Andrea Polastri

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.

Analytical Approach to Establishing the Elastic Behavior of Multipanel CLT Shear Walls Subjected to Lateral Loads

AbstractStructures assembled with cross-laminated timber (CLT) panels, and designed to resist gravity and lateral loads, are being considered as viable options for low-rise to mid-rise buildings. I...

The Traditional Wooden House in Bucovina, a Model for Durability

The wooden house in Bucovina evolved over hundreds if not thousands of years of permutations and assimilations to reach, by the end of the XIXth century, a coherent and rich original style that was diffused throughout the region. With a name derived from the Slavic word buk that means beech, the region thus named land of beech trees has always been and continues to be a very rich source of wood. Unsurprisingly, this was the material of choice for the houses in the land. Constructed entirely in wood, including apparent beams to the interior and exterior and wood shingles for the roof, the traditional house in Bucovina elevated the craftsmanship of woodwork to the level of an art. This is obvious when analyzing the constructive details or the ornaments that adorn the windows or the columns of the porch. Similar to the houses of the Moldavian region, on which the style originates, the pattern for the house in Bucovina implies larger dimensions, due to the abundance of the material, larger windows, classical proportions and the use of specific decorative elements. The wooden houses evolved for thousands of years, so the people who built them got an empirical knowing of the material that helped them adopt in time the best measures to insure the durability of the constructions. This article analyses the style characteristics of the house in Bucovina and focuses on the means of constructions that ensured the durability of this dwellings. It is with the purpose of learning from a historical pattern that proved its durability in time and establishing the rules for constructing today with the same material and in the same climatic conditions, those of Bucovina.

Seismic analysis of multi-storey timber buildings braced with a CLT core and perimeter shear-walls

The seismic behaviour of multi-storey heavy-frame timber building superstructures braced by Cross-Laminated-Timber (CLT) shear-walls is investigated based on numerical linear dynamic simulations. All systems analysed have the same rectangular plan footprint dimensions, type of framework and shear-walls arrangement at each storey. For structural efficiency, the layout of lateral load-resisting systems combines a central building core with partial length perimeter shear-walls. What differs between cases is the number of storeys (3, 5, or 7), components specifications, and shear-walls anchoring methods. Special attention is paid to examining how the vertical joints between CLT shear-walls affect the seismic response. The properties of connections used in the analyses are obtained from testing of hold-down anchors and angle-bracket shear connectors. Results of the simulations demonstrate that mid-rise buildings are prone to effects of the lateral flexibility and transfer high uplift loads to the foundations during design level seismic events. By implication, special design measures may be necessary to limit the lateral drifts to the levels prescribed by the standards. Simplified representations of connection properties may yield to inappropriate predictions of lateral drifts of superstructures during seismic events, and to an improper design of connections. In future, the efficient realisation of multi-storey heavy-frame timber building superstructures braced by CLT shear-walls depends on the use of proper connection devices. Suitable devices may include metal tie-downs capable of reducing the inter-storey drift, while transferring forces to foundations in a manner that does not locally damage frameworks, shear-walls, or floor and roof diaphragms.