

Abstract

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.

A Sensitivity Analysis Approach for Assessing the Effect of Design Parameters in Reducing Seismic Demand of Base-Isolated Storage Racks

“…In this regard, Maureira-Carsalade et al [13] developed a numerical model that reproduces the behavior of a novel base isolation kinematic device (BIKD). This device has significant tensile strength, similar to that of Pellegrino et al [14]. Unlike Pellegrino's isolator, the device allows racks to be seismically isolated from an earthquake that attacks them in any horizontal direction.…”

“…The schematic model of the selective rack typology analyzed is shown in Figure 1. In this research, the most common cross sections used for the structural elements were considered in the modeling [1,14,26,27,31,32]: TX 100 × 105 × 3, TC 100 × 50 × 2, CA 45 × 22 × 2 and C 58 × 22 × 2, for the column, beam, horizontal brace, and diagonal brace, respectively. Table 2 shows the properties of those element's cross-sections.…”

“…The event had a magnitude of 8.0 M w and a peak ground acceleration (PGA) of 0.712 g. This was one of the most severe seismic events in central Chile, the most densely populated area of the country. Álvarez et al [14] justify that it is acceptable to use only one seismic record in the dynamic analyzes, when said record has been scaled in the frequency domain to make its response spectrum fit with the design spectrum of any standard or design code. This is because within the range of 0.1 s to 10 s, it is possible to excite virtually any civil structure, achieving a good fit of the response spectrum of the scaled register with any spectrum of design of structures.…”

“…Such tension is transmitted from the BIKD to the superstructure through a connecting cable, allowing the isolator to resist relatively high levels of traction compared with the requesting axial load. In addition, it provides friction energy dissipation in the ball joint that serves as basal support [13,14].…”

“…These density-based methods have been so named because they investigate the probability density function of the model output, rather than just its variance. One of the density-based GSA methods is the PAWN method [10][11][12][13][14][15][16]. This has been used successfully in various investigations focused on environmental and hydrological models [24,25]; however, its use was not found in the area of structural or earthquake-resistant engineering.…”