Projects / Programmes
Seismic resilience and strengthening of precast industrial buildings with concrete claddings
| Code |
Science |
Field |
Subfield |
| 2.01.04 |
Engineering sciences and technologies |
Civil engineering |
Earthquake engineering |
| Code |
Science |
Field |
| T230 |
Technological sciences |
Building construction |
| Code |
Science |
Field |
| 2.01 |
Engineering and Technology |
Civil engineering |
seismic risk reduction, claddings, connections, seismic strengthening, innovative restrainers, shaking table experiments, seismic codes, Eurocode 8
Researchers (14)
Organisations (2)
Abstract
Recent earthquakes clearly demonstrated that precast industrial buildings with concrete claddings are highly vulnerable in the case of seismic loading. Due to the lack of knowledge and understanding as well as for the complexity of the problem, the connections of the cladding panels to the structural system were never explicitly designed for seismic loading in the plane of the panels. The cladding-to-structure interaction was neglected.
One of the key goals of the project is therefore to develop and to evaluate innovative retrofitting techniques to protect a large number of existing industrial buildings with vulnerable claddings in order to increase seismic resilience of industrial areas and to enhance their ability for faster and more effective recovery after the expected earthquakes. Special attention will be devoted to re-strainers prefabricated of the modern high-performance synthetic ropes. The development of their terminations and anchoring will represent a special challenge.
Some of these problems were partly addressed by the European project SAFECLADDING. So the proposed project will be built on the solid background and clear outlines. This will enable effective management and achievements of the ambitious project goals. The proposed project will provide dynamic and shaking table experiments of the existing and innovative connections and in particular of the full-scale prototypes of the complete structural systems, while previous research of the existing systems was limited to monotonic and cyclic tests of isolated connections. This will provide more realistic insight into the actual dynamic behaviour and interaction between the panels and structure.
The focus point of the project is a set of shaking table experiments on full-scale structures. The main investigated parameters in these studies will be:
- The orientation of the panels (vertical or horizontal);
- The type of the connections (existing connections: sliding and cantilever; as well as innovative solutions: connections with increased deformation capacity and dissipative connections);
- The direction of loading (uni-axial or bi-axial);
- The type of re-strainers.
The proposed experimental set-up enables multiple uses of the individual components and consequently enables faster and more efficient testing as well as increases the number of possible variations of the investigated parameters.
The research will give insight into the very complex behaviour of the cladding systems and re-strainers at seismic loading. Efficient, experimentally verified FEM models will be used to develop practically applicable force-displacement based macro-models.
Using these models extensive seismic risk analyses will be made considering the cladding-to-structure interaction. The probability of failure will be studied for the complete structural system as well as for the cladding system itself. The reduction of seismic risk due to the installed re-strainers and the use of dissipative connections will be studied in detail. These results will provide useful data for seismic response emergency planning and for the efficient insurance policy. This is particularly important in the case of industrial buildings, where the cost of the interruption of the business should be the key factor for insurance. This was clearly demonstrated during the recent earthquakes in Northern Italy, where this cost exceeded 13 billion EUR.
The procedure for the realistic estimate of the demand on the connections, re-strainers and structure, taking into account the cladding-to-structure interaction, will be developed and explicit expressions to determine the capacity of different connections and re-strainer components at seismic loading will be provided. The results will contribute to the improved design guidelines for the precast buildings with concrete claddings. They will also serve as the background for possible modifications and improvements of the relevant sections in the European standards
Significance for science
The proposed project will give better insight into the complex seismic behaviour of the cladding-to-structure connections, which is not enough explored and understood. The experimental and numerical investigations will give information on highly non-linear behaviour of the cladding system at random dynamic loading. This includes contact problems at the interface of the steel inserts and concrete, 3D stress distribution, dynamic deterioration of materials, wedging of the components, and large plastic deformations.
All these phenomena will be studied by dynamic or shaking table experiments, which were never done before. It is obvious that many characteristics, which are listed in the previous paragraph, strongly depend on the dynamic characteristic of the seismic action and response. However, this was never explicitly explored in the previous research.
The nearly full-scale prototype of the analysed precast structural system with claddings will be tested on a large shaking table, as opposed to the cyclic tests of the single connections in the past. This is crucial to understand the behaviour of the connections considering realistic boundary conditions at the large relative drifts during a strong earthquake and their complex interaction with the structure.
Efficient, experimentally verified FEM models will be proposed to account for the above characteristics. Practically applicable force-displacement based macro-models will be developed and calibrated by both, the FEM analyses and the experimental results.
The application of the re-strainers in the precast buildings is a new field of research. This is in particular true for the fibre ropes made of innovative materials, and even more to their terminations and anchoring into the concrete elements. The procedures for the demand evaluation will be defined and the formulas for the capacity evaluation of all critical parts of the re-straining system will be proposed.
The developed numerical models will enable realistic estimate of the interaction of the cladding panels and the structure, which was not possible before. Considering this interaction, a realistic seismic risk assessment procedure will be formulated and done for a large sample of realistic structures.
Significance for the country
The proposed project has a very strong applicative component. Therefore all the results, which are important for the development of the scientific field, have also the direct impact on the application, economy and society; in particular:
1) It has been very disturbing to realize that a great share of the existing cladding systems is not safe in the case of the earthquake, which is expected in central Slovenia and southern Europe. The results of the project will provide economical, fast and practically applicable methods of strengthening. The initial investigations demonstrated that the expected cost of a typical re-strainer should not exceed a couple of 10 EUR.
2) Safer cladding systems will reduce indirect losses (i.e. the down-time of the production), which comprise the predominant share of all losses. This will increase seismic resilience of the industrial regions in Europe and enhance their ability for faster and more effective recovery after the expected earthquakes.
3) Useful data for seismic response emergency planning and for the efficient insurance policy will be provided. The latter is particularly important in the case of the industrial buildings where the cost of the interruption of the business should be the key factor in insurance policy.
4) Cladding panels might be considered in design as “non-structural” elements, but the fall of the panel with the weight of 10 tons still represents a great hazard. In Slovenia (and probably in some other parts of Europe) precast buildings are extremely popular for shopping centres (precast buildings offer fast construction, open space and /too/ low cost). These centres are visited by thousands of people at any time of the day.
5) In parallel of steel re-strainers, fibre ropes made of high performance plastic materials will be explored. They have better corrosion and environmental performances as well as strength. They can be also recycled to e.g. nonwoven fabric, yarn, and insulation material.
6) An important document “Improved design guidelines for the cladding systems in precast industrial buildings” will be published.
7) This publication will also serve as the background document for the proposed modifications and improvements of the relevant sections in Eurocode 8. While a single application of the research in a specific structure is important, the multiplicative effect of any code improvement is even much more important.
8) Better estimation of seismic risk will assist to re-establish and increase the competiveness of European precast industry, which has been strongly affected after the recent earthquakes in Italy. Industrial precast structures used to have a great share in the Slovenian construction industry before the economic crisis. It is believed that the results of the proposed research will contribute to the re-establishment of this important sector of construction business.
Most important scientific results
Interim report,
final report
Most important socioeconomically and culturally relevant results
Interim report,
final report
