85 publications from this institution
This study investigates the effectiveness of a range of timber-based solutions for seismic and energy retrofitting of existing masonry buildings. These solutions are designed not only to prevent structural collapse during earthquakes but also to create integrated interventions that enhance thermo-physical performance and reduce emissions in existing buildings. Various case scenarios were considered and both mechanical and energetic behavior post-intervention were evaluated. Timber-engineered products serve as foundational components for the retrofit approach, encompassing one-dimensional vertical elements (strong-backs) and various types of panels (cross-laminated timber panels, laminated veneer lumber panels, and oriented strand board panels). The analyzed retrofit techniques share a common principle, involving the attachment of these timber-based elements to the building's wall surfaces through mechanical point-to-point connections. The proposed solutions integrate strong-backs and timber panels with membranes and insulation layers, yielding cohesive and highly effective interventions. Finite element modeling was employed to analyze the mechanical and thermal responses of the retrofitted walls. A comprehensive comparative analysis of various techniques was conducted to determine the most effective solution for each specific scenario.
1 Ivan Giongo, Department of mechanical and structural Engineering, University of Trento, via Mesiano 77, I-38123 Trento, Italy, ivan.giongo@ing.unitn.it 2 Maurizio Piazza, Department of mechanical and structural Engineering, University of Trento, via Mesiano 77, I-38123 Trento, Italy, maurizio.piazza@ing.unitn.it 3 Roberto Tomasi, Department of mechanical and structural Engineering, University of Trento, via Mesiano 77, I-38123 Trento, Italy, roberto.tomasi@ing.unitn.it Cambering of timber composite beams by means of screw fasteners
In refurbishment operation of existing timber floors could prove of some interest the possibility of hogging the existing timber beams, in case of the presence of excessive permanent midspan deflections. In the case of sagged timber floors which cannot be buttressed due to heritage issues, the possibility of cambering a timber beam by simply putting another wooden beam on the top of it and inserting screws inclined at 45° relative to the beam axis has been experimentally investigated, with some promising result. The cambering procedure has proved to be more effective when the fastener are inserting starting from the internal part of the beam, permitting to obtain significant values of upward deflection (it has been observed an upward deflection of about one three-hundredth of the total beam length): the values could possibly be increased by reducing the screw spacing or by using fasteners able to generate a greater pressure. The effectiveness of this method is based on the capability of self-tapping screws to induce internal stress in timber element during the drilling procedure: the horizontal component of the resultant pressure yielded by the inclined screws is directly related to the possibility to hog the composite system. The aim of the experimental campaign described in this paper was to investigate the values of the internal stress induced by different type of fasteners during the drilling procedure, studying the influence of different parameters such as screw angle with respect to the grain direction, initial pressure, head penetration length, threaded part length, connector typology, wood density, time-dependence.
The in-plane stiffness of timber diaphragms commonly found in vintage unreinforced masonry (URM) buildings is largely determined by the rigidity of the fastener connections. Currently in the literature, however, there is limited experimental data on the behavior of floorboard-to-joist connections, and consequently the aim of the present study was to supplement that knowledge. The existing data provided the paramount input parameters for the finite element modeling of timber diaphragms, in order to model and validate the results obtained from the experimental testing of full-scale timber diaphragms. The floorboard-to-joist connections were extracted from two vintage URM buildings and were tested using three different test setups to address various realistic loading configurations. In addition, the floorboard-to-joist connections were improved using new nails or new screws. Specimens comprising plywood or fire-rated gypsum-board panels connected to the salvaged floorboards or joists were also tested as a method for improving the overall diaphragm lateral behavior. The experimental study of timber diaphragm fastener connections consisted of 43 samples, of which the results are presented here.
Construction of vertical expansions on top of existing structures can be considered as an economical and practical solution to contain urban sprawl.The use of timber, due to its lightness, suitability for modularity and prefabrication, and due to environmental benefits, emerges as an interesting option for the realisation of vertical additions in existing buildings.Unfortunately, in seismic-prone areas, the construction of vertical expansions clashes with seismic safety.Current standards require that the safety level of the existing structure after the expansion be that prescribed for new buildings.This requirement represents a major obstacle to vertical expansion because vintage buildings rarely comply with the provisions of the seismic standards even without any addition, making costly retrofit intervention necessary.In this paper, a case study is selected and analysed to try and understand how the vertical timber addition of existing buildings can impact their seismic behaviour.The selected case study is a 1980s four-story RC frame building with masonry infill walls.Following current design practices, a one-storey timber vertical expansion was designed by adopting a cross-laminated timber shear-wall system.The seismic response of the building with and without the timber expansion was then simulated via finite element modelling.The outcomes of the numerical simulations were then used to perform a seismic fragility analysis and assess the effect of vertical expansion on the seismic performance of the case study building.The results of the analysis showed how, in some cases, the vertical timber addition not only does not worsen the safety level of the building but can actually improve it.This outcome opens new paths for future research to further investigate the effect of vertical expansions and maximize their beneficial effect on the seismic response of existing buildings.
It is well known that the in-plane behavior of flexible timber diaphragms has a large influence on the global earthquake response of unreinforced masonry (URM) buildings. The type and the activation of out-of-plane URM wall failure mechanisms are strictly related to diaphragm stiffness, which is a property that also governs the effectiveness of the diaphragm to distribute earthquake-induced loads between lateral load resisting wall elements. However, there is a lack of reported experimental campaigns pertaining to these issues, and in particular, few experimental data have been published on the in situ behavior of existing vintage flexible timber floor diaphragms such as single straight sheathed diaphragms that are typically encountered in New Zealand URM buildings. To address this paucity of available in situ test data, an experimental campaign was executed to investigate the as-built cyclic and dynamic behavior of full-scale vintage flexible timber floor diaphragms with the outcomes being presented herein. Two sections of a diaphragm located in a vintage two-story URM building, measuring 6.4×9.6 m and 4.6×9.6 m, were subjected to a series of cyclic and snap back tests in the direction orthogonal to the floor joists. In order to reproduce a realistic inertial load distribution to the test specimens, an ad hoc loading system using wire ropes and steel pulleys was developed. The loading system was designed to be lightweight, versatile, and relocatable between test specimens. From the obtained test results, it was identified that the equivalent stiffness of existing timber diaphragms (in the direction orthogonal to the joists) is predicted with a certain degree of conservativeness using the most recent procedures currently available in literature, while reliance on the ASCE standard can lead to an overestimation of the floor diaphragm stiffness, even at small displacements. Due to the nonlinear behavior of the tested flexible timber diaphragms, the measured natural period proved to be highly dependent on the target displacement.
The use of timber for seismic reinforcement of existing structures is gaining significant attention, thanks to recent developments in engineered wood products such as CLT and LVL. This study, carried out within the framework of the RELUIS WP5 2022-2024 project, explores various reinforcement techniques including timber strong-backs, light timber frames sheathed with OSB panels, CLT panel coatings, endoskeletons, and exoskeletons. Each method is evaluated for its advantages, disadvantages, and applicability, with a focus on sustainability and intervention effectiveness. Results show that timber solutions offer significant improvements in the strength and deformation capacity of reinforced structures, presenting a promising option for integrated and sustainable seismic retrofitting.
