Periodic Reporting for period 2 - Endure (Fuse-based segmentation design: Avoiding failure propagation in building structures)
Reporting period: 2023-07-01 to 2024-12-31
Endure aims to develop a novel fuse-based segmentation design approach to arrest the propagation of failures in building structures subjected to extreme events.
Extreme events (e.g. floods, vehicle impacts, explosions) often cause initial failures of critical elements in buildings. Such local failures can propagate to other parts of the structure, resulting in a disproportionate collapse that extends to the entire structure or to a large part of it and has huge negative consequences for society. As the world faces more frequent and intense extreme events, it is now more important than ever to design robust structures that are insensitive to initial damage. At present, most robustness design methods included in relevant codes rely on providing extensive continuity within a structural system to ensure that alternative load paths are available to redistribute loads supported by a structural element after its failure. Although this approach can be effective, it can also increase the risk of a disproportionate collapse in some situations. These include, for example, cases of large initial failure or of buildings with wide spans between columns. In such cases, continuity can contribute to a collapsing part pulling down other parts of the structure that would otherwise be unaffected. To address this limitation of current design methods, a novel fuse-based segmentation approach is being developed in Endure. This approach synergistically combines the advantages of two opposite concepts: continuity and segmentation. The structural system is designed with sufficient continuity to prevent collapse after small initial failures. At the same time, it is also designed to segment into different parts after larger initial failures that inevitably trigger a collapse, effectively isolating the collapse.
To achieve its overall aim, Endure is organised in three scientific work packages (WPs). WP1 aims to develop a performance-based framework for the design of fuse-based segmented buildings. WP2 focuses on designing, manufacturing and testing segment borders for achieving fuse-based segmentation. WP3 involves validating the effectiveness of the proposed approach by implementing it in three full-scale buildings of different structural type and testing them. The three types of structures that are to be tested as part of the project are precast reinforced concrete (RC), monolithic RC, and steel/composite frame buildings.
Extreme events (e.g. floods, vehicle impacts, explosions) often cause initial failures of critical elements in buildings. Such local failures can propagate to other parts of the structure, resulting in a disproportionate collapse that extends to the entire structure or to a large part of it and has huge negative consequences for society. As the world faces more frequent and intense extreme events, it is now more important than ever to design robust structures that are insensitive to initial damage. At present, most robustness design methods included in relevant codes rely on providing extensive continuity within a structural system to ensure that alternative load paths are available to redistribute loads supported by a structural element after its failure. Although this approach can be effective, it can also increase the risk of a disproportionate collapse in some situations. These include, for example, cases of large initial failure or of buildings with wide spans between columns. In such cases, continuity can contribute to a collapsing part pulling down other parts of the structure that would otherwise be unaffected. To address this limitation of current design methods, a novel fuse-based segmentation approach is being developed in Endure. This approach synergistically combines the advantages of two opposite concepts: continuity and segmentation. The structural system is designed with sufficient continuity to prevent collapse after small initial failures. At the same time, it is also designed to segment into different parts after larger initial failures that inevitably trigger a collapse, effectively isolating the collapse.
To achieve its overall aim, Endure is organised in three scientific work packages (WPs). WP1 aims to develop a performance-based framework for the design of fuse-based segmented buildings. WP2 focuses on designing, manufacturing and testing segment borders for achieving fuse-based segmentation. WP3 involves validating the effectiveness of the proposed approach by implementing it in three full-scale buildings of different structural type and testing them. The three types of structures that are to be tested as part of the project are precast reinforced concrete (RC), monolithic RC, and steel/composite frame buildings.
At the start of the project, the Endure team analysed 40 real cases of progressive collapse in buildings, systematically recording information on the context and the structure itself as well as on the initial failure and its propagation. This information was used to define generic building designs and initial damage scenarios to be simulated in order to better understand the limitations of current design methods and to characterise situations for which fuse-based segmentation is beneficial. Simulations were performed using both a simplified approach and a more advanced one that can accurately represent all phases of a collapse process. Simulations with the simplified approach were used to propose a practical methodology for objectively assessing the ability of a building to prevent collapse initiation through load redistribution. Moreover, both the analysis of the real cases as well as simulation results were used to develop a heuristic methodology for defining fuse-based segmentation configurations that enhance robustness based on structural and geometric characteristics. Finally, a risk-based approach to perform cost-benefit analysis of possible segmentation configurations is also being developed. The methodology for defining possible segmentation configurations combined with the risk-based cost-benefit analysis approach constitute a performance-based framework to support decisions on when and how to segment a structure to reduce the risk of disproportionate collapse.
To implement fuse-based segmentation, segment borders to arrest a moving collapse front can consist of strong elements and/or force-limiting elements. Bespoke designs of force-limiting elements for cast-in-place reinforced concrete (RC) buildings (made of modified couplers) have been designed, manufactured, and tested in the laboratory. Construction details and structural design procedures have also been elaborated to ensure adequate performance of suitable segment borders in precast RC, cast-in-place RC, and steel frame buildings. Design processes have also been created to estimate the required lower- and upper-bound load-carrying capacity of such elements. A novel test set-up for studying fuse-based segmentation in subassemblies (representing key parts of a complete building system) has also been developed. Finally, two scaled cast-in-place RC subassemblies have been built and tested using this novel set-up.
The Endure team has also performed a unique partial collapse test of a full-scale precast concrete building (https://youtu.be/4QhqyenIFIQ?si=ZcLuD9UZW7jaMt7e(opens in new window)) , demonstrating that fuse-based segmentation can be effectively implemented in this type of structure. The results of this work have been published in Nature and featured on its cover.
To implement fuse-based segmentation, segment borders to arrest a moving collapse front can consist of strong elements and/or force-limiting elements. Bespoke designs of force-limiting elements for cast-in-place reinforced concrete (RC) buildings (made of modified couplers) have been designed, manufactured, and tested in the laboratory. Construction details and structural design procedures have also been elaborated to ensure adequate performance of suitable segment borders in precast RC, cast-in-place RC, and steel frame buildings. Design processes have also been created to estimate the required lower- and upper-bound load-carrying capacity of such elements. A novel test set-up for studying fuse-based segmentation in subassemblies (representing key parts of a complete building system) has also been developed. Finally, two scaled cast-in-place RC subassemblies have been built and tested using this novel set-up.
The Endure team has also performed a unique partial collapse test of a full-scale precast concrete building (https://youtu.be/4QhqyenIFIQ?si=ZcLuD9UZW7jaMt7e(opens in new window)) , demonstrating that fuse-based segmentation can be effectively implemented in this type of structure. The results of this work have been published in Nature and featured on its cover.
The fuse-based segmentation approach clearly has the potential to revolutionise the present robustness design philosophies for buildings, which focus on increasing continuity. This will open a new research area since it can be foreseen that the new approach will require further studies for widespread implementation.
At the end of the project, the most important results will include:
• A performance-based framework for defining segmentation configurations of fuse-based segmented buildings to prevent disproportionate collapse.
• A methodology for the structural design of segment borders to achieve fuse-based segmentation.
• A novel test setup for evaluating fuse-based segmentation response in subassemblies.
• Tested and validated designs of segment borders for ensuring fuse-base segmentation in precast reinforced concrete (RC), monolithic RC, and steel/composite frame buildings.
• Unique experimental data on collapse propagation and isolation in three full-scale buildings.
At this point in time, the main advances beyond the state of the art include:
• New insights on real past cases of progressive collapse.
• An improved understanding of how continuity, as prescribed in current codes, can contribute to disproportionate collapse.
• A practical methodology for assessing the ability of building structures to prevent collapse initiation through load redistribution.
• A heuristic framework to define suitable fuse-based segmentation configurations based on structural and geometric characteristics.
• Improved understanding of how isolating elements introduced to achieve fuse-based segmentation influence structural response in both operational and extreme situations.
• Design of novel test setup for evaluating fuse-based segmentation response in subassemblies.
• Full-scale implementation and validation of fuse-based segmentation in precast building .
• Experimental observations of collapse phenomena and of damage levels in part of a precast building remaining upright after segmentation.
At the end of the project, the most important results will include:
• A performance-based framework for defining segmentation configurations of fuse-based segmented buildings to prevent disproportionate collapse.
• A methodology for the structural design of segment borders to achieve fuse-based segmentation.
• A novel test setup for evaluating fuse-based segmentation response in subassemblies.
• Tested and validated designs of segment borders for ensuring fuse-base segmentation in precast reinforced concrete (RC), monolithic RC, and steel/composite frame buildings.
• Unique experimental data on collapse propagation and isolation in three full-scale buildings.
At this point in time, the main advances beyond the state of the art include:
• New insights on real past cases of progressive collapse.
• An improved understanding of how continuity, as prescribed in current codes, can contribute to disproportionate collapse.
• A practical methodology for assessing the ability of building structures to prevent collapse initiation through load redistribution.
• A heuristic framework to define suitable fuse-based segmentation configurations based on structural and geometric characteristics.
• Improved understanding of how isolating elements introduced to achieve fuse-based segmentation influence structural response in both operational and extreme situations.
• Design of novel test setup for evaluating fuse-based segmentation response in subassemblies.
• Full-scale implementation and validation of fuse-based segmentation in precast building .
• Experimental observations of collapse phenomena and of damage levels in part of a precast building remaining upright after segmentation.