Davide Trutalli

Behaviour factor for innovative massive timber shear walls

Four massive wooden shear walls were analysed via experimental tests and numerical simulations. The specimens differ mainly in the method used to assemble the layers of timber boards: two of them are the well-known Cross-Laminated-Timber panels with glued interfaces, the other two are innovative massive timber panels adopting steel staples or wooden dovetail inserts to connect the layers. Quasi-static cyclic-loading tests were performed for each wall and main results are presented and analysed. A non-linear numerical model was calibrated on experimental results and used to perform non-linear dynamic analyses on specifically designed three-storey shear wall. The methods ensuring a reliable estimation of the intrinsic behaviour factor are presented and the definition of yielding and failure condition is discussed. The intrinsic behaviour factor values were calculated using results from non-linear dynamic analyses. Three limits of failure condition were analysed to estimate the correlated Peak Ground Acceleration and therefore the behaviour factor. A final interpretation of the obtained results is presented and some instructions about the choice of the suitable behaviour factor are given.

Concrete-Plated Wooden Shear Walls: Structural Details, Testing, and Seismic Characterization

AbstractThis paper discusses the structural characterization of a novel hybrid shear-wall system formed by coupling standard platform-frame panels with an external reinforced concrete shelter formed of precast slabs screwed to the wooden frames. The external RC skin is intended as a supplementary bracing system, increasing strength and dissipative capacity of the bare timber frame. The structural performance of such hybrid shear wall under monotonic and cyclic loading was first theorized analytically on the basis of code provisions and then confirmed via experimental tests. The novel shear walls demonstrated to fulfill the requirements prescribed by Eurocode 8. In particular, the analyzed system belongs to high ductility class (HDC). Finally the seismic response of a reference building realized with the innovative hybrid shear walls was simulated by means of a numerical model validated on experimental tests; the suitable behavior factor for the building was estimated.

An analytical formulation of q-factor for mid-rise CLT buildings based on parametric numerical analyses

The 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.

Light Steel-Timber Frame with Composite and Plaster Bracing Panels

The proposed light-frame structure comprises steel columns for vertical loads and an innovative bracing system to efficiently resist seismic actions. This seismic force resisting system consists of a light timber frame braced with an Oriented Strand Board (OSB) sheet and an external technoprene plaster-infilled slab. Steel brackets are used as foundation and floor connections. Experimental cyclic-loading tests were conduced to study the seismic response of two shear-wall specimens. A numerical model was calibrated on experimental results and the dynamic non-linear behavior of a case-study building was assessed. Numerical results were then used to estimate the proper behavior factor value, according to European seismic codes. Obtained results demonstrate that this innovative system is suitable for the use in seismic-prone areas thanks to the high ductility and dissipative capacity achieved by the bracing system. This favorable behavior is mainly due to the fasteners and materials used and to the correct application of the capacity design approach.

A Dissipative Connector for CLT Buildings: Concept, Design and Testing

This paper deals with the conception and characterization of an innovative connection for cross-laminated timber (CLT) panels. The connection is designed to provide an adequate level of dissipative capacity to CLT structures also when realized with large horizontal panels and therefore prone to fragile shear sliding failure. The connector, named X-bracket, has been theorized and designed by means of numerical parametric analyses. Furthermore, its cyclic behavior has been verified with experimental tests and compared to that of traditional connectors. Numerical simulations of cyclic tests of different CLT walls anchored to the foundation with X-brackets were also performed to assess their improved seismic performances. Finally, the analysis of the response of a 6 m × 3 m squat wall demonstrates that the developed connection provides good ductility and dissipation capacities also to shear walls realized with a single CLT panel.

Seismic design of floor–wall joints of multi-storey CLT buildings to comply with regularity in elevation

The 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.

NUMERICAL SIMULATION OF THE COUPLED TENSION-SHEAR RESPONSE OF AN INNOVATIVE DISSIPATIVE CONNECTION FOR CLT BUILDINGS

This work presents a numerical macro-element model able to simulate the dynamic response of an innovative ductile and highly dissipative bracket for assembling of crosslaminated timber structures. This bracket resists to both tensile and shear forces and has been conceived to realize all the seismic-resistant joints of the building with a unique type of connection able to maximize the seismic capacity of the entire structure. The main issue of these kinds of connection is the reliability of numerical models in reproducing the coupled tensionshear behaviour and dissipative capacity with reduced computational effort, so as to simulate the non-linear response of complex buildings. With this aim, a numerical macro-element model was developed within the finite-element framework OpenSees using an assembly of linear beams and plastic hinges capable of simulating the complete tension-shear strength domain of the connection. The macro-element model was calibrated referring to the results from quasi-static cyclic-loading tests of the connector performed in pure shear and pure tension. The coupled tension-shear behaviour of the macro-element model was then validated on the results from independent numerical simulations performed using detailed 3D models with solid finite elements, including material and geometric non-linearity. Obtained results demonstrate that the developed macro-element model is able to describe accurately the hysteretic behaviour of the bracket with a very low computational effort. Therefore, it can be conveniently adopted to simulate the seismic response of complex structures. 247 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 247-254

Dynamic simulation of an irregular masonry building with different rehabilitation methods applied to timber floors

Abstract. The in-plane stiffening of timber floors is normally supposed to be an improvement of the seismic performance of un-reinforced masonry buildings. A modelling strategy to simulate the non-linear behaviour of masonry buildings with simple or strengthened timber floors is presented: it allows to implement the in-plane hysteretic response of the floors and different types of failure of the masonry walls. This model was used to predict the modification of the seismic response of a two-storey masonry building subjected to different rehabilitation techniques applied to the timber floors. The case-study building is irregular in plan to study also torsional effects and out-of-plane deformation of the walls. The mechanical parameters of the non-linear elements representing masonry piers and floors were calibrated replicating experimental tests available in literature. The outcomes of this work were obtained with non-linear dynamic analyses, in order to allow the model to consider not only the actual elastic and post-elastic stiffness of the floors but also their energy dissipation capacity. Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 2269-2282