Imperial College London

Dr Christian Malaga-Chuquitaype

Faculty of EngineeringDepartment of Civil and Environmental Engineering

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 5007c.malaga Website

 
 
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Assistant

 

Ms Ruth Bello +44 (0)20 7594 6040

 
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Location

 

322Skempton BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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104 results found

Biswas RK, Iwanami M, Chijiwa N, Saito T, Malaga-Chuquitaype Cet 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.

Journal article

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

Conference paper

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.

Conference paper

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.

Conference paper

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.

Conference paper

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

Conference paper

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.

Conference paper

Maqdah J, Memarzadeh M, Kampas G, Malaga Chuquitaype Cet 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.

Conference paper

Gharehbaghi VR, Kalbkhani H, Farsangi EN, Yang TY, Nguyen A, Mirjalili S, Malaga-Chuquitaype Cet 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.

Journal article

MálagaChuquitaype C, McLean T, Kalapodis N, Kolonas C, Kampas Get 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.

Journal article

Zhang Y, Thiers-Moggia R, Málaga-Chuquitaype C, 2022, Impact and clutch nonlinearities in the seismic response of inerto-rocking systems, Bulletin of Earthquake Engineering, 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

Journal article

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.

Journal article

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

Journal article

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.

Journal article

Reza Gharehbaghi V, Noroozinejad Farsangi E, Noori M, Yang TY, Li S, Nguyen A, Malaga Chuquitaype C, Gardoni P, Mirjalili Set 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

Journal article

Melchor-Placencia C, Malaga Chuquitaype C, 2021, OpenMoist: a Python code for transient moisture transfer analysis, SoftwareX, Vol: 15, ISSN: 2352-7110

The analysis of the moisture diffusion inside structural elements is key to assess their time-dependent behaviour and performance, not least in the case of natural materials like wood. Although software exists to solve the moisture transfer problem indirectly, there is a dearth of user-friendly open-source codes tailored to the peculiarities of structural timber. This work presents a Python-based code called OpenMoist developed within a procedural programming framework to perform moisture transfer analysis. The code can handle solid and hollow section geometries, moisture dependent parameters as well as orthotropic diffusion properties typically encountered in wood.

Journal article

McLean T, Málaga-Chuquitaype C, Kalapodis N, Kampas Get al., 2021, OpenArch: An open-source package for determining the minimum-thickness of arches under seismic loads, SoftwareX, Vol: 15, Pages: 1-8, ISSN: 2352-7110

Arches are elegant and efficient structural forms that can be used in a wide variety of applications, from bridges to extraterrestrial shielding structures. Oftentimes their design hinges around the identification of the minimum-thickness required to ensure their stability when subjected to gravity and lateral (inertial) loading. This work presents a MATLAB-based code called OpenArch developed within a procedural programming framework for the preliminary design and assessment of optimal arch forms of minimum thickness when subjected to combined self-weight and seismically induced loads. The code, which is based on limit thrust-line analysis can handle any classical or non-classical no-tension arch form and the results compare excellently with the few available analytical solutions.

Journal article

Freddi F, Galasso C, Cremen G, Dall'Asta A, Di Sarno L, Giaralis A, Gutierrez-Urzua F, Malaga-Chuquitaype C, Mitoulis SA, Petrone C, Sextos A, Sousa L, Tarbali K, Tubaldi E, Wardman J, Woo Get al., 2021, Innovations in earthquake risk reduction for resilience: recent advances and challenges, International Journal of Disaster Risk Reduction, Vol: 60, ISSN: 2212-4209

The Sendai Framework for Disaster Risk Reduction 2015–2030 (SFDRR) highlights the importance of scientific research, supporting the ‘availability and application of science and technology to decision making’ in disaster risk reduction (DRR). Science and technology can play a crucial role in the world's ability to reduce casualties, physical damage, and interruption to critical infrastructure due to natural hazards and their complex interactions. The SFDRR encourages better access to technological innovations combined with increased DRR investments in developing cost-effective approaches and tackling global challenges. To this aim, it is essential to link multi- and interdisciplinary research and technological innovations with policy and engineering/DRR practice. To share knowledge and promote discussion on recent advances, challenges, and future directions on ‘Innovations in Earthquake Risk Reduction for Resilience’, a group of experts from academia and industry met in London, UK, in July 2019. The workshop focused on both cutting-edge ‘soft’ (e.g., novel modelling methods/frameworks, early warning systems, disaster financing and parametric insurance) and ‘hard’ (e.g., novel structural systems/devices for new structures and retrofitting of existing structures, sensors) risk-reduction strategies for the enhancement of structural and infrastructural earthquake safety and resilience. The workshop highlighted emerging trends and lessons from recent earthquake events and pinpointed critical issues for future research and policy interventions. This paper summarises some of the key aspects identified and discussed during the workshop to inform other researchers worldwide and extend the conversation to a broader audience, with the ultimate aim of driving change in how seismic risk is quantified and mitigated.

Journal article

Alavi A, Mele E, Rahgozar R, Noroozinejad Farsangi E, Takewaki I, Málaga-Chuquitaype Cet al., 2021, Uniform deformation design of outrigger braced skyscrapers: A simplified method for the preliminary design stage, Structures, Vol: 31, Pages: 395-405, ISSN: 2352-0124

A stiffness-based method for the preliminary design of outrigger braced skyscrapers is proposed. The method is founded on the concept of uniform distribution of deformation. This approach originates from the minimum-compliance optimization, in which the stiffest layout for the structure is sought for a given amount of material. Design variables include: the flexural stiffness of the core structure, the outrigger-belt elevation, and the peripheral column dimensions. These parameters are specified by requiring the curvature to be kept constant, yet minimum, as long as the allowable stress and displacement constraints are imposed. The resulting procedure is presented through a simplified hand-calculation algorithmic framework, which may be used during the preliminary design stage to estimate the size of elements and to give an initial assessment of the structural behavior. In order to show the practical application of the proposed method, a structure equipped with one outrigger is designed using the proposed algorithm. The comparative analysis of the results reveals that the presented method provides a rather high degree of accuracy in practice.

Journal article

Kampas G, Kalapodis N, McLean T, Malaga Chuquitaype Cet al., 2021, Limit-state analysis of parabolic arches subjected to inertial loading in different gravitational fields using a variational formulation, Engineering Structures, Vol: 228, Pages: 1-20, ISSN: 0141-0296

For thousands of years, arches have been used as durable structures that are easy to build and that rely on gravity for their inherent stability. Since then, many researchers and engineers have studied their stability either when subjected to gravity or inertial loading. Currently, given the Insight mission to Mars and the ambitious Artemis program to the Moon, it has become apparent that there will soon be the need to design and build the first resilient extraterrestrial structures and arches represent an ideal option for such structures. This paper focuses on the stability of parabolic arches with different embrace angles subjected to different levels of equivalent inertial loading in low-gravity conditions. The results are contrasted with the well-studied circular arches. More specifically, this investigation employs variational principles to identify the imminent mechanisms and numerical methods based on the limit thrust line concept in order to estimate the minimum required thickness of parabolic arches for a given loading and in different gravitational fields. The paper shows that although parabolic arches can be much more efficient than their circular counterparts for gravitational-only loading, this is not the case for different combinations of inertial loading and embrace angles where the opposite can be true. It highlights the dominant effect of low-gravity conditions on the minimum thickness requirements for both types of arches and considers the effect of a potential additional infill for shielding from radiation. Furthermore, this study reveals a self-similar behaviour, introduces a “universal” inertial loading and showcases through the use of master curves the areas where the parabolic arches are more efficient than the circular and the opposite. These areas can be used for the preliminary design of such structures. Additionally, the paper identifies hidden patterns associated with the developed mechanisms between the two different geometri

Journal article

Málaga-Chuquitaype C, 2021, Strong-motion duration and response scaling of yielding and degrading eccentric structures, Earthquake Engineering and Structural Dynamics, Vol: 50, Pages: 635-654, ISSN: 0098-8847

Plan irregular structures, whose complex response represents a generalisation of the simpler de-coupled motion ascribed to symmetric buildings, make up a large proportion of the failures during major earthquakes. This paper examines the seismic response scaling of degrading and no-degrading eccentric structures subjected to bidirectional earthquake action and its relationship with the duration of the ground motion by means of dimensional and orientational analyses. Structures with reflectionally symmetric stiffness distribution and mass eccentricity subjected to orthogonal pairs of ideal pulses are considered as the fundamental case. The application of Vaschy–Buckingham's (Formula presented.) -theorem reduces the number of variables governing the peak orthogonal displacements leading to the emergence of remarkable order in the structural response. If orientationally consistent dimensionless parameters are selected, the response becomes self-similar. By contrast, when degradation is introduced, peak inelastic displacements are dramatically affected and the self-similarity in the response is lost immediately after the onset of inelastic deformations. Conversely, if the uniform duration, instead of the period, of the strong motion is adopted as a timescale, a practically self-similar response is observed. This offers unequivocal proof of the fundamental role played by the ground-motion duration in defining the peak displacement response of degrading structures even at small inelastic demands, although its importance increases with increasing deformation levels. Finally, the existence of complete similarities, or similarities of the first kind, are explored and the practical implications of these findings are briefly outlined in the context of real pulse-like ground motions with varying degrees of coherency.

Journal article

Thiers-Moggia R, Malaga Chuquitaype C, 2021, Effect of base-level inerters on the higher mode response of uplifting structures, Journal of Engineering Mechanics - ASCE, ISSN: 0733-9399

Allowing slender structures to uplift has been used as an efficient means of controlling their seismic response. Often-times rocking structures will exhibit some degree of flexibility and cannot be adequately represented by single-mass or rigid systems. In this paper, we examine the dynamic response of multi-storey flexible rocking bodies equipped with inerters at their ground level. Firstly, numerical models of inerter-equipped rocking structures are formulated and validated. These models are used to assess the effect of the inerter on the elastic deformations and base rotations demands of a set of structures ranging from 3 to 9 storeys. Importantly, we examine the interaction between impact forces and higher vibration modes and evaluate the effectiveness of the inerter in controlling the associated acceleration demands and increased bending moments along the height. The efficiency of the inerter was not found to be affected by practical variations of the stiffness of the rocking surface. Although the inerter increased the moment demands at the first level, the proposed strategy successfully controlled seismic demands along the height of the structure.

Journal article

Junda E, Málaga-Chuquitaype C, Escudero JM, 2021, Influence of panel fragmentation on the seismic response of cross-laminated timber buildings

Multi-storey cross-laminated timber (CLT) buildings are being increasingly built in earthquake prone regions. However, given the relative novelty of this building system, there is a lack of detailed studies on the influence of CLT panel fragmentation levels on their seismic performance. This paper presents an examination of the influence of panel fragmentation on the seismic demands of multi-storey timber buildings by means of advanced data science methods. To this end, various feature selection techniques are applied, namely: Correlation analysis, Stepwise regression, and Lasso regression. Numerical results from a large database of nonlinear dynamic analyses involving 69 prototypical CLT buildings under real earthquake ground motions are used. The building database covers mid- to high-rise CLT buildings with different panel geometries and designed to several behaviour factors (q). The influence of panel fragmentation on maximum inter-storey drift ratio, maximum shear forces, and peak floor accelerations is studied. The results indicate that, although the level of panel fragmentation can affect the drift and shear demands of CLT buildings to some extent, it is not an essential parameter for seismic response estimation since it has relatively minor influence on the seismic response of CLT structures which is strongly dominated by the ground-motion.

Conference paper

Thiers-Moggia R, Málaga-Chuquitaype C, 2021, Performance-based seismic assessment of rocking CLT buildings protected with inerters

Post-tensioned rocking systems are an attractive alternative for timber construction in seismic prone regions. Although experimental results show that these systems can efficiently control structural damage, the high inter-storey drifts and floor accelerations associated with the rocking motion can cause significant non-structural and contents damage, hence reducing the overall performance of the buildings. In this paper, the use of inerters to reduce peak drifts and accelerations and improve the seismic response of post-tensioned rocking CLT buildings is assessed. In a first stage, the performance of bare and protected structures with different levels of apparent mass ratios is evaluated and compared considering a set of 7 records consistent with the displacement design spectrum. Subsequently, a performance-based assessment is conducted considering a database of 202 pulse-like ground motion records. The results of these analyses show that the inerter can effectively reduce inter-storey drifts and floor accelerations demands in rocking timber structures.

Conference paper

Dehghani S, Fathizadeh S, Yang T, Noroozinejad Farsangi E, Vosoughi A, Hajirasouliha I, Malaga Chuquitaype C, Takewaki Iet al., 2021, Performance evaluation of curved damper truss moment frames designed using equivalent energy design procedure, Engineering Structures, Vol: 226, ISSN: 0141-0296

Curved damper truss moment frame (CDTMF) system is a novel seismic force-resisting structural system which utilizes the curved dampers integrated into a semi-rigid moment frame to dissipate the earthquake input energy. To ensure the CDTMF has high performance, the state-of the art equivalent energy design procedure (EEDP) is applied to its design. EEDP allows engineers to design CDTMF to achieve different performance objectives at different levels of earthquake shaking intensities. In this study, two different prototype buildings (three and nine-story) were designed using EEDP. The seismic performance of the buildings was assessed using nonlinear time history analysis (NTHA) and incremental dynamic analysis (IDA). The results of the nonlinear dynamic analyses demonstrate that the CDTMFs can achieve the predefined performance targets (selected by the designer) at different earthquake intensity levels. The results of the IDA also show that the EEDP designed CDTMF has a sufficient margin against collapse. The results of this study in general confirm that CDTMF can be used as an effective seismic force-resisting system.

Journal article

Kalapodis N, Kampas G, McLean T, Malaga-Chuquitaype Cet al., 2021, Comparison of the efficiency of minimum-thickness circular and parabolic arches for various gravity conditions, ISSN: 2623-3347

Arches are structural forms that have been used for thousands of years and rely on gravity for their inherent stability. Currently, given the space race for lunar and martian exploration, it has become apparent that soon enough, there will be a need to design and build the first resilient shielding structures on the Moon and Mars against extreme radiation. Arches represent an ideal option for such structures given that they are durable and can be easily built. This paper is based on previous work of the authors and focuses on the stability of circular and parabolic arches with different embrace angles subjected to different levels of equivalent inertial loading in low-gravity conditions. More specifically, it reveals that although parabolic arches can be much more efficient than the corresponding circular for gravitational-only loading, this is not the case for different combinations of inertial loading and embrace angles where the opposite can be true. It highlights the dominant effect of low-gravity conditions on the minimum thickness requirements for both types of arches and considers the effect of a potential additional infill for radiation shielding. Furthermore, this study reveals a self-similar behavior and introduces a “universal” inertial loading.

Conference paper

Thiers-Moggia R, Málaga-Chuquitaype C, 2020, Dynamic response of post-tensioned rocking structures with inerters, International Journal of Mechanical Sciences, Vol: 187, Pages: 1-15, ISSN: 0020-7403

Post-tensioned rocking systems have proved to be highly effective in controlling structural damage during strong ground motions. However, recent events have highlighted the importance of looking at both thestructural and non-structural components within a holistic framework. In this context, the high rotations and accelerations associated with the rocking motion can cause significant non-structural damage and affect the performance and functionality of the entire system. In this paper, we examine analytically the fundamental dynamics of post-tensioned rocking structures and investigate the bene fits of using supplemental rotationalinertia to reduce their seismic demands and improve their overall performance. The newly proposed strategy employs inerters, a mechanical device that develops a resisting force proportional to the relative acceleration between its terminals. Analyses conducted for a wide range of acceleration pulses and real pulse-like groundmotions show that post-tensioned structures equipped with inerters consistently experience lower demands and have reduced probabilities of exceeding limit states typically associated with damage. Importantly, thenew vibration control strategy advanced in this paper opens the door for an expedient modification of the fundamental dynamic response of rocking systems without altering their geometry.

Journal article

Thiers-Moggia R, Malaga Chuquitaype C, 2020, Seismic control of flexible rocking structures using inerters, Earthquake Engineering and Structural Dynamics, Vol: 49, Pages: 1519-1538, ISSN: 0098-8847

Allowing flexible structures to uplift and rock during earthquakes can significantly reduce the force demands and residual displacements. However, such structures are still susceptible to large deformations and accelerations that can compromise their functionality. In this paper,we examine the dynamic response of elastic rocking oscillators and suggest that their lateral drifts and accelerations can be limited effectively by using inerter devices. To this end, we offer a detailed examination of the effects of structural flexibility on the efficiency of the proposed system. The analytical expressions governing the motion of deformable structures with base uplift are revisited to incorporate the effects of the supplemental rotational inertia. The proposed model is then used to study the structural demands of flexible rocking structures under coherent pulses as well as non-coherent real pulse-like ground-motions. Our results show that combining rocking with inerters can be an efficient strategy to control the deformation and acceleration demands in uplifting flexible systems.

Journal article

Pan X, Malaga Chuquitaype C, 2020, Seismic control of rocking structures via external resonators, Earthquake Engineering and Structural Dynamics, Vol: 49, Pages: 1180-1196, ISSN: 0098-8847

Tall rigid blocks are prevalent in ancient historical constructions. Such structures are prone to rocking behaviour under strong ground motion, which is recognisably challenging to predict and mitigate. Our study is motivated by the need to provide innovative non-intrusive solutions to attenuate the rocking response of historical buildings and monuments. In this paper, we examine a novel scheme that employs external resonators buried next to the rocking structure as a means to control its seis- mic response. The strategy capitalizes on the vibration absorbing potential of the structure-soil-resonator interaction. Advanced numerical analyses of discrete mod- els under coherent acceleration pulses with rocking bodies of different slenderness ratios under various ground motion intensities highlight the significant vibration absorbing qualities of the external resonating system. The influence of key system parameters such as the mass, stiffness and damping of the resonator and those of the soil-structure-resonator arrangement are studied. Finally, a case study on the evaluation of the response of rocking structures with external resonators under real pulse-like ground-motion records confirms the important reductions in peak seismic rotational demands obtained with the proposed arrangement.

Journal article

Fathizadeh S, Dehghani S, Yang T, Noroozinejad Farsangi E, Vosoughi A, Hajirasouliha I, Takewaki I, Malaga Chuquitaype C, Varum Het al., 2020, Trade-off Pareto optimum design of an innovative curved damper truss moment frame considering structural and non-structural objectives, Structures, ISSN: 2352-0124

This research aims to develop a novel and cost-effective seismic force-resisting system called “curved damper truss moment frame” (CDTMF) by coupling the recently developed curved dampers (CDs) with conventional steel trusses. In this proposed system, the CDs are adopted as primary fuses, while semi-rigid connections are used as secondary fuses to dissipate the input seismic energy through a two-phased energy dissipation mechanism called the equivalent energy design procedure (EEDP). To validate the adequacy and feasibility of incorporating the CDTMF system in multi-story framed structures, the multi-objective NSGA II optimization technique was applied to the optimum seismic design of selected CDTMF prototypes. Their seismic performance was then compared with the recently proposed buckling restrained knee braced truss moment frame (BRKBTMF) systems, which were designed based on the same procedure to make a consistent comparison. This comparison was based on the results of nonlinear static analysis (pushover), nonlinear time history analysis (NTHA) and incremental dynamic analysis (IDA) on three-, six- and nine-story steel framed structures (low- to mid-rise systems). Since damage to non-structural acceleration-sensitive elements would depend on the floor acceleration, and because the main cause of damage in non-structural displacement-sensitive elements and structural members is generally due to the story drift, the objective functions of the optimization process were the median maximum story drift and the peak floor acceleration. In order to achieve the two-phased energy dissipation mechanism, the primary constraints (PCs) and secondary constraints (SCs) corresponding to the primary and secondary fuses are applied. The outcomes of the pushover analysis showed that the optimal CDTMF structures exhibited higher ductility and energy dissipation capacity compared to the BRKBTMFs. The results of the nonlinear dynamic analysis also indicated that the newly pr

Journal article

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