PSI - Issue 44

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2022) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2022) 000 – 000

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 44 (2023) 1–2

XIX ANIDIS Conference, Seismic Engineering in Italy Preface Luciana Restuccia a  , Giuseppe Andrea Ferro a a Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Turin, Italy XIX ANIDIS Conference, Seis ic Engineering in Italy reface Luciana Restuccia a  , Giuseppe Andrea Ferro a a Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Turin, Italy

© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review Statement: Peer-review under responsibility of the scientific committee of XIX ANIDIS Conference, Seismic Engineering in Italy © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review Statement: Peer-review under responsibility of the scientific committee of XIX ANIDIS Conference, Seismic Engineering in Italy

Keywords: Preface, ANIDIS Conference, Seismic Engineering. Keywords: Preface, ANIDIS Conference, Seismic Engineering.

1. Preface The Italian real estate assets, in particular the historical and infrastructural ones, continue to show their fragility in relation to seismic events, as dramatically highlighted by the recent earthquakes in Emilia Romagna (2012) and Central Italy (2016). For this reason, in recent years, scholars have promoted several initiatives at a scientific, technical and regulatory level, in order to improve the seismic performance of new buildings and to mitigate the seismic risk of the existing building and infrastructural heritage. In particular, the New Technical Standards for Constructions (2018), the Explanatory Circular (2019) and the Guidelines for the Seismic Risk Classification of Constructions (2017) were published, increasingly focusing on the issue of seismic risk. ANIDIS (Italian National Association of Seismic Engineering) is an Association that has the following aims: (i) To promote, encourage and disseminate in Italy, also through the publication and sale of specific documents, the culture concerning seismic problems among professionals working in sectors: Structural Engineering, Geotechnics, Geology, Urban Planning, Architecture, Restoration, Civil Protection and Environmental Protection; (ii) Identify scientific research topics deriving from professional practice and promote their study; (iii) Establish and maintain national and international contacts between those who are interested in the problems referred to in point (i) and with the Associations having similar aims; (iv) Collaborate with the competent authorities in the drafting of rules and regulations concerning seismic engineering. ANIDIS managed to organize in Turin its biannual meeting. The XIX ANIDIS meeting took place in the wonderful venue of the Politecnico di Torino in September 11-15, 2022. It is possible to state that it was a successful event: during the conference more than 300 presentations were showed and 6 plenary lectures were carried out by M. Sarkisian (SOM, USA), F. Ballio (Politecnico di Milano, Italy), F. Braga (Università di Roma La Sapienza, Italy), W. Salvatore (Università di Pisa, Italy) and E. Chatzi (ETH Zurich, Switzerland). The presentations were scheduled in 16 General Sessions and 18 Special Sessions, covering a wide range of topics related to theory, modelling and experiments in the field of Seismic Engineering. The topics covered among others: Seismic hazard, Soil dynamics and seismic geotechnics, Dynamic soil-structure interaction, Vulnerability and seismic risk, Safety and seismic risk, 1. Preface The Italian real estate assets, in particular the historical and infrastructural ones, continue to show their fragility in relation to seismic events, as dramatically highlighted by the recent earthquakes in Emilia Romagna (2012) and Central Italy (2016). For this reason, in recent years, scholars have promoted several initiatives at a scientific, technical and regulatory level, in order to improve the seismic performance of new buildings and to mitigate the seismic risk of the existing building and infrastructural heritage. In particular, the New Technical Standards for Constructions (2018), the Explanatory Circular (2019) and the Guidelines for the Seismic Risk Classification of Constructions (2017) were published, increasingly focusing on the issue of seismic risk. ANIDIS (Italian National Association of Seismic Engineering) is an Association that has the following aims: (i) To promote, encourage and disseminate in Italy, also through the publication and sale of specific documents, the culture concerning seismic problems among professionals working in sectors: Structural Engineering, Geotechnics, Geology, Urban Planning, Architecture, Restoration, Civil Protection and Environmental Protection; (ii) Identify scientific research topics deriving from professional practice and promote their study; (iii) Establish and maintain national and international contacts between those who are interested in the problems referred to in point (i) and with the Associations having similar aims; (iv) Collaborate with the competent authorities in the drafting of rules and regulations concerning seismic engineering. ANIDIS managed to organize in Turin its biannual meeting. The XIX ANIDIS meeting took place in the wonderful venue of the Politecnico di Torino in September 11-15, 2022. It is possible to state that it was a successful event: during the conference more than 300 presentations were showed and 6 plenary lectures were carried out by M. Sarkisian (SOM, USA), F. Ballio (Politecnico di Milano, Italy), F. Braga (Università di Roma La Sapienza, Italy), W. Salvatore (Università di Pisa, Italy) and E. Chatzi (ETH Zurich, Switzerland). The presentations were scheduled in 16 General Sessions and 18 Special Sessions, covering a wide range of topics related to theory, modelling and experiments in the field of Seismic Engineering. The topics covered among others: Seismic hazard, Soil dynamics and seismic geotechnics, Dynamic soil-structure interaction, Vulnerability and seismic risk, Safety and seismic risk,

* Corresponding author. Tel.: +39 0110904844 E-mail address: luciana.restuccia@polito.it * Corresponding author. Tel.: +39 0110904844 E-mail address: luciana.restuccia@polito.it

2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. 10.1016/j.prostr.2023.01.001 2452-3216 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy 2452-3216 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy

2 2

Luciana Restuccia et al. / Procedia Structural Integrity 44 (2023) 1–2 Luciana Restuccia, Giuseppe Andrea Ferro / Structural Integrity Procedia 00 (2022) 000 – 000

Technical standards and design/verification methods, Methods of analysis, modelling and capacity models, Reinforced concrete buildings, Masonry and reinforced masonry constructions, Constructions in steel and mixed steel-concrete, Wooden buildings, Prefabricated buildings, Traditional and innovative materials, Bridges, tunnels and strategic and special structures, Non-structural elements (technical networks) and plants, Testing, diagnostics and monitoring of structures and infrastructures, Analysis and reduction of the seismic risk of buildings: intervention strategies, methods and techniques, Reinforced concrete buildings, Masonry and reinforced masonry constructions, Constructions in steel and mixed steel-concrete, Wooden buildings, Prefabricated buildings, Evaluation and improvement of the structural behaviour of the listed cultural heritage, Examples of achievements: architecture and structures, recent projects and constructions, Passive, semi-active and active protection of structures and systems, Big Data and IoT for existing structures and infrastructures. The constructive and vibrant discussions taken at the end of each presentation were a further confirmation of the high scientific quality of the event as well as of the significant level of interactions among the participants. This special issue of Procedia Structural Integrity collects about 300 papers related to the presentations given during the XIX ANIDIS Conference. The Guest Editors of this special issue wish to warmly thank all the authors for the quality of their contributions.

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2022) 000 – 000 Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 44 (2023) 1458–1465

XIX ANIDIS Conference, Seismic Engineering in Italy 3D numerical characterization of a dissipative connection system for

retrofit of prefabricated existing RC sheds C. Pettorruso a *, V. Quaglini a , E. Bruschi a , L. Mari b a Politecnico di Milano, Department of Architecture, Built environment and Construction engineering ABC b DVS; l.mari@dvs.vision

Abstract

© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. In the second part of the study, non-linear dynamic analyses are performed on a finite element model of a portal frame implementing, at beam-column joints, either the DCS or a pure friction connection. The results highlight the effectiveness of the DCS in controlling beam-to-column displacements, reducing shear forces on the top of columns, and limiting residual displacements that can accrue during ground motion sequences. © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license ( https://creativecommons.org/licenses/by-nc-nd/4.0 ) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy Keywords: prefabricated sheds, energy dissipation, seismic retrofit, beam-to-column connection, recentering b LSE Prefabricated industrial sheds featured a high seismic vulnerability during the 2012 Emilia earthquake (Italy). The buildings typically exhibited a rigid collapse mechanism that was a consequence of the loss of support between columns, beams and roof elements. The study presents a numerical characterization of a novel dissipative connection system (DCS) designed to improve the seismic performance of industrial sheds. The device, which is placed on the top of the columns, exploits the movement of a rigid body on a sloped surface to provide horizontal stiffness and control the lateral displacement of the beam. A 3D finite element model of the prototype is formulated in Abaqus and used to switch the backbone curve from the scaled model to the full-scale device. A parametric study is conducted to evaluate the influence of the slope of the contact surface and the coefficient of friction on the output force of the system.

* Corresponding author. Tel.: +390223995108 E-mail address: carlo.pettorruso@polimi.it

2452-3216 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy

2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. 10.1016/j.prostr.2023.01.187

C. Pettorruso et al. / Procedia Structural Integrity 44 (2023) 1458–1465 C. Pettorruso et al./ Structural Integrity Procedia 00 (2022) 000 – 000

1459

2

1. Introduction Recent earthquakes have dramatically reaffirmed the seismic vulnerability of prefabricated industrial sheds typical of past Italian practice. The Emilia earthquake of May 2012 hit an area with a high density of productive activities, striking mainly industrial buildings in precast reinforced concrete (RC) [Belleri et al. (2015a), Bosio et al. (2020)] rather than in steel [Formisano et al. (2018)]. The structural deficiencies of this kind of structures are primarily related to the mechanisms of transmission of horizontal loads between structural elements [Belleri et al. (2015b)]; in fact, their static scheme consists of structural elements (beams, columns, and roof elements) connected with joints usually realized in simple support or through pin-end connections with insufficient resistance to seismic loads. This kind of connections relies solely on friction and is inadequate to properly transfer the horizontal loads [Belleri et al. (2014), Liberatore et al. (2013), Magliulo et al. (2008)] and accommodate compatible rotations and displacements [Brunesi et al. (2015), Casotto et al. (2015), Colombo et al. (2016)]. Indeed, the most common failures, causing the collapse of entire portions of buildings, included drop of roof elements and precast beams due to the loss of support, and collapse of the forks at the top of columns caused by off-axis loads. Within the framework of global retrofit interventions, the study aims at introducing a novel dissipative connection system (DCS), designed to improve the behavior of beam-to-column connections and reduce the seismic vulnerability of precast RC industrial buildings [Mari et al. (2021)]. The DCS, which is placed on the top of columns, is basically composed of two mating truncated-pyramidal steel plates, one concave and the other one convex in shape and is intended to transmit vertical and horizontal loads at the node. The system exploits the movement of a rigid block sliding on a sloped surface to provide horizontal stiffness and a certain re-centering effect and dissipates part of seismic energy by friction. In the present study, a 3D model of the DCS is firstly formulated based on experimental data [Quaglini et al. (2022), Mari et al. (2021)], and then the DCS is assessed under seismic loading by means of nonlinear analyses conducted on a portal frame of an industrial shed. 2. 3D characterization 2.1. Prototype and response The study is conducted by referring to a DCS unit rated for a vertical load N d = 360 kN and a horizontal deflection d bd = 60 mm. In order to match the capacity of the available testing equipment, the experimental characterization was performed on a DCS prototype scaled by a geometric factor S L = 0.4 and fabricated in steel, which resulted in a design vertical load of the prototype N d,s = 57.6 kN and a related design deflection d bd,s = 24 mm [Mari et al. (2021), Quaglini et al. (2022)]. The main dimensions of the DCS prototype are shown in Fig. 1 . The experiments were performed at the Materials Testing Laboratory of Politecnico di Milano, using a proprietary biaxial testing system [Quaglini et al. 2012].

Fig. 1 – Geometry [in mm] of the small-scale prototype of the DCS: (a) convex plate; (b) concave plate [Quaglini et al. (2022)]

C. Pettorruso et al. / Procedia Structural Integrity 44 (2023) 1458–1465 C. Pettorruso et al. / Structural Integrity Procedia 00 (2022) 000 – 000

1460

3

The prototypes exhibited an almost rigid-plastic behavior in X and Y direction, where it is possible to recognize four different phases, as shown in Fig. 2: (1) at the beginning of the motion, before sliding between the mating surfaces of the two plates is triggered, the force follows an almost proportional relationship with the displacement; (2) when sliding between the convex and the concave plate is engaged, a constant force is developed independently of the deflection; (3) when the convex plate reaches the boundary of the concave plate, and the actual contact area between the mating surfaces of the two plates decreases, the force too undergoes a decrease; (4) when the convex plate moves back to the origin, the reaction force is virtually negligible.

Fig. 2 – Constitutive behavior of the DCS and different phases of motion [Quaglini et al. (2022)]

2.2. Numerical description Numerical model of the DCS described above was developed using the Abaqus CAE finite element calculation program and its references. The geometry of the numerical model replicated the dimensions of the prototype subjected to experimental characterization tests at the Politecnico di Milano. The numerical model included only the two plates, disregarding the connections (Fig. 3). Numerical analyses were performed by subjecting the FEM model, to a biaxial load. The boundary conditions that characterize the convex element are the distributed pressure of 11 MPa, whose resultant is 57,6 kN, applied on the external face, and the harmonic displacement with amplitude 24 mm. The concave element is fixed. The numerical model was divided into a mesh of finite elements type C3D8 (three-dimensional hexahedral element with 8 nodes) with maximum dimension equal to 8 mm. A total of #1016 elements were used for the convex element and #2034 elements for the concave element (Fig. 3). The contact between the surfaces was modeled through the surface-to-surface contact command, defining the convex element as the master element, and formulating a hard contact constitutive behavior in the direction perpendicular to the contact surface, and a penalty constitutive behavior tangentially the contact surface [Quaglini et al. (2019)] with coefficient of friction μ = 0.11, as determined from the experiments on DCS. The additional information on element properties is reported in Mari et al. (2021). An implicit dynamic analysis with full Newton solution technique was carried out.

b)

a)

Fig. 3 – FEM model of the DCS:(a) convex element; (b) concave element The results of the numerical analyses are shown below for two trajectories of motion of the convex component with respect to the concave component defined by angle θ ( Fig. 4). The DCS is analyzed according to the angles θ = 0° and θ = +90° ; the results are expressed in the form of force displacement curves and reaction moment-displacement curves (Fig. 5).

C. Pettorruso et al. / Procedia Structural Integrity 44 (2023) 1458–1465 C. Pettorruso et al./ Structural Integrity Procedia 00 (2022) 000 – 000

1461

4

Fig. 4 – Definition of the reference system for the displacements

a)

b)

Fig. 5 – (a) Force-displacement and (b) Moment-displacement at top of column

The component of the reaction force developed in the direction of motion is almost constant and the component along the perpendicular direction is zero (Fig. 5a), and this is justified by the symmetry of the contact surfaces with respect to the direction of motion. The reaction bending moment evaluated at the top of the column (Fig. 5b), in agreement with the reaction, acts only in the plane parallel to the direction of displacement, while in the perpendicular plane is zero. The moment can be split in two contributions, the first due to the horizontal reaction force F and the second due to the eccentricity of the vertical force N due to the displacement of the convex element. Eventually, Fig. 6 compares the force-displacement curves obtained from the numerical analyses and the experimental curves from the tests conducted at Politecnico di Milano.

Fig. 6 – Comparison between experimental and numerical force-displacement curves The correspondence between the experimental curves and the results of the numerical analyses is very fair. The biggest deviations occurring close to the origin of the displacement axis and are attributed to the effect of the inertial forces at the onset of the motion, not reproduced in the numerical analyses.

C. Pettorruso et al. / Procedia Structural Integrity 44 (2023) 1458–1465 C. Pettorruso et al. / Structural Integrity Procedia 00 (2022) 000 – 000

1462

5

3. Numerical Investigation - Case study To assess the performance of the DCS and evaluate its effectiveness in comparison to the pure friction beam-to column joints typical of past building practices, non-linear dynamic analyses of a prefabricated shed structure were performed. The model consists of a two-dimensional portal frame comprising two 50×60 cm columns and a 50×80 cm beam, with geometry and overall dimensions as shown in Figure 7. It was implicitly assumed that no secondary beams were placed orthogonally to the frame in order to ensure a 3D response of the structure. The columns are made of C40/50 concrete, reinforced longitudinally with 16 Ø20 steel bars (B450C class [Italian Building Code]) and transversally with Ø8 two-arm stirrups at 10 cm spacing. The distributed load acting on the beam, including its weight and the load from the contributory area of the roof, is 26.9 kN/m, resulting in a total seismic mass of 146.84 ton evaluated according to the Italian Building Code, and in a vertical force at either support of 360 kN, matching the design load of the DCS units.

Fig. 7 – Portal frame model The structural model was implemented in Sap2000 v21.1.0 software. The two columns were rigidly fixed to the ground and modelled as linear elastic elements, with a plastic (rotational) hinge at the basis formulated according to Table 10-8 (concrete columns) of ASCE 41-13 in order to account for anelastic concrete deformation. The beam was assumed to behave as a linear elastic body, and a “ body ” constraint [SAP2000 Analysis Reference] was introduced to enforce that the displacements at either end of the beam are identical. For the beam-to- column pure friction connection, a constant friction coefficient μ cc = 0.30 was assigned, coupled to an isotropic hysteresis type (it must be noted that, to be conservative, one half of the concrete-to-concrete friction coefficient recommended in Eurocode 8 for smooth surfaces was adopted). The fundamental period of the frame is T = 0.838 s. The internal structural damping is modeled as Raileigh damping, with parameters assigned to achieve 5% damping ratio at T 1 = 0.838 s and T 2 = 0.611 s. Non-linear dynamic analyses were performed assuming a functional class II with nominal life 50 years, located in Potenza, South Italy, topographic category T1, soil type B. The target elastic spectrum was determined according to the Italian Building Code provisions for Life Safety Limit State (SLV). A set of seven unidirectional ground motions consistent with the target spectrum was selected with REXEL v3.4 beta [Iervolino, I. et al. (2010)] software from the European Strong-motion Database [Ambraseys, N. et al]. The magnitude (M w ) of the seven ground motions was chosen within the interval (6.4 – 7), with epicentral distance (Rep) in the range 0-30 km. The waveforms were scaled to the design Peak Ground Acceleration of 2.375 m/s 2 calculated according to the Italian Building Code. Relevant information on the ground motion data set is reported in Table 1. To be conservative, a vertical acceleration of 0.4 g was assumed, in order to reduce the resisting force of the connections and engage sliding at the beam-to-column interface either with the DCS or the pure friction joint. Table 1. Accelerograms dataset. Record Waveform EQ Mw(-) Rep(-) PGA(m/s2) PGV(m/s) SF South Iceland 6263ya 1635 6.5 7 5.018 0.4975 0.47338 South Iceland (aftershock) 6328ya 2142 6.4 12 3.8393 0.2005 0.61871 South Iceland 4673xa 1635 6.5 15 2.0382 0.122 1.1654 Montenegro 196ya 93 6.9 25 2.9996 0.253 0.79191 Campano Lucano 291ya 146 6.9 16 1.7247 0.2745 1.3773 Montenegro 199 93 6.9 16 3.5573 0.5202 0.66776 Campano Lucano 291xa 146 6.9 16 1.5256 0.271 1.557

C. Pettorruso et al. / Procedia Structural Integrity 44 (2023) 1458–1465 C. Pettorruso et al./ Structural Integrity Procedia 00 (2022) 000 – 000

1463

6

6.71 0.95022 Mw: magnitude; Rep: epicentral distance; PGA: Peak Ground Acceleration; PGV: peak Ground Velocity; SF: Scale Factor. 15.3 2.9575 0.3055

Fig. 8 – Scaled ground motion acceleration spectra and target spectrum according to the Italian Building Code (ξ = 5%).

The effectiveness of the DCS over the pure friction (P-F) joint has been examined in terms of (i) maximum resisting force of the beam-to-column joint F max , (ii) maximum horizontal displacement of the beam with respect to the column d max , and (iii) residual displacement of the beam at the end of the ground motion d res . Fig. 9 shows the comparison of the seismic response of the DCS and P-F joints in terms of maximum force, maximum displacement and residual displacement of the seven accelerograms, while Fig. 10 shows the mean of the maxima of the response parameters over the set of seven accelerograms.

a) c) Fig. 9 – Comparison of the seismic response of DCS and pure friction (P-F) joints in terms of maximum force (a) a maximum displacement (b) and residual displacement for the set of 7 accelerograms The P-F joint develops a maximum resisting force Fmax about 40% greater than the DCS; however, it better limits the displacement of the beam during the earthquake, with a maximum slippage of 38 mm vs. 58 mm of the DCS (Fig. 10). Nevertheless, it must be noted that the maximum displacement of the beam supported by the DCS, i.e., d max = 57.8 mm, matches the design value d bd = 60 mm of the system, and can therefore be accommodated by the mechanical joint. The most interesting result is the comparison in terms of the residual displacement: with the DCS the offset of the beam at the end of the ground motion is as small as d res = 4 mm, whereas with the P-F joint the residual displacement is about 20 mm. b)

a) c) Fig. 10 – Comparison of the seismic response of DCS and (P-F) joint in terms of: (a) maximum force; (b) maximum displacement; (c) residual displacement [Quaglini et al. (2022)] b)

C. Pettorruso et al. / Procedia Structural Integrity 44 (2023) 1458–1465 C. Pettorruso et al. / Structural Integrity Procedia 00 (2022) 000 – 000

1464

7

Analyzing the hysteretic loops of the two joints for accelerogram 291xa, Fig. 11, it is possible to notice both the elastoplastic behavior of the DCS, with the expected recentering behavior as the driving force changes its direction, and the unbalanced behavior, in terms of displacements, in the P-F case. In particular it is evident in the response of the PF-system the occurrence of a permanent deformation which is not recovered but increases each time the driving force is enough to trigger sliding of the surfaces. This is reflected in the relevant displacement histories (Fig. 11c), and it is interesting to note the accrual of permanent deformation affecting the response of the P-F joint, whereas the residual displacement of the DCS at the end of the ground motion is negligible.

d 1

d 2

d res

a)

b)

d res

d 2

d 1

c) Fig. 11 - Response of the connection systems to accelerogram 291xa: (a) hysteretic loop of P - F joint; (b) hysteretic loop of DCS joint; (c) displacement histories This is due to the fact that the sliding motion of the P-F joint is engaged when the seismic action exceeds the friction resistance at the beam-to-column interface, and therefore occurs only during the strong motion stage of the earthquake. During the coda stage the ground acceleration is not sufficient to trigger sliding, and the beam remains in the offset position achieved at the end of the previous stage, leading to a huge residual displacement. In contrast, the DCS develops larger displacements during the strong motion stage (Fig. 11b) but owing to the restoring force provided by the sloped surfaces, it tends naturally to recover the original configuration as the ground acceleration gets down. 4. Conclusions In the present work a dissipative connection system (DCS), intended for the seismic protection of precast RC industrial sheds, has been investigated in an experimental campaign and by formulating a 3D numerical model and performing non-linear dynamic analyses to prove the effectiveness of this system over the traditional pure friction joints. The force-displacement curves obtained from the 3D numerical analyses carried out on the prototype and the corresponding experimental curves show an acceptable correspondence. Non-linear dynamic analyses proved the effectiveness of the DCS to control the relative displacements at the beam to-column joint, and the maximum shear force transmitted to the column head, and most importantly, the restoring capacity of the system, which is able to control the residual displacement at the end of the ground motion within small values. This feature is really important to guarantee the capability of the structure to withstand aftershocks, which can occur within a short time from the main shock, as occurred for example in the Centro Italia Earthquake 2016. Acknowledgements The authors wish to thank Mr. Roberto Minerva and the Materials Testing Laboratory of the Politecnico di

C. Pettorruso et al. / Procedia Structural Integrity 44 (2023) 1458–1465 C. Pettorruso et al./ Structural Integrity Procedia 00 (2022) 000 – 000

1465

8

Milano for making the experimental equipment available and Mr. Giacomo Vazzana for assistance during the execution of the tests. References Abaqus/CAE 2017 Documentation. Analysis User’s Manual, Simulia; 2017. Ambraseys N, Smit P, Sigbjornsson R, Suhadolc P, Margaris B. Internet-Site for European Strong-Motion Data, European Commission, Research-Directorate General, Environment and Climate Programme. Available online: http://www.isesd.cv.ic.ac.uk/ESD/ (accessed on 24 November 2021). ASCE/SEI 41-13 Seismic Evaluation and Retrofit of Existing Buildings; American Society of Civil Engineers: Reston, VA, USA, 2014. Belleri A, Moaveni B, Restrepo JI (2014) Damage assessment through structural identification of a three-story large-scale precast concrete structure, Earthquake Engineering & Structural Dynamics, 43(1), p. 61-76. Belleri A, Torquati M, Riva P, Nascimbene R (2015a) Vulnerability assessment and retrofit solutions of precast industrial structures, Earthquakes and Structures, Vol. 8 No. 3, p. 801-820. Belleri A, Brunesi E, Nascimbene R, Pagani M, Riva P (2015b) Seismic performance of precast industrial facilities following major earthquakes in the Italian territory. Journal of Performance of Constructed Facilities, 29, 04014135, DOI: 10.1061/(ASCE)CF.1943-5509.0000617. Bosio M, Belleri A, Riva P, Marini A (2020) Displacement-based simplified seismic loss assessment of Italian precast buildings, Journal of Earthquake Engineering, Vol. 24, No. S1, p. 60-81. Brunesi E, Nascimbene R, Bolognini D, Bellotti D (2015) Experimental investigation of the cyclic response of reinforced precast concrete framed structures, PCI Journal15 (2), p. 57 – 79, DOI: 10.15554/pcij.03012015.57.79. Casotto C, Silva V, Crowley H, Nascimbene R, Pinho R (2015) Seismic fragility of Italian RC precast industrial structures, Engineering Structures 94, p. 122 – 136, DOI: 10.1016/j.engstruct.2015.02.034. Colombo A, Negro P, Toniolo G, Lamperti M (2016) Design guidelines for precast structures with cladding panels, JRC Technical report, ISBN 978-92-79-58534-0. Italian Building Code - CSLLPP (Consiglio Superiore dei Lavori Pubblici). D.M. 17 gennaio 2018 in materia di “norme tecniche per le costruzioni”. Gazzetta ufficiale n.42 del 20 febbraio 2018, Supplemento ordinario n.8, Ministero delle Infrastrutture e dei trasporti, Roma; 2018, in Italian. Formisano A, Di Lorenzo G, Landolfo R (2018) Seismic retrofitting of industrial steel buildings hit by the 2012 Emilia-Romagna earthquake: a case study, Conference Proceedings – October 2018. Liberatore L, Sorrentino L, Liberatore D, Decanini LD (2013) Failure of industrial structures induced by the Emilia (Italy) 2012 earthquakes, Engineering Failure Analysis, 34, p. 629-647. Iervolino I, Galasso C, Cosenza E (2010) REXEL: Computer aided record selection for code-based seismic structural analysis. Bulletin of Earthquake Engineering, 8, p. 339 – 362, DOI: 10.1007/s10518-009-9146-1. Magliulo G, Fabbrocino G, Manfredi G (2008) Seismic assessment of existing precast industrial buildings using static and dynamic nonlinear analyses”, Eng. Struct., 30(9), 2580 -2588. Mari L, Quaglini V, Pettorruso C, Bruschi, E (2021) Experimental and numerical assessment of isolation seismic device for retrofit of industrial shed, In Proceedings of the COMPDYN 2021 and 8th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Athens, Greece, 27 – 30 June 2021; Papadrakakis, M.; Fragiadakis, M. (Eds.), p. 3187. Quaglini V, Dubini P, Poggi C (2012) Experimental assessment of sliding materials for seismic isolation systems, Bulletin of Earthquake Engineering, 10, 717-740, DOI: 10.1007/s10518-011-9308-9 . Quaglini V, Gandelli E, Dubini P (2019) Numerical investigation of curved surfaced sliders under bidirectional orbits, Ingegneria Sismica - International Journal of Earthquake Engineering, Vol. 2. Quaglini V, Pettorruso C, Bruschi, E, Mari L (2022) Experimental and numerical investigation of a dissipative connection for the seismic retrofit of precast RC industrial sheds. Geosciences 2022, 12, 25. https://doi.org/10.3390/ geosciences12010025. SAP2000 Analysis Reference, Volume 1; Computer and Structures Inc.: Berkeley, CA, USA, 1997.

ScienceDirect Structural Integrity Procedia 00 (2022) 000–000 Structural Integrity Procedia 00 (2022) 000–000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 44 (2023) 2082–2089

© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. Abstract Recent earthquakes have demonstrated that monumental structures located in regions characterized by high seismic hazard are particularly sensitive to damage, stimulating a growing attention to the formulation of cost-effective and long-lasting methods for damage assessment. Generally, the evaluation of a healthy or damaged state is data-driven and it can be subjected to a large amount of uncertainty. In order to associate a damage symptom to an actual structural damage, including all the uncertainties involved in the process, a Bayesian-based data fusion methodology is proposed. To this purpose, different sources of information are combined, such as dynamic structural properties extracted from monitoring data (natural frequencies and mode shapes), static response data (crack amplitudes) and visual inspections. More in depth, the proposed procedure comprises three fundamental steps: i) calibration of a finite element (FE) model, partitioned in well-thought-out macro-elements on the basis of engineering judgments and/or numerical simulations and, subsequently, construction of a tuned surrogate model (SM) considering pre-selected uncertain parameters as inputs, such as the Young's modulus, shear modulus, Poisson's ratio and mass density associated to each macro element; ii) solve the Bayesian-based inverse problem aimed at deriving the posterior statistics of the uncertain parameters over the space of the surrogate model’s classes in a computational effective manner by using dynamic data; iii) adjust the posterior distribution on the basis of the information obtained from static data and visual inspections, i.e., data fusion. The suitability of the proposed approach is demonstrated by using the monitoring data pertaining to a monumental palace, located in Gubbio (Italy) and named Consoli Palace, which has been monitored by the Authors since 2017. © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license ( https://creativecommons.org/licenses/by-nc-nd/4.0 ) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy Keywords: Bayesian Data fusion, Damage detection, Surrogate model, Structural Health Monitoring, Architectural heritage. XIX ANIDIS Conference, Seismic Engineering in Italy A Bayesian-based data fusion methodology and its application for seismic structural health monitoring of the Consoli Palace in Gubbio, Italy Laura Ierimonti a* , Ilaria Venanzi a , Nicola Cavalagli a , Enrique García-Macías a,b , Filippo Ubertini a Department of Civil and Environmental Engineering, University of Perugia, Via G. Duranti, 93 06125 Perugia (PG) Italy b Department of Structura Mechanics and Hydraul c Engineering, University of Gran da, Av. Fuentenueva sn, 18002 Granada, Spain Abstract Recent earthquakes have demonstrated that monumental structures located in regions characterized by high seismic hazard are particularly sensitive to damage, imula ing a growing ttention to the formulation f cost-effect v and long-lasting metho s for d mage asse sment. Generally, the eva uation of a healthy or damaged state is data-driven and it an be subjected to a large amount of unc rtainty. In order to ssociate a damage symptom to an ctual structural damage, including all the un ertainties involved in the process, a Bayesian-based dat fusion methodology is proposed. To this purpose, different sources of informat on are combined, such as dyn mic structur l propertie extrac ed from monit ring ata (natural frequencies and mode shapes), s atic resp nse data (crack amplitudes) and visual inspections. More in depth, the proposed procedur comprises three fundamental steps: i) calibration of finite elem nt (FE) model, partitioned in well-thought-out macro-el ments n the basis o e gin ering judgments and/ r numerical simulations and, subsequently, co struction of a tuned surrogat m del (SM) consider g pre-selected uncertain parameters as inputs, such as the You g's m dul s, shear mod lus, Poisson's ratio and mass density associated to ach macro elemen ; ii) solve the Bayesian-based i verse problem aimed at deriving the pos erior statistics of the uncert in parameters over th space of the surrog te model’ classes in a comput tional eff ctive manner by using dynamic data; iii) djust the po terio distribution on the basis of the inform tion obt ined from static data and visual inspections, i.e., data fusion. The suitability of the proposed approach is demonstrated by usi g the monit ring data pert ining to a monume tal palace, located in Gubbio (Italy) and named Consoli Palace, which h s been monitor d by he Authors since 2017. © 2022 The Authors. Publ s ed by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license ( https://creativecommons.org/licenses/by-nc-nd/4.0 ) Peer-review u der re ponsibility of scientific committe of the XIX ANIDIS C nfere ce, Seismic Engineering in Italy K ywords: Bayesian Data fu ion, Damage detection, Surrogate model, Structural Health Monitoring, Architectural heritag . XIX ANIDIS Conference, Seismic Engineering in Italy A Bayesian-based data fusion methodology and its application for seismic structural health monitoring of the Consoli Palace in Gubbio, Italy Laura Ierimonti a* , Ilaria Venanzi a , Nicola Cavalagli a , Enrique García-Macías a,b , Filippo Ubertini a a Department of Civil and Environmental Engineering, University of Perugia, Via G. Duranti, 93 06125 Perugia (PG) Italy b Department of Structural Mechanics and Hydraulic Engineering, University of Granada, Av. Fuentenueva sn, 18002 Granada, Spain

2452-3216 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy 2452-3216 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the sci ntific committee of the XIX ANIDIS Conference, Seismic Engin ering in Italy

2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. 10.1016/j.prostr.2023.01.266

Laura Ierimonti et al. / Procedia Structural Integrity 44 (2023) 2082–2089 L. Ierimonti et al./ Structural Integrity Procedia 00 (2022) 000–000

2083

2

Introduction Nowadays, the damage identification process of monumental structures located in regions characterized by high levels of seismic risk is a challenging task. Recently, SHM-based approaches are a fast-growing techniques due to their ability to respond to structural changes (Cavalagli etal., 2018, Venanzi etal., 2020) through the post-processing of the data acquired from an array of sensors deployed on the structure. The main goal is to monitor the health of the structure based on measurable response parameters, as these can ultimately become signs of possible damage due to excessive loads, earthquakes, material’s degradation and so on. Usually, these data-driven methodologies can be classified as unsupervised approaches. Then, different works in literature have contributed to the development of SHM-based probabilistic approaches for damage detection (Behmanesh etal., 2015, Sun etal., 2020) and semi supervised methodologies (Ierimonti etal., 2021). Nowadays, the challenge is to make robust decisions considering the complex nature of the real-world applications and the high level of uncertainties during the SHM-based data pre processing and post-processing. In this context, a fundamental role is played by data fusion, an attractive multi informative approach aimed at collecting and interpreting data of different nature. According to Hall, 1997, three levels of data fusion can be identified: (i) data-level, consisting of combining data derived from multiple sources with the same physical meaning; (ii) feature-level, consisting of analyzing and processing heterogeneous input data which are then concatenated, also with different physical meaning; (iii) decision-level, consisting of separately addressing the results from different sources and then the final decision is achieved by means of selected combination rules. Different works in the literature make use of data fusion approaches aimed at quantify a post-event damage (Chatzis etal., 2015 and Li etal., 2020). In light of the brief literature review, this paper presents a real-time decision-level Bayesian-based data fusion methodology for decision making, where SHM is used as a complimentary method to visual inspections. Thus, different sources of information are merged together to achieve a more reliable assessment of the health of the investigated structure. To do so, a high-fidelity model of the structure is constructed to capture the physics involved in the problem. Then, the model is used for identifying damage-sensitive portions on the basis of engineering judgement (EJ) and nonlinear static analysis (NLSA). The material’s mechanical characteristics of each damage-sensitive portion are assumed as uncertain. Then, a surrogate twin model is calibrated, i.e., a mathematical relationship between the uncertain parameters and the modal features of the structure. The posterior statistics of the uncertain parameters are evaluated through the Bayes theorem. Given the complexity of structures and the inability to perfectly model all aspects of the system, Bayesian-based results, static measurements and visual inspections are merged together to aid engineers in detecting the onset of damage in real-time. The effectiveness of the proposed approach is demonstrated by analyzing the effects of a low-intensity earthquake occurred on May 2021 on the Consoli Palace, located in Gubbio, central Italy. The palace has been equipped with a permanent SHM system since 2017 and the actual configuration has been enhanced in July 2020 with a dense array of sensors. The rest of the paper is organized as follows. Section 1 describes the steps of the proposed methodology. Section 2 gives a general frame of the case study, its FE/surrogate model and the installed SHM system. Section 3 highlights some preliminary results. Section 4 concludes the paper. 1. The Bayesian-base data fusion procedure The Bayesian-based procedure can be divided in two phases: i) the offline phase; ii) the online procedure. Detailed information about each phase are summarized in the following Sections. 1.1. Description of the offline phase The main purpose of the offline phase is to calibrate a SMwhich is then used in the Bayesian-based model updating stage to make predictions on the possible damage.

Laura Ierimonti et al. / Procedia Structural Integrity 44 (2023) 2082–2089 L. Ierimonti et al./ Structural Integrity Procedia 00 (2022) 000–000

2084

3

Fig. 1. Schematic representation of the offline phase.

The fundamental steps of this phase are: 1) Construction of the FE model . The FE model can be constructed and calibrated on the basis of Ambient Vibration Tests (AVT) and in situ material characterization tests. 2) Evaluation of damage-sensitive portions . The building is subdivided in N regions R ={R1, .. , R j , .., RN} potentially prone to damage, defined on the basis of NLSA and EJ. Each region is considered homogeneous in terms of material’s mechanical characteristics. Vector K ={ k 1 (R1), .. , k j (R j ), .., k N (RN)} collects the damage parameters associated to the j- th region. 3) Calibration of a SM . In order to reduce the computational effort of the analysis, a SM( K ) is calibrated as a function of the uncertain parameters to be updated. The SM is proposed to present the numerical relationship between FE model, in terms of frequencies and mode shapes, and K . 1.2. Description of the online procedure The online procedure is performed by running the following steps: 1) Start continuous SHM . A network of sensors of different nature allows to store acceleration/velocity data, temperature/humidity data and static measurements, such as crack amplitudes and tilt rotations. 2) Feature extraction . The SHM data are post-processed and the modal features MF of the structure are evaluated, i.e., fundamental natural frequencies and vibration modes. Furthermore, environmental effects are removed from original signals. For the purpose, the MOSS integrated software (García-Macías etal., 2020) is used, which is an automated tool based on the stochastic subspace identification (SSI) technique. 3) Novelty detection. If a novelty is detected go to step 4, otherwise go back to step 1. The novelty at time t is related to the estimation of the square Mahalanobis distance T 2 (Hotteling, 1947) of the residual E(t), i.e., ! ( ) = ( ( ) − * ) " ∑ ( ( ) − * ) " #$ , where * represents a vector collecting the mean values of the residuals empirically estimated in the training period and ∑ the corresponding covariance matrix. 4) Intermediate analysis. Perform the Bayesian model updating of the uncertain parameters and proceed with visual inspections. More in detail, the posterior distribution of the j- th uncertain parameter is evaluated as follows: - % ∣ , 3 = ⋅ - ∣ % , 3 ⋅ - % ∣ % ( − 1)3 (1) where % is the mean value of % ; is a constant ensuring the posterior distribution integrates to 1; - ∣ % , 3 is the likelihood function modeled as a Gaussian distribution with zero mean (Behmanesh etal., 2015, Ierimonti etal., 2021); - % ∣ % ( − 1)3 is the prior distribution calculated as the posterior distribution at previous time step − 1 . Visual inspections can be numerically quantified by means of a damage index DI, accounting for the importance , extension K1 and intensity K2 of damage. The index DI can be evaluated as follows: DI % => & '($ %' ⋅ K1 %' ⋅ K2 %' (2)

Laura Ierimonti et al. / Procedia Structural Integrity 44 (2023) 2082–2089 L. Ierimonti et al./ Structural Integrity Procedia 00 (2022) 000–000 where is the number of damages observed in region R j. The term could be, 1,2 or 5 on the basis of the observed damage, i.e., absence of damage, local mechanism, global mechanism. The terms K1 and K2 , on the basis of the observed extension/intensity, could be 0.2, 0.5 or 1. 2085

4

Fig. 2. Schematic representation of the online phase.

5) Data fusion. Combine all the information sources as follows: i) Evaluate the visual inspection-related DI % for each region. If DI % > 0, the region is considered "damaged"; ii) Evaluate the crack index CI, i.e., assign CI=1 if the crack measurement exhibits a permanent closure or opening, otherwise assign CI=0; iii) Define the j -th Bayesian-based Index BI, i.e., assign BI=1 if the updated values are reduced more than or equal to 10 % with respect to the undamaged state, otherwise assign BI=0; iv) Calculate the data fusion results by means of the well-known 2-out-of-3 (2oo3) method (majority criterion), named 2oo3 voter and assign 1 if the specific region has the majority of 1, assign 0 otherwise. In the absence of crack/deformation information for a specific region, the value of DI is counted twice. v) Adjust the posterior statistics % )*,,- by means of a correction coefficient Ψ % ,- which multiplies the posterior distribution % )* : % )*,,- = Ψ % ,- ⋅ % )* (3) If the 2oo3 voter is 1 (damaged state) assign Ψ % ,- = 1 , otherwise assign Ψ % ,- = % ./0 / % )* 2. The Consoli Palace: SHM system, FE model and corresponding SM The Consoli Palace is a 60 meters high medieval building, located in Gubbio, Umbria, central Italy. The Palace is built in calcareous stone masonry with a regular and homogeneous texture.