The effectiveness of a method to strengthen/repair unreinforced masonry (URM) by using timber-based products was investigated through experimental in situ testing. The strategy consists of timber-based panels connected to the masonry by means of screw fasteners. URM piers obtained from a century-old building were subjected to in-plane semi-cyclic quasi-static loading in as-built, repaired and retrofitted configurations. The application of the reinforcement on previously damaged piers led to a notable increase in the in-plane capacity while the initial stiffness of the repaired specimens was found to be consistent with that of the specimens tested as-built. When applied to undamaged masonry, the retrofit system allowed an in-plane force 40% higher than the capacity of the unreinforced walls, with the initial stiffness comparable with that of the repaired specimens. Both repaired and retrofitted specimens exhibited remarkable displacement capacity (drift levels > 2.0%) and energy dissipation.
Unreinforced masonry (URM) building construction is prominent in the form of load-bearing, partition, and infill walls. Significant out-of-plane (OOP) failures of URM walls often occur during moderate and severe earthquake shaking and such walls are often identified in structural engineering assessments as being amongst the most vulnerable elements to OOP demands, especially earthquakes. For undamaged, in situ wall conditions where material properties are known and boundary conditions reflect idealised conditions assumed in analytical predictive models, these predictive models are easily applied, although the accuracy of the model outputs may still not be well understood. Furthermore, when in situ conditions do not reflect idealised conditions assumed in analytical predictive models, engineers are often uncertain as to which analytical models and inputs are most appropriately applied. Hence, an analytical campaign was undertaken to provide specific examples for structural engineering practitioners assessing the OOP seismic behaviour of URM walls, and the predictive results reported herein were compared to previously reported experimental results of eighteen tests on existing URM walls performed in situ. The considered wall configurations represented a variety of geometries, boundary conditions, pre-test damage states, and material properties. The average ratio and associated coefficient of variation (CV) of predicted strengths to measured strengths were determined to be 0.84 (CV 0.56) and 0.93 (CV 0.25) for the unbounded and bounded wall conditions, respectively, and corresponding recommendations for analytical assessment were made for practicing engineers.
Unreinforced masonry (URM) buildings are characterized by high vulnerability to lateral loading, which is often manifested when an earthquake occurs.The present study investigates the effectiveness of a timber-based retrofit solution aimed at reducing the seismic vulnerability of existing URM structures.The retrofit technique consists of connecting timber-based panels, to the interior surface of the walls of a building using mechanical or adhesive pointto-point connections.The application of those panels allows to considerably increase both the in-plane and the out-of-plane capacity of the URM walls, while preserving the original external facades of the retrofitted building.This solution resulted to be relatively fast and easy to install and the reversible nature of the system allows to reduce the impact of the retrofit intervention.In this work the in-plane behaviour of the retrofitted walls was investigated numerically, building on previous preliminary analyses and in the lights of the results of experimental evidence collected by the authors' research team.The effectiveness of this retrofit solution was analysed on several masonry types, considering different masonry properties and geometries.The influence of various parameters (such as masonry-to panel connection typology, connectors number and position) on the increase of lateral capacity of the retrofitted walls was studied by means of a series of non-linear quasi-static simulations.
Two modeling approaches with different levels of refinement were used to numerically investigate the influence of different parameters on the response of straight sheathed timber diaphragms when subjected to in-plane loading. The investigated parameters included diaphragm aspect ratio, scale factor (i.e., diaphragm size), impact of board-to-board contact phenomena, and the effects of board-to-board shear force exchange. The aim of the work presented herein was to use numerical modeling to investigate the aspects that potentially contribute to the difference in experimental behavior reported in literature and that consequently might have influenced provisions encompassed in the most recent standards for the assessment of timber diaphragms. The modeling strategies were validated against a wide range of available experimental data on newly constructed and vintage timber floor specimens. Analysis results confirmed that the in-plane behavior of straight sheathed diaphragms is significantly influenced by parameters that are often neglected by numerical studies and assessment procedures.
The susceptibility of unreinforced masonry (URM) walls to collapse under seismic loading has been repeatedly observed and documented across a multitude of earthquakes worldwide. The out-of-plane failure of walls is commonly the critical failure mechanism for URM structures and poses a significant risk to life. Despite various seismic improvement techniques being applied previously there is a significant lack of experimentally validated simple and cost-effective solutions that also consider the impact on the building tenants, building aesthetics, and heritage fabric of the structure. Such retrofits are needed to facilitate the preservation of the URM building stock and to ensure the safety of those who work and live in and around these structures. The retrofit technique studied herein consisted of connecting vertical timber elements (strong-backs), to the interior surface of a building’s walls using mechanical anchors. Non-structural timber framing commonly exists to support the inner wall lining of URM buildings and its use, as a part of the retrofit, results in a cost effective and low impact solution. The out-of-plane behavior of as-built and retrofitted masonry walls was investigated by conducting full scale semi-static cyclic airbag tests. The outcomes of this testing regime include (i) quantification of improvement in seismic capacity and out-of-plane displacement capacity and (ii) comparison of the performance using different strong-back configurations.
The paper presents a new connection system for cross-laminated timber (CLT) structures, named X-RAD. This innovative connection system is characterised by the use of a single connector type that is positioned at the corners of the CLT panels. X-RAD is formed by a metal part surrounding a hardwood insert that is fixed to the panels by means of all-threaded screws introduced with double inclination. The peculiar geometry of the connector and the combination of different materials allow the full exploitation of the capacity of the CLT panels while ensuring a ductile response of the connection. Construction modularity, fast assembly/disassembly speed and prefabrication are some of the aspects that can be associated with X-RAD development. The outcomes of an extensive testing campaign on the new connector are also presented in the paper.
