Periodic Reporting for period 2 - STAND4HERITAGE (New STANDards for seismic assessment of built cultural HERITAGE)
Periodo di rendicontazione: 2021-03-01 al 2022-08-31
STAND4HERITAGE (S4H in short) ambitiously engages in introducing new standards for safeguarding built cultural heritage for the next generations, which is a major societal demand. Due to its large diversity, the accurate description of the structural behaviour and safety of heritage buildings is still an open issue, particularly when subjected to earthquake ground motions. Among the most frequently observed seismic damage mechanisms in these buildings, the out-of-plane of masonry walls is acknowledged as the main cause for building loss and injuries to people. There are many unresolved challenges to effectively assess the out-of-plane seismic behaviour of masonry structures. First, it is necessary to understand less well-known phenomena in masonry dynamics, which largely influence the out-of-plane behaviour and capacity of heritage buildings. A recent blind exercise to predict the capacity of benchmark masonry structures to resist dynamic excitations demonstrated that, although advanced simulation tools are available, leading international researchers are still unable to consistently provide a collapse estimate. S4H addresses the aspects for successful development of approaches for seismic response prediction of masonry structures, integrating the necessary stages for out-of-plane assessment. Specifically, it aims to generate novel: integrated stochastic-based models to consider the seismic signal in the dynamic response and capacity; datasets of the dynamic response evaluated after an extensive shake table testing program; numerical approaches for simulation of the out-of-plane seismic behaviour; an integrated analytical approach for out-of-plane seismic assessment of heritage buildings. S4H objectives are in line with the UN 2030 agenda for sustainable cities and communities. The project is founded on the experience of the PI in the topic, and on the interdisciplinary expertise of his team in facing the challenges to provide optimal intervention solutions for heritage buildings.
The S4H team designed, ordered, and received tilting (1.5x1.5m) and settlement (1.0x1.5m) tables. Experiments on masonry corners have already been conducted on the tilting table highlighting the effect of loading orientation on their collapse. The shaking table (3x3m) has also been installed at UMinho and the first rocking tests are under way. The new DIC system with 6 cameras is also successfully mounted and all the required stone material for these tests is available.
S4H team has investigated the dry-joint interface stiffness and damping parameters of block-based structures. A new experimental procedure based on vibration tests has been proposed to identify such properties. In addition, S4H team has developed a novel methodology to correlate the numerical viscous damping with the analytical coefficient of restitution for the dynamic analysis of rocking structures, based on extensive numerical simulations. It also revealed the conditions under which rocking motion terminates even when the structure is still subjected to ground motion. Finally, the S4H team demonstrated the great impact of low dry-joint stiffness on the seismic capacity of masonry structures underlining that current design recommendations are not appropriate for these structures.
The S4H team is producing datasets of simulated earthquake ground motions. First, a methodology was proposed to generate randomised seismic signals based on real records of the same area (herein, Europe). As an example, direct simulations of underground effects and their propagation through the soil layers give a thorough understanding of the possible future earthquake events in the region of Azores (Portugal). The outcomes of these simulations are being used to understand the effect of signal characteristics on the response of masonry and rocking structures.
Engineering tools are being developed, with a comprehensive limit analysis model for the failure of masonry corners. In particular, a rapid tool for the seismic assessment of masonry structures has been proposed. It combines limit analysis and rocking dynamics and serves as a fast methodology for engineering practice in the built cultural heritage field. Further works on these aspects are under development. The team is also preparing graphic tools to quickly generate masonry structures to facilitate the structural analysis of various masonry patterns, including rubble masonry.
S4H team has investigated the dry-joint interface stiffness and damping parameters of block-based structures. A new experimental procedure based on vibration tests has been proposed to identify such properties. In addition, S4H team has developed a novel methodology to correlate the numerical viscous damping with the analytical coefficient of restitution for the dynamic analysis of rocking structures, based on extensive numerical simulations. It also revealed the conditions under which rocking motion terminates even when the structure is still subjected to ground motion. Finally, the S4H team demonstrated the great impact of low dry-joint stiffness on the seismic capacity of masonry structures underlining that current design recommendations are not appropriate for these structures.
The S4H team is producing datasets of simulated earthquake ground motions. First, a methodology was proposed to generate randomised seismic signals based on real records of the same area (herein, Europe). As an example, direct simulations of underground effects and their propagation through the soil layers give a thorough understanding of the possible future earthquake events in the region of Azores (Portugal). The outcomes of these simulations are being used to understand the effect of signal characteristics on the response of masonry and rocking structures.
Engineering tools are being developed, with a comprehensive limit analysis model for the failure of masonry corners. In particular, a rapid tool for the seismic assessment of masonry structures has been proposed. It combines limit analysis and rocking dynamics and serves as a fast methodology for engineering practice in the built cultural heritage field. Further works on these aspects are under development. The team is also preparing graphic tools to quickly generate masonry structures to facilitate the structural analysis of various masonry patterns, including rubble masonry.
At the end of the project, the S4H project will provide an extensive experimental dataset of (i) static tilting tests, helpful to demonstrate the adequacy of different materials to be used on repeated masonry testing, (ii) free and forced rocking tests to validate rocking modelling approaches, and (iii) dynamic tests on masonry structures to understand the seismic behaviour of heritage buildings.
The dynamic signals used in the experimental campaign will come from a massive dataset of artificial seismic signals generated by the project, based on stochastic analysis of the most important seismic features of real accelerograms recorded during earthquakes. Both seismic input signals datasets and experimental shaking table results will be shared with the broadest community.
S4H will develop fast numerical and analytical tools for the seismic analysis of masonry structures. At the end of the project, numerous analytical rocking simulations would have been conducted to prove their efficiency to predict the response of masonry specimens under stochastic loading and therefore to be used in practice as a simplified analysis tool. Similarly, an all-integrated macro-block approach will be validated to facilitate rapid assessments of masonry structures. This model will also include an automated generation of the geometry for faster and easier practical use.
The dynamic signals used in the experimental campaign will come from a massive dataset of artificial seismic signals generated by the project, based on stochastic analysis of the most important seismic features of real accelerograms recorded during earthquakes. Both seismic input signals datasets and experimental shaking table results will be shared with the broadest community.
S4H will develop fast numerical and analytical tools for the seismic analysis of masonry structures. At the end of the project, numerous analytical rocking simulations would have been conducted to prove their efficiency to predict the response of masonry specimens under stochastic loading and therefore to be used in practice as a simplified analysis tool. Similarly, an all-integrated macro-block approach will be validated to facilitate rapid assessments of masonry structures. This model will also include an automated generation of the geometry for faster and easier practical use.