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Abstract

This paper presents a numerical study conducted on a seven-story timber building made of cross-laminated (X-lam) panels, equipped with a linear translational tuned mass damper (TMD). The TMD is placed on the top of the building as a technique for reducing the notoriously high drifts and seismic accelerations of these types of structures. TMD parameters (mass, stiffness, and damping) were designed using a genetic algorithm (GA) technique by optimizing the structural response under seven recorded earthquake ground motions compatible, on average, with a predefined elastic spectrum. Time-history dynamic analyses were carried out on a simplified two-degree-of-freedom system equivalent to the multistory building, while a detailed model of the entire building using two-dimensional elastic shell elements and elastic springs for modeling connections was used as a verification of the evaluated solution. Several comparisons between the response of the structure with and without TMD subjected to medium- and high-intensity recorded earthquake ground motions are presented, and the effectiveness and limits of these devices for improving the seismic performance of X-lam buildings are critically evaluated.

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... The use of GAs as optimisation tool for designing this type of devices was also explored in [20] and [21]. A similar approach was used by the authors in [22], where a set of spectrum-consistent accelerograms were applied to a simplified 2-DOFs model of the TMD-equipped structure and the response optimised in average. ...
... The FE modelling of the seven-storey building, implemented in the general FE solver ABAQUS [27] and already presented in [22,28], is briefly described in the following. The actual geometry of horizontal and vertical X-Lam panels was reproduced by means of a purposely developed meshing software [28], needed to mesh each wall with shell elements of proper size to fit the actual positions of the metal connectors such as hold-downs, angle brackets and self-drilling screws. ...
... The two fundamental frequencies estimated by the numerical model are 4.40 Hz and 2.88 Hz for X and Y direction respectively ( Figure 2). The discrepancies with the experimental values (3.32 Hz and 2.34 Hz, respectively), which are under 20% in terms of periods, were considered acceptable given the uncertainties always present in numerical modelling [22]. More accurate response predictions could be obtained with complex nonlinear models [33]. ...
Article
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In this paper, the effectiveness of different design solutions for tuned mass dampers (TMD) applied to high-rise cross-laminated (X-Lam) timber buildings as a means to reduce the seismic accelerations was investigated. A seven-storey full-scale structure previously tested on shaking table was used as a reference. The optimal design parameters of the TMDs, i.e. damping and frequency ratios, were determined by using a genetic algorithm on a simplified model of the reference structure, composed by seven masses each representing one storey. The optimal solutions for the TMDs were then applied to a detailed finite element model of the seven-storey building, where the timber panels were modelled with shell elements and the steel connectors with linear spring. By comparing the numerical results of the building with and without multiple TMDs, the improvement in seismic response was assessed. Dynamic time-history analyses were carried out for a set of seven natural records, selected in accordance with Eurocode 8, on the simplified model, and for Kobe earthquake ground motion on the detailed model. Results in terms of acceleration reduction for different TMD configurations show that the behaviour of the seven-storey timber building can be significantly improved, especially at the upper storeys.
... New approaches are developed for the seismic design of tall buildings. For instance innovative low-damage structural systems such as pre-stressed re-centring walls (Buchanan et al. 2008), new types of dissipative steel connections (Cesare et al. 2019a(Cesare et al. , 2019b or innovative energy dissipators (Wrzesniak et al. 2013) and tuned mass dampers (Poh'sie GH et al.. 2016;Hervé Poh'Sié et al. 2016) have been developed. Deformable floor diaphragms or multi-storey segmental rocking walls should be further investigated (Pei et al. 2014). ...
Article
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An efficient implementation of the capacity design requires high ductility combined with a low overstrength of the critical regions. Conventional timber connections do not generally offer such ideal combination, resulting in modest behaviour and relatively high overstrength factors. Inspired by the Buckling Restrained Brace a new hold-down has been developed where the timber wall directly acts as a casing. The new hold-down has been given an adaptive stiffness allowing the structure to be stiff in the wind, while becoming more flexible in the case of an earthquake. Furthermore, local crushing of the timber members is completely avoided, and the new hold-down could be replaced after an earthquake. Experimental investigations were performed on hold-down specimens. The results show ultimate displacement values vu,c of more than 30 mm in a cyclic test according to EN12512. Eleven Cross Laminated Timber shear walls, in which the new hold-down has been implemented, were tested following monotonic and static-cyclic tests procedures, with and without vertical load. A very high ductility has been achieved with almost no strength degradation, little pinching and limited overstrength.
... Refs. [26][27][28][29][30]), although it is acknowledged that this technology can be a catalyst for fostering building construction of mid-and high-rise timber buildings in areas of high seismic hazard [31]. ...
Article
Based on a six-storey cross-laminated timber building equipped with a base isolation system, this article proposes predictive models for the fundamental period of vibration, a parameter that needs to be selected in early stages of a seismically isolated building's design process, in relation to economic losses, such as repair costs and repair time, and environmental losses, such as repair-related carbon footprint and embodied energy. The predictive models were calibrated using a dataset of 114 bidirectional accelerograms recorded in Chile between 1985 and 2020, with event magnitudes ranging from Mw 7 to Mw 8.8. A single functional form was selected for the four resilience parameters used, having an average coefficient of determination of R² = 0.62. Results suggest that the selection of the fundamental period of vibration of a mid-rise seismically isolated CLT building can have a significant impact on the potential economic and environmental losses likely to occur when subjected to severe seismic events, and therefore, its selection should be based not only on technical aspects but also resilience and sustainability parameters.
... In general, the selection of TMD parameters take into a complicated situation when the structures are complex [15]. And when the structures are taller, the process gets harder to deal with; hence to overcome such issue optimization is preferable instead of manual tuning [19]. Therefore, an optimization will assist to overcome the drawbacks of sub-optimal tuning of parameters. ...
Article
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This study investigates the performance of tall buildings using tuned mass damper (TMD) under dynamic loads such as harmonic loads, and the Loma Prieta Earthquake 1989 data. The numerical investigations are performed by considering a sixteen-storied dynamical system. To do this end, the aforementioned system is considered to be uncontrolled (meaning no damper is used) and a controlled case is assumed where a TMD is placed on the top floor. TMD performance mainly relies on the set of parameters (mass ratio, damping ratio, and stiffness). In reality, the tuning process of those parameters take serious effort and gets worse with the complicacy of the structure. Hence to obtain better performance of the TMD the damping ratio and the frequency of the TMD are optimized by using unconstrained derivative-free method. Finally, the uncontrolled and controlled performance of the sixteen-storied structure has been evaluated and compared. The results show that the dynamical response of the studied problem can be reduced significantly via the use of optimized parameters.
... Of these, passive control is a prevalent strategy due to its independence from reliance on extra energy input (Casciati and Faravelli 2009). Among the numerous passive control devices, a tuned mass damper (TMD), which can dissipate the input energy by tuning frequency, is most widely used for wind-induced vibration control due to its simple characteristics, convenient installation, low cost, and favorable control effects under specific tuned frequencies (Roffel et al. 2013;Elias et al. 2016;Poh'sie et al. 2016;Roffel and Narasimhan 2016). ...
Article
This paper investigates the dynamic behavior of structures with a particle damper (PD) and a tuned mass damper (TMD) by shaking table tests and aeroelastic wind tunnel tests. The influence of parameters including seismic waves, peak ground accelerations, damping ratios, mass ratios, and wind angles of attack are analyzed. A systematic comparison between the PD and TMD shows that the vibration-control effects of the PD are generally better than those of the TMD under both earthquake and wind loads. The reason lies in the fact that the PD can dissipate the input energy not only by tuning frequency (similar to TMD) but also by the impact and friction between particles and between the particles and the wall of the container. Moreover, a theoretical analysis of a single-degree-of-freedom (SDOF) system with optimum PD and TMD was also carried out by numerical simulations, and the hidden vibration-control mechanism is discussed. The results indicate that the optimum vibration-control effects of both dampers are comparable, but the swing amplitude of the additional mass of the PD is much smaller than that of the TMD. Through a series of experiments with various parameters, the results demonstrate that the characteristics of the seismic input and the wind angle of attack have a larger influence on the damping performance of the TMD compared with the PD, indicating that the PD is less sensitive to the changing parameters.
... To this end, several midrise and high-rise CLT-based buildings are constructed in Europe, North America, and Australia (Fragiacomo and van de Lindt 2016;Pei et al. 2014). To increase the applicability of CLT constructions located in moderate and high seismic risk areas, several experimental and numerical studies have been recently conducted (Hervé Poh'sié et al. 2015;Popovski and Garvic 2015;Yasamura et al. 2015;Ceccotti et al. 2013;Gagnon and Pirvu 2011;Popovski et al. 2010). Specifically, Pei et al. (2013) and Zhang et al. (2015) have developed seismic force reductions factors for CLT system and mass-timber hybrid building, respectively. ...
Article
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In this paper, to supplement the Canadian building code for a timber-steel hybrid structure, over-strength, and ductility-related force modification factors are developed and validated using a collapse risk assessment approach. The hybrid structure incorporates cross-laminated timber (CLT) infill walls within steel moment resisting frames. Following the FEMA P695 procedure, archetype buildings of 3-story, 6-story, and 9-story height with middle bay infilled with CLT were developed. Subsequently, a nonlinear static pushover analysis was performed to quantify the actual over-strength factors of the hybrid archetype buildings. To check the FEMA P695 acceptable collapse probabilities and adjusted collapse margin ratios (ACMRs), incremental dynamic analysis was carried out using 60 ground motion records that were selected to regional seismic hazard characteristics in southwestern British Columbia, Canada. Considering the total system uncertainty, comparison of the calculated ACMRs with the FEMA P695 requirement indicates the acceptability of the proposed over-strength and ductility factors.
... To this end, several midrise and high-rise CLT-based buildings are constructed in Europe, North America, and Australia (Fragiacomo and van de Lindt 2016;Pei et al. 2014). To increase the applicability of CLT constructions located in moderate and high seismic risk areas, several experimental and numerical studies have been recently conducted (Hervé Poh'sié et al. 2015;Popovski and Garvic 2015;Yasamura et al. 2015;Ceccotti et al. 2013;Gagnon and Pirvu 2011;Popovski et al. 2010). Specifically, Pei et al. (2013) and Zhang et al. (2015) have developed seismic force reductions factors for CLT system and mass-timber hybrid building, respectively. ...
Article
In this paper, to supplement the Canadian building code for a timber-steel hybrid structure, over-strength, and ductility-related force modification factors are developed and validated using a collapse risk assessment approach. The hybrid structure incorporates cross-laminated timber (CLT) infill walls within steel moment resisting frames. Following the FEMA P695 procedure, archetype buildings of 3-story, 6-story, and 9-story height with middle bay infilled with CLT were developed. Subsequently, a nonlinear static pushover analysis was performed to quantify the actual over-strength factors of the hybrid archetype buildings. To check the FEMA P695 acceptable collapse probabilities and adjusted collapse margin ratios (ACMRs), incremental dynamic analysis was carried out using 60 ground motion records that were selected to regional seismic hazard characteristics in southwestern British Columbia, Canada. Considering the total system uncertainty, comparison of the calculated ACMRs with the FEMA P695 requirement indicates the acceptability of the proposed over-strength and ductility factors.
... Within this work, the problem of evaluating the behavior factor of this structural typology has been examined, assessing the experimental results on real scale buildings and developing a set of multiple transient dynamic analyses (MTDA) with a FE model developed in DRAIN-3D [4]. The experimental and numerical analyses have revealed that, even though CLT panel buildings can exhibit a satisfactory performance under seismic loading conditions, with the current system of connections they should be designed using a maximum value of the behavior factor only equal to 3. Additional studies on CLT structures have also been performed more recently in [8][9][10][11]. ...
Article
The aim of this paper is to analyze the possibility to improve the seismic performance of cross-laminated timber (CLT) panel buildings introducing in the structure dissipative connectors in substitution of the classical hold-downs. In fact, as demonstrated by past experimental tests and numerical analyses, hold-downs exhibit a limited dissipation capacity. The proposed dissipative connector is called XL-stub and applies the concept usually adopted for ADAS devices. In order to prove the effectiveness of the proposed system the results of an experimental program devoted to characterize the force–displacement response under cyclic loads and low fatigue behavior of the XL-stub are presented and compared to the results of cyclic tests of hold-downs with same resistance. Afterwards, the comparison is extended at the level of the building, evaluating the influence of the connection on the seismic performance of the whole CLT panel building. To this scope, a FE model of the three-storey building tested within the SOFIE project is calibrated and multiple transient dynamic analyses are performed both for the building with the classical layout of connections and for the building equipped with XL-stubs. The obtained results are compared and the values of the behavior factor for the two solutions are calculated.
... Depending on the specific aim of the retrofitting action, different objectives may be selected. As an example, Poh'sie et al. (2016) designed a Tuned Mass Damper system according to different objectives related to the response under ground motion of the structure equipped with the device, i.e., minimizing the peak acceleration/displacement or the average of the higher acceleration or displacement. This implied evaluating the dynamic response under several ground motions and working on appropriate statistics of the single responses. ...
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n this study, a multi-objective Genetic Algorithm (GA) optimization procedure is proposed for the seismic retrofitting of Reinforced Concrete (RC) building frames via Fiber-Reinforced Polymer (FRP) jackets. The optimization problem is solved via numerically efficient but accurate Finite-Element (FE) models able to take into account the strengthening and ductility increase contribution for a given FRP jacketing configuration. Based on a reference RC frame case study, an optimization approach aimed to maximize the frame ductility and minimize the FRP volume/cost is proposed, by taking into account different FRP jackets thicknesses for the internal and external columns and well as for each separate frame floor. In doing so, careful consideration is paid also to the expected collapse mechanism for the frame and the approach to embed a further objective able to control the collapse mechanism into the procedure is described. The results show the potential of the approach, which not only provides the entire Pareto Front of the multi-objective optimization problem, but also allows for general considerations about the influence of the design variables on the response of a given RC building.
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Traditional structural design involves repeated modeling and parameter tuning of buildings, which is time-consuming work. To solve the problem, the automatic structural optimization design of a multi-lateral force resist system is proposed out. The aim is to minimize the cost of structural materials based on initial determinate structural model subjected to multiple constraints according to the design codes. A simplified model including mega braces, mega frames, truss systems, shear walls etc. is employed, which can be easily generalized to other types of structures. The finite element method is used to obtain the structural responses by ETABS, while two modified algorithms are adopted for structural optimization. The first one is total penalty cost-based constant incremental sensitivity analysis method that is introduced with full-level constraints as a whole and the adaptive adjustment mechanism. The second one is structural constraint-based Hooke-Jeeves algorithm considering different building modulus and discreteness of design variables. The influence of their parameter settings on optimization performances are discussed such as different initial designs. The results show that the sensitivity-based methods are useful tools for automatic optimization design of an existing building with known structural parameters and the recommended parameter settings of algorithms are provided. As a result, both the structural safety and economic benefit of the discussed structure can be achieved with high efficiency. A prompt convergence rate and a good approximation to a deterministic solution can also be observed. It can provide a reference to the structural design in practice.
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Tuned Mass Dampers (TMDs) can represent an attracting solution to mitigate vibrations of a structure under seismic excitation, but their effectiveness can be considerably altered by the dynamic interaction with the foundation soil. The available design criteria for TMDs do not account for these effects and can therefore lead to a non-optimised structural performance. In this paper an investigation on the dynamic interaction of the TMD with the whole soil-structure system is presented, with the objective of highlighting the system parameters governing the response and the effectiveness of the device as seismic protection. An interpretative model of the soil-structure-TMD system expressed in a rigorous non-dimensional form is proposed, and an extensive global sensitivity analysis on its performance under harmonic loading is carried out. The identification of the typical performance regions shows that the seismic effectiveness of a TMD is mainly controlled by a limited number of parameters describing the structural behaviour and the soil-structure interaction, such as the structure-to-soil relative stiffness and those governing foundation rocking. The non-dimensional system parameters leading to either a favourable or detrimental effect on the TMD performance due to soil-structure interaction are also identified, and two design methodologies proposed in the literature are critically assessed in light of the framework proposed.
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Conductor galloping is known to be a complicated phenomenon as different aerodynamic characteristics, galloping mechanisms are involved. To tackle the galloping problem of ultra-high-voltage transmission lines, this study designs a torsional tuned mass damper (TTMD) with eddy current mechanism. For a full-span iced conductor with multiple TTMDs (MTTMD), motion equations of galloping are derived and discretized using the Galerkin method. A multi-objective optimization framework using genetic algorithm for anti-galloping of conductors is proposed. The optimization objectives include critical wind speed at galloping initiation, galloping amplitude and damper displacement, which cover the wind conditions with frequent occurrence and large galloping amplitude. By using satisfaction function and weighting factor for each objective, the multi-objective optimization problem is transformed into a single objective optimization problem. For the weighting factors, the Analytic Hierarchy Process and random sampling method are employed to simulate the expert decision-making process with high efficiency, and reasonable ranges of the weighting factors are available for selection. The results of a numerical study show that the MTTMD with optimum design can achieve satisfying anti-galloping effectiveness on the bundled conductor, significantly increasing critical wind speed and suppressing the galloping amplitude. The robustness of the optimization method is also verified.
Chapter
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Tuned Mass Dampers (TMDs) are aimed at mitigating vibrations of a structure under seismic or wind excitation by tuning the characteristics of the device to control specific resonance frequencies of the structure. However, the vibration modes of a structure can be considerably altered by the interaction with soil, leading to a loss of efficiency of the device. This paper shows the preliminary results of a study aimed at formulating a methodology for the design of TMDs accounting for soil-structure interaction. Taking as a reference an illustrative case study of a timber building equipped with a TMD, the results of a parametric study on the effects of soil-structure interaction are presented. This is accomplished through finite element simulations in which soil-structure interaction is described by dynamic impedance functions, in order to have computationally efficient models to study the properties of the soil-structure system. The results are expressed in terms of non-dimensional performance curves of the TMD accounting for soil-structure interaction. The performance curve describes the progressive decay of the TMD efficiency as a function of the structure-to-soil relative stiffness, highlighting the main features of the response of the soil-structure system. This also allowed a clear quantification of the relative contributions of soil stiffness and TMD to the attenuation of the structural displacements.
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Tuned Mass Dampers (TMDs) are aimed at mitigating vibrations of a structure under seismic or wind excitation by tuning the characteristics of the device to control specific resonance frequencies of the structure. However, the vibration modes of a structure can be considerably altered by the interaction with soil, leading to a loss of efficiency of the device. This paper shows the preliminary results of a study aimed at formulating a methodology for the design of TMDs accounting for soil-structure interaction. Taking as a reference an illustrative case study of a timber building equipped with a TMD, the results of a parametric study on the effects of soil-structure interaction are presented. This is accomplished through finite element simulations in which soil-structure interaction is described by dynamic impedance functions, in order to have computationally efficient models to study the properties of the soil-structure system. The results are expressed in terms of non-dimensional performance curves of the TMD accounting for soil-structure interaction. The performance curve describes the progressive decay of the TMD efficiency as a function of the structure-to-soil relative stiffness, highlighting the main features of the response of the soil-structure system. This also allowed a clear quantification of the relative contributions of soil stiffness and TMD to the attenuation of the structural displacements.
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Many structural engineering problems, e.g. parameter identification, optimal design and topology optimisation, involve the use of optimisation algorithms. Genetic algorithms (GA), in particular, have proved to be an effective framework for black-box problems and general enough to be applied to the most disparate problems of engineering practice. In this paper, the code TOSCA, which employs genetic algorithms in the search for the optimum, is described. It has been developed by the authors with the aim of providing a flexible tool for the solution of several optimisation problems arising in structural engineering. The interface has been developed to couple the programme to general solvers using text input/output files and in particular widely used finite element codes. The problem of GA parameter tuning is systematically dealt with by proposing some guidelines based on the role and behaviour of each operator. Two numerical applications are proposed to show how to assess the results and modify GA parameters accordingly, and to demonstrate the flexibility of the integrated approach proposed on a realistic case of seismic retrofitting optimal design.
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The paper is interesting and the discusser didn’t see any discussion.Threedimensional (3D) analyses of buildings controlled with tuned mass dampers (TMDs) by considering three components of the earthquake ground motion is original contribution. The paper seems to have several issuesin assumptions and modeling. However, the information might not be given due to the length.
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This paper presents some of the results of an extensive experimental programme on typical X-Lam connections, conducted at CNR-IVALSA research institute. The goal of this research is to provide a better understanding of the seismic performance of connections in cross-laminated timber buildings subjected to seismic actions. In-plane monotonic and cyclic shear tests were performed on mechanical screwed connections between adjacent parallel wall-wall and floor-floor X-Lam panels. In addition, monotonic and cyclic tests were carried out on orthogonally connected panels (wall-wall and wall-floor) subjected to shear and withdrawal load. Mechanical properties in terms of strength, stiffness, energy dissipation, ductility ratio and impairment of strength were evaluated. The overstrength factor, which is of great importance in capacity-based design, was also evaluated for the different types of connection tested.
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The irregular shape of three large balconies in a performing arts center resulted in areas at the balcony tip and edge susceptible to potentially annoying levels of vibration. To mitigate this effect, the building designers added tuned mass dampers to the underside of each of the three balconies. Proper implementation of tuned mass dampers requires reliable information about the dynamic properties of the structural system. Finite-element models of the structure were constructed and experimentally verified. These models were used to determine the size, frequency, and damping ratio of three tuned mass dampers, two of which targeted the first bending mode of the edge and the remaining one targeted the first bending mode of the tip, for each balcony. The suspensions of the tuned mass dampers were made up of two laminar flow viscous damping units along with eight precompressed helical steel springs. The mass of the tuned dampers were selected as a small percentage of the modal mass of the modes targeted for damping. On completion of the tuned mass dampers installation, the effectiveness of the damping solution was evaluated via further testing.
Article
In this paper, a method is proposed for the robust design of tuned mass damper (TMD) systems for seismic protection of multistory buildings. The seismic excitation is a random ground motion acceleration modeled by a stationary filtered white noise process. The protected building consists of a generic multi-degree-of-freedom (MDOF) structure, represented by its modes of vibration and linear mass dampers. The design properties of the TMD system are mass, frequency and damping ratio of the TMD units, along with their location within the structure, considered as fixed at its base. Uncertainties in the properties of both the building and the input seismic excitation are explicitly accounted for in the robust design of the TMD system. In particular, the uncertain parameters considered are stiffness and damping of the structure, and frequency and damping properties of the Kanai-Tajimi model used for representing the surface ground filter of the white noise process acting at the bedrock. The response quantity chosen to be representative of the seismic demand in the building is the interstory drift ratio. Its variation to the uncertainties is treated with the direct perturbation method, by applying a mixed-order approach. Robustness in the design of the TMD properties is formulated as a multiobjective optimization problem, in which both mean and standard deviation of the building response, produced by the considered uncertain parameters, are minimized. The weighted sum method is applied for transforming the multiple objective into an aggregated scalar objective function and then solving the minimization problem. The proposed design procedure is implemented on an illustrative example, consisting of a multistory building protected with a TMD system made from two units that have to be tuned with the first-and second-mode period of the structure, respectively. Parametric analyses on protected systems characterized by different properties are carried out, and the significance of the effects produced by the variation of such properties on the optimum design of the TMD system is shown. Differences between a robust design with the proposed procedure and a more conventional one that does not account for uncertainties in the system properties are finally evaluated. (C) 2014 American Society of Civil Engineers.
Article
Cross-laminated timber (CLT) is a growing phenomenon and a recent building solution alternative in timber construction in North America by using massive or solid wood plates as roof, floor, and wall elements. In this paper a variation of the conventional CLT is considered by studying the performance of box-based CLT systems, which refer to box beams with multiple voids. In some loading situations, such as out-of-plane bending, these systems, which can reduce structural weight without significant loss of strength or stiffness, may be structurally efficient and cost competitive. Comprehensive three-dimensional finite-element models, which can be used to analyze the mechanical behavior of such box structures, were developed. Four prototype layups, each having five replicates, were designed, manufactured in-house, and tested under symmetric four-point bending (also known as third-point loadings). The numerical analysis agreed well with experimental data in terms of vertical deflection and flexural rigidity. This paper contributes to the understanding of the structural performance of box-based CLT systems for the commercial and residential applications.
Article
An extended experimental programme on typical cross-laminated (CLT) connections was performed at IVALSA Trees and Timber Institute. The paper discusses the results of monotonic and cyclic tests in shear and tension (pull-out) carried out on hold-downs and steel angle brackets used to anchor the wall panels to foundations or to connect wall panels to floor panels. Mechanical properties such as strength, stiffness, energy dissipation, impairment of strength and ductility were evaluated and are critically discussed in the paper. Significant ductility and energy dissipation was attained in most of the tests. Nevertheless, brittle failure modes were observed in some tests, indicating the need for introduction of capacity based design principles for CLT connections. The overstrength factors, which are needed for capacity based design, were also evaluated for the different types of connection tested. A comparison between the test results and the analytical formulas provided by current codes of practice and new proposals is also provided. The approach developed by Uibel and Blaß gives slightly more accurate CLT metal strength predictions compared to the existing formulas in Eurocode 5. Both approaches lead to very conservative results. However, analytical models for the prediction of CLT metal connectors’ stiffness significantly overestimate the experimental values. Therefore, it is recommended that currently only experimental strength and stiffness values of hold-downs and angle brackets be used in seismic analyses. Some proposals to improve the mechanical performance of metal connectors in terms of strength and stiffness are also given based on this experimental and analytical study.
Article
Multi-storey buildings made of cross-laminated timber panels (X-lam) are becoming a stronger and economically valid alternative in Europe compared with traditional masonry or concrete buildings. During the design process of these multi-storey buildings, also their earthquake behaviour has to be addressed, especially in seismic-prone areas such as Italy. However, limited knowledge on the seismic performance is available for this innovative massive timber product. On the basis of extensive testing series comprising monotonic and reversed cyclic tests on X-lam panels, a pseudodynamic test on a one-storey X-lam specimen and 1D shaking table tests on a full-scale three-storey specimen, a full-scale seven-storey building was designed according to the European seismic standard Eurocode 8 and subjected to earthquake loading on a 3D shaking table. The building was designed with a preliminary action reduction factor of three that had been derived from the experimental results on the three-storey building. The outcomes of this comprehensive research project called ‘SOFIE – Sistema Costruttivo Fiemme’ proved the suitability of multi-storey X-lam structures for earthquake-prone regions. The buildings demonstrated self-centring capabilities and high stiffness combined with sufficient ductility to avoid brittle failures. The tests provided useful information for the seismic design with force-based methods as defined in Eurocode 8, that is, a preliminary experimentally based action reduction factor of three was confirmed. Valid, ductile joint assemblies were developed, and their importance for the energy dissipation in buildings with rigid X-lam panels became evident. The seven-storey building showed relatively high accelerations in the upper storeys, which could lead to secondary damage and which have to be addressed in future research. Copyright
Article
SUMMARY In this paper, a numerical model to estimate the dissipative capacity and describe the cyclic response of cross-laminated (X-lam) timber buildings is presented. The connections between panels and to the foundation (metal hold-downs and angle brackets, and screwed connectors) are modelled with nonlinear hysteretic multispring elements taking into account the strength interaction between different degrees of freedom according to a predefined domain. The timber components (solid X-lam floors and wall panels) are modelled using elastic shell elements. By calibration on experimental cyclic tests carried out on each degree of freedom, important features of timber connection behaviour such as post-peak strength, pinching and stiffness degradation can all be considered. In addition, the effect of friction at the interface between panels and with foundation can be taken into account. These springs have been implemented as external subroutines in a widespread software package such as Abaqus. By comparison with the experimental results of cyclic tests carried out on single X-lam walls, coupled X-lam walls and a single-storey X-lam building, the accuracy of the proposed model is demonstrated. Copyright © 2013 John Wiley & Sons, Ltd.
Article
The paper discusses the seismic design of multi-storey buildings made from cross-laminated timber panels (‘crosslam’). The use of seismic analysis methods such as the modal response spectrum and the non-linear static (push-over) analysis is discussed at length, including issues such as the modelling of crosslam walls and connections, the evaluation of the connection stiffness, and the schematization of floor panels. It was found that it is crucial to account for the flexibility of the connections (hold-downs and angle brackets) between upper and lower walls, since otherwise the vibration periods of the building would be underestimated. The basics of capacity design to ensure the attainment of ductile mechanisms in crosslam timber structures under seismic actions are presented. The ductile failure mechanism is characterized by plasticization of connectors (hold-downs, angle brackets and screws) between adjacent wall panels and between panels and foundations. The crosslam panels and the connections between adjacent floor panels must be designed for the overstrength of the connectors to ensure that they remain elastic during the earthquake and the ductile failure mechanism is attained. Based on the results of preliminary quasi-static cyclic tests, a value of 1.3 was found for the overstrength factors of hold-downs and angle brackets. A case study multi-storey crosslam massive wooden building was then analysed using the non-linear push-over analysis as implemented in the N2 method recommended by the Eurocode 8. The building was modelled using shell elements and non-linear links to schematize the hold-downs and angle brackets. The building ductility, calculated from the bilinear curve equivalent to the actual non-linear push-over curve, was then investigated. Such a quantity, defined as the ratio of the displacement at the near collapse state and the maximum elastic displacement of the top floor, was found to rise from 1.7 to 2.5 when ductile instead of brittle hold-downs and angle brackets are used. Furthermore, the maximum peak ground acceleration the building can resist raised from 0.2g to 0.4g, demonstrating the importance of using ductile connectors in seismic design.
Article
This paper presents computational graphs that determine the optimal linear vibration absorber for linear damped primary systems. Considered as independent parameters are the main system damping ratio and the mass ratio examined over the range 0 to 0.50 and 0.01 to 0.40, respectively. The remaining nondimensional parameters were optimized using numerical methods based on minimum-maximum amplitude criteria. With independent parameters specified the computational graphs can be used to find the response amplitudes as well as the optimal absorber characteristics. This procedure is illustrated in a design example. A qualitative discussion of the sensitivity to parameter errors is presented.
Article
A semiactive magnetorheological device is used in a pendulum tuned mass damper (PTMD) system to control the excessive vibrations of building floors. This device is called semiactive pendulum tuned mass damper (SAPTMD). Analytical and experimental studies are conducted to compare the performance of the SAPTMD with its equivalent passive counterpart. An equivalent single degree of freedom model for the SAPTMD is developed to derive the equations of motion of the coupled SAPTMD-floor system. A numerical integration technique is used to compute the floor dynamic response, and the optimal design parameters of the SAPTMD are found using an optimization algorithm. Effects of off-tuning due to the variations of the floor mass on the performance of the PTMD and SAPTMD are studied both analytically and experimentally. From this study it can be concluded that for the control laws considered here an optimum SAPTMD performs similarly to its equivalent PTMD, however, it is superior to the PT]MD when the floor is subjected to off-tuning due to floor mass variations from sources other than human presence. It is also found that for the case of off-tuning due to floor mass variations from the human occupants when the human-structure dynamic interactions are not considered in the analytical modeling, large inconsistencies between the analytical and experimental results can be expected.
Article
In recent papers the author has shown that when determining optimum parameters for an absorber which minimizes the vibration response of a complex system, the latter may be treated as an equivalent single degree-of-freedom system if its natural frequencies are well separated. Emphasis was on minimizing the displacement response when the excitation was a harmonic force. In the present paper simple expressions for optimum absorber parameters are derived for undamped one degree-of-freedom main systems for harmonic and white noise random excitations with force and frame acceleration as input and minimization of various response parameters. These expressions can be used to obtain optimum parameters for absorbers attached to complex systems provided that optimization is with respect to an absolute, rather than a relative, quantity. The requirement that the natural frequencies should be well separated is investigated numerically for the different cases. The effect of damping in the main system on optimum absorber parameters is investigated also.
Article
In the classical problem a damped one degree-of-freedom absorber system is attached to a main system, which has one degree of freedom and is undamped. The optimum values of absorber stiffness and damping, which will minimize the resonant response of the main mass, are well known. In this paper the effect on these optimum conditions of light damping in the main system is studied. The authors show that optimum parameters for absorbers, which are attached to beams and plates, can be obtained simply and accurately from those for an equivalent one degree-of-freedom main system. This depends upon the concept of an effective mass for the elastic body and the representation of its response by the single relevant mode. It will be shown in a later paper that for more complex elastic bodies such as cylindrical shells, for which the natural frequencies are more closely spaced, these simple concepts do not predict accurately optimum absorber parameters.
Article
The multi-membered Evolution Strategy (ES) acting on parents and offspring is analyzedfor real-valued, N-dimensional parameter spaces (N? 30). N-dependent progress rate formulasare derived for (1; ) and (; ) strategies on spherical models. The analytical results obtainedare compared with simulation experiments for the (hyper)sphere and the inclined (hyper)plane.KeywordsEvolution Strategy(ES), progress rate theory, multi-membered ES, (; )-selection, truncationselection1...
Conference Paper
In this paper we introduce interval-schemata as a tool for analyzing real-coded genetic algorithms (GAs). We show how interval-schemata are analogous to Holland's symbol-schemata and provide a key to understanding the implicit parallelism of real-valued GAs. We also show how they support the intuition that real-coded GAs should have an advantage over binary coded GAs in exploiting local continuities in function optimization. On the basis of our analysis we predict some failure modes for real-coded GAs using several different crossover operators and present some experimental results that support these predictions. We also introduce a crossover operator for real-coded GAs that is able to avoid some of these failure modes.
Article
David Goldberg's Genetic Algorithms in Search, Optimization and Machine Learning is by far the bestselling introduction to genetic algorithms. Goldberg is one of the preeminent researchers in the field--he has published over 100 research articles on genetic algorithms and is a student of John Holland, the father of genetic algorithms--and his deep understanding of the material shines through. The book contains a complete listing of a simple genetic algorithm in Pascal, which C programmers can easily understand. The book covers all of the important topics in the field, including crossover, mutation, classifier systems, and fitness scaling, giving a novice with a computer science background enough information to implement a genetic algorithm and describe genetic algorithms to a friend.
Introduction to structural motion control
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Connor, J. J. (2003). Introduction to structural motion control, Prentice Hall, New York.
Timber structures-Test methods-Cyclic testing of joints made with mechanical fasteners
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Comparison of (a) time histories of acceleration in X-direction at sixth floor; (b) distribution of peak accelerations in X-direction at each floor for seven-story X-lam building with and without TMD subjected to high-intensity seismic record
  • Fig
Fig. 9. Comparison of (a) time histories of acceleration in X-direction at sixth floor; (b) distribution of peak accelerations in X-direction at each floor for seven-story X-lam building with and without TMD subjected to high-intensity seismic record (JMA Kobe 3D)
Progetto SOFIE—New architecture with wood
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CNR-IVALSA Trees and Timber Institute. (2008). " Progetto SOFIE—New architecture with wood. " 〈http://www.progettosofie.it/〉.
BSPhandbuch: Holz-Massivbauweise in Brettsperrholz-Nachweise auf Basis des neuen europäischen Normenkonzepts
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Schickhofer, G., Bogensperger, T., and Moosbrugger, T. (2010). "BSPhandbuch: Holz-Massivbauweise in Brettsperrholz-Nachweise auf Basis des neuen europäischen Normenkonzepts." Verlag der Technischen Universität Graz (in German).
〈http://www.3ds.com/products/simulia
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SOFIE project-3D shaking table test on a seven-storey full-scale cross-laminated timber building
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Ceccotti, A., Sandhaas, C., Okabe, M., Yasumura, M., Minowa, C., and Kawai, N. (2013). "SOFIE project-3D shaking table test on a seven-storey full-scale cross-laminated timber building." Earthquake Eng. Struct. Dyn., 42(13), 2003-2021.
Downloaded from ascelibrary.org by UNIVERSITA DEGLI STUDI DI TRIESTE on 07/07/15. Copyright ASCE. For personal use only
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J. Struct. Eng. Downloaded from ascelibrary.org by UNIVERSITA DEGLI STUDI DI TRIESTE on 07/07/15. Copyright ASCE. For personal use only; all rights reserved.
A component approach for the hysteretic behaviour of connections in cross-laminated wooden structures
  • G Rinaldin
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Rinaldin, G., Amadio, C., and Fragiacomo, M. (2013). "A component approach for the hysteretic behaviour of connections in cross-laminated wooden structures." Earthquake Eng. Struct. Dyn., 42(13), 2023-2042.