Browsing by Author "Pinto, Francisco J."

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    (33, 33) Pinto, Francisco J.; Toledo, José; Birrell, Matías; Bazáez, Ramiro; Hernández, Francisco; Astroza, Rodrigo; 33
    Bridges are essential structures in the logistic chain of countries, making it critical to design them to be as resilient as possible. One way to achieve this is through performance-based seismic design (PBSD), which involves using nonlinear Finite Element (FE) models to predict the response and potential damage of different structural components under earthquake excitations. Nonlinear FE models need accurate constitutive models of material and components. Among them, seismic bars and laminated elastomeric bearings play an important role in a bridge’s response to earthquakes; therefore, properly validated and calibrated models should be proposed. Only default parameter values from the early development of the constitutive models widely used by researchers and practitioners for these components tend to be used, and low identifiability of its governing parameters and the high cost of generating reliable experimental data have prevented a thorough probabilistic characterization of their model parameters. To address this issue, this study implements a Bayesian probabilistic framework using Sequential Monte Carlo (SMC) for updating the parameters of constitutive models of seismic bars and elastomeric bearings and proposes joint probability density functions (PDF) for the most influential parameters. The framework is based on actual data from comprehensive experimental campaigns. The PDFs are obtained from independent tests conducted on different seismic bars and elastomeric bearings, to then consolidate all the information in a single PDF for each modeling parameter by means of the conflation methodology, where the mean, coefficient of variation, and correlation between calibrated parameters are obtained for each bridge component. Finally, findings show that the incorporation of model parameter uncertainty through a probabilistic framework will allow for a more accurate prediction of the response of bridges under strong earthquakes.
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    (33, 33) Pinto, Francisco J.; Dashti, Shideh; Ledezma, Christian; Abell, Jose A.; 33
    The construction of tall buildings has recently undergone exponential growth in major cities, creating new challenges in earthquake engineering and design. For instance, existing analytical procedures for evaluating seismic lateral earth pressures on basement walls connected to these buildings typically ignore the inertia and dynamic properties of the superstructure. The inertial forces from a tall superstructure may cause additional displacements and rotations in its basement, affecting the distribution and magnitude of seismic lateral earth pressures. These additional soil-basement-structure-interaction (SBSI) effects are currently not well understood. Hence, the applicability and reliability of existing procedures to the basements of tall buildings remain questionable. In this paper, we use an experimental-numerical approach to provide insight into how the lateral resisting system of tall superstructures may impact the magnitude and distribution of seismic earth pressures on basement walls buried in dry sand and gravel. Numerical simulations are first validated in 3D using a prior centrifuge experiment that included a simplified model of a 42-story, high-rise structure in medium-dense, dry sand. Then, the numerical tool is used to perform 156 2D, nonlinear simulations of more realistic buildings and basements, ground motion characteristics, and sandy and gravely soil profiles. Nonlinear numerical simulations successfully capture the building's inertial and kinematic seismic interactions with the basement and an adjacent underground structure. The subsequent numerical sensitivity study showed that inertial forces from the dynamic lateral movements of the tall superstructure increase the total lateral earth pressures on the basement walls. This increase is particularly notable in the top two-thirds of the basement wall, and it can be approximated by a trapezoidal distribution. These effects and reliability of existing analytical procedures are shown to be highly sensitive to the building's modal frequencies in relation to the frequency content of the input motion as well as the stiffness of the structure-basement system with regard to the underlying soil. The results highlight the importance of considering the building's dynamic properties and inertia in evaluating seismic earth pressures on basement walls to avoid unsafe estimations or the need for overdesign.
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    (33, 33) Pinto, Francisco J.; Ledezma, Christian; Abell, Jose A.; Astroza, Rodrigo; Dashti, Shideh; 33
    The need to build tall buildings has been increasing worldwide, creating new challenges in earthquake engineering and design. Many of the current analysis methods cannot be extrapolated beyond the definition under which they were established. Prior studies and existing seismic design guidelines have indicated that the current fixed-base hypothesis for evaluating the seismic response of structures is not sufficient to properly represent the boundary conditions and behavior of tall buildings with basement levels. Studies of soil-structure interaction (SSI) for tall buildings have, however, typically been inconclusive. It is not clear under which conditions consideration of soil-basement-structure interaction (SBSI) is necessary for the design of the superstructure, foundation, and basement levels and when it can safely be avoided. Given the rising demand, it is essential to evaluate the relation of global system variables such as the basement depth, structure height, and soil characteristics with the building's response via numerical and experimental modeling. Therefore, an experimental-numerical approach is presented to better understand the seismic response of tall buildings with basement levels, considering explicit SBSI modeling. Chilean tall buildings and soil conditions are used as study cases, analyzed using nonlinear finite element analyses in conjunction with results from centrifuge experiments. The results show how seismic response parameters and modal characteristics, such as inter-story drifts, shear force, bending moment, natural frequencies, and damping ratios, change when SBSI is appropriately incorporated. The results point to the importance of considering soil-basement-interaction effects to evaluate the seismic response of tall buildings with basement levels and avoid unsafe estimations or the need for overdesign.