Fatigue crack growth analysis of welded bridge details

The paper investigates the fatigue crack growth in typical bridge weldments by means of numerical analysis. The extended finite element (XFEM) method is coupled with the low-cycle fatigue (LCF) approach in ABAQUS, and parametric analyses are carried out in order to assess the influence of the main sample/testing features on the fatigue life of the investigated structures. The numerical results are found to be robust and reliable by performing comparisons with past experimental data and regulation design correlations

Fatigue crack growth in metallic components: numerical modelling and analytical solution

The paper presents innovative approaches for the simulation of fatigue crack growth (FCG) in metallic compact tension (CT) specimens using finite element (FE) analysis and analytical solution. FE analysis is performed in ABAQUS using the extended finite element method (XFEM) coupled with the direct cyclic low-cycle fatigue (LCF) approach. Novel methods are developed for the computation of the numerical crack growth by processing the analysis outputs. The numerical modelling is validated by considering past experimental data. The analytical solution for the fatigue life evaluation is formally reviewed, and novel fatigue damage descriptors are defined. The influence of the main sample/testing features on numerical and analytical fatigue life is extensively assessed by a parametric study. The discrepancy between the numerical and analytical estimations of the fatigue life of the components is investigated and correlated to the features of the testing/modelling. A statistical-based correction factor is finally proposed in order to enhance the analytical solution

Characterisation of the damaging micromechanisms in a pearlitic ductile cast iron and damage assessment by acoustic emission testing

The damaging micromechanisms in a pearlitic (EN-GJS700-2) Ductile Cast Iron (DCI) are investigated by means of Scanning Electron Microscope (SEM) analysis and Acoustic Emission (AE) testing. Monotonic uniaxial tensile tests are performed on microtensile specimens under strain control. SEM analysis is applied under in-situ conditions by means of a tensile holder. The multiple damaging micromechanisms are identified, and their evolution along with the mechanical response is characterised. The traditional AE features are found to be qualitatively correlated to the onset of the fracture damage over the elastic behaviour. The Information Entropy of the AEs evaluated according to both Shannon and Kullback-Leibler formulations is proven to be well correlated to the ongoing damage, and the incipient failure. Tentative failure criteria are finally proposed. The assessment approach is found to be promising for structural health monitoring purposes

Failure criteria for real-time assessment of ductile cast irons subjected to various loading conditions

The paper presents an innovative approach for the damage assessment of ductile cast irons (DCIs) by using a probabilistic-based methodology. The study is based on the experimental results of acoustic emissions (AEs) tests performed on pearlitic DCIs subjected to both monotonic and fatigue tensile loading. The information entropy of the AEs data is confirmed to be well correlated to both the damage progress and the occurrence of the incipient failure. Robust failure criteria are finally provided for real-time assessment in structural health monitoring applications

Analysis of acoustic emission entropy for damage assessment of pearlitic ductile cast irons

The paper shows the preliminary results of uniaxial tension tests on a pearliticDuctile Cast Iron (DCI) by using the Acoustic Emission (AE) technique as wellas the Scanning Electron Microscope (SEM) analysis. The experimental testsdemonstrate the damage initiation and evolution occurring within the graphitenodules produce AE activity. The evaluation of the Shannon Entropy of theAE data is found to promising for the assessment of DCIs

Methodological guidance and quantitative measures regarding seismic capacity and safety of freestanding and inelastic anchored nonstructural elements housed in ordinary and critical facilities

The study provides a comprehensive investigation of the seismic capacity and safety assessment of nonstructural elements (NEs). A general and extendable methodology is developed for robust assessment of two representative model categories of NEs: rocking-dominated rigid blocks (RBs) and inelastic single-degree-of-freedom (SDOF) systems, accounting for most acceleration-sensitive elements housed in ordinary and critical facilities. Numerical analysis is carried out implementing nonlinear dynamic models for NEs and accounting for multiple features, such as loading history types (ground and floor motions), NE dynamic properties, intensity measures (IMs), and multiple damage states (DSs). Quantitative capacity measures are provided, as well as novel closed-form equations are proposed for expeditious capacity assessment of NEs, including both capacity curves and surfaces. The seismic safety of the investigated NEs is estimated considering both ordinary and critical buildings, over low- to high-seismicity sites in Italy

Fatigue crack growth analysis of welded bridge details

The paper investigates the fatigue crack growth in typical bridge weldments by means of numerical analysis. The extended finite element (XFEM) method is coupled with the low-cycle fatigue (LCF) approach in ABAQUS, and parametric analyses are carried out in order to assess the influence of the main sample/testing features on the fatigue life of the investigated structures. The numerical results are found to be robust and reliable by performing comparisons with past experimental data and regulation design correlations.</jats:p

Seismic certification of unanchored components: reliability assessment of the ICC-ES AC156 protocol

The paper presents the preliminary results of a study on the seismic certification of unanchored acceleration-sensitive components by means of shake table testing. The application of the ICC-ES AC156 protocol for seismic assessment of unanchored blocks is preliminarily reviewed. Numerical rigid block analysis of several component geometries is performed considering (a) a wide reference set of real records (ATC63), and (b) artificial inputs generated according to the AC156 protocol. The fragility curves of the components are evaluated considering several damage states, and reliable dimensionless intensity measures. The ATC63 results are compared to the AC156 protocol ones checking whether the protocol records are representative of realistically severe earthquake scenarios. The reliability index related to the protocol is assessed according to the first-order reliability method. The real accelerogram results are considered as a capacity measure, and the protocol ones as demand measure. The criticalities of the AC156 protocol are finally evidenced as well as guidelines for a safe application of the protocol are provided