Publications
122 results found
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.
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.
Kibriya L, Malaga Chuquitaype C, Kashani M, et 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.
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.
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
Kibriya L, Malaga Chuquitaype C, Kashani M, et 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.
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
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.
Demirci C, Malaga Chuquitaype C, Macorini L, 2017, Seismic drift demands in multi-storey cross-laminated timber buildings, Earthquake Engineering and Structural Dynamics, Vol: 47, Pages: 1014-1031, ISSN: 0098-8847
This paper investigates the seismic response of multi-storey cross-laminated timber (CLT) buildings and its relationship with salient ground-motion and building characteristics. Attention is given to the effects of earthquake frequency content on the inelastic deformation demands of platform CLT walled structures. The response of a set of 60 CLT buildings of varying number of storeys and panel fragmentation levels representative of a wide range of structural configurations subjected to 1656 real earthquake records is examined. It is shown that, besides salient structural parameters like panel aspect ratio, design behaviour factor and density of joints, the frequency content of the earthquake action as characterised by its mean period has a paramount importance on the level of nonlinear deformations attained by CLT structures. Moreover, the evolution of drifts as a function of building to ground-motion periods ratio is different for low and high-rise buildings. Accordingly, nonlinear regression models are developed for estimating the global and inter-storey drifts demands on multi- storey CLT buildings. Finally, the significance of the results is highlighted with reference to European seismic design procedures and recent assessment proposals.
Lyu Z, Malaga Chuquitaype C, Ruiz-Teran AM, 2017, Feasability of timber-concrete composite road bridges with under-deck stay cables, 39th International IABSE Symposium
Timber‐concrete composite (TCC) bridges represent an attractive structural system due to the synergistic use of wood and reinforced‐concrete. However, the benefits of TCC bridges can be hampered by their relatively large flexibility that limits their application to long spans. This paper presents an alternative solution for TCC bridges that incorporates post‐tensioned under‐deck tendons. These steel tendons are deviated by two struts and anchored to the cross beams at the support section, effectively subdividing the total span of the TCC bridge into three sub‐spans. The advantages of the newly proposed system are evaluated for 60 m span TCC bridges. This paper shows that the incorporation of under‐deck post‐tensioning effectively changes the critical limit states governing the design of TCC bridges. In addition, the application of post‐tensioned tendons leads to a significant increase in the allowable slenderness and efficiency of structures.
Teslim-Balogun A, Malaga Chuquitaype C, Stafford PJ, 2017, Assessment of efficiency of intensity measures for performance-based travelling fire design, 39th International IABSE Symposium
Kashani M, Malaga Chuquitaype C, Yang S, et al., 2017, Influence of non-stationary content of ground-motions on nonlinear dynamic response of RC bridge piers, Bulletin of Earthquake Engineering, Vol: 15, Pages: 3897-3918, ISSN: 1573-1456
This paper quantifies the impact of the non-stationary content (time-varying parameters that are not captured by power spectral density alone) of different ground-motion types (near/far field, with/without pulses time-series) on the nonlinear dynamic response of reinforced concrete (RC) bridge piers, taking into account the material cyclic degradation. Three groups of ground motions are selected to represent far-field, near-field without pulse and near-field pulse-like ground motions. Three analysis cases are considered corresponding to acceleration series matched to the mean response spectrum of: (i) far field, (ii) near-field without pulse and (iii) near-field pulse-like ground- motions, respectively. Using the selected ground motions, several nonlinear incremental dynamic analyses (IDAs) of prototype reinforced concrete bridge piers with a range of fundamental periods are conducted. Finally, a comparison between the response of the structures using the material model accounting for both buckling and low-cycle fatigue of reinforcing steel and the more conventional material model that does not account for these effects is made. The results show that the inelastic buckling and low-cycle fatigue have a significant influence on the nonlinear response of the RC bridge piers considered and that pulse effects can increase the mean acceleration response by about 50%.
Camara A, Cristantielli R, Astiz MA, et al., 2017, Design of hysteretic dampers with optimal ductility for the transverse seismic control of cable-stayed bridges, Earthquake Engineering & Structural Dynamics, Vol: 46, Pages: 1811-1833, ISSN: 1096-9845
Cable-stayed bridges require a careful consideration of the lateral force exerted by the deck on the towersunder strong earthquakes. This work explores the seismic response of cable-stayed bridges with yieldingmetallic dampers composed of triangular plates (TADAS) that connect the deck with the supports in thetransverse direction. A design method based on an equivalent single-degree of freedom approximation isproposed. This is proved valid for conventional cable-stayed bridges with 200 and 400 m main spans, butnot 600 m. The height of the plates is chosen to (1) achieve a yielding capacity that limits the maximum forcetransmitted from the deck to the towers, and to (2) control the hysteretic energy that the dampers dissipate bydefining their design ductility. In order to select the optimal ductility and the damper configuration, a multi-objective response factor that accounts for the energy dissipation, peak damper displacement and low-cyclefatigue is introduced. The design method is applied to cable-stayed bridges with different spans and deck-support connections.The results show that the dissipation by plastic deformation in the dampers preventssignificant damage in the towers of the short-to-medium span bridges under the extreme seismic actions.However, the transverse response of the towers in the bridge with 600 m span is less sensitive to the TADASdampers.
Karagiannis V, Malaga Chuquitaype C, Elghazouli AY, 2017, Behaviour of hybrid timber beam-to-tubular steel column moment connections, Engineering Structures, Vol: 131, Pages: 243-263, ISSN: 0141-0296
This paper presents an experimental and numerical study into the response of bolted connections between Glulam timber beams and tubular steel columns. Six specimens involving two different connection types subjected to monotonically increasing bending action are examined. The first connection type incorporates top and seat angles blind-bolted to the column and jointed to the beam through long bolts. The second connection type is formed by a steel T-stub slotted into the timber beam and connected to it by means of transverse bolts. In addition, two reinforcing techniques aimed at enhancing the response of the slotted-in T-stub configuration are investigated. These include the provision of a bottom wedge angle between the beam and the column as well as the use of perpendicular-to-grain screws to delay wood splitting. The experimental set-up, connection configurations and material properties are introduced followed by a detailed account of the test results and observations. The main behavioural patterns are identified from the experiments and key response characteristics such as stiffness, capacity and failure mechanism are discussed. This paper shows that the use of bottom wedge angles leads to significant enhancement in the flexural yield strength of the T-stub connections, accompanied by a relatively small change in the location of the bolt-group point of rotation (monitored herein by means of Digital Image Correlation techniques). Besides, the use of reinforcing screws is shown to be an effective detail for substantially increasing the rotational ductility of the connections. Finite element simulations of the tests are also presented, together with a detailed description of the modelling approaches employed, in order to gain further insight into the behaviour of the connections. Finally, the applicability of simplified component-based expressions, which are suitable for practical design assessment procedures, for the estimation of the stiffness and capacity of the
Sirumbal Zapata LF, Malaga Chuquitaype C, Elghazouli AY, 2017, Coupled plasticity-damage material constitutive model for timber subjected to cyclic loading, 16th World Conference on Earthquake Engineering, Pages: Paper No 1122-Paper No 1122
Kashani M, Malaga Chuquitaype C, Yang S, et al., 2017, Impact of material cyclic degradation on the nonlinear dynamic response of RC bridge piers, 16th World Conference on Earthquake Engineering
Demirci C, Malaga Chuquitaype C, Macorini L, 2017, Seismic behaviour and design of tall cross-laminated timber buildings, 16th World Conference on Earthquake Engineering
Malaga Chuquitaype C, Bougatsas K, 2017, Scalar and vector-IM-based drift hazard estimations for steel buildings with alternative framing configurations, 16th World Conference on Earthquake Engineering
Malaga Chuquitaype C, Elghazouli AY, 2017, Design of Timber Structures, Seismic Design Of Buildings To Eurocode 8, Editors: Elghazouli, Pages: 213-234
Malaga Chuquitaype C, Bougatsas K, 2016, Vector-IM-based assessment of alternative framing systems under bi-directional ground-motion, Engineering Structures, Vol: 132, Pages: 188-204, ISSN: 1873-7323
This paper examines the seismic performance of steel buildings with alternative framing systems subjected to bi-directional ground-motion. Peak drifts of one-way (perimeter framing) and two-way (space framing) systems are assessed by means of scalar and vector-valued probabilistic methods. Extensive non-linear response history analyses over idealized 3D structures representing 6- and 9-storey buildings are performed under pairs of linearly scaled ground-motions. Both far-field and near-field non-pulselike acceleration series are considered. The spectral acceleration of the geometric mean of the two horizontal components (Sa,GM) is taken as the primary intensity measure (IM) while four other ground-motion parameters are employed to construct IM-vectors including: the spectral acceleration ratio (RT3,T1), the spectral shape parameter (Np), and two frequency content parameters (Tm and To). This paper shows that incorporating the vector ⟨Sa,GM,Np⟩ into the assessment of bi-directionally loaded 3D buildings yields up to 40 % lower conditional standard deviations than a purely scalar formulation at large drift levels while the vector ⟨Sa,GM, RT3,T1⟩ is more efficient at smaller drifts. The effects of alternative framing systems on structural fragilities are found to differ depending on the number of storeys. For 6-storey structures, consistently higher capacities are observed in two-way layouts with respect to one-way systems but they are associated with increasing variabilities at larger demand levels. Conversely, the 9-storey two-way building experiences 5 % lower mean capacities than its one-way counterpart. Finally, drift hazard curves are calculated by combining the building fragilities with idealized ground-motion hazard estimates. The results indicate that one-way buildings experience consistently lower drift exceedance rates regardless of the ground-motion type, especially for drift levels larger than 2 % although the differences are larger for the 9-storey frames
Sadowski AJ, Camara A, Malaga Chuquitaype C, et al., 2016, Seismic analysis of a tall metal wind turbine support tower with realistic geometric imperfections, Earthquake Engineering & Structural Dynamics, Vol: 46, Pages: 201-219, ISSN: 1096-9845
The global growth in wind energy suggests that wind farms will increasingly bedeployed in seismically active regions, with large arrays of similarly-designedstructures potentially at risk of simultaneous failure under a major earthquake. Windturbine support towers are often constructed as thin-walled metal shell structures, wellknownfor their imperfection sensitivity, and are susceptible to sudden buckling failureunder compressive axial loading.This study presents a comprehensive analysis of the seismic response of a 1.5 MWwind turbine steel support tower modelled as a near-cylindrical shell structure withrealistic axisymmetric weld depression imperfections. A selection of twentyrepresentative earthquake ground motion records, ten ‘near-fault’ and ten ‘far-field’,was applied and the aggregate seismic response explored using lateral drifts and totalplastic energy dissipation during the earthquake as structural demand parameters.The tower was found to exhibit high stiffness, though global collapse may occur soonafter the elastic limit is exceeded through the development of a highly unstable plastichinge under seismic excitations. Realistic imperfections were found to have asignificant effect on the intensities of ground accelerations at which damage initiatesand on the failure location, but only a small effect on the vibration properties and theresponse prior to damage. Including vertical accelerations similarly had a limited effecton the elastic response, but potentially shifts the location of the plastic hinge to a moreslender and therefore weaker part of the tower. The aggregate response was found to besignificantly more damaging under near-fault earthquakes with pulse-like effects andlarge vertical accelerations than far-field earthquakes without these aspects.
Malaga Chuquitaype C, Skinner J, Dowdall A, et al., 2016, Response of CLT shear walls under cyclic loads, World Conference on Timber Engineering
Málaga-Chuquitaype C, Elghazouli AY, 2016, Design of timber structures, Seismic Design of Buildings to Eurocode 8, Second Edition, Pages: 213-234, ISBN: 9781498751605
Well-designed and well-constructed timber structures can have an excellent response under earthquake loading due primarily to the high strength to weight ratio of wood. Nevertheless, the seismic performance of timber buildings involves various inter-related factors that need to be properly understood. Many of the aspects related to the resistance of timber buildings spring from the atypical mechanical characteristics of wood as a construction material. In particular, there are significant differences in wood strength and stiffness depending on the orientation of the load with respect to the grain direction as depicted in Figure 8.1. It follows from the schematic strain-stress curves, indicated in Figure 8.1, that tension failures in wood are brittle and should be avoided while compressive behaviour (parallel to the grain) is a preferred mode of failure but should be limited. In fact, it is a typical approach of codes of practice to ensure a ductile failure mechanism by inducing yielding in metallic connectors between timber members instead of the wood material itself in order to provide a sustained source of energy dissipation during seismic shaking.
Malaga Chuquitaype C, 2015, Estimation of peak displacements in steel structures through dimensional analysis and the efficiency of alternative ground-motion time and length scales, Engineering Structures, Vol: 101, Pages: 264-278, ISSN: 1873-7323
This paper deals with the estimation of maximum displacements in single-degree-of-freedom (SDOF) systems simulating typical steel structures by means of dimensional analysis. Peak deformation demands in bilinear systems (representative of moment resisting frames) are considered as well as additional pinching models depicting Partially-Restrained (PR) and Concentrically-Braced (CB) frames subjected to a series of non-coherent acceleration records. Particular attention is given to the identification of efficient length and time scales in non-pulselike earthquake motions. The relative merits of incorporating the mean period of the ground-motion (TmTm), predominant period (TpTp), significant duration (tsigtsig) as well as peak ground acceleration (PGA), peak ground velocity (PGV), root mean square acceleration (aRMSaRMS), root mean square velocity (vRMSvRMS) and Arias Intensity (IaIa) within the dimensionless functional form are evaluated. When the normalized peak displacements of bilinear, PR and CB oscillators are presented as a function of the normalized yield displacement and dimensionless characteristic structural strengths (both total and at pinching intervals), a clear pattern emerges and the response becomes self-similar. This paper demonstrates that the use of the mean period (TmTm) as a time scale produces consistently lower dispersion and bias in the estimations of maximum displacements in comparisons with other ground-motion time scales. Similarly, the root mean square acceleration (aRMSaRMS) is found to be the most efficient amplitude-related parameter for the estimation of maximum displacements in bilinear and CB structures whereas the peak ground acceleration (PGA) is the most efficient ground-motion parameter for the prediction of peak deformations in PR systems. Finally, simple expressions for the assessment of displacement demands in steel structures based on the most-efficient dimensionless master curves are proposed and verified.Keywords Steel str
Karagiannis V, Malaga Chuquitaype C, Elghazouli AY, 2015, Modified foundation modelling of dowel embedment in glulam connections, Construction and Building Materials, Vol: 102, Pages: 1168-1179, ISSN: 0950-0618
This paper examines the embedment behaviour of single-dowel connections in Scandinavian Spruce Glulam by means of experimental and numerical investigations. First, the experimental results of a series of single-dowel tests on samples of different geometry and grain directions are presented. The evolution of local strain concentrations around the fastener at increasing levels of bearing deformation, is reported in detail by means of non-contact field strain measurements and its implications are discussed. Detailed Finite Element simulations are also carried out and subsequently employed to highlight the main features of the response of doweled connections in glulam. A foundation model, initially developed for Douglas-fir (Pseudotsuga menziesii) timber, is upgraded and adapted for Scandinavian Spruce Glulam (Picea abies) elements subjected to loads acting perpendicular and parallel to the grain direction. The proposed model is based on the definition of equivalent material parameters for the crushing region around the dowel hole. To this end, relationships for the estimation of material characteristics as a function of the crushing volume are suggested. The validity and accuracy of the proposed modified foundation models are examined against the experimental results. It is shown the improved foundation model is able to simulate the embedment stiffness, capacity and inelastic behaviour of single-dowel connections on glulam with reasonable accuracy for strains of up to 8%, and can therefore be used for design and assessment purposes.
Abeysekera I, Málaga-Chuquitaype C, 2015, Dynamic response of tall timber buildings, SECED 2015
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