PROBABILISTIC STRUCTURAL ANALYSIS

Determination of Dynamic Characteristics for an Aerospace Structure Using Experimental and Numerical Methods

This research provides an in‐depth investigation into the dynamic behavior of a riveted aerospace structural component, integrating both experimental testing and numerical simulations. The primary objective is to validate a Finite Element Analysis (FEA)‐based computational methodology for accurately identifying the natural frequencies and corresponding mode shapes of complex mechanical assemblies used in the aerospace industry. The physical component was modeled in CATIA V5 based on precise dimensional measurements and subsequently analyzed in COMSOL Multiphysics to obtain a detailed numerical representation. In parallel, an experimental campaign was carried out using the Bump Test for Resonances (BTR) under fixed boundary conditions, with vibration data recorded through a high‐resolution laser vibrometer system. The comparison between numerical and experimental outcomes demonstrated strong agreement, confirming the accuracy and reliability of the developed computational model. The validated approach proves suitable for assessing the vibrational response of aerospace structures, particularly in cases where structural integrity may be affected by manufacturing imperfections or operational degradation. Moreover, the findings establish a solid foundation for future research aimed at correlating dynamic characteristics with early indicators of damage, contributing to the advancement of structural health monitoring and predictive maintenance in aerospace engineering.

Reliability Engineering and System Safety

Optimal Design of Geometrically Nonlinear Steel Structures Using Advanced Analysis

Advanced analysis has been shown to improve material efficiency in statically indeterminate steel-framed structures compared with member-based linear elastic design methods. However, limited research has investigated its applicability to geometrically nonlinear steel structures where residual stresses are induced by the bending process. In this study, the material optimization potential of advanced analysis has been quantified for two arch-based structures by comparing the volume of steel required to satisfy the criteria of both the system and member-based analysis methods in accordance with AS 4100:2020. The two structures were analyzed using the finite element analysis software Strand7 (R3.1.6) and subjected to combined gravity and wind loading in alignment with the serviceability and ultimate limit states specified in AS 1170.0:2002. System behavior was analyzed through the Arc-length plastic zone method. The results indicate that in one of the arch-based structures, advanced analysis can improve material utilization by 8.1%. Provided that future research both validates the use of the reduced stiffness method for treatment of initial geometric imperfections and verifies system reliability factors for structures with curved geometries, advanced analysis presents a practical design method for this structure. Comparison of the two case studies found that advanced analysis has the potential to improve material efficiency only when linear elastic failure is governed by ultimate limit state criteria. It is therefore evident that the material optimization findings of this research cannot be generalized to all arch-based structures, as they are contingent upon the geometry of the model analyzed, the loading scenarios considered, and the deflection limits adopted.

A computational model for probabilistic analysis using the pseudo-dynamic method: a case study of the effects of seismicity on the structural behavior of the Jucazinho Dam in Pernambuco

Abstract The study of the behavior of gravity dams under seismic actions has, over time, been little explored in engineering projects in Brazil. In Brazil, although the occurrence of large magnitude earthquakes is uncommon, seismicity is not zero, especially in passive margin areas with intraplate seismicity. This study presents a method for evaluating the probability of seismic fragility of a dam's structural system. The method is based on computational simulation procedures involving pseudo-dynamic analyses and kriging modeling to establish the probabilistic characterization of the structure's safety factors, taking into account uncertainties in parameters related both to material properties and loading conditions, as well as ground motion characteristics. Stress analysis revealed critical concentration near the gallery, with maximum tensile stresses of 2.69 MPa and compressive stresses of -2.39 MPa. In stability assessment, all sliding safety factors exceeded the minimum design threshold (1.0), with the most critical case observed in the intermediate section under full reservoir conditions (1.05). Probabilistic analysis indicated failure probabilities ranging from 10−3 to 3.74 × 10−2 and reliability indices between 1.60 and 3.09, identifying the dam-foundation section as the most vulnerable and the intermediate section as the most resilient. The results highlight that foundation stiffness plays a decisive role in dam response, amplifying dynamic effects through multidomain interaction. Overall, the integration of numerical modeling with probabilistic methods proved effective for identifying critical sections, quantifying uncertainties, and supporting monitoring and reinforcement strategies. This approach strengthens dam safety management, contributing to failure prevention and mitigation of potential socio-economic impacts.

STRUCTURAL MASS PROPERTY

A Mechanics-Based Sensitivity Analysis of Nuclear Piping Stress Under Design-Parameter Uncertainty

Design deviations introduced during the fabrication and installation of nuclear-grade piping systems can alter structural response and substantially increase reanalysis effort. This study develops a mechanics-based framework to identify critical parameters controlling the code-stress ratio of a representative nuclear piping system. Finite-element analysis, Monte Carlo sampling, and Sobol global sensitivity analysis were combined to evaluate the effects of gravity, thermal-pressure loading, and seismic excitation. The results show that parameter sensitivity is strongly load-dependent. Under Level-A conditions, the response is governed mainly by constrained thermal deformation, and the dominant parameters are support locations that control deformation compatibility and the redistribution of secondary stress. By contrast, structural and weight-related parameters have only limited influence in this regime. Under Level-D conditions, however, the governing mechanism shifts to inertia-driven amplification. The dominant variables then become those associated with dynamic constraint, concentrated mass, and eccentric loading, including key support positions, valve eccentricity, and valve weight. Multi-parameter analyses further reveal clear interaction effects, showing that simultaneous deviations in critical supports, concentrated masses, or eccentricities can significantly amplify the stress response and, in some cases, drive the stress ratio beyond the allowable limit. These results show that the mechanical importance of design parameters depends on both the loading regime and system-level parameter interactions, and they provide a quantitative basis for condition-specific tolerance allocation in nuclear piping design.