The existing building stock in several countries worldwide features masonry structures with timber floors, whose vulnerability to seismic events has been widely documented by academic research as well as by the catastrophic consequences of recent earthquakes. Several seismic retrofits and protection technologies have been explored throughout the years, prioritizing (among others) lightweight interventions, such as timber-based strengthening, or advanced systems involving seismic isolation and vibration control strategies (e.g. inter-story seismic isolation). The use of timber-based retrofits, particularly based on engineered wood panels fastened to existing floors and roofs, has shown to increase the hysteretic energy dissipation of these diaphragms, beneficially reducing seismic shear forces transferred to the walls when the strengthening measure is appropriately designed. Similarly, the seismic isolation of the masses localized at the roof level, can provide a strong reduction in shear loads on the walls, acting as a Tuned Mass Damper for the existing building. On the basis of the described framework, this work examines a case-study archetype masonry building with timber diaphragms: by performing numerical analyses in DIANA FEA software, this study compares (i) the application of timber-based retrofitting solution on the floors and roof, (ii) the use of an additional, superimposed roof structure acting as tuned mass damper with properly calibrated isolators, and (iii) the combination of the two systems, discussing the benefits and applicability of each seismic protection method and their integration with other retrofits, for instance from the energetic and environmental point of view.

The majority of bridges in Amsterdam’s historic city centre are built on timber foundation piles, typically 12 to 15 meters in length, which function as end-bearing elements reaching the underlying stiff sand layer. Currently, many timber foundations have been in service for up to 300 years, raising concerns about their remaining load-bearing capacity and the overall safety of the bridges they support. The timber piles beneath the bridges remain fully submerged, where their outer cross-section is exposed to slow bacterial decay in anaerobic conditions, leading to a reduction in the sound load-bearing core of the piles. Despite decay, the piles maintain their structural capacity for many years, although their load-bearing capacity gradually decreases over time. The two primary risks are attributed to the applied loads exceeding the load-bearing capacity of the timber piles, and progressive damage accumulation over time due to sustained loading, ultimately leading to large settlements or failure. In this context, 201 pile segments were extracted from two bridges in Amsterdam and mechanically characterised, with respect to their amount of biological decay and service durations ranging from 100 to 300 years. Large-scale compression tests were carried out to determine the remaining saturated short-term compressive strength of the piles. Micro-drilling measurements were conducted to assess the amount of bacterial decay, validated with Computed Tomography (CT) scanning. On this basis, this study investigates the load history and current loads acting on the timber foundation of Bridge 30 (De Isa van Eeghenbrug) in Amsterdam, to assess the remaining load-bearing capacity of the historical piles, considering mechanical damage and decay as function of time.

This study explored the most employed techniques for the assessment of the state of conservation of traditional wooden foundation piles in Amsterdam and Venice. The techniques were evaluated for their relevance and effectiveness in assessing decay impact on centuries-old waterlogged wooden piles. The techniques adopted in Amsterdam and Venice were complementary. In Amsterdam, underwater micro-drilling was employed to accurately estimate the amount of decay and the remaining strength of the piles. In contrast, the techniques in Venice were based on microscopic and mechanical testing of small wood samples to provide a detailed decay analysis. The successful use of underwater micro-drilling in Amsterdam, which allows for fast and accurate pile decay assessment, presents an opportunity to enhance the piles conservation database of Venice. Adopting this technique in Venice could support more timely and effective preservation strategies.

In the historic city centre of Amsterdam (NL), the most widespread foundation system consists of wooden piles. Since these foundations are fully below the water table, they are mostly subjected to bacterial decay. This biodegradation phenomenon proceeds slowly over time, and usually involves the less durable sapwood, with heartwood remaining sound. Hence, obtaining an estimate of sapwood and heartwood proportions in wooden piles can provide information on how deep in the cross section bacterial decay is expected to proceed. This is relevant, for instance, when developing service life models, since the remaining sound cross section of a pile can be estimated. Thus, the present work involves a comprehensive investigation on sapwood and heartwood proportions in spruce, pine and fir wooden foundation piles from different construction periods, ranging from 1727 to 2019. The amount of sapwood and heartwood was determined with computed tomography (CT) scans on 49 wet discs retrieved from the piles. Such measured sapwood width was then compared with that predicted with an empirical model from literature, based on the number of annual rings and growth rate, obtaining a successful validation. Micro-drilling measurements were also conducted on the discs to identify decayed portions, which appeared to always affect (part of) the sapwood only. Finally, this outcome was further validated against a broader dataset of micro-drilling measurements taken on over 200 pile segments, for which the sapwood widths were predicted with the aforementioned empirical model, and were found to be overall greater than the corresponding decayed portions, even in wooden piles having been in service for 300 years.

This article presents a dataset from an experimental campaign investigating the out-of-plane (OOP) seismic response of unreinforced masonry (URM) gables in existing buildings. Addressing a critical gap in published research, the dataset provides novel experimental data on the incremental dynamic OOP behavior of three URM gables tested under seismic loading until full collapse. All three gables were nominally identical but differed in their interaction with the supporting roof structure. This interaction was experimentally reproduced by imposing differential motions at the top of the gables, which were either linearly amplified or both amplified and phase-shifted relative to the motion at the base. This approach ensured idealized and numerically replicable boundary conditions, making the dataset an ideal benchmark for refining existing and developing new modeling approaches for URM structures. The dataset includes measured and calculated acceleration, displacement, and force time histories. Beyond supporting the validation and development of numerical models, it can also contribute to improving guidelines for the out-of-plane seismic assessment of URM gables and is openly available for further research and engineering applications.

The lack of strength values for timber foundation piles in the current Eurocode 5 hinders their appropriate engineering design and assessment. Timber piles, often submerged for their entire service life, endure high moisture levels, highlighting the need to define strength parameters of round wood under fully saturated conditions. To ensure reliable material properties, a large-scale study was conducted on 70 European softwood piles, determining strength and stiffness through axial compression tests on saturated segments extracted along the pile. Mean and characteristic wet compressive strength and stiffness values were derived, applicable to the whole pile and/or its parts. The mechanical properties of the piles were analysed in relation to grading parameters that may influence the saturated compressive strength, leading to the classification of three strength classes for visual grading. Additionally, two regression models were developed-one based on the most influencing visually graded parameters, and the other on the dynamic modulus of elasticity. The saturated compressive strength values and grading boundaries presented in this study contribute to the engineering design of European softwood foundation piles in the context of a new circular construction ecosystem, and support the integration of reliable design values into future versions of Eurocode 5.

Timber modular buildings are an emerging construction method, due to the environmental and construction speed benefits. However, the inherent discontinuity and limited deformation capacity, hinders their ability to effectively redistribute loads under accidental load cases and thus, their robustness. A method to quantify the robustness of a building is to assess its behavior under notional column removal scenarios. This study numerically investigates the behavior of a hypothetical five-storey timber post-and-beam modular building under accidental damage events represented by four different column removal scenarios. The findings indicate that the structure could develop sufficient alternative load paths to sustain the amplified accidental limit state design load in most cases, primarily through flexural mechanisms. However, due to the limited ductility of these mechanisms, modular connections were optimally redesigned to enhance axial elongation and capacity, enabling the development of catenary action. The most effective strategy for achieving a robust catenary response was the introduction of a fuse element, significantly improving the ductility of the connection and enhancing the overall structural robustness.

Low-rise masonry buildings worldwide frequently feature unreinforced masonry (URM) walls coupled with various pitched roof configurations supported by masonry gables. Past earthquakes have highlighted the vulnerability of these components to out-of-plane seismic loads due to their high slenderness, insufficient roof connections, and exposure to amplified accelerations while being subjected to minimal overburden due to their location at the upper part of buildings. This study presents key insights from the experimental campaign of the ERIES-SUPREME project, aimed at enhancing the understanding of the out-of-plane seismic behavior of masonry gables. Incremental dynamic tests were performed on three full-scale URM gables, simulating both induced and tectonic earthquake scenarios until collapse, using two shake tables. Differential motions at the top and bottom tables reproduced the interaction of the gables with three different roof diaphragm configurations, each introducing a unique filtering effect on the seismic input. The outcomes of the experiments can be used for refining existing numerical modelling strategies as well as contribute to developing improved tools for the seismic assessment of URM gables.

Large parts of banks of canals in the Netherlands are protected by azobé timber sheet piles. Many kilometers of sheet piles in the province of Noord-Holland, are planned to be replaced or to undergo maintenance. Yet, there is insufficient knowledge on the current state of the azobé sheet piles and their residual service life. Based on this, a series of investigations on azobé sheet piles after 57 years of service were performed. Visual inspections showed surface deterioration on the water-exposed side for all boards. Nondestructive testing using micro drilling technique showed no signs of internal deterioration. A maximum reduction in thickness of 17% and an average thickness reduction of 6.7% of original thickness were observed. CT scanning showed that the remaining cross sections of the azobé boards were intact and had comparable density of new azobé boards. An exponential damage accumulation model was used to predict the residuals service life of the timber sheet piles subjected to earth stress. Conservative estimates based on physical measurements and residual bending strength indicate that the sheet piles have an additional service life of 22–43 years from the current state.

Wooden piles are the most common foundation system in the historic city of Amsterdam (NL). The piles are fully submerged below water table and subject to bacterial decay. This study investigated sapwood and heartwood proportions in spruce, pine, and fir piles from different construction periods, in relation to their degradation. X-ray computed tomography scans on 49 wet discs were performed to measure the piles’ sapwood width, which was then validated against an empirical model based on annual rings and growth rate. Degraded areas, identified with micro-drilling measurements, were found to affect sapwood only. These outcomes were further validated on 201 pile segments, with the predicted sapwood widths being greater than or equal to the decayed portions, even in 300-year-old piles. Therefore, estimating sapwood width can contribute to determine the remaining sound cross section of the piles, providing useful input for service life models for planning timely maintenance interventions.

Unreinforced masonry gables are widely present in low-rise existing buildings and are particularly vulnerable to seismic events, as demonstrated by the several observed out-of-plane collapses of these structural elements during earthquakes. Since the structural behaviour of gable walls has been scarcely investigated in the literature, a large-scale testing programme (ERIES-SUPREME) has been initiated by research institutions in the Netherlands (TU Delft, TNO) and Italy (EUCENTRE, University of Pavia, IUSS Pavia), to dynamically characterise the gable out-of-plane seismic response. Shake-table tests on full-scale masonry gables are being conducted at the 9D LAB facility in EUCENTRE (Pavia, Italy), incorporating the effects of different ground motions, structures and roof stiffnesses. This facility features both a top and a bottom shake table, allowing for separate input motions: therefore, the effect of the roof dynamic behaviour can be accounted for by applying differential signals. This work presents the procedure used to define such input motions. While for tectonic signals direct earthquake recordings at floor level are accessible from existing monitored masonry buildings in Italy, for induced signals in the Netherlands such data are not available. Thus, in the latter case, numerical analyses are conducted considering a reference unreinforced masonry building subjected to induced earthquakes, with three roof configurations representing flexible, semi-flexible, and stiff diaphragms. Based on the obtained outcomes, input signals are derived for both induced and tectonic earthquake scenarios, leading to the final definition of the testing protocol for the ERIES-SUPREME experimental campaign. The findings of this study are also broadly applicable for the derivation of input motions in the planning of benchmark experiments where parts of the structural system cannot be explicitly reproduced due to testing constraints.

Typical low-rise masonry buildings worldwide often feature unreinforced masonry (URM) walls paired with pitched roof configurations supported by masonry gables. Past earthquakes indicate that these components are vulnerable to out-of-plane seismic loads. This study presents key findings from the experimental campaign of the ERIES SUPREME project, which aims to advance understanding of the out-of-plane seismic response of masonry gables. Incremental dynamic tests simulating induced and tectonic seismicity scenarios were conducted on three full-scale URM gables, using two shake tables. Differential motions applied to the top and bottom tables allowed the simulation of gable interaction with distinctly different roof configurations. The experimental results are presented in terms of failure mechanisms, force-displacement hysteresis behavior, and acceleration and displacement capacities. These findings will contribute to refining and calibrating existing numerical models.

This work presents an extensive static and seismic retrofitting intervention performed on a relevant historic case-study building, the Venetian sawmill of Vallaro (Brescia, Italy). This heritage construction from the end of the 19^th century features three building portions, two realized in timber and one consisting of a masonry structure with timber floors and roofs. The building had been neglected for decades and was in a poor state of conservation, despite representing a valuable example of the typical historic architectures of the mountainy area in the Province of Brescia. With the support of the local municipality, a complete restoration of the sawmill has started, with the objective of transforming it into a territorial museum. To this end, a series of reversible and compatible timber-based interventions were planned in consultation with the local superintendence for architectural heritage. The structural design aimed at preserving the historic value of the sawmill, especially in its original timber components, such as trusses, braced columns, and diaphragms. The present case study enables to showcase the advantages of the applied strengthening methods in such a complex architectural restoration and the importance of tailored structural detailing, combining the improvement in static and seismic performance with the protection and preservation of ancient timber members.

Typical low-rise masonry buildings worldwide commonly feature unreinforced masonry (URM) walls, often paired with various pitched roof configurations supported or finished by masonry gables. These buildings constitute a significant portion of the building stock in several seismic-prone regions, including areas vulnerable to both natural and induced seismicity. Masonry gables in such buildings are frequently associated with high seismic vulnerability, as evidenced by damage observed after past earthquakes. This paper presents key results from an experimental campaign aimed at enhancing the understanding of the seismic out-of-plane response of masonry gables. Incremental full-scale shake-table tests were performed on three densely instrumented URM gables until the complete collapse. Within this context, the study systematically investigated the effects of motions applied at the top of the gable, both being linearly amplified as well as amplified and out-of-phase, with respect to the motion applied at the base of the gable. Such differential motions simulate the effect of the gable interaction with three different roof configurations, each exerting a different filtering effect on the seismic motion. The response of the gables to both induced and tectonic earthquakes was considered. The experimental findings are presented in terms of failure mechanisms, force-displacement hysteresis behaviour, and acceleration and displacement capacities. All generated experimental data, along with the associated instrumentation schemes, are openly available for download at https://doi.org/10.60756/euc-1avy7q49.

The majority of bridges and quay walls in the inner city of Amsterdam rely on wooden foundation piles. Most of these were constructed 100–300 years ago, implying several challenges for the assessment of the current residual load-carrying capacity and their reliability. In Amsterdam, the wooden piles supporting bridges and quay walls remain entirely under the water table, which means that only bacterial decay can occur. Bacterial degradation proceeds at a slow rate, allowing the piles to perform their function for many years, although causing a reduction of the load-carrying capacity over time. To this end, the municipality of Amsterdam started a large project where non-destructive micro-drilling measurements were employed, with the goal of capturing the in-situ level of decay and the remaining strength of wooden foundation piles. The applicability of micro-drilling was studied on 60 wooden piles with various decay levels, driven between 1727 and 1922, and retrieved from two bridges in Amsterdam. An algorithm was developed for analysing the micro-drilling signals, aimed at determining the decayed outer layer of the pile (soft shell). The micro-drilling approach was validated with the results of mechanical testing on the piles. This study contributes to reliably assessing the decay and remaining load carrying-capacity of wooden foundation piles utilizing in-situ micro-drilling measurements.

Masonry structures occupy a significant share of the current building stock due to widespread material availability and cost-effectiveness. Regions with high seismicity, such as the Himalayas, have often developed a local seismic culture over the centuries. This has led to improved construction techniques providing an enhanced seismic performance, as evident from post-earthquake surveys in this area. In this framework, Bhatar is a building typology found in the greater Himalayan region, which features embedded horizontal timber bands in masonry walls, enhancing the box-behaviour and in turn avoiding their premature out-of-plane failure. This work aims to quantify the improvement of the out-of-plane performance of masonry walls because of the presence of horizontal timber bands. In order to achieve this research objective, numerical analyses were conducted in DIANA FEA finite element software starting from the few experimental results on this building typology available in the literature. These were used to calibrate the properties of masonry, which was represented as a homogeneous isotropic continuum, with nonlinearities taken into account by means of a total strain rotating crack model. Firstly, a U-shaped masonry wall having the same geometry and boundary conditions as the experimental tests was simulated using a 3D modelling approach. Non-linear static analyses were performed and very good agreement was obtained with the results from the literature. On this basis, the calibrated numerical model was then employed to conduct sensitivity analyses considering varying factors, such as masonry material properties, geometry, opening configurations, timber section sizes and properties. The outcomes of this extensive study show a considerable improvement in the out-of-plane response of the masonry walls in the presence of horizontal timber bands. Given the limited research conducted on the Bhatar building typology in the past, this work constitutes a further step towards a better understanding of the behaviour of Himalayan masonry structures under earthquakes, promoting more effective seismic risk reduction strategies. This improved understanding into timber’s role in imparting greater seismic resilience to masonry structures can inform better maintenance, conservation and preservation of heritage and historical masonry structures in the Himalayas.

This case study explores the utilization of distributed fiber optic sensors (DFOS) in wooden foundation piles, for assessing and monitoring the stress distribution along their length. Three spruce and three pine foundation piles instrumented with DFOS were driven into the soil in a testing field in Amsterdam and axially loaded in compression. Since DFOS provided strain information, calculating the stress distribution in the piles required knowledge of their stiffness properties, which inherently vary from the head to the tip. Consequently, the piles were extracted and their overall wet dynamic elastic modulus (E_c,0,dyn,wet) was determined through frequency response measurements. Subsequently, the piles were segmented, transported to the TU Delft Laboratory and subjected to mechanical testing. For each segment, the mechanical properties were determined and their variability along the pile was studied, in particular for the static modulus of elasticity (E_c,0,stat,wet). This enabled a comprehensive assessment of the actual in-situ stress distribution (Δσ_actual,stat and Δσ_actual,dyn) along the length of the piles, calculated with DFOS strains and the pile stiffness (E_c,0,stat,wet and E_c,0,stat,dyn). Given the novelty of the DFOS application to timber piles, a validation of the accuracy was conducted on 3 pile segments equipped with DFOS. These segments underwent laboratory compression testing, allowing for a direct comparison between DFOS strain readings and strains measured with linear potentiometers attached to the pile segments. The results revealed good accuracy of DFOS in controlled lab conditions, with a maximum stress deviation of 0.65 MPa. Since the testing field featured a 6-meter-deep predrilled layer, where negligible shaft friction was mobilized, the no-friction stress (Δσ_no-friction) approximately aligned with Δσ_actual,stat on the piles. At pile tips, the maximum applied 300–350 kN compressive load (i.e. Δσ_no-friction = 20–26 MPa), resulted in Δσ_actual,stat = 4–7 MPa, highlighting shaft friction effect. The calculated Δσ_actual,dyn with a single E_c,0,stat,dyn for the whole pile, led to 3 MPa stress overestimation at pile tip. Although this calculation is conservative, the detailed knowledge of the variation of stiffness properties along the pile would result in a more efficient structural use.

Reversible retrofitting techniques for protecting architectural heritage against seismic events have found increasing application in existing or historical buildings in the last years. In this framework, the use of wood-based strengthening solutions for both timber and masonry structures has shown promising results, as proved by several recent research studies, highlighting benefits such as reversibility, compatibility, lightness, sustainability, and effectiveness of these techniques. With specific reference to existing timber floors, the superposition of a plywood panels overlay fastened to the sheathing has proved to be an excellent method to improve the seismic response of such structural components. One of the main benefits of this intervention is related to the combination of a great improvement of in-plane strength and stiffness of the diaphragms, with a considerable increase in their hysteretic energy dissipation. In other words, the method does not only improve the capacity of the floors, but also contributes to a reduction in seismic demand, because of the damping effect induced by the yielding of the numerous fasteners. In order to facilitate the design and use of this reversible, efficient and sustainable retrofitting method in practice, this work first presents the derivation of nomograms, based on previously formulated analytical models. The graphs can be adopted by professional engineers as useful tool for a preliminary structural analysis of timber diaphragms strengthened with plywood panels, enabling a more in-depth understanding of the key design parameters and resisting mechanisms. In addition to that, the implementation of a calculation tool is presented, enabling structural engineers to visualize the expected in-plane force-displacement response and energy dissipation of the retrofitted diaphragms. This work can contribute to the promotion of timber-based techniques in the combined structural, seismic, and conservation upgrading of existing buildings belonging to the architectural heritage of seismic-prone countries.

In the historic city centre of Amsterdam (NL), the predominant foundation system is comprised of wooden piles. Due to their placement below the water table, these foundations are susceptible to bacterial decay. This study aims to investigate and compare various methods for characterizing decay patterns within the cross sections of piles retrieved from two bridges in Amsterdam. The examined piles span different construction years: three originate from 1727, four from 1886, and two from 1922. Following extraction, the piles were transported to TU Delft Stevin II Laboratory, where they underwent further subdivision into three segments, each representing the head, middle, and tip, resulting in a total of 27 segments. The effects of bacterial decay were characterised by performing micro-drilling measurements, small-scale material and compressive tests on prismatic samples extracted from the segments' cross sections, computed tomography scans, and light microscopy observations. Microscopic examination revealed severe degradation in all segments dating back to 1727, extending 20–50 mm from their surface. This outcome was also confirmed by the other adopted methods: the corresponding prisms had large moisture contents and poor mechanical properties, while low basic densities and drilling amplitudes were obtained from CT scans and micro-drilling measurements, respectively. On the contrary, the internal sections of the 1727 segments exhibited no evidence of decay and demonstrated properties consistent with those observed in sound segments from 1886 and 1922. Finally, the observed gradients of density, strength, and stiffness were well correlated with micro-drilling measurements, which can therefore be reliably used as on-site assessment method to reconstruct the properties of the piles.

The application of timber-based strengthening solutions to existing wooden and masonry structures, combines several benefits, such as reversibility, compatibility, lightness, sustainability, affordability, and effectiveness. With reference to existing timber floors, an efficient method to enhance their seismic response is the fastening of an overlay of plywood panels to the existing sheathing, an intervention that greatly improves in-plane strength, stiffness, and energy dissipation. In order to promote the use of this retrofitting solution in practice, this work presents a set of calculation tools supporting the design and advanced numerical modelling of timber diaphragms strengthened with plywood panels. The suite of tools allows to first estimate the full nonlinear, cyclic in-plane response of the strengthened diaphragms starting from the geometrical and material properties of the existing sheathing and the plywood overlay, as well as the mechanical characteristics of the fasteners. As second step, such estimated in-plane response can be transformed into a constitutive law for performing nonlinear numerical simulations, by means of a user-supplied subroutine developed for finite element software DIANA FEA. The presented calculation examples and the performed validation against reference studies from literature, show that the developed tools can provide an accurate estimate of the in-plane response of the diaphragms, and enable an efficient numerical simulation of their seismic behaviour. The implemented tools can be used to both obtain preliminary indication for plywood-based seismic retrofitting design, and to calibrate the interventions on existing diaphragms based on the specific characteristics and needs of a building, relying on the adaptability and versatility of this strengthening method.