1,604 research outputs found
A study about optimal stiffening of timber floors in URM buildings
No full textTimber floors in traditional masonry buildings normally have limited in-plane stiffness, which may be not
sufficient to avoid out-of-plane failure of walls or to transmit efficiently seismic forces among walls. Therefore,
various stiffening techniques of timber floors have been developed with the aim of improving the global behaviour
of the building. The evaluation of the efficiency of the stiffening intervention needs adequate numerical modelling
strategy, taking into account the nonlinear in-plane behaviour of masonry piers and spandrels, the out-of-plane
stiffness and strength of walls, the actual stiffness and hysteretic behaviour of timber floors. The macro-element
modelling can be considered an intermediate strategy in terms of model complexity, as it requires experimental
data for its calibration, but can be quite easily adapted to the building geometry. Nonlinear incremental dynamic
analyses of different case-study buildings are presented, varying the type of floor, the seismic signal and the
modelling criteria as the complexity and accuracy of the adopted technique, with the aim of analysing the effects
of the stiffening techniques on the building response. The comparative analyses show that the seismic capacity of
a traditional masonry building may decrease if a retrofitting method leading to excessive floor stiffening and/or
mass increase is adopted, depending on the geometry and mechanical characteristics of walls and floors. This
means that the need of increasing the in-plane stiffness of floors should be evaluated on a case-by-case basis,
comparing the actual capacities of floors and walls
Timber-concrete composite connections using GFRP notches fastened with self-tapping screws: Conceiving, numerical modelling and testing
No full textIn the structural engineering field, injection moulded Glass Fibre Reinforced Polymer (GFRP) components are typically used as parts or accessories of fastening systems. In this paper, an extended numerical and experimental study on a Timber-Concrete Composite Connection (TCCC) realized with an injection-moulded GFRP notch fastened to the timber beam with self-tapping screws is presented. Numerical simulations performed to predict the performance of the investigated TCCC in terms of force-displacement curves are compared with the outcomes from forty push-out tests. Results demonstrate how the GFRP notch assure the full exploitation of the screws withdrawal capacity without incurring in sudden concrete failures independently from the type of concrete used (normal and light-weight)
An analytical formulation of q-factor for mid-rise CLT buildings based on parametric numerical analyses
No full textThe seismic response of cross-laminated timber buildings is analysed with the aim of assessing the correlation between the dissipative capacity (i.e., q-factor) and the assembling methodologies and geometrical properties. A parametric study was performed by means of incremental dynamic analyses on various building configurations with varying constructive features such as density of panel-to-panel joints and building slenderness. The results are firstly used to define parameters representative of the building geometry and assembling methodology and then to develop an analytical relationship to compute their most suitable q-factor starting from such parameters. The proposed method is finally validated referring to significant case studies available in literature
Seismic design of floor–wall joints of multi-storey CLT buildings to comply with regularity in elevation
No full textThe effects of irregularity in elevation of cross-laminated timber buildings have not been fully analysed in literature to provide useful information for the design. In this work, a number of building configurations, regular or irregular in elevation, characterized by a different arrangement per storey of the floor–wall joints have been analysed by means of non-linear dynamic analyses. Comparative results in terms of ratio between the behaviour q-factor of the investigated irregular configurations and that of reference regular ones, show that less dissipative capacity can be expected if the building is irregular due to a disequilibrium among storeys between the actual and the required strength provided by the floor–wall joints. A correlation method to estimate the behaviour q-factor for perfectly regular cross-laminated timber buildings is here presented and extended to in-elevation irregular ones. A new empirical formulation to assess the reliable corrective factor accounting for the irregularity in elevation of cross-laminated timber buildings, according to Eurocode 8 provisions, is also proposed. A final discussion about the implications of in elevation irregularity on the building design is reported
Proposal for a standardized design and modeling procedure of tall CLT buildings
No full textA crucial issue in the design of a mid-rise Cross Laminated Timber (CLT) building under horizontal seismic action, is the definition of the principal elastic vibration period of an entire superstructure. Such vibration period depends on the mass distribution and on the global stiffness of the buildings. In a CLT structure the global stiffness of the buildings is highly sensitive to deformability of the connection elements. Consequently for a precise control of the vibration period of the building it is crucial to define the stiffness of each connections used to assemble a superstructure. A design procedure suitable for a reliable definition of the connection stiffness is proposed referring to code provisions and experimental tests. Discussion addresses primary issues associated with the usage of proposed procedure for numerical modeling of case study tall CLT buildings is reported
Role of fastenings in modifying the hysteretic response of panel-to-panel joints for CLT structures
No full textHigh performance dampers are a key component in low-damage earthquake-resistant timber structures and they should be designed according to displacement-based design criteria. In this case, a well-defined non-linear force vs displacement relationship of the connection is to be known by the designer (e.g., to evaluate inter-storey drifts), underlying the importance of their careful experimental characterization. In this study, the cyclic shear response of a panel-to-panel joint, fastened to the wooden elements with three alternative solutions, was experimentally tested. Results showed that, although fulfilling the capacity design criteria and allowing an easy replacement of the damper, the semi-rigid nature of fastenings produces important modifications to the mechanical properties of the whole connection type, such as elastic stiffness, yielding point, ductility and equivalent viscous damping
Un falso placito per il monastero dei Santi Felice e Fortunato di Ammiana (935 febbraio)
No full textInfluence of wall assembly on behaviour of cross-laminated timber buildings
No full textThis paper describes a new wood-joint numerical model which applies commercial software and illustrates how it can be used for reliable estimation of appropriate behaviour factor (q) in multi-storey, cross-laminated timber buildings. The model is based on a macro-element approach and can reproduce the load–displacement hysteretic response of the steel–wood and wood–wood joints typically used in such structures. The panels are regarded as elastic and all non-linearities are assumed to take place in the connections, which are modelled by appropriate macro-elements. The model was calibrated and validated according to the results of cyclic shear wall tests and fullscale shake table tests. After validation, the model was used to carry out a parametric study to assess q values of three-storey buildings. Lastly, the influence of the two different wall assemblies on the building’s seismic response and q values was examined
Valutazione numerica del comportamento sismico e del fattore di struttura “q” di edifici in legno con pareti tipo XLam
No full textIn the X-Lam buildings, the energy dissipation capacity through inelastic behavior is concentrated in the connections between the wall panels and the footings. It has been possible to reproduce the behavior of wood-to-wood and wood-to-footings connections by properly combining several springs with simple work-hardening elasto-plastic constituent models in a complex macro-element. By using such nonlinear multi-springs connections in a finite element model it has been possible to reproduce the experimental results of monotonic and cyclic tests on single panels and plane walls as well as of a three-storey cross-laminated wooden building tested on a shaking table.
The Xlam buildings modeling rests on the hypothesis that the nonlinear behavior of the wall is exclusively due to the (angular and hold-down) connections, whereas the XLam panels are always in the elastic field. The numerical simulations that have been performed have accurately reproduced the results of the experimental tests both in terms of shape of the force-displacement hysteresis curve and assessment of dissipated energy. The experimental tests carried out on a three-storey building tested on the shaking table have been numerically reproduced. The results of the nonlinear analysis in the time domain have confirmed the effectiveness of the numerical model in reproducing the behavior of the whole building. On the basis of these preliminary validations, the model has also been used to predict the displacements and forces on the structure subjected to seismic excitations and, therefore, their most appropriate ‘q ductility factor’. Two different approaches have been used. The first one calculates ‘q’ as the ratio between the acceleration leading the structure to a near-collapse condition and the acceleration leading the structure to the elastic limit. The second one defines the ‘ductility factor’ as the ratio between the base shear calculated for near-collapse seismic intensity in case of elastic response and in case of dissipative response of the connections. The results from such analyses confirm that the adoption of a ‘q’ factor equal to 3 is appropriate for the design of the examinated structures
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