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  • Journal article
    Bedrinana LA, Landeo JG, Sucasaca JC, Malaga Chuquitaype Cet al., 2024,

    Over-sampling for data augmentation in data-driven models for the shear strength prediction of RC membranes

    , Structures, ISSN: 2352-0124

    Complex reinforced concrete (RC) structures are generally assessed as a group of individual membrane elements subjected to in-plane combined stresses; however, an accurate prediction of the shear strength of such elements is still a complex task. In addition, the limited availability of experimental data of RC panels, which also presents an unbalanced statistical distribution towards lower strength values, limits the development of data-driven models. Thus, it is crucial to explore data augmentation techniques with a view to supporting the development of more accurate and generalizable predictive models in structural engineering. This paper evaluates over-sampling techniques for data augmentation and their use in the creation of an explainable, data-driven model for the shear strength prediction of RC panels. A dataset of 195 experimental tests of RC panels under different loading conditions is initially collected. Five over-sampling techniques are implemented to extend the original dataset and to reduce the imbalance. Three ensemble models (Random Forest, AdaBoost, and XGBoost) are trained with each of the generated datasets. It is observed that all the over-sampling techniques produced predictive models with better performance than the original dataset; however, the results show that by applying the Random Over-Sampling (ROS) the performance metrics of the model can significantly increase (around 39% for some metrics) compared to the model with the original dataset, without any overfitting issues. This strategy allowed to develop an accurate XGBoost model (with a value of R2 = 0.97 for the testing set). The explainability of the final predictive model (XGBoost model obtained from ROS) is evaluated using the SHAP (SHapley Additive exPlanations) analysis. The proposed predictive model outperformed traditional mechanics-based models (improvement of approximately 27% over SMCS and 33% over MCFT for some performance metrics) and with a more controlled error distributio
  • Book chapter
    Zhang Y, Lavan O, Málaga-Chuquitaype C, 2024,

    MIXED LAGRANGIAN FORMULATION FOR MODELLING THE NON-SMOOTH BEHAVIOR OF CLUTCHING INERTER

    , World Conference on Earthquake Engineering Proceedings

    Clutched inerter dampers (CID), represent a novel improvement on inerter dampers (ID) that has shown great potential for suppressing structural vibrations under severe ground-motions. However, the inherent nonlinearity and discontinuity of the clutching phenomena in CIDs can create significant difficulties for their accurate numerical modelling. In general, conventional existing methods either oversimplify the physics involved in dynamic contact or are inherently unstable, requiring excessive computing power. The Mixed Lagrangian Formulation (MLF), developed over the years, has shown to be a powerful tool for simulating non-smooth dynamics. In this context, this paper presents an alternative way of modelling structures equipped with CIDs. A proposed clutching inerter element, consisting of an inerter and a plasticity element, is introduced into the MLF framework. Then, the proposed formulation is validated through a simple numerical example, from which the results are compared to those from existing models used for clutching inerter. Finally, the advantages of MLF model and some implications on the modelling of clutched inerters are discussed.
  • Journal article
    Riedel K, Vollum R, Izzuddin B, Rust Get al., 2024,

    Robustness assessment of precast concrete connections using component-based modelling

    , Structures, Vol: 59, ISSN: 2352-0124

    Employing highly optimised precast concrete product-based building solutions increases on-site productivity through elimination of formwork and reduction in propping as well as reducing waste, accidents and embodied carbon. The construction related benefits of precast concrete product-based building solutions are maximised by eliminating structural topping and designing connections between members for ease of assembly. A key challenge in the design of precast concrete buildings is the achievement of robustness under accidental loading. In this paper, sudden column removal is used to assess the robustness of a precast-concrete building system without structural topping. In this case, the development of an alternative load path under sudden column removal relies on the joint response. Joint behaviour is replicated using a component-based design procedure which captures localised failure modes. Robustness is evaluated using a ductility-centred approach and quantified in terms of the pseudo-static resistance. Two types of connection are considered for the provision of continuity at a critical half-lapped joint. The first is a plated connection which was designed initially to meet the tying requirements outlined in Eurocode 2. Under sudden column removal the plated connection’s deformational capacity is limited, which in turn reduces the pseudo-static resistance. An alternative bracketed coupler connection is proposed in which the ductility supply is controlled through debonding of reinforcement. The design concept for the bracketed connection is validated with test results from two full scale sub-assemblies. The experimental results are used to validate a component-based numerical model which is subsequently used to investigate the influence of boundary conditions, and debonding length on the pseudo-static resistance following sudden column loss. The paper shows that the pseudo-static resistance can be significantly enhanced by flexure and compressive membrane act
  • Journal article
    Junda E, Málaga-Chuquitaype C, 2024,

    Seismic acceleration demands in tall CLT buildings, predictive models and intensity measures

    , Engineering Structures, Vol: 298, ISSN: 0141-0296

    An accurate prediction of floor accelerations is crucial for estimating damage to contents and non-structural components in a building. Oversimplifying the nature of acceleration demands might result in biased estimates of building damage and consequently bias in the calculation of economic losses. However, given the relative novelty of multi-storey tall timber buildings, dedicated studies and models of their seismic acceleration demands are lacking. The need for these is stressed further when we recognise that the behaviour of walled timber structures is decidedly different from that of other conventional structural types. In this study, we apply modern data-driven approaches to evaluate efficient intensity measures (IMs) and develop regression models for predicting the peak floor acceleration (PFA) of multi-storey cross-laminated timber (CLT) buildings. Twenty-four IMs are evaluated and their prediction performance is compared. The sensitivity of acceleration demands to different IMs over a wide range of CLT buildings is investigated. We perform a systematic feature selection process using three different data-driven techniques. The selected features are then used to develop nine regression models to estimate PFA. Various modelling techniques, consisting of conventional (Linear and Polynomial regressions) as well as machine learning algorithms (Decision trees, Random forest, K-nearest neighbour, and Support vector regression) are used. The dataset used to train the models is obtained from numerical results of 69 CLT building models with variations in building height, panel fragmentation levels, and q-factors (ductility levels) subjected to a large set of strong earthquakes. After assessing the accuracy of our model predictions, their PFA estimates obtained are compared against previous research and design codes. Finally, simplified expressions for estimating peak floor accelerations in CLT structures are provided for practical purposes.
  • Journal article
    Weber B, Meng X, Zhang R, Nitawaki M, Sagawa T, Gardner Let al., 2024,

    Tensile behaviour of WAAM high strength steel material and members

    , Materials and Design, Vol: 237, ISSN: 0264-1275

    Wire arc additive manufacturing (WAAM), a method of metal 3D printing, has the capacity to create large scale elements suitable for construction applications with a high degree of design freedom and structural efficiency. There is currently however a lack of fundamental experimental data on the material and structural performance of such elements. Towards addressing this limitation, the tensile behaviour of WAAM high strength steel produced using different printing strategies is the focus of the present study. WAAM steel plates and tubular tension members manufactured with different interpass temperatures and toolpaths using ER110S-G welding wire were examined. A total of 60 tensile coupons, consisting of 40 as-built and 20 machined specimens, and 8 as-built circular hollow section (CHS) tension members, were tested. The examined WAAM materials were found to exhibit very little anisotropy, corroborated by a nearly homogeneous crystallographic texture observed by microstructural analysis, while the inherent surface undulations were shown to result in a varying degree of reduction in the material stiffness, strength and ductility at different angles to the print layer orientation. The different printing strategies led to varying surface geometries; combined with different interpass temperatures, they also resulted in different thermal histories and thus different mechanical properties. The tension members showed good structural resistance, but a considerable reduction in ductility compared to the coupon tests, due to the greater geometric variability and manufacturing defects.
  • Conference paper
    Zahra F, Macedo J, Malaga-Chuquitaype C, 2024,

    A Hazard-consistent Residual Drift Model for SMRF

    , 12th International Conference on Structural Dynamics (EURODYN), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
  • Conference paper
    Zahra F, Malaga-Chuquitaype C, 2024,

    Seismic Behaviour of Damaged Steel Frames Retrofitted with Inerters

    , 11th International Conference on the Behaviour of Steel Structures in Seismic Areas (STESSA), Publisher: SPRINGER INTERNATIONAL PUBLISHING AG, Pages: 243-254, ISSN: 2366-2557
  • Journal article
    Chen Y, Izzuddin BA, 2023,

    A simplified finite strain plasticity model for metallic applications

    , Engineering with Computers: an international journal for simulation-based engineering, Vol: 39, Pages: 3955-3972, ISSN: 0177-0667

    In this work, a finite strain elastoplastic model is proposed within a total Lagrangian framework based on multiplicative decomposition of the deformation gradient, with several simplifications aimed at facilitating more concise code implementation and enhancing computational efficiency. Pre- and post-processors are utilised for conversion between different stress and strain measures, sandwiching the core plastic flow algorithm which preserves the small strain form. Simplifications focus on the pre- and post-processor components by substituting certain arithmetic operations associated with high computational demands with simpler ones without compromising accuracy. These modifications are based on assumptions, which are valid for most metals, that the elastic strains are small compared to plastic strains, and that the incremental plastic deformations are small for each step. In addition, the consistent tangent modulus matrix is derived in a reduced form, both for the general full model and the new simplified model, facilitating more straightforward computations in both cases. The models are verified against two classical numerical examples where favourable comparisons are achieved. Overall, the simplified model is shown to provide a significant reduction in computational demand for the two considered numerical problems, with negligible deviation in the results compared to the full model, subject to fulfilling the underlying assumptions with the adoption of a sufficiently small step size.
  • Journal article
    Lou T, Wang W, Izzuddin BA, 2023,

    A framework for performance-based assessment in post-earthquake fire: Methodology and case study

    , ENGINEERING STRUCTURES, Vol: 294, ISSN: 0141-0296
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    • Citations: 12
  • Journal article
    Lesiv H, Izzuddin BA, 2023,

    Consistency and misconceptions in co-rotational 3D continuum finite elements: A zero-macrospin approach

    , INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, Vol: 281, ISSN: 0020-7683

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