84 results found
Freddi F, Galasso C, Cremen G, et 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.
Alavi A, Mele E, Rahgozar R, et 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.
Melchor-Placencia C, Malaga Chuquitaype C, 2021, OpenMoist: A Python Code for Transient Moisture Transfer Analysis, SoftwareX, ISSN: 2352-7110
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.
Kampas G, Kalapodis N, McLean T, et 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
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.
Dehghani S, Fathizadeh S, Yang T, et 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.
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.
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.
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.
Fathizadeh S, Dehghani S, Yang T, et 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
Sadowski A, Wei Jun W, Simon Li SC, et 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.
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.
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.
Kibriya LT, Málaga-Chuquitaype C, Kashani MM, 2020, Damage-avoidance steel rocking frames with buckling-enabled composite bracing, Pages: 3117-3126, ISSN: 2311-9020
The severe social and economic impacts of recent earthquakes have inspired a growing interest in smart structural systems that offer immediate post-disaster occupancy. Post-tensioned rocking frames are emerging damage-avoiding seismic-resistant structures that employ rocking joints at member connections (to avoid major damage to primary structural elements) and unbonded post-tensioned strands (to provide self-centring capability). Nevertheless, currently available passive load-resisting systems to control the peak structural responses in steel rocking frames rely on sacrificial yielding components that accumulate damage during strong dynamic action. This results in a system with limited durability and a requirement for regular maintenance throughout the building's lifetime. By contrast, the recently proposed Buckling-Enabled Composite Bracing (BECB) elements can provide a thorough damage-avoidance solution by means of carefully controlled elastic buckling behaviour. In these systems, compression-only elements with circular-arc-shaped cross-sections are incorporated into steel rocking frames as lattice bracing in order to improve their dynamic performance. The proposed system has been shown to perform successfully under static loading and discrete sine-sweep ground motions for single-storey rocking frames. This further examines this innovative concept by performing numerical investigations on three-storey four-bay post-tensioned steel rocking buildings under real earthquake ground motions. The performances of conventional moment frames (MRFs) and their rocking frame counterparts (RFs) with and without BECB elements are compared through numerical simulations. Glass-fibre reinforced polymer (GFRP) is selected for the BECB elements. Static Pushover, Discrete Sine-sweep and Incremental Dynamic (IDA) analyses are performed to evaluate the buildings' performances. Damage measures investigated include maximum inter-storey drifts and floor accelerations. It is demonstrated t
Thiers-Moggia R, Málaga-Chuquitaype C, 2020, Seismic protection of multi-storey rocking structures with inerters, Pages: 1528-1544, ISSN: 2311-9020
Recent studies on seismic control of rocking structures have proposed the use of inerters, mechanical devices that develop resisting forces proportional to the relative acceleration between their terminals. Analytical analyses have shown that these devices effectively reduce the frequency parameter of a rocking block resulting in lower seismic demands and enhanced stability due to the well-known size effect of the rocking behaviour. As with most of such strategies, the efficiency of the inerter has been assessed for perfectly rigid bodies in the first place. However, in real practical applications, rocking structures will exhibit some degree of flexibility. Moreover, some of the underlying assumptions of the analytical models used to study rigid bodies imply that the structures are slender, and therefore more likely to deform during the rocking motion. In this paper, the dynamic response of multi-mass flexible rocking bodies equipped with inerters is examined. Firstly, a numerical model is formulated and implemented in OpenSees. This model is then validated against analytical analyses of single-mass flexible structures. Subsequently, the responses of buildings ranging from 3 to 9 stories are studied and compared in terms of elastic deformations, base rotations and floor accelerations. The effect of increasing levels of flexibility in the efficiency of the inerter is also assessed.
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.
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.
Di Pilato D, Tubaldi E, Castaldo P, et al., 2019, Risk assessment of bridge's piers subjected to multiple earthquakes: comparison between different approahces, ANIDIS 2019, L'Ingegneria sismica in Italia
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
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
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
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
Málaga-Chuquitaype C, Psaltakis ME, Kampas G, et 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.
Lyu Z, 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.
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.
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.
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
Kibriya L, Malaga Chuquitaype C, Kashani M, et 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.
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.
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