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Journal articleWang J, Mo YL, Izzuddin B, et al., 2023,
Exact Dirichlet boundary Physics-informed Neural Network EPINN for solid mechanics
, COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING, Vol: 414, ISSN: 0045-7825 -
Journal articleJunda E, Malaga Chuquitaype C, Ketsarin C, 2023,
Interpretable machine learning models for the estimation of seismic drifts in CLT buildings
, Journal of Building Engineering, Vol: 70, Pages: 1-20, ISSN: 2352-7102An accurate estimation of drift demands is crucial for designing and assessing structures under seismic loads. Given the novelty of massive timber buildings, predictive models for the estimation of drifts in mid- to high-rise CLT structures are lacking, particularly in the form of simple models suitable for preliminary design evaluations or regional seismic assessments. In this paper, we present and compare several Machine Learning (ML) models for the estimation of peak inter-storey and roof drifts in multi-storey Cross-Laminated Timber (CLT) walled structures. The ML techniques used include: Multiple Linear Regression, Regression Trees, Random Forest, K-nearest Neighbour, and Support Vector Regression. To this end, 69 structures spanning mid-rise to tall timber buildings are subjected to a large collection of acceleration records and used to create the training and testing datasets. Different structural configurations and behaviour factors, related to the assumed energy dissipation capacity of the buildings, are considered. A diversity of feature selection techniques informs our choice of parameters to the reduced input space leading to a set of six most efficient features: the spectral acceleration at the building’s fundamental period (Sa(T1)), the Peak Ground Velocity (PGV), tuning ratio (T1/Tm), behaviour factor (q), wall height (Hw), and the wall subdivision ratio (Wr). After verifying the high accuracy of our model predictions, the SHapley Additive exPlanation method (SHAP) is used to gain insight into the influence of key input features on the ML model outputs. Finally, our ML drift estimations are compared against previous proposals and design code assumptions, and the potential causes of disagreement are discussed.
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Conference paperEl Ashri MS, Grosman S, Macorini L, et al., 2023,
Numerical investigation of 3D response characteristics of masonry bridges by detailed mesoscale masonry models
, IALCCE 2023, Publisher: Taylor & Francis Group, Pages: 1352-1359This paper adopts a detailed 3D mesoscale modelling strategy to tackle the pressing challenge of assessment for masonry arch bridges. Most of these structures have undergone severe deterioration during their service-life under both increasing traffic loads and environmental actions. However, they still represent a major portion of existing infrastructure for roadway and railway traffic in Europe. The development of reliable assessment methods for such structures is urgently required. However, this is clearly hindered by their complex behaviour. In the adopted modelling strategy, the heterogeneous nature of masonry arch bridges is addressed by adopting a discrete mesoscale modelling for masonry components in conjunction with a continuous modelling for backfill. In addition, the interaction between the different bridge parts is accounted for using nonlinear interface elements at the physical interfaces, where a mesh tying approach is employed to connect non-conforming meshes. The computational effort associated with such detailed models is efficiently optimised using a domain partitioning technique, where the bridge is subdivided into smaller partitions allowing for an efficient parallel computation. This modelling strategy aims at capturing the overall behaviour of masonry arch bridges, which is dominantly three-dimensional mainly due to the asymmetry of typical traffic loads and the complex geometry in the case of skew bridges. In the paper, the response of realistic 3D bridge samples with various loading and geometric configurations is investigated leading to an improved understanding of their typical 3D behaviour to collapse.
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Journal articleZahra F, Macedo J, Malaga Chuquitaype C, 2023,
Hybrid data-driven hazard-consistent drift models for SMRF
, Earthquake Engineering and Structural Dynamics, Vol: 52, Pages: 1112-1135, ISSN: 0098-8847The seismic design and assessment of steel moment resisting frames (SMRFs) rely heavily on drifts. It is unsurprising, therefore, that several simplified methods have been proposed to predict lateral deformations in SMRFs, ranging from the purely mechanics‐based to the wholly data‐driven, which aim to alleviate the structural engineer's burden of conducting detailed nonlinear analyses either as part of preliminary design iterations or during regional seismic assessments. While many of these methods have been incorporated in design codes or are commonly used in research, they all suffer from a lack of consideration of the causal link between the seismic hazard level and the ground‐motion suite used for their formulation. In this paper, we propose hybrid data‐driven models that preserve this critical relationship of hazard‐consistency. To this end, we assemble a large database of non‐linear response history analyses (NRHA) on 24 SMRFs of different structural characteristics. These structural models are subjected to 816 ground‐motion records whose occurrence rates and spectral shapes are selected to ensure the hazard consistency of our outputs. Two sites with different seismic hazards are examined to enable comparisons under different seismic demands. An initial examination of the resulting drift hazard curves allows us to re‐visit the influence of salient structural modelling assumptions such as plastic resistance, geometric configurations and joint deterioration modelling. This is followed by a machine learning (ML)‐guided feature selection process that considers structural and seismic parameters as well as key static response features, hence the hybrid nature of our models. New models for inter‐storey drift and roof displacements are then developed. A comparison with currently available formulations highlights the significant levels of overestimation associated with previously proposed non‐hazard consistent models.
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Journal articleZhang R, Gardner L, Amraei M, et al., 2023,
Testing and analysis of additively manufactured stainless steel corrugated cylindrical shells in compression
, Journal of Engineering Mechanics, Vol: 149, ISSN: 0733-9399Initial geometric imperfections have been identified as the main cause for the large discrepancies between experimental and theoretical buckling loads of thin-walled circular cylindrical shells under axial compression. The extreme sensitivity to imperfections has been previously addressed and mitigated through the introduction of stiffeners; however, sensitivity still remains. Optimized corrugated cylindrical shells are largely insensitive to imperfections and hence exhibit excellent load-bearing capacities, but their complex geometries make their construction difficult and costly using conventional manufacturing techniques. This was overcome in the present study through additive manufacturing (AM). Nine optimized corrugated shells with different diameter-to-thickness ratios, together with one reference circular cylindrical shell, were additively manufactured by means of powder bed fusion (PBF) from austenitic and martensitic precipitation hardening stainless steel. The structural behavior of the AM shells was then investigated experimentally with the testing program comprising tensile coupon tests, measurements of basic geometric properties, and axial compression tests. Numerical analyses were also conducted following completion of the physical experiments. The experimental and numerical results verified the effectiveness of optimized corrugated cylindrical shells in achieving improved local buckling capacity and reduced imperfection sensitivity. Initial recommendations for the structural design of the studied cross-sections are made.
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Journal articleZhang Y, Thiers-Moggia R, Málaga-Chuquitaype C, 2023,
Impact and clutch nonlinearities in the seismic response of inerto-rocking systems
, Bulletin of Earthquake Engineering, Vol: 21, Pages: 1713-1745, ISSN: 1570-761XRocking bodies can be found at all structural scales, from small museum exhibits to uplifting buildings. These structures, whose dynamic stability springs from the difficulty of mobilizing their rotational inertia, are ideal candidates for benefiting from the supplemental inertia provided by inerters. This benefit can be limited, however, if the inerter drives the structural response towards potentially undesirable motions by transferring back the kinetic energy accumulated within it at inconvenient times. To control this phenomenon, a clutching system can be employed to direct the interaction between the interter and the structure improving further its dynamic behaviour. To date, however, most of the studies dealing with clutching inerto-elastic or inerto-rocking systems under seismic excitation have adopted a rather simplistic idealisation of the clutch engagement-disengagement response. In this paper, we re-visit the impact effects on inerto-rocking structures and propose an improved mechanistic model of the clutching system. First, the effects of the inerter on the transition upon impact and the impact effects on the acceleration response of rocking blocks are analysed. Then, a set of original analytical expressions for rigid and flexible rocking structures equipped with a pair of clutched inerters are derived. The newly proposed models are used to examine the evolution of the energy dissipation in the device and the influence of key parameters like the clutch stiffness, gears play, viscous damping and dry friction on its response. We conclude by evaluating the behaviour of the detailed rocking model with clutched inerters to a set of realistic earthquake ground motions. Although important differences are observed in the evolution of energy dissipation and engagement response depending on the type and characteristics of the clutch model, largely comparable peak values of displacement are obtained. On the other hand, a more accurate representation of the clutch b
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Conference paperShehzad MK, Forth JP, Nikitas N, et al., 2023,
Investigation of the influence of external edge restraint on reinforced concrete walls
, Pages: 622-633, ISSN: 2474-3941Externally restraining volume changes of concrete, i.e., thermal effects and shrinkage, may result in tensile stresses and eventually cracking. Such cracking risk is controlled / mitigated by the provision of steel reinforcement, which presumes correct understanding of the cracking patterns under different types of restraint conditions. Reinforced concrete (RC) members may be restrained at their edges or end, or in many cases a combination of the two. Existing guidance on the subject is mostly based on end restrained members, however it is applied to predict the behaviour under edge restraint too. Researchers have identified that the mechanisms of cracking associated to edge and end restraints are quite different. To this purpose, findings from an experimental investigation aiming to understand the behaviour of edge restrained RC walls were utilized to validate a finite element (FE) model. Subsequently, this FE model was used to study the edge restrained walls having different aspect ratios. Cracking patterns, widths and extent appeared to greatly depend on the wall aspect ratio. The study provides clear evidence on why similar studies related to all forms of restraint are needed to support engineers in designing against cracking due to restraints.
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Conference paperGrosman S, Fang Q, Macorini L, et al., 2023,
Multi-fidelity modelling of masonry arch bridges under traffic loading
, Pages: 1368-1375Masonry arch bridges are part of the historical heritage from the Industrial Age in the UK and Europe. To preserve this infrastructure, robust assessment methodologies are required to adequately account for the effects of evolving loading and material degradation. This work presents 3D multi-fidelity modelling strategies for masonry viaducts which can be used for accurate assessment. The masonry components of the bridge structure are modelled using high-fidelity mesoscale models or efficient macroscale models. Filling materials are represented using elasto-plastic models considering their cohesive and frictional nature. The interaction between the different parts is taken into account by adopting nonlinear interface elements allowing for sliding and separation. The results of numerical investigations on a realistic viaduct under traffic loading, which were conducted by performing nonlinear simulations under transient loading, showcase the potential of accurate 3D modelling comparing the results from mesoscale and macroscale models.
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Conference paperGrosman S, Fang Q, Macorini L, et al., 2023,
Computational strategy for the design of monitoring for masonry arch bridges using DIC procedures
, Pages: 1530-1537Masonry arch bridges are old structures characterised by a complex behaviour. Detailed monitoring is essential to improve the understanding of the response under different loading conditions, to identify damaged structures, and to validate numerical models for accurate structural assessment. Generally, standard monitoring techniques necessitate direct access and contact to the analysed structure, which can be problematic in many cases. The use of Digital Image Correlation (DIC) overcomes these critical limitations offering an improved potential for detailed and streamlined monitoring. This work focuses on the development of advanced computational tools to support the practical application of DIC monitoring in field conditions. The proposed procedure utilises results from 3D numerical models to generate synthetic video files representing the bridge response under traffic loading, which can be subsequently employed to calibrate camera setups for DIC monitoring.
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Journal articleLapira L, Gardner L, Wadee MA, 2023,
Elastic local buckling formulae for thin-walled I-sections subjected to shear and direct stresses
, Thin Walled Structures, Vol: 182, ISSN: 0263-8231Formulae for calculating the elastic local buckling stresses of doubly-symmetric thin-walled I-section girders subjected to combined shear and direct stresses, accounting for the interaction between the plate elements are presented. The interaction between the plate elements (i.e. the flanges and web) is bounded by a theoretical lower-bound, where there is no interaction and the critical plate is considered to be simply-supported, and a theoretical upper-bound where interaction is strongest and the critical plate is considered to have rotationally fixed edges. The interaction is accounted for by introducing an interaction coefficient ζ that quantifies the relative level of fixity between the aforementioned lower and upper bounds. Expressions to calculate ζ are calibrated using results from finite element analyses generated in Abaqus. Doubly-symmetric I-sections of varying geometric proportions loaded in shear, major axis bending, compression and a full range of combinations thereof are considered. Using the developed formulae, the elastic local buckling stresses of the studied cross-sections are accurately predicted, typically within 5% of the values obtained from FE models; this is a significant improvement over the results determined in the traditional manner in which plate element interaction effects are ignored, where the full cross-section buckling stress is shown to be underestimated by as much as 40%.
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