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Feb, 16 2022 (v1) Journal article Open Access

Optimization of the structural coupling between RC frames, CLT shear walls and asymmetric friction connections

Aloisio, Angelo; Pelliciari, Matteo; Sirotti, Stefano; Boggian, Francesco; Tomasi, Roberto;

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This paper focuses on the optimum design of the e-CLT technology. The e-CLT technology consists in adding cross laminated timber (CLT) walls to an existing reinforced concrete (RC) inflled frame via asymmetric friction connection (AFC). The authors carried out quasi-static and nonlinear dynamic analyses. The RC frame is modeled in OpenSees by fber-section-based elements with force based formulation. The contribution of the infill is simulated using a degrading data-driven Bouc–Wen model with a slip-lock element while the AFC is modelled with a modified Coulomb model. Different types of infill, aspect ratio, scaling, and member size are considered. The benefits of using e-CLT technology are discussed and the ranges of optimum performance of the AFC are estimated. A comparison of the performance of traditional infill with the e-CLT system is presented. The authors provide optimum intervals of the ratio between slip force and in-plane stiffness of the CLT panel, following energy and displacement-based criteria. The seismic displacement demand under various seismic scenario is investigated. Correlations between the RC characteristics and the optimum design ratios bestow possible criteria for the design of the AFC

Jan, 21 2022 (v1) Journal article Open Access

Design of a novel seismic retrofitting system for RC structures based on asymmetric friction connections and CLT panels

Aloisio, Angelo; Boggian, Francesco; Tomasi, Roberto;

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Friction-based dampers are a valid solution for non-invasive seismic retrofitting interventions of existing structures, particularly reinforced-concrete (RC) structures. The design of friction-based dampers is challenging: underestimating the slip force prevents the full use of the potential of the device, which attains the maximum admissible displacement earlier than expected. By contrast, overestimating the slip force may cause delayed triggering of the device when the structure has suffered extensive damage. Therefore, designing the appropriate slip force is an optimization problem. The optimal slip force guarantees the highest inter-story drift reduction.

The authors formulated the optimization problem for designing a specific class of friction-based dampers, the asymmetric friction connection (AFC), devised as part of the ongoing multidisciplinary Horizon 2020 research project e-SAFE (Energy and Seismic AFfordable rEnovation solutions). The seismic retrofitting technology involves the external application of modular prefabricated cross-laminated timber (CLT) panels on existing external walls. Friction dampers connect the CLT panels to the beams of two consecutive floors. The friction depends on the mutual sliding of two metal plates, pressed against each other by preloaded bolts. This study determines the optimal slip force, which guarantees the best seismic performance of an RC structural archetype.

The authors investigate the nonlinear dynamic response of a coupled mechanical system (RC frame-friction damper) under a set of strong-motion earthquakes, using non-differential hysteresis models calibrated on the experimental cyclic responses. The solution of the optimization leads to the proposal of a preliminary simplified design procedure, useful for practitioners.

Nov, 16 2021 (v1) Figure Open Access

Multi-level stakeholder engagement

Victoria Taranu;

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Visualisation indicating the multi-level stakeholder process pursued in e-SAFE. The visualisation indicates how different stakeholder engagement processes are linked together.

The Advisory Board gives advice about the design and implementation of the real pilot in Catania (where one building is renovated with the e-SAFE technical solution) as well as the co-design and stakeholder engagement protocol. These protocols are informed by the results from the real pilot in Catania, and tested in two virtual pilots in other seismic prone cities outside of Italy. 

The EU-stakeholder forum exchanges feedback and information with the real and virtual pilots, and gets access to the co-design and stakeholder engagement protocol. In that way, local, regional and European level stakeholders are engaging with the e-SAFE project.

Oct, 28 2021 (v1) Presentation Open Access

The e-SAFE solutions for the energy and seismic renovation of hon-historical buildings

Evola Gianpiero;

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This file is the presentation shown by Gianpiero Evola during his "Energy Talk"  at the EU Sustainable Energy Week.
The talk presented the main challenges and scopes of e-SAFE: stakeholders interested to have more information, to join our stakeholders community, and to participate to the upcoming "call for expression of interest" for virtual pilots are invited to contact us through the reported social media.

I recall that "virtual pilot" means that, inside e-SAFE, we will follow the entire renovation design process, until the preparation of a detailed design of all renovation works. The renovation of the buildings wil not be realized within e-SAFE: possible sinergies and clustering with other project are welcome.

Jun, 28 2021 (v1) Conference paper Open Access

Optimization of the slip force in a novel friction-based connection for thw e-CLT technology

Tomasi Roberto; Boggian Francesco; Aloisio Angelo;

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The European Union has sponsored the development of a new friction dissipating system, for improving seismic behaviour of existing buildings. The proposed system consists of CLT-elements connected to the external beams of existing reinforced concrete building using steel profiles. Each of the steel profiles consists of two separate plates connected by a friction connection made by preloaded bolts in elongated holes. The authors carried out the experimental testing of the friction connection by estimating the corresponding hysteresis curve. A Duhem-like mechanical model, matching with the experimental results, simulates the cyclic response of the connection. The authors investigate the seismic performance of a structural archetype, a plane RC frame with CLT shear walls equipped with this sort of friction dampers. It is assessed the optimum preload condition to achieve an optimal seismic performance according to the Italian seismic scenario by the fragility assessments. A selected suite of earthquakes
is the basis of Incremental Dynamic Analysis (IDA) of the structural archetype, without and with the friction device. The optimum preload of the dissipating systems descends by optimizing the structural performance: maximizing the dissipated energy by preventing damage to the CLT panel and the reinforced concrete frame.

Sep, 08 2021 (v1) Conference paper Open Access

Technological analysis of prefabricated timber-based panels for the integrated renovation of RC framed buildings

Tardo Carola; Fiore Giulia; Margani Giuseppe;

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In earthquake-prone countries, the need for interventions aimed at improving both the seismic resistance and energy efficiency of the existing building stock is widely recognized, although the implementation of such interventions is currently limited by economic and technical barriers, as well as socio-cultural ones.

In order to overcome these barriers, a new holistic design approach to the building renovation is strongly needed, which can result in innovative and integrated retrofitting interventions able to specifically meet the current needs of cost-effectiveness, quick installation, reduced users’ disturbance and low environmental impact.

To this purpose, the use of Cross Laminated Timber (CLT) has been recently investigated as an alternative and sustainable solution to seismic strengthen the existing buildings, thanks to its high mechanical performance. In this research context, an innovative integrated (seismic-energy-architectural) renovation technology for reinforced concrete (RC) framed buildings is currently under development within the ongoing multidisciplinary Horizon 2020 innovation project, called e-SAFE (energy and Seismic AFfordable rEnovation solutions). The proposed technology consists in the application of prefabricated timber-based panels on the existing outer walls, combining structural CLT panels (called e-CLT), equipped with innovative friction dampers for seismic energy dissipation, with non-structural wooden framed panels hosting high-performing windows (called e-PANEL).

This paper illustrates a possible technical and functional application solution of this new renovation system, aimed at ensuring a correct and easy installation and operation. To this end, the proposed solution has been applied to a specific case study, i.e. a typical apartment building located in the city of Catania, in Southern Italy.

Sep, 29 2021 (v1) Conference paper Open Access


Tardo Carola; Boggian Francesco; Hatletveit Magnus; Marino Edoardo Michele; Margani Giuseppe; Tomasi Roberto;

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Deep renovation interventions on existing buildings remain currently unattractive due to technical, financial and cultural/social barriers. Now that the European Union 2018 Energy Performance Directive aims to “reach the long-term greenhouse gas emission goal and decarbonize the building stock”, Member States may use their long-term renovation strategies to address risks also related to fire hazards and seismic loads in addition to energy renovation. This opens a wider market for innovative approaches in retrofit of existing buildings.                                                                                                                                                                                 The current paper illustrates the primary outcomes of an ongoing multidisciplinary Horizon 2020 research project (called e-SAFE), tackling the integration of energy, seismic and architectural renovation interventions through an innovative and combinable technological solution, applicable to non-historic RC framed buildings (i.e. built after 1950) and easily adaptable to specific climatic conditions, seismicity levels and other boundary conditions. Hence, the proposed solution will contribute to the de-carbonization of the EU building stock, reducing the occurrence of natural hazards related to climate changes, and, at the same time, to the improvement of the social resilience against earthquakes and to the enhancement of buildings architectural image.                              The seismic retrofit technology consists in the external application of modular prefabricated Cross Laminated Timber (CLT) panels on the existing perimetral walls. These panels are connected to the beams of two consecutive floors by means of friction dampers and provide additional lateral stiffness and strength to the existing structure, thus reducing the storey drift demand in case of earthquake. The friction dampers cut the force transmitted by the CLT panel to the structure and dissipate energy, which further reduce the drift demand. Strength, stiffness and dissipation capacity provided by the system are controlled by modulating the thickness and the number of CLT panels, as well as the friction dampers size.                                                                                      In this research phase, friction damper prototypes have been designed in order to optimize both mechanical performance and production process. Detailed numerical models allowed to investigate the stress distribution in the dissipative connections. The results of the preliminary testing campaign will be presented and discussed in this paper, also in relation with the findings of the numerical analysis and future tests.

Jun, 30 2021 (v1) Conference paper Open Access


Barbagallo Francesca; Margani Giuseppe; Marino Edoardo Michele; Moretti Alberto; Tardo Carola;

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In Italy, as well as in other earthquake-prone countries, most buildings have been erected with-out considering the effects of seismic excitation or according to obsolete seismic design provi-sions. Furthermore, they also suffer from significant structural deficiencies because of the low mechanical characteristics or the natural decay of the materials. The seismic vulnerability of the existing building stock is a serious economic and social concern and the need for retrofit-ting or rebuilding grows as time progresses. In this framework, this study investigates a newly developed retrofit technique for buildings with RC framed structure. The intervention is realized by means of Cross-Laminated Timber (CLT) panels placed over the exterior walls and connected to the RC structure by friction dampers. The CLT panels provide the existing structure with addi-tional lateral stiffness and strength. The role of the friction dampers is twofold. On one hand they cap the internal forces of CLT panels, thus controlling the reaction forces transmitted to the exist-ing structure and avoiding the failure of CLT panels themselves. On the other, friction dampers dissipate part of the input earthquake energy. The effect of these multiple features could reduce the storey drifts demanded by the earthquake to values compatible with the structure capacity. This paper aims at sounding the impact of the proposed retrofit solution on the response of the RC framed structure to be upgraded. To this end, a one storey RC frame representative of existing RC framed structures designed considering only gravity loads is upgraded by a CLT panel and friction dampers of usual size. The impact of the retrofit intervention is investigated in terms of the achieved increase of stiffness, strength and energy dissipation capacity. The bare RC frame and the frame equipped with CLT panel and friction dampers are modelled in OpenSEES environment. Hence, the nonlinear responses of the two frames are assessed by mon-otonic and cyclic pushover analyses and the comparison between the results obtained for the bare and the upgraded frame quantifies the expected impact of the proposed retrofit intervention.

Oct, 11 2021 (v1) Conference paper Open Access

e-SAFE: energy and seismic affordable renovation solutions for the decarbonisation and seismic safety of the EU building stock

Evola Gianpiero; Margani Giuseppe; D'Urso Sebastiano; Marino Edoardo Michele; Saija Laura; Semprini Giovanni; Mazzotti Claudio; Ferrante Annarita; Arnone Diego; Moran Marianna; Yumlu Serdar; Dorizas Vivian; Zagorianakos Christos; Vivani Laura; Tomasi Roberto; Halmdienst Christian; Voortman Bart; Baratta Ida;

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This paper aims at showing the concept, the scope and the main challenges of the four-year innovation project e-SAFE, started in October 2020 and funded by the EU in the framework of the H2020 Programme. e-SAFE aims to develop a new deep renovation system for non-historical reinforced concrete (RC) framed buildings, which combines energy efficiency and anti-seismic retrofitting actions with a series of further advantages including affordability, improved architectural image and reduced implementation time, costs and occupants’ disruption. e-SAFE will also address strategies to activate new value chains to boost the deep renovation market throughout Europe, including financial and social aspects. The paper will also present some preliminary results about the expected energy and carbon reduction ensured by the e-SAFE solutions.

Sep, 09 2021 (v2) Conference paper Open Access

Preliminary investigation on the transient hygrothermal analysis of a CLT-based retrofit solution for exterior walls

Vincenzo Costanzo; Gianpiero Evola; Luigi Marletta; Giorgio Roccella;

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This paper investigates the transient hygrothermal performance of an innovative energy and seismic renovation solution for reinforced concrete (RC) framed buildings, based on the addition of Cross-Laminated Timber (CLT) panels to the outer walls, in combination with wood-based insulation. This solution is being developed in the framework of a four-year EU-funded project called e-SAFE. The investigation relies on numerical simulations in DELPHIN 6.1, by considering combined heat and mass transfer (HAMT) due to water vapour diffusion and capillary transport. The proposed solution is tested in three different climates in Italy, to verify whether the CLT layer and the outer waterproof vapour-open membrane, inserted to protect the wood-based insulation from rain, still allow the effective drying of the vapour accumulated in liquid form in the walls, while also preventing mould formation. The results show that the increased thermal resistance of the wall assembly significantly reduces the total water content, although moderate risks of mould growth in the wooden materials may occur in coldest climates.