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
to

78 results found

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

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

Kampas G, Kalapodis N, McLean T, Malaga Chuquitaype Cet al., 2020, Limit-state analysis of parabolic arches subjected to inertial loading in different gravitational fields using a variational formulation, Engineering Structures, 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

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

Sadowski A, Wei Jun W, Simon Li SC, Málaga-Chuquitaype C, Pachakis Det al., 2020, Critical buckling strains in thick cold-formed circular hollow sections under cyclic loading, ASCE Journal of Structural Engineering, Vol: 146, Pages: 1-13, ISSN: 0733-9445

Contrary to the large dataset of test results exploring the monotonic bending response of steel tubes, the corresponding dataset of cyclic bending tests remains very small. Seven compact and semi-compact S355J2H cold-formed circular hollow sections with diameter to thickness (D/t) ratios between 20 to 60, representative of piles used in piers and wharves, were brought to failure in three-point cyclic bending tests. Digital Image Correlation was employed to estimate average cross-sectional curvatures, and hence the critical bending strains, during local buckling at the midspan plastic hinges. These estimates were compared against those from two simplified localised hinge models and differed by up to a factor of two. A parametric study was performed with a validated finite element model to ascertain the suitability of proposed design equations at predicting critical strains in piles with D/t from 20 to 60 under cyclic loading. Test and simulation data both show that critical buckling strains are lower under cyclic loading than under monotonic loading. This work can inform the future development of seismic design standards such as ASCE 61-14.

Journal article

Kasinos S, Chatzi E, Malaga Chuquitaype C, 2020, Response of nonlinear secondary oscillators in cascade to random excitation, XI International Conference on Structural Dynamics (EURODYN 2020)

The paper deals with the steady-state stationary response of single-degree-of-freedom nonlinear secondary oscillators in stochastically driven linear primary structures. Equations governing the primary-secondary dynamic interaction are presented, followed by a concise exposition of a two-degree-of-freedom system assembly with dimensionless coefficients. Stochastic forcing is successively modelled as monochromatic, white noise, and filtered white noise process, representing extreme forms of narrow-band and wide-band excitations, as well as an intermediate case, characterised by the Clough-Penzien stationary power spectrum, commonly adopted in earthquake engineering applications. A decomposition-synthesis approach is presented in order to analytically approximate the response of the secondary system in cascade,by quantifying the statistics to individual forcing components, and synthesising the results to obtain the response of an equivalent linear secondary system. Demonstrated to the case of a Duffing secondary oscillator, and compared with pertinent Monte-Carlo simulations, the derived formulas permit accurate and efficient quantification of the secondary system’s response as a function of the design input parameters of the system assembly and the excitation.

Conference paper

Kibriya LT, Málaga-Chuquitaype C, Kashani MM, 2020, Buckling-enabled composite bracing for damage-avoidance rocking structures, International Journal of Mechanical Sciences, Vol: 170, ISSN: 0020-7403

Post-tensioned rocking frames have been proposed as damage-free seismic-resistant structures. However, currently available load resisting systems for rocking frames rely on sacrificial yielding components that accumulate damage during strong dynamic action. To address this shortcoming, this study proposes a novel thoroughly damage-avoidance solution by means of bracing elements with carefully controlled buckling behaviour. To this end, a proof-of-concept study is presented, whereby the elastic buckling response of buckling-enabled composite bracing (BECB) elements with circular-arc shaped cross-section is numerically investigated. Varying geometric properties are considered and validated against analytical approximations. Besides, a finite element study of a single-storey steel post-tensioned frame under static and dynamic actions is performed. The case study incorporates BECB elements made from glass-fibre reinforced polymer (GFRP). It is demonstrated that BECB enhances the non-linear static and dynamic response of rocking frames by providing stability and significantly reducing storey drifts and accelerations without accumulating damage.

Journal article

Málaga-Chuquitaype C, 2020, Strong-motion duration and response scaling of yielding and degrading eccentric structures, Earthquake Engineering and Structural Dynamics, ISSN: 0098-8847

© 2020 The Authors. Earthquake Engineering & Structural Dynamics published by John Wiley & Sons Ltd. 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

Sirumbal-Zapata LF, Malaga Chuquitaype C, Elghazouli A, 2019, Experimental assessment and damage modelling of hybrid timber beam-to-steel column connections under cyclic loads, Engineering Structures, Vol: 200, ISSN: 0141-0296

This paper presents an experimental and numerical study on the behaviour of timber beam-to-steel column connections under cyclic loads. Special attention is given to the accumulation of damage in the timber com- ponents and to its simulation. To this end, the fundamental nonlinear cyclic response of three specimens involving di↵erent configurations of top and seat angle connections with long bolts is examined. The experi- mental set-up, connection details and material properties are introduced first, followed by a detailed account of the testing procedure and results. The experimental outcomes enable a direct comparative assessment of the connection strength, hysteretic response, joint ductility, failure mode and energy dissipation capacity. In addition, finite element analyses employing a newly proposed damage-plasticity constitutive model of wood are presented together with a detailed description of the adopted modelling approach. The numerical output of these simulations at the local level, expressed in terms of strains and damage indices, is discussed and com- pared against the experimental measurements of local damage in the wood obtained through Digital Image Correlation (DIC) techniques. It is demonstrated that the connections under consideration are able to sus- tain their bending capacity without a significant deterioration in their sti↵ness or strength even up to large levels of deformation and several repetitions of loading cycles. Besides, the results and discussion presented in this paper support the conventional definition of global failure as a post-peak strength reduction higher than 20% of the capacity but so long as the strength measurements are obtained from the stabilized envelope curves of the specimens. The applicability of damage mechanics concepts to provide a reliable prediction of crack zones and damage accumulation in timber structures under the action of cyclic loads is also highlighted.

Journal article

Demirci C, Malaga Chuquitaype C, Macorini L, 2019, Seismic shear and acceleration demands in multi-storey cross-laminated timber buildings, Engineering Structures, Vol: 198, ISSN: 0141-0296

A realistic estimation of seismic shear demands is essential for the design and assessment of multi-storey buildings and for ensuring the activation of ductile failure modes during strong ground-motion. Likewise, the evaluation of seismic floor accelerations is fundamental to the appraisal of damage to non-structural elements and building contents. Given the relative novelty of tall timber buildings and their increasing popularity, a rigorous evaluation of their shear and acceleration demands is all the more critical and timely. For this purpose, this paper investigates the scaling of seismic shear and acceleration demands in multi- storey cross-laminated timber (CLT) buildings and its dependency on various structural properties. Special attention is given to the influence of the frequency content of the ground-motion. A set of 60 CLT buildings of varying heights representative of a wide range of structural configurations is subjected to a large dataset of 1656 real earthquake records. It is demonstrated that the mean period (Tm) of the ground-motion together with salient structural parameters such as building aspect ratio (λ), design force reduction factor (q) and panel subdivision (β) influence strongly the variation of base shear, storey shears and acceleration demands. Besides, robust regression models are used to assess and quantify the distribution of force and acceleration demands on CLT buildings. Finally, practical expressions for the estimation of base shears, inter-storey shears and peak floor accelerations are offered.

Journal article

Di Pilato D, Tubaldi E, Castaldo P, Malaga Chuquitaype Cet al., 2019, Risk assessment of bridge's piers subjected to multiple earthquakes: comparison between different approahces, ANIDIS 2019, L'Ingegneria sismica in Italia

Conference paper

Thiers-Moggia R, Malaga Chuquitaype C, 2019, Seismic control of post-tensioned rocking walls with inerters, SECED 2019, Earthquake Risk and Engineering Towards a Resilient World

Conference paper

Kibriya L, Malaga Chuquitaype C, Kashani M, 2019, Application of Buckling-Enabled Composite Bracing (BECB) to steel rocking Frames, SECED 2019, Earthquake Risk and Engineering Towards a Resilient World

Conference paper

Lee-Lewis T, Malaga Chuquitaype C, Nanos N, 2019, On The Use of Open-Source Low-Cost Vibration Sensing Technologies for Seismic Assessment in Urban Areas, SECED 2019, Earthquake Risk and Engineering Towards a Resilient World

Conference paper

Demirci C, Malaga Chuquitaype C, Macorini L, 2019, Seismic demands in multi-storey Cross-Laminated Timber (CLT) structures, SECED 2019, Earthquake Risk and Engineering Towards a Resilient World

Conference paper

Málaga-Chuquitaype C, Psaltakis ME, Kampas G, Wu Jet al., 2019, Dimensionless fragility analysis of seismic acceleration demands through low-order building models, Bulletin of Earthquake Engineering, Vol: 17, Pages: 3815-3845, ISSN: 1570-761X

This paper deals with the estimation of fragility functions for acceleration-sensitive com- ponents of buildings subjected to earthquake action. It considers ideally coherent pulses as well as real non-pulselike ground-motion records applied to continuous building mod- els formed by a flexural beam and a shear beam in tandem. The study advances the idea of acceleration-based dimensionless fragility functions and describes the process of their formulation. It demonstrates that the mean period of the Fourier Spectrum, Tm, is associ- ated with the least dispersion in the predicted dimensionless mean demand. Likewise, peak ground acceleration, PGA-, and peak ground velocity, PGV-based length scales are found to be almost equally appropriate for obtaining efficient ‘universal’ descriptions of maxi- mum floor accelerations. Finally, this work also shows that fragility functions formulated in terms of dimensionless -terms have a superior performance in comparison with those based on conventional non-dimensionless terms (like peak or spectral acceleration values). This improved efficiency is more evident for buildings dominated by global flexural type lateral deformation over the whole intensity range and for large peak floor acceleration levels in structures with shear-governed behaviour. The suggested dimensionless fragil- ity functions can offer a ‘universal’ description of the fragility of acceleration-sensitive components and constitute an efficient tool for a rapid seismic assessment of building con- tents in structures behaving at, or close to, yielding which form the biggest share in large (regional) building stock evaluations.

Journal article

Zhan L, Malaga Chuquitaype C, Ruiz-Teran A, 2019, Design of timber-concrete composite (TCC) bridges with under-deck stay cables, Engineering Structures, Vol: 189, Pages: 589-604, ISSN: 0141-0296

Timber-concrete composite (TCC) bridges represent an attractive structural system due to the synergistic use of its wood and reinforced-concrete constituent components. However, their relatively large flexibility limits their applica- tion for larger spans. This paper presents an alternative solution for TCC bridges involving the implementation of post-tensioned under-deck tendons. Based on a series of design and numerical studies, the advantages of the newly proposed system for 30-m, 60-m and 90-m spans are evaluated. This paper shows that the incorporation of under-deck post-tensioning changes the critical limit states governing the design of TCC bridges, and allows for a significant increase in their slendernesses at medium and long spans. Timber’s shear-deformation contribution to the vertical deflection of TCC bridges is significant and should be accounted for, especially when the span/depth ratio l/h is less than 20. However, this additional deformation can be neglected when stay cables are implemented, especially for bridges with medium and long spans. In order to achieve a more efficient structure, it is proposed that shear connection with an efficiency coefficient, γ, greater than 0.8 be used. Finally, the best practical eccentricity of the under-deck tendons and the best location of the deviators are determined on the basis of parametric analyses.

Journal article

Malaga Chuquitaype C, Menendez-Vicente C, Thiers-Moggia R, 2019, Experimental and numerical assessment of the seismic response of steel structures with clutched inerters, Soil Dynamics and Earthquake Engineering, Vol: 121, Pages: 200-211, ISSN: 0267-7261

Supplemental rotational inertia devices provide an efficient means of suppressing ground-induced vibrations over a large range of structural periods. The beneficial effects of the inerter can be further enhanced by coupling it with a clutch system that prevents it from driving the structural response and ensures that its supplemental rotational inertia is only employed to resist the motion. In this paper, we examine the behaviour of single-degree-of-freedom and multi-degree-of-freedom structures equipped with twin inerter- clutch devices subjected to strong ground-motion. The influence of the clutch stiffness, gears play, viscous damping and dry friction, on the dynamics of the system are explored first, by analysing the stable periodic solutions of a structure with inerters under harmonic-sweeps. We demonstrate that, for the range of param- eters typically expected in earthquake engineering practice, the influence of dry-friction and clutch damping are limited, although the clutch stiffness and gear play may need to be accounted for when large inertances or defective clutches are considered. Based on these findings, we propose a simplified numerical modelling strategy suitable for implementation in conventional Finite Element simulations. Small scale experiments on bare elastic structures as well as structures equipped with inerter and inerter-clutch twins are presented and employed for concept demonstration and for the validation of the numerical model proposed. Finally, a series of studies on detailed numerical models of multi-storey steel frames under idealized and real pulse-like ground-motions are used to demonstrate the vibration absorbing capabilities brought about by the twin inerter-clutch system and to highlight practical aspects related to their structural implementation.

Journal article

Thiers-Moggia R, Malaga Chuquitaype C, 2019, Seismic protection of rocking structures with inerters, Earthquake Engineering and Structural Dynamics, Vol: 48, Pages: 528-547, ISSN: 0098-8847

The seismic behaviour of a wide variety of structures can be characterized by the rocking response of rigid blocks. Nevertheless, suitable seismic control strategies are presently limited and consist mostly on preventing rocking motion all together, which may induce undesirable stress concentrations and lead to impractical interventions. In this paper, we investigate the potential advantages of using supplemental rotational inertia to mitigate the effects of earthquakes on rocking structures. The newly proposed strategy employs inerters, which are mechanical devices that develop resisting forces proportional to the relative acceleration between their terminals and can be combined with a clutch to ensure their rotational inertia is only employed to oppose the motion. We demonstrate that the inclusion of the inerter effectively reduces the frequency parameter of the block, resulting in lower rotation seismic demands and enhanced stability due to the well-known size effects of the rocking behaviour. The effects of the inerter and inerter-clutch devices on the response scaling and similarity are also studied. An examination of their overturning fragility functions reveals that inerter-equipped structures experience reduced probabilities of overturning in com- parison with un-controlled bodies, while the addition of a clutch further improves their seismic stability. The concept advanced in this paper is particularly attractive for the protection of rocking bodies as it opens the possibility of non-locally modifying the dynamic response of rocking structures without altering their geometry.

Journal article

Teslim-Balogun A, Malaga-Chuquitaype C, Stafford PJ, 2019, A Numerical Study on the Structural Response of Steel Structures under Post-Blast Travelling Fires, Structures Congress - Blast, Impact Loading, and Research and Education, Publisher: AMER SOC CIVIL ENGINEERS, Pages: 59-69

Conference paper

Kibriya L, Malaga Chuquitaype C, Kashani M, Alexander Net al., 2018, Nonlinear dynamics of self-centring rocking steel frames using finite element models, Soil Dynamics and Earthquake Engineering, Vol: 115, Pages: 826-837, ISSN: 0267-7261

Rocking post-tensioned steel frames capitalise on the use of rocking joints, and unbonded post-tensioning strands to provide self-centring action. Investigations on the complex and unconventional nonlinear dy- namics of tied rocking steel frames, exclusive of supplemental damping methods, are presently limited. Increasing levels of energy-dissipation reduce the probability of observing nonlinear dynamic phenomena such as co-existing (high/low) amplitude responses at and around the system’s nonlinear resonance. To this end, a finite element (FE) modelling framework is presented, validated and extended to multi-storey steel buildings. It is shown that the simulation strategies proposed enable an accurate representation of the complex nonlinear dynamics of self-centring structures, over a wide range of excitation frequencies and amplitudes. The methodology, applied to multi-storey steel frames, captures the presence of sub-harmonic resonances and higher-modes. It is also demonstrated that the additional demands observed in the rocking columns are the consequence of the asymmetry of the member boundary conditions.

Journal article

Malaga Chuquitaype C, Ilkanaev J, 2018, Novel digitally-manufactured wooden beams for vibration reduction, Structures, Vol: 16, Pages: 1-9, ISSN: 2352-0124

The low modal mass and stiffness of timber floors impose a number of motion- control challenges to the structural designer. These difficulties can often led to the implementation of sub-optimal solutions, such as the addition of supple- mental mass and stiffness in the form of concrete slabs, that conflict with the claimed sustainability and lightweight advantages of wood. In this paper, we present a novel beam configuration that enhances the vibration comfort response of timber flooring systems while retaining the original environmental benefits of wood in construction. By taking advantage of modern digital-fabrication tools, we devise, test and analyse new beam configurations that incorporate flexural resonators tuned to key structural frequencies of the system. These resonators are integrated into the body of the beam and the structure is sized to satisfy typical strength and stiffness demands. A series of numerical, experimental and parametric studies demonstrate the vibration absorbing capabilities of the new designs and the feasibility of their implementation to satisfy current occupant comfort criteria.

Journal article

Lyu Z, Malaga Chuquitaype C, Ruiz-Teran A, 2018, Dynamic response of an under-deck cable-stayed Timber-Concrete Composite bridge under a moving load, World Conference on Timber Engineering

Timber-Concrete Composite bridges have the potential to achieve significant levels of structural efficiency through the synergistic use of Engineering Wood Products (EWPs) and reinforced concrete. With the implementation of post-tensioned under-deck tendons, the range of application of TCC bridges can be extended to medium spans. However, little work has been done to date to study the dynamic response of these newly proposed bridges. In this paper, a set of FE models representing 60-m span structures are analysed to gain understanding on the dynamic response of post-tensioned under-deck TCC bridges. Two models with Euler and Timoshenko beam idealizations are considered in order to evaluate the significance of shear deformations on deflection, structural stresses and connector shear forces. Besides, an analytical model is formulated and compared against the numerical predictions. The results show that timber shear deformations should be considered in the design of post-tensioned under-deck TCC bridges. The dynamic characteristics of the bridge models were studied. The dynamic amplification caused by a moving point load on key response parameters such as deflection, stresses and connector shear forces is discussed. Also, a sensitivity study on the speed of moving load is conducted to investigate its influence on the bridge dynamic response.

Conference paper

Kibriya L, Malaga Chuquitaype C, Kashani M, Alexander Net al., 2018, Finite element investigation of multi-story post-tensioned rocking frames, Eleventh US National Conference on Earthquake Engineering

Modern code-conforming buildings have a high probability of surviving major seismic events without collapse, hence minimizing the number of casualties. Nevertheless, the risk of substantial post-earthquake economic losses remains high, as a consequence of inadequate damage prevention guidelines in current earthquake design codes. Rocking post-tensioned moment-resisting frames present a viable damage-free structural solution, with a nominal increase in building costs compared with conventional buildings. This structural system comprises of: (i) unbonded post- tensioned strands to provide overturning resistance and self-centering capability, and (ii) opening joints at the column-foundation and beam-column interfaces designed to rock during a seismic event. Rocking frames with various forms of supplemental damping have been previously examined numerically, adopting different finite element frameworks. However, there is a shortage of numerical studies studying the non-linear dynamic response of pure rocking multi-story post- tensioned moment frames, exclusive of supplementary energy-dissipation elements and devices. Hence, it is critical to develop modelling procedures for multiple stories which adequately capture the full range of their nonlinear dynamic behavior due to the joint rocking mechanism, and investigate the resulting response. Numerical studies are presented herein, including static and dynamic analyses of three- to nine-story building models. The proposed modelling methods are shown to effectively predict the non-linear response of multi-story rocking frames over a wide range of forcing frequencies and amplitudes. It is further concluded that the structural response is influenced by both sub-harmonic resonances and beam-column interactions.

Conference paper

Thiers Moggia R, Malaga Chuquitaype C, 2018, Seismic protection of cross-laminated timber buildings with supplemental inertia devices, 16th European Conference on Earthquake Engineering (16ECEE)

Multi-storey Cross-Laminated Timber (CLT) buildings are gaining popularity throughout the world due to their many constructive and environmental advantages. Several researchers have proposed the use of post-tensioned rocking connections to improve the seismic performance of timber walled buildings. Although experimental results show that this system has a ductile behaviour and good energy dissipation characteristics, previous research also suggests that high inter-storey drifts and floor accelerations can develop in medium and high-rise timber buildings during earthquakes causing excessive non-structural and content damage. This paper studies the possibility of incorporating inerter-based dampers to reduce these demands and improve the overall seismic performance of Rocking CLT Walled buildings. Firstly, the seismic performance of a series of benchmark buildings designed using Direct Displacement Based Design (DDBD) procedures is assessed. Multiple Stripe Analyses (MSA) are performed to study the response of the buildings for a wide range of seismic intensity levels. The structural performance is examined in terms of peak inter-storey drifts and floor acceleration demands. Secondly, a Tuned InertoViscous Damper (TIVD) system is designed to obtain an effective mass ratio for the first mode of μr=0.1. A numerical model for the TIVD is defined and incorporated into the structural models previously analysed. Response history analyses are then performed on complete numerical models and the corresponding performance parameters compared in order to assess the effectiveness of the protective measure.

Conference paper

Demirci C, Malaga Chuquitaype C, Macorini L, 2018, Drift response of tall cross-laminated timber buildings under realistic earthquake loads, 16th European Conference on Earthquake Engineering (16ECEE)

This paper examines the drift response of tall cross-laminated timber (CLT) buildings subjected to a large set of real strong ground motions. Particular focus is placed on the influence of ground-motion frequency content on the inelastic drift demands of multi-storey CLT building structures. A total of 68 CLT buildings with varying structural characteristics were modelled and subjected to a set of 1656 real acceleration records. The effect of the frequency content of ground-motion, characterised by its mean period, Tm, is found to be determinant on the inelastic deformation demands of CLT walled buildings. Furthermore, the evolution of drift demands as a function of tuning ratio reveals different trends for low and high-rise CLT buildings. Prediction models for the estimation of global and inter-storey drift response on low-, mid- and high-rise CLT buildings are developed by means of nonlinear regression analysis. Finally, a comparative study is performed with reference to Eurocode 8 equal displacement rule and recent assessment proposals is outlined

Conference paper

Kibriya L, Malaga Chuquitaype C, Kashani M, Alexander Net al., 2018, Numerical investigation of the nonlinear dynamic response of self-centring rocking frames, 16th European Conference on Earthquake Engineering (16ECEE)

Conventional seismic design standards are rooted in the notion of collapse-prevention to ensure life-safety during major seismic events. To this end, modern code-conforming buildings are designed to accept a certain level of damage during earthquakes. Nevertheless, this design philosophy does not explicitly address damage mitigation, which leads to substantial post-earthquake economic losses. Rocking post-tensioned frames are a highly sustainable seismic design solution which remains operational after an earthquake event. They capitalise on the use of: (i) unbonded post-tensioned strands to provide overturning resistance and self-centring action, and (ii) rocking (opening) joints at the column-foundation and beam-column connections. Preceding research has proposed modelling strategies to capture the highly nonlinear behaviour of rocking structures. Nevertheless, numerical modelling techniques generating frequency response functions for the study of the non-linear dynamic properties of post-tensioned rocking moment frames without sacrificial elements or external damping, are presently limited. Thus, it is imperative to develop modelling procedures which enable an accurate representation of the fundamental nonlinear dynamic behaviour of rocking frames over a range of ground-motion excitations. The physical model of a steel post-tensioned rocking frame, which has been formerly tested under static and dynamic conditions, is employed in this paper in order to validate a new advanced finite element framework. A numerical study is presented, which incorporates a one-storey model, and includes static and dynamic responses. The results are compared with experimental and discrete-element models, and generalizable modelling considerations are presented. It is shown that the proposed method encompasses a simplified modelling approach and effectively represents the complete nonlinear response of rocking moment-resisting frames.

Conference paper

Sirumbal-Zapata LF, Málaga-Chuquitaype C, Elghazouli AY, 2018, A three-dimensional plasticity-damage constitutive model for timber under cyclic loads, Computers and Structures, Vol: 195, Pages: 47-63, ISSN: 0045-7949

© 2017 Elsevier Ltd The performance of timber structures is governed by the nonlinear response at their connections, where high deformation levels and stress concentrations are developed, particularly when subjected to load reversals. To date, no constitutive model for wood under cyclic load exists which is able to incorporate its most important failure modes while considering plastic deformations and cyclic stiffness and strength degradation simultaneously. This paper presents the formulation and implementation of a plasticity-damage model with these characteristics within a continuum mechanics approach. The theoretical framework of both plasticity and damage models is described, and a detailed derivation of the constitutive equations required for their computational implementation and coupling as well as the return mapping and iterative algorithms for their integration are presented. The damage evolution process is handled by two independent scalar variables for tension and compression. A general orthotropic plasticity yield surface with isotropic hardening is employed to incorporate timber plastic flow in compression. A closed-form expression for the plasticity-damage consistent tangent operator is derived. It is demonstrated that the proposed constitutive model captures all the key characteristics required for an accurate modelling of timber under large deformation levels until failure.

Journal article

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