Resumen en Inglés:

Abstract In this paper, the transient dynamics of a rotor-foundation-structure-soil system is studied to obtain unbalance response of the rotor considering the influence of the structure and the unbounded soil. Transient responses are obtained through iterative coupling between the rotor subsystem and the frame-soil subsystem. The non-linear rotor subsystem is represented by a Laval rotor with rigid bearings and external and internal damping. These equations of motion are solved with the fourth-order Runge-Kutta method. The frame is modeled by the Finite Element Method, while the homogeneous half-space is modeled by the 3D Direct Boundary Element Method in the frequency domain. To derive time-domain equivalent equations of motion, a methodology is proposed based on extracting modal parameters from Frequency Response Functions of the coupled soil-foundation system, using the Rational Fraction Polynomial Method. The methodology renders transient response for the rotor and structure with small time steps, allowing an accurate simulation of the rotor runup phase and the dynamics of the system going through resonance frequencies.

Resumen en Inglés:

Abstract This study proposes a multi-scale model formulation for saturated porous media, centered on the concept of the Representative Volume Element (RVE). The linkage between scales is established by enforcing the equivalence of the total virtual power per unit volume at the larger scale with its corresponding volume-averaged counterpart at the smaller length scale. By employing the Principle of Multiscale Virtual Power (PMVP) along with appropriate constraints on micro-scale displacements and pore pressures, a robust variational theory is established. The formulation can be implemented using the finite element squared (FE2) strategy through spatial discretization. The theoretical evidence presented in this work reveal a pathological inconsistency in the objectivity of the macro scale response with respect to the RVE size. The primary contribution of this work is to offer an alternative solution to the aforementioned issue, aiming to restore the fundamental concept of RVE. To achieve this, a conveniently fine-scale constitutive approach is proposed, introducing useful adjustments in the micro-scale pore pressure field expansion.

Resumen en Inglés:

Abstract This work develops a topology optimization method for multi-component structures to minimize dynamic compliance under harmonic loads. While most research focuses on single-domain systems, real structures are complex multi-component assemblies. This study proposes a methodology for optimizing multi-component structures under dynamic loading, evaluating compliance minimization in the frequency domain. The approach involves four steps: multi-component mesh generation, dynamic analysis via Finite Element Method, sensitivity analysis using an adjoint method, and an optimization solver. The optimization follows the SIMP (Solid Isotropic Material with Penalization) method. To improve stability, Helmholtz filtering and Heaviside projection are applied. The problem addresses dynamic compliance minimization and stiffness maximization, presenting case studies of 3D structures with different substructuring conditions. A key finding is the emergence of structural connectivity issues under high-frequency excitation, highlighting a critical challenge for dynamic topology optimization.

Resumen en Inglés:

Abstract This work presents a methodology for stress-based topology optimization using the bidirectional evolutionary structural optimization method, considering static failure theories. The base problem is formulated in a general form as the maximization of the P-measure — an aggregation function derived from the P-norm — of the safety factor associated with an arbitrary static failure criterion, under a volume constraint. The formulation is examined for von Mises-Hencky and Drucker-Prager static failure theories, allowing the proposed approach to be applied to a wide range of ductile and brittle materials. Through selected numerical examples, it is demonstrated that the method successfully produces topologies with maximum stress magnitudes consistent with reference results for the von Mises-Hencky criterion. Moreover, it achieves topologies with reduced stress concentration and higher safety factors compared to the traditional mean-compliance-based approach when using the Drucker-Prager failure criterion.

Resumen en Inglés:

Abstract The operation of offshore platforms depends on the functions performed by umbilical cables, among other structures. These slender multi-layered structures are designed to resist stresses imposed on them by the sea current and movement of the free-surface platform. Therefore, design interest lies on knowledge regarding their dynamic behaviour, in particular, their damping properties. The present work aims to experimentally characterize the structural damping ratio of a 6-meter long sample of a real umbilical cable, by means of decay tests and cyclical bending tests in air. Two dissipation regimes were observed during the decay tests. The most intense one, characterized by internal accommodation, is preponderant for larger displacements. It induces substantial increases in the damping ratio and natural oscillation period. The cyclical bending test corroborate this scenario. Furthermore, an assessment of the model applied to evaluate the damping ratio from the bilinear hysteretic cycle revealed an overestimation of this quantity for large pos-slip displacements. A correction is proposed.

Resumen en Inglés:

Abstract This work addresses the challenge of detecting early-stage scour damage, a hidden, leading cause of roadway bridge failures, using indirect monitoring data. The main contribution is the systematic investigation of the Convolutional Neural Network (CNN) capability to detect low-intensity damage, representing the initial stages of foundation scour, under a comprehensive set of Environmental and Operational Variabilities (EOVs). The dataset is generated from a numerical finite element code (VBI-2D) simulating the vehicle-structure dynamic interaction. Damage is modeled as a reduction in foundation support stiffness at the midspan. The EOVs incorporated include variations in vehicle properties, speed fluctuations, and stochastic road surface irregularities (ISO Class 'A'). Additionally, the study evaluates the damage-classification performance for different sensor locations along the vehicle and quantifies the uncertainties arising from both data variability and the stochastic nature of the learning algorithm. The optimal CNN architecture accuracy demonstrates the feasibility of using supervised CNNs with indirect monitoring data for early scour detection in highway bridges.