Browsing by Author "Medalla, Miguel"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    A mathematical model to simulate the cyclic behavior of exposed base plates with extended anchor bolts in steel moment frames subjected to earthquakes
    (2025) Torres Rodas, Pablo; Medalla, Miguel; López-García González, Diego; Herrera, Marco; Benitez, Diego; Camacho, Óscar
    This paper presents a mathematical model to predict the cyclic behavior of Exposed Base Plates with Extended Anchor Bolts (the EBP-EAB model) typically used in industrial and residential steel buildings in countries located in high seismic zones. The research is motivated by the potential integration of these connections as part of the energy dissipative mechanisms of steel moment frames due to their high deformation capacities and excellent hysteretic characteristics. The EBP-EAB model simulates the connection behavior as an arrangement of two parallel springs. The first spring consists of a trilinear backbone curve and a set of rules for describing unloading, reloading, pinching, and modes of cyclic deterioration for strength and stiffness. The second spring allows the simulation of the intermediate plateau observed in the connection response by means of a multi-linear elastic material, where the behavior is nonlinear but elastic. A total of 10 parameters are required to define the coordinates of the EBP-EAB model, where six parameters (core) are obtained using mechanical principles while the remaining four (ancillary) are obtained using a constrained optimization process. Four bio-inspired optimization algorithms were explored to find the best solutions to minimize the error defined in this paper for the empirical calibration of the ancillary parameters. Validation results show that the EBP-EAB model is capable of integrating the features of the nonlinear behavior observed in these connections with reasonable accuracy. Recommendations for estimating the core parameters are detailed, while limitations of the EBP-EAB model are outlined. Finally, as an example application, the model is implemented in a nonlinear dynamic analysis of a steel moment frame representative of an office building subjected to earthquake loading. Results indicate that the model is numerically robust and that the frame equipped with EBP-EABs achieves similar interstory drift demands to those with conventional base plate connections, while preventing plastic hinge formation in the columns.
  • No Thumbnail Available
    Item
    Cyclic behavior and design methodology of exposed base plates with extended anchor bolts
    (2022) Torres-Rodas, Pablo; Medalla, Miguel; Zareian, Farzin; Lopez-Garcia, Diego
    This paper investigates the behavior of a ductile detail of exposed base plates. This detail consists of a base plate anchored to the concrete foundation through bolts extended to a steel chair configuration. The intention is to concentrate plastic strains mainly in the extended region of the anchor bolts, forcing the other connection components to remain elastic. The scientific background of this research consists of a series of sophisticated nonlinear finite element models subjected to a cyclic load protocol in the presence of an axial compressive force. The models were validated against an experimental test reported in the literature. Forces within the connection components, stresses, strain distributions, and deformation modes were examined. A total of sixteen three-dimensional nonlinear models were created using the ABAQUS simulation platform. The models were sepa-rated into two groups: the first consists of models with dimensions similar to the specimens tested in recent experimental programs reported in the past, while the second group simulates connections representative of mid-rise industrial frames. Building on the insights gained from the simulations of the first group, a methodology is proposed to design these column base connections. This suggested methodology is validated with the second group of simulations. Results indicate that the studied configuration detail presents some advantages compared with the traditional detail presented in Design Guide 1. For instance, plastic strains are developed almost exclusively in the anchor rods, and no damage is expected at the remaining components. Another essential characteristic is the exposed stretch length, with which it is possible to achieve a target design rotation without significant strain concentrations in the anchor rods. This characteristic facilitates post-earthquake inspections and repairs, and damage is virtually eliminated in the first story.
  • Thumbnail Image
    Item
    Seismic characterization of steel special moment frames subjected to megathrust earthquakes
    (2020) Medalla, Miguel; López García, Diego; Zareian, Farzin