Project

The Development and validation of economic and sustainable retrofitting techniques for seismic risk mitigation of steel storage pallet racks - DESRACK project was created in the framework of the PROGETTI DI RICERCA DI RILEVANTE INTERESSE NAZIONALE - PRIN call 2022 of the Italian Minister of the University and Research - MUR. It involves four Italian universities: University School for Advanced Studies IUSS Pavia (IUSS), the University of Pavia (UniPV), Politecnico di Milano (PoliMI), and the University of Salento (UniSA), one research center: Eucentre Foundation, and one industrial partner: SACMA S.p.A.  The project aims to increase the life cycle and lifetime of existing stock of steel storage pallet racks by reducing their seismic vulnerability. This will aid in reducing economic and environmental impact for new constructions but also avoiding downtime in logistics, which may cause high direct and indirect economic loss (e.g. cost of dismantling and replacement or downtime/business interruption along with issues for workers). DESRACK will address this need by delivering an innovative seismic dissipative device that will be used to enhance the seismic performance of existing racks. As is well-known, the seismic behavior of racks is strongly influenced by the structural response of the beam-to-column and base-plate connections, which concentrate the material nonlinearities and are responsible for the ductility capacity of racks. Therefore, DESRACK targets the improvement of the strength and ductility of the connections, producing a very cost-effective dissipator that will be located in the rack connections. The proof-of-concept for such a device will start with the selection of case-study rack configurations, after which several prototypes of the device will be developed and characterized to define their behavior in terms of cyclic stress-strain relationship. The next phase of the project will foresee the integration of the different developed devices in the beam-to-column connections and a series of cyclic tests for obtaining the moment-rotation curve will be performed. At the same time, an extensive numerical modelling campaign of the dynamic behavior of the selected racks, with and without the device, as well as a numerical calibration of refined models for the connections will assure the extension of the experimental outcomes to additional configurations. The final step of DESRACK will include the experimental testing of the rack configurations (with and without the device) on a new-generation shake-table, thereby simulating real earthquake inputs to effectively gauge the improvement given by the device in the seismic performance of the structures. The numerical analyses previously performed on the prediction of the seismic response of the racks will guarantee the success and the completion of the tests. Finally, DESRACK will propose guidelines to assist stakeholders in producing and correctly employing the device in current practice.

Impact

DESRACK is framed within cluster 3 (Civil security for society - areas of intervention: disaster-resilient societies, protection and security) of the new Horizon Europe research and innovation program. The DESRACK results are expected to promote better risk assessment and risk management of steel rack structures, improving the overall response and reducing potential failures in logistics infrastructure. As discussed in the Strategic Plan of Horizon Europe, the research actions should achieve the reduction of losses from natural disasters with better societal preparedness and improved resilience and disaster risk management. In this sense, DESRACK will enhance the resilience capacity of the logistics sector against seismic risk, which is one of the most important threats to such infrastructure.

The possible integration of the project results into national and European regulations, such as the EN 16681 approved in 2016 by the European Commission, is very much present and could lead to an overall improvement of current design and maintenance practices, with direct socio-economic impacts. In fact, cost-effective interventions targeting robustness upgrades can extend the service life of the existing infrastructure stock, whilst improving its resilience and end-users’ safety. Furthermore, the project results are expected to clarify the interventions on existing rack structures that might have already reached their ultimate condition over the service life. Note that this important aspect is completely neglected by current design codes: even in the most updated version of the European standards for racks (EN 16681), the safety assessment and the design of interventions on existing racks are simply based on ultimate limit state considerations, ignoring the fact that, when exposed to seismic hazard and human-induced impacts, deterioration and damage can quickly evolve and lead to collapse also under serviceability conditions.

To maximize impact, the interdisciplinary research outcomes are aimed at attracting the interest of multiple stakeholders, such as universities and research organizations, public authorities, construction industry, practitioners and professional associations active in the field of rack manufacturing and design. Of particular note is the fact that some producers, rack companies and research institutions, with whom the partners composing DESRACK have already interacted for several past research activities (e.g. SACMA, METALSISTEM, ROSSS, Dalmine Logistic Solutions (DLS), ERF) have already expressed their interest in the project.

Considering the present, precarious condition of a large share of the Italian logistics market (most of the racks have already spent a service life approaching 30 years or even more), the project results are expected to foster the spread of effective structural improvements for seismic compliance, which at present are frequently avoided or guided only by urgency-driven choices. This is the case of structural members with sudden plastic deformations, extremely dangerous for rack-type structures, due to their minimal robustness. The effectiveness of the proposed intervention will be proven on a representative case study, thus being instrumental in demonstrating the reliability of the whole proposed approach on practical examples.

From a technological standpoint, the DESRACK project is expected to promote the use of possibly patentable economic dissipative devices, which would overcome other expensive and cumbersome structural retrofitting techniques. Furthermore, the industrialization of such devices could improve their cost-effectiveness, simultaneously saving labor times. It is important to emphasize that the adoption of low impacting solutions through a life cycle assessment (LCA) approach will ensure the economic, environmental and social sustainability of the proposed intervention. As a matter of fact, DESRACK is expected to bring environmental benefits with respect to the European Green Deal Communication. Racks collapse and failure imply loss of structural steel and goods, with significant direct and indirect costs. A sustainable product policy should have the potential to reduce the losses in terms of both steel waste and commercial goods (of any type). DESRACK addresses and embraces the European cause of building and renovating in an energy and resource efficient way, as the racks’ collapse prevention allows lengthening the life of the steel structure and, at the same time, protecting the stored goods. Moreover, within the scope of DESRACK, an innovative seismic device, to be located either in new or existing racks, will be developed, useful to increase the level of safety against seismic collapse.

The overall impact of DESRACK results will allow to: 

1. Evaluate the level of safety of the actual racks against earthquakes, designed in accordance with the EN 16681 and experimentally tested. 

2. Develop a new low-cost dissipative device easy to be installed and replaced. The device will be fully tested under cyclic conditions.

3. Enhance the performance of existing and new racks against one or multiple earthquake events by studying the optimal distribution of the device along the racks.

4. Develop technical guidelines with a set of pre-normative design recommendations. 

5. Avoid economic losses due to failure of rack structures, recently estimated to amount up to €27.5 millions/year, including direct and indirect costs. The European racking industry will benefit, at the global market level, from implementing durable rack structures, which has not been the case until now.

Working plan

DESRACK has an expected duration of 24 months, is divided into 6 Work Packages (WPs), plus the WP0, which is related to the coordination and management of the project.

WP1 - Selection, design and risk assessment of existing racks.

WP1 will start by selecting and designing a typical configuration for existing racks, which were mostly built prior to the development of seismic rack standards and designed only for vertical loads. For this purpose, a literature review will be conducted, providing a comprehensive understanding of the structural characteristics of racks, as well as the state-of-the-art of seismic performance and retrofitting strategies investigated so far in this context.

WP2 - Device development.

WP2 will deal with the production, testing and validation of the dissipative devices to be adopted for the improvement of the seismic performance of steel storage racks, mitigating their seismic risk level in a cost-effective manner.

WP3 - Assessment of the beam-to-column connections.

WP3 will focus on the experimental tests and modelling validation of the beam-to-column connections of the selected steel storage pallet rack, both with and without the dissipative device, to compare the hysteretic behavior of the traditional and improved connections.

WP4 - Advanced numerical modelling.

WP4 will perform nonlinear numerical analyses of 3D global finite element models. These models will reproduce the global frame identified in WP1 and the cyclic components behaviour, tested and simulated in WP3.

WP5 - Demonstration and validation.

WP5 will validate the effectiveness of the devices on the structural performance of the rack. To this aim, full-scale tests on a shake-table equipped with 9 degrees of freedom (9DOFs) will be conducted. In addition, WP5 will develop pre-normative design guidelines that will be useful for each rack producer and designer in Italy and Europe, to contribute to the gap given by the fact that the actual seismic design rules in EN 16681 are not able to portray an exhaustive picture of the behavior of racks under seismic loads.

WP6 - Dissemination.

The dissemination strategy and activities will be devised and overseen by the project coordinator, while jointly implemented by all the research units.