Publications
120 results found
Zahra F, Macedo J, Malaga Chuquitaype C, 2024, The importance of hazard-consistency when estimating seismic residual drifts in steel moment frames, Journal of Building Engineering, ISSN: 2352-7102
Residual drifts are routinely used to assess the post-earthquake safety of buildings. Despite their importance, studies on the probabilistic assessment of residual drifts in multi-storey buildings with Steel Moment Resisting Frames (SMRF) are far less common than those dealing with their transient peak drift counterpart. More seriously, although residual drift prediction models have been developed with a particular broad ground-motion type or soil condition in mind, all models proposed to date remain oblivious to the central issue of hazard consistency. Hence, missing the causal connection between the seismic hazard level and the ground-motion suite used and potentially compromising the meaningfulness of their results. This oversight is expected to introduce a bias in the estimation of residual drifts but its magnitude has not yet been properly evaluated. In this paper, we evaluate and quantify the significance of these effects. To this end, we use the Conditional Scenario Spectra framework, which provides a set of realistic earthquake spectra with assigned rates of occurrences based on their spectral shape and intensity, thus preserving the critical relationship of hazard consistency. Nonlinear response history analyses (NRHA) of 24 deteriorating SMRFs under 816 ground-motion records are performed to construct a database of residual drift demands. These NRHA results are used to examine the residual drift trends and to construct benchmark residual drift hazard curves. An extensive feature selection process employing several Machine Learning (ML) algorithms precedes the development of hybrid data-driven predictive models. Finally, we compare our hazard-consistent predictions with currently available models and quantify the massive under- and overestimations associated with previously proposed non-hazard-consistent assumptions.
Shen S, Malaga Chuquitaype C, 2024, Physics-informed artificial intelligence models for the seismic response prediction of rocking structures, Data-Centric Engineering, Vol: 5, ISSN: 2632-6736
The seismic response of a wide variety of structures, from small but irreplaceable museum exhibits to large bridge systems, is characterized by rocking. Besides, rocking motion is increasingly being used as a seismic protective strategy to limit the amount of seismic actions (moments) developed at the base of structures. However, rocking is a highly nonlinear phenomenon governed by non-smooth dynamic phases that make its prediction difficult. This study presents an alternative approach to rocking estimation based on a Physics-informed Convolutional Neural Network (PICNN). By training a PICNN framework using limited datasets obtained from numerical simulations and encoding the known physics into the PICNNs, important predictive benefits are obtained relieving difficulties associated with over-fitting and minimizing the requirement for large training database. Two models are created depending on the validation of the deep PICNN: the first model assumes that state variables including rotations and angular velocities are available, while the second model is useful when only acceleration measurements are known. The analysis is initiated by implementing K-means clustering. This is followed by a detailed statistical assessment and a comparative analysis of the response-histories of a rocking block. It is observed that the deep PICNN is capable of effectively estimating the seismic rocking response history when the rigid block does not overturn.
Bedrinana LA, Landeo JG, Sucasaca JC, et 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
Vicencio F, Alexander NA, Málaga-Chuquitaype C, 2024, Seismic Structure-Soil-Structure Interaction between inelastic structures, Earthquake Engineering and Structural Dynamics, ISSN: 0098-8847
Frequently, buildings in urban areas are designed by considering their stand-alone response, that is, as single structures with no neighboring buildings. Nevertheless, the existence of a high density of buildings in large metropolitan areas inevitably results in the likelihood of an important seismic interaction between adjacent buildings through the underlying soil. This paper explores the effects of Structure-Soil-Structure Interaction (SSSI) on the seismic response of two yielding structures embedded in a linear elastic soil. A simple two-dimensional nonlinear reduced-order parametric model is proposed, where different building parameters are considered. A nonlinear phenomenological Bouc–Wen model is assumed for the buildings. A database of 15 strong ground motion records and an additional spectrally matched seismic ground motion are considered. An extensive parametric study comprising over two million nonlinear cases is conducted. The results show important differences between nonlinear SSSI and nonlinear SSI for particular parameter configurations. Nevertheless, due to energy dissipation and increases in damping in the nonlinear case, the effects of SSSI are less relevant compared with the linear case.
Melchor-Placencia C, Málaga-Chuquitaype C, 2024, A nonlinear modelling framework for unbonded post-tensioned timber members, Structures, Vol: 59, ISSN: 2352-0124
Post-tensioned timber elements have become a competitive alternative for long-span structures such as bridges or open-plan buildings. Post-tensioning can add an improved load-bearing capacity and enhanced deflection control to the well established structural efficiency and sustainability advantages of wood as a construction material. Despite of these improvements, the use of unbonded post-tensioning tendons introduces several complexities to the already intricate response of timber structures such as strain incompatibility and second-order effects that require careful consideration. In this study, a fibre-based finite element (FE) analysis framework for the simulation of the full nonlinear response of post-tensioned timber members up to their ultimate failure state is presented. In this framework, the exerted post-tensioning force is assessed using a constantly updated equivalent load which is dependent on member deformations. A description of the FE formulation, modelling assumptions and robust solution algorithms of the fibre-based framework within a corotational formulation is discussed first. Also, a robust numerical procedure is described to evaluate the initial state immediately after the post-tensioning operation. Then it is shown, with reference to available experimental and numerical results, that the approach adopted can simulate effectively the behaviour of post-tensioned timber elements with different post-tensioning layouts while complementary simulations on post-tensioned reinforced concrete (RC) beams demonstrate its versatility. Finally, a study on the influence of deviator spacing on the ultimate response of post-tensioned timber beams, that is known to be largely dependent on second order effects, is conducted. Besides the good agreement with experimental and numerical results, the proposal features promising adaptability, numerical robustness and computational efficiency. This study constitutes a first step towards the realistic simulation of the
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.
Tello-Ayala K, Garcia-Troncoso N, Silva CE, et al., 2023, Comparative analysis of the sustainability and seismic performance of a social interest house using RC moment frames and bahareque as structural systems, Frontiers in Built Environment, Vol: 9, Pages: 1-13, ISSN: 2297-3362
This study compares the seismic performance and environmental impact of a social housing structure designed with reinforced concrete with a structure using Guadua angustifolia “Kunth” cane. The aim is to contrast the implementation of an ecological material such as the Guadua cane, which is an accessible alternative due to its cost and construction time, versus the traditional reinforced concrete (RC) construction method. Both applied to social housing structures. The seismic performance of both methods is analyzed through nonlinear static analysis (pushover) with the objective of establishing the performance; structural and nonstructural damage, performance point, maximum displacements, and structural elements that induce structural failure; and acting forces, against a design earthquake (established by the NEC DS 2015 Standard), with a return period of 475 years. The environmental impact is evaluated through a life cycle assessment of the structure (LCA). Thus, the embodied carbon obtained from each structural element (foundations, beams, columns, floors, and roof support elements) was determined, considering material manufacturing, transportation, and construction. The results obtained demonstrated a higher seismic performance, with 70% less environmental impact on the Guadua cane structure.
Junda 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: 2352-7102
An 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.
Turchetti F, Tubaldi E, Patelli E, et al., 2023, Damage modelling of a bridge pier subjected to multiple earthquakes: a comparative study, Bulletin of Earthquake Engineering, Vol: 21, Pages: 4541-4564, ISSN: 1570-761X
This paper discusses and compares two recently developed methodologies for the prediction of damage accumulation in structures subjected to multiple earthquakes within their lifetime, one based on a regression model and one based on a Markov-chain based approach. A stochastic earthquake hazard model is considered for generating sample sequences of ground motion records that are then used to estimate the probabilistic distribution of the damage accumulated during the time interval of interest using the various methodologies. A simulation-based approach provides a reference solution against which the other methodologies are compared. Besides assessing the effectiveness and accuracy of the two methodologies, some improvements of the regression model are proposed and evaluated. The comparison between the methodologies is carried out by examining a reinforced concrete (RC) bridge pier model and using the Park-Ang damage index to describe the damage accumulation. The study results demonstrate the importance of considering the possibility of occurrence of multiple shocks in estimating the life-cycle performance of structures and highlight strengths and drawbacks of the investigated methodologies.
Zahra 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: 0098-8847
The 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.
Maqdah J, Memarzadeh M, Kampas G, et al., 2023, AI-aided exploration of lunar arch forms under in-plane seismic loading, Acta Mechanica, Pages: 1-17, ISSN: 0001-5970
Increasing computational power has led to the expansion of civil engi- neering research into using machine learning concepts for developing improved design strategies. These strategies are particularly useful for the design of extra-terrestrial habitats under uncertain environmental conditions. This paper focuses on building an unsupervised machine learning model (convolutional autoencoder) capable of detecting patterns in arch shapes and differentiating between their stress and displacement contours. Foremost, detailed discussions of the model’s architecture and input data are presented. The variation of arch shapes and con- tours between cluster centroids in the latent space is determined, proving the capability of optimisation by moving towards clusters with optimal contours. Finally, a regression model is built to investigate the rela- tionship between the input geometric variables and the latent space representation. We prove that the autoencoder and regression mod- els produce arch shapes with logical structural contours given a set of input geometric variables. The results presented in this paper provide essential tools for the development of an automated design strategy capable of finding optimal arch shapes for extra-terrestrial habitats.
Zhang 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: 1570-761X
Rocking 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
Junda E, Malaga-chuquitaype C, 2023, A SEISMIC RESPONSE ESTIMATION MODEL FOR CROSS-LAMINATED TIMBER WALLS USING MACHINE LEARNING, World Conference on Timber Engineering 2023 (WCTE2023), Publisher: World Conference on Timber Engineering (WCTE 2023)
Biswas RK, Iwanami M, Chijiwa N, et al., 2022, A simplified approach to estimate seismic fragility of corrosion damaged RC bridge piers, Developments in the Built Environment, Vol: 12, ISSN: 2666-1659
Safety of the existing corrosion damaged reinforced concrete (RC) bridges during a seismic event is a matter of increasing concern. To reduce the enormous economic loss and casualties, it is important to examine the potential seismic risk of corroded RC bridge structures. This paper presents a simplified method to determine the seismic fragility of corroded RC bridge piers by developing a simplified FEM model and seismic fragility analysis. To make the proposed approach realistic, the numerical model is validated with two different experimental studies available in the literature. Obtain results from the simplified numerical model demonstrated excellent agreement with the experimental tests, making it suitable for seismic vulnerability analysis. After validation, the numerical model is further adopted to perform non-linear static pushover analysis of corroded RC bridge piers. Finally, a recently developed software tool SPO2FRAG is utilized to carry out seismic fragility analysis by defining three different damage levels.
Mite-Anastacio F, Tello-Ayala K, García-Troncoso N, et al., 2022, Structural behavior of cemented bahareque for social housing: A case study in Guayaquil City, Ecuador, Frontiers in Built Environment, Vol: 8, Pages: 1-20, ISSN: 2297-3362
The need for social housing creates challenges for engineering. One of the most economical and ecological structural systems for certain areas is the cemented bahareque, which uses Guadua cane, a type of Bamboo with favorable properties for construction. Despite being an ancient technique for the construction of houses, there is not an extensive bibliography that allows making justified decisions regarding their design in most cases. One of the objectives of this article is to present a prototypical design of a housing case with appropriate characteristics to allow a decent occupant’s life with this construction system. For the selected house, the structural behavior is evaluated under gravitational and seismic loads. The constructive criteria that will provide good performance under seismic events are recommended. The most important criteria to follow for the design of wall systems are regularity, continuity, symmetry, bolted connections, rigid diaphragms for mezzanines and continuous maintenance of the Guadua cane elements that make up the framework of the walls. Finally, it is concluded that following the basic criteria of earthquake-resistant design for this type of housing, adequate structural performance can be obtained.
Zahra F, Malaga Chuquitaype C, Jorge M, 2022, Towards a hazard-consistent predictive model for drifts in steel MRFs, 3rd EUROPEAN CONFERENCE ON EARTHQUAKE ENGINEERING & SEISMOLOGY, Pages: 431-439
Performance-Based Earthquake Engineering (PBEE) approaches have been permitted by nearly every code for almost a century already, and the importance of developing accurate drift predictive models in support of PBEE is widely recognised. For this aim to be fully realised, it is crucial to identify the most influential structural and ground motion parameters that govern the seismic response. This study applies feature selection Machine Learning (ML) techniques to the identification of the best predictors of maximum inter-storey drift of steel Moment Resisting Frames (MRFs). Several ML techniques are applied to a database assembled from extensive results of nonlinear response history analyses on 24 steel MRFs of different structural characteristics. A suite of 596 ground motions is used to cover a wide range of intensities. These ground motions were selected by means of the Conditional Scenario Spectra (CSS) methodology to ensure the hazard consistency of the estimates, a key concept at the heart of the PBEE. Although the identified best predictors are not surprising, interesting conclusions are obtained from the application of the feature selection methods used in this study and the need for a careful interpretation of the results of ML tools is highlighted.
Malaga Chuquitaype C, Zahra F, Macedo J, 2022, Hazard-consistent floor acceleration demands in steel MRFs, Bucharest, Romania, 3rd EUROPEAN CONFERENCE ON EARTHQUAKE ENGINEERING & SEISMOLOGY, Pages: 315-322
Despite their known importance, Non-structural Components (NSCs) are still inadequately designed, leading to significant losses and delaying the recovery of the post- earthquake functionality of structures. This study performs NSC seismic performance assessments through the height-wise peak floor acceleration (PFA) demand within a Performance-Based Earthquake Engineering (PBEE) framework. The hazard consistency of the results, a key consideration in the PBEE, is enforced in this study by utilising Conditional Scenario Spectra (CSS) methodologies. Extensive nonlinear response history analyses, carried out on 24 steel moment-resisting frames subjected to 596 ground motions, are employed to construct PFA hazard curves where the corresponding PFA demands of performance levels of interest can be obtained. These PFA demands are compared to those estimated from available codes and standards. It is shown that the popularly adopted linear function estimations could not accurately predict the PFA demands, and that current procedures are unable to give a clear and consistent view of the seismic performance level associated with their estimates.
Malaga Chuquitaype C, 2022, Hazard-consistent comparisons of alternative rocking modelling approaches, 3rd EUROPEAN CONFERENCE ON EARTHQUAKE ENGINEERING & SEISMOLOGY, Pages: 2854-2861
Rocking behaviour due to support motion is experienced by a wide range of structures, from small museum exhibits to large bridge piers. Besides, rocking can also be used as a resilient isolation strategy in seismic protective systems. Despite its deceivingly simple configuration, predicting the response of a rigid rocking body is a challenging task complicated by its enormous sensitivity to impact and imperfection modelling that have called into question a reliance on wholly deterministic approaches. To overcome these limitations, emphasis is now shifting towards the estimation of statistical descriptors of the rocking response rather than deterministic estimates of rotational histories. These efforts, however, need to be balanced against practical considerations of time, availability of computational resources and, importantly, they need to have in mind the intended use of the predicted outcomes. In this context, one aspect that has been left out from current discussions on statistical methods applied to rocking structures is the engineering need to establish hazard consistent estimates and the influence that alternative modelling approaches may have on these predictions. This study aims to contribute to this discussion by analysing a large number of response history analyses on rigid rocking blocks. Models based on the direct numerical solution of the rotational equation of motion as well as on solutions to the linear complementary problem arising from non-smooth dynamics idealizations are explored. Although the behaviour of the rocking block is known to depend on various ground-motion intensity measures, the peak ground acceleration is selected here as a first attempt to rationalize the influence of the variability of the ground motion and seismic demands are expressed in the form of hazard curves. The results of this study offer an initial point of view on the importance of different modelling strategies within a performance-based rocking response evaluation fra
Malaga Chuquitaype C, Zahra F, Macedo J, 2022, On the influence of deterioration modelling on the hazard-consistent seismic response of steel moment frames, 3rd EUROPEAN CONFERENCE ON EARTHQUAKE ENGINEERING & SEISMOLOGY, Pages: 3000-3007
The importance of an adequate model of hysteretic behaviour is undeniable in developing an accurate prediction of structural response. However, this needs to be balanced with practical considerations of time and availability of computational resources and, importantly, the intended use of the estimations. This study aims to illuminate this matter by employing a large number of hazard-consistent nonlinear response history analyses of non- deteriorating and deteriorating steel Moment Resisting Frames (MRFs) within a Performance-Based Earthquake Engineering (PBEE) framework. The evaluation of the seismic demands of the frames was carried out through inter-storey drift demands in the form of hazard curves. Although the behaviour of non-deteriorating and deteriorating frames were found to rely on several factors, the results generally show that the greater and consistent demand differences notably occur at higher hazard levels beyond the collapse prevention performance level and that at medium drift demands deteriorating models can even lead to reduced demand predictions. In agreement with prior studies and contrary to more recent ones that have argued in favour of the consideration of seismic deterioration models at low or moderate demand levels usually employing single sets of scaled but hazard-inconsistent records, the results indicate that when looked from a hazard-consistent perspective, the inherent variability overtakes any deterioration effect making it sensible to avoid the complexity of advanced models for assessments that are not intended to reach collapse cases.
Lee-Lewis T, Nanos N, Malaga Chuquitaype C, 2022, Vulnerabilities of Low-cost Sensors to Electro Magnetic Interference, 3rd EUROPEAN CONFERENCE ON EARTHQUAKE ENGINEERING & SEISMOLOGY, Pages: 2256-2263
Turchetti F, Tubaldi E, Patelli E, et al., 2022, Bridge's piers damage subjected to multiple earthquakes: Markov model vs Regression model, 32nd European Safety and Reliability Conference
Recently developed methodologies based on a probabilistic seismic demand model (PSDM) and based on a Markovian model for the prediction of damage accumulation in structures subjected to multiple earthquakes within their lifetime are compared. A stochastic earthquake hazard model is used for generating sample sequences of ground motion records providing the reference solution and then used to estimate the probabilistic distribution of the damage accumulated during the time interval of interest. Besides evaluating the effectiveness of each approach, possible improvements of the cumulative demand model are tested. A reinforced concrete bridge model with a single pier is examined as case study and Park-Ang damage index is considered to describe the damage accumulation. The results demonstrate the importance of considering the occurrence of multiple shocks.
Maqdah J, Memarzadeh M, Kampas G, et al., 2022, AI-Based Structural Exploration of Lunar Arches, 3rd International Conference on Natural Hazards & Infrastructure - ICONHIC 2022
AI and Machine Learning are becoming particularly useful for the exploration of the design alternatives and can offer a range of advantages when applied to the exploration of innovative forms of extra-terrestrial infrastructure under uncertain environmental conditions. This paper focuses on building an unsupervised machine learning model (convolutional autoencoder) capable of detecting patterns in- and differentiating between- different arch shapes and contours for extraterrestrial outposts. Foremost, detailed discussions of the model’s architecture and input data are presented. The variation of arch shapes and contours between cluster centroids in the learned latent feature space is determined, opening the door for design optimizations by moving towards clusters with more desirable features. Finally, a regression model is built to investigate the relationship between the input geometric variables and the latent space representation. It is proved that the autoencoder and regression models produce arch shapes with logical structural contours given a set of input geometric variables. The results presented in this paper provide essential tools for the later development of an automated design strategy capable of finding optimal arch shapes for extra-terrestrial habitats.
Kalapodis N, Malaga Chuquitaype C, Kampas G, 2022, Can lunar regolith-based varying-thickness arches become more attractive structural forms than constant-thickness arches?, 3rd International Conference on Natural Hazards & Infrastructure - ICONHIC 2022
Following the current trend towards the space exploration, this study focuses mainly on the conceptualisation of the most efficient lunar arch forms to be adopted by the future structural designers. More specifically, the static behaviour of varying-thickness arches (VTAs) produced by an iterative form-finding algorithm against constant-thickness arches (CTAs) is examined herein. These optimised arches are assumed to be constructed by laser-sintered additive manufactured lunar regolith, following a 3D-printing technique. The paper initiates with finite element analysis (FEA) of both VTAs and CTAs where it is witnessed that VTAs need to be geometrically enhanced, by means of thickening certain weak/narrow parts of their cross-section, in order to minimise the principal compressive and tensile stresses and the amount of strain energy exhibited locally. The work concludes with the quantification of the efficiency of the enhanced VTA shapes over the typical CTAs in lunar gravitational environments.
Gharehbaghi VR, Kalbkhani H, Farsangi EN, et al., 2022, A novel approach for deterioration and damage identification in building structures based on Stockwell-Transform and deep convolutional neural network, Journal of Structural Integrity and Maintenance, Vol: 7, Pages: 136-150, ISSN: 2470-5314
In this paper, a novel deterioration and damage identification procedure (DIP) is presented and applied to building models. The challenge associated with applications on these types of structures is related to the strong correlation of responses, an issue that gets further complicated when coping with real ambient vibrations with high levels of noise. Thus, a DIP is designed utilizing low-cost ambient vibrations to analyze the acceleration responses using the Stockwell transform (ST) to generate spectrograms. Subsequently, the ST outputs become the input of two series of Convolutional Neural Networks (CNNs) established for identifying deterioration and damage on the building models. To the best of our knowledge, this is the first time that both damage and deterioration are evaluated on building models through a combination of ST and CNN with high accuracy.
MálagaChuquitaype C, McLean T, Kalapodis N, et al., 2022, Optimal arch forms under in‐plane seismic loading in different gravitational environments, Earthquake Engineering & Structural Dynamics, Vol: 51, ISSN: 0098-8847
This paper is motivated by the renewed interest in space exploration and the need to provide structurally sound and resource-efficient shielding solutions for valuable assets and future habitable modules. We present, implement and test a methodology for the preliminary design and assessment of optimal arch forms subjected to self-weight as well as seismically induced loads. The numerical framework, built around a limit thrust-line analysis, previously published by the authors, is summarized first. This is followed by a detailed account of the form-finding algorithm for arches of variable thickness. Special attention is placed on the physical feasibility of our assumptions and the justification of the engineering inputs adopted. The newly form-found arches achieve material efficiencies between 10% and 50% in comparison with their constant minimum-thickness circular or elliptical counterparts, depending on the relative intensity of the seismic action. The influence of the initial input geometry and the stabilising presence of additional shielding material against extreme radiation are also evaluated with emphasis on the effects of low-gravity conditions. Finally, a case study is presented and Discrete Element Models of constant and varying thickness arches (VTAs) are assessed under a set of representative ground-motions on a lunar setting. The significant over-conservatism of constant thickness arches (CTAs) is made manifest and potential improvements of the optimally found arch shape are highlighted. Although developed with extraterrestrial applications in mind, the results and methods we present herein are also applicable to terrestrial conditions when material efficiency is of utmost concern.
Malaga Chuquitaype C, 2022, Machine learning in structural design: an opinionated review, Frontiers in Built Environment, Vol: 8, ISSN: 2297-3362
The prominence gained by Artificial Intelligence (AI) over all aspects of human activity today cannot be overstated. This technology is no newcomer to structural engineering, with logic-based AI systems used to carry out design explorations as early as the 1980’s. Nevertheless, the advent of low-cost data collection and processing capabilities have imprinted new impetus and a degree of ubiquity to AI-based engineering solutions. This review paper ends by posing the question of how long will the human engineer be needed in structural design. However, the paper does not aim to address this question, not least because all such predictions have a history of going wrong. Instead, the paper assumes throughout as valid the claim that the need for human engineers in conventional design practice has its days numbered. In order to build the case towards the final question, the paper starts with a general description of the currently available AI frameworks and their Machine Learning (ML) sub-classes. The paper then proceeds to review a selected number of studies on the application of AI in structural engineering design. A discussion of specific challenges and future needs is presented with emphasis on the much exalted roles of ’engineering intuition’ and ’creativity’. Finally, the conclusion section of the paper compiles the findings and outlines the challenges and future research directions.
Kalapodis N, Malaga-Chuquitaype C, Kampas G, 2022, Structural efficiency of varying-thickness regolith-based lunar arches against inertial loading, ACTA ASTRONAUTICA, Vol: 191, Pages: 438-450, ISSN: 0094-5765
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Thiers-Moggia R, Málaga-Chuquitaype C, 2021, Performance-based seismic design and assessment of rocking timber buildings equipped with inerters, Engineering Structures, Vol: 248, Pages: 1-20, ISSN: 0141-0296
Over the last decades, performance-based design objectives have shifted towards damage control and continuity of operation after a design-level earthquake. In this context, the advantages of rocking have been applied to the development of a family of self-centring systems that can sustain large lateral deformations without noticeable damage. However, the bending moments and shear forces in uplifting structures can increase significantly due to the effects of higher modes, an issue to which timber structures are particularly prone. This paper assesses the seismic response of post-tensioned timber rocking walls combined with inerters as a means to control the rotation amplitude and suppress higher-mode effects on the system. To this end, a representative set of three post-tensioned rocking walled structures, comprising 3, 6 and 9 storeys, are designed following direct-displacement based design procedures. A simplified method to pre-dimension the inerter device is proposed and used to design a set of ball screw and gear inerters, with and without clutches. The performance of bare and protected structures with different levels of apparent mass ratios is assessed and compared considering a set of 7 records consistent with the displacement design spectrum. Special attention is paid to the resisting force developed in the inerter and the mechanism to transfer it safely to the structural diaphragm. Finally, a detailed performance-based assessment is conducted considering a database of 202 pulse-like ground motion records. It is concluded that the innovative combination of inerters and rocking is an efficient way to improve the seismic control of self-centring structures.
Reza Gharehbaghi V, Noroozinejad Farsangi E, Noori M, et al., 2021, A Critical Review on Structural Health Monitoring: Definitions, Methods, and Perspectives, Archives of Computational Methods in Engineering, ISSN: 1134-3060
The benefits of tracking, identifying, measuring features of interest from structure responses have endless applications for saving cost, time and improving safety. To date, structural health monitoring (SHM) has been extensively applied in several fields, such as aerospace, automotive, and mechanical engineering. However, the focus of this paper is to provide a comprehensive up-to-date review of civil engineering structures such as buildings, bridges, and other infrastructures. For this reason, this article commences with a concise introduction to the fundamental definitions of SHM. The next section presents the general concepts and factors that determine the best strategy to be employed for SHM. Afterward, a thorough review of the most prevalent anomaly detection approaches, from classic techniques to advanced methods, is presented. Subsequently, some popular benchmarks, including laboratory specimens and real structures for validating the proposed methodologies, are demonstrated and discussed. Finally, the advantages and disadvantages of each method are summarized, which can be helpful in future studies
Junda E, Malaga Chuquitaype C, 2021, Efficient Predictors for Estimating the Seismic Response of Cross-Laminated Timber Buildings, 17th World Conference on Earthquake Engineering
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