Stefano Invernizzi

• MS Civil Engineering, PhD Structural Engineering
• Professor (Associate) at Polytechnic University of Turin

Gridshell structures are characterized by an impressive strength-to-weight ratio, allowing their application in large-span roofing structures. However, their complex construction process and maintenance limited their widespread application. In recent years, the development of parametric and computational design tools has rekindled interest in this...

This paper presents a comparative study of a gridshell roof structure designed for the Islamic Cultural Center in Dakar, Senegal. The structure, conceived by Fragomeli & Partners, emulates the shape of a dune to seamlessly integrate with the surrounding environment. To define an optimal structural shape while preserving the architectural intent, tw...

The architectural heritage of the 20th century is affected by several conservation problems in terms of material preservation, structural analysis, and reuse. Among these, material degradation and durability issues are the ones that have the most effect on the health state and, consequently, the survival of the constructions of the period. In order...

In the present paper, a very high cycle fatigue test campaign carried out with an ultrasonic testing machine up to 10 ¹⁰ cycles is presented. The aluminum alloy hourglass and dog‐bone samples have dimensions spanning over a very wide range, with the diameter in the middle cross‐section comprised between 3 and 30 mm. From the experimental results, t...

Orthotropic steel deck (OSD) bridges are lightweight constructions which are convenient, especially for the achievement of long spans. Conversely, due to the stress concentration in correspondence to the numerous and unavoidable welded construction details, this bridge typology is prone to fatigue cracking under the effect of cyclic loading with hi...

Size effects concern the anomalous scaling of relevant mechanical properties of materials and structures over a sufficiently wide dimensional range. In the last few years, thanks to technological advances, such effects have been experimentally detected also in the very high cycle fatigue (VHCF) tests. Research groups at Politecnico di Torino are ve...

In the architectural and cultural heritage of the Arsenale of Venice, the authors have worked on several interventions for diagnosis and recovery of roofs, foundations and floors of the so-called “woods of Venice”. The work refers to the complex of the “Sale d’Armi” located in the central area of the Arsenale, currently used as exhibition space for...

In recent decades, ultrasonic testing machines have allowed to investigate the very-high cycle fatigue (VHCF) range, featuring feasible gigacycle fatigue testing in a very short time, although the influence of frequency is still partly controversial. The fatigue behaviour depends on the random distribution of initial defects, whatever the stress ra...

A possible scenario is proposed to put into evidence how the combined effect of fatigue at very high number of cycles and corrosion could have been responsible for the failure of one of the strands and the subsequent collapse of the so-called balanced system of the Polcevera Bridge designed by Morandi. The analysis accounts for an actual estimation...

In this paper the mechanical characteristics of an innovative bioplastic material, the HBP ® -HempBioPlastic ® filament, is investigated. HBP ® was recently patented by an Italian company Kanésis that focused its activity on nature-derived materials. The filaments are the upshot of an original process allowing to reuse the surplus of the agricultur...

Featured Application The work provides a robust methodology for the determination of fatigue life expectation in the VHCF regime of the EN-AW6082 aluminium alloy, taking into account the influence of specimen size. In this way, correct fatigue life expectation for EN-AW6082 aluminium alloy full-scale components can be obtained. Abstract The presen...

On August 14, 2018, a few spans of the cable-stayed viaduct crossing the Polcevera river (Genoa, Italy) collapsed, causing tens of fatalities along with considerable material damage and hundreds of people displaced. The viaduct, as well as many others belonging to the national road network, was built in the second half of the last Century and has b...

The present paper investigates the influence of the specimen size of EN-AW6082 wrought aluminium alloy subjected to very high cycle fatigue (VHCF) tests. The hourglass specimens were tested under fully reversed loading condition, up to 10^9 cycles, by means of the ultrasonic fatigue testing machine developed by Italsigma® (Italy). Three specimens g...

The paper investigates the issue of finite element model development for the structural assessment of existing structures on the basis of detailed (terrestrial laser scanning and image-based) point clouds to parametric models generated using HBIM (Heritage Building Information Modelling) technology. Different procedures and software combinations ar...

The present contribution investigates size effects on Wöhler's curve in accordance with dimensional analysis and intermediate asymptotics theory. These approaches provide a generalised equation able to interpret the specimen‐size effects on Wöhler's curve. Subsequently, using a different approach based on lacunar fractality concepts, analogous scal...

Fatigue life assessment can be carried out according to two well-known approaches. The first is based on the so-called Paris’ law that express the sub-critical crack growth rate as a function of the stress-intensity factor range. The second is based on Wöhler’s curve that relates the applied stress range with the number of cycles to failure. Both a...

On August 14, 2018, a few spans of the cable-stayed viaduct crossing the Polcevera river (Genoa, Italy) collapsed, causing tens of fatalities along with considerable material damage and hundreds of people displaced. The viaduct, as well as many others belonging to the national road network, was built in the second half of the last Century, and has...

The Sanctuary "Beata Vergine Maria del Monte Carmelo" in Colletto, Pinerolo, Italy, is an outstanding renaissance architectural complex located in high hills region nearby Turin, Italy. The church is well known both for its architectural relevance and for the artistic value of the paintings and statues. In addition, thanks to the optimal acoustic p...

In the context of our architectural heritage, timber structures represent an important sector in terms of historical relevance, architectural technology and construction materials. Roof structures constitute an integral part of the architectural complex in which they are located and should be treated with the same attention and respect due to their...

The paper describes the finite element model simulation of reinforced adobe walls to assess the feasibility of an innovative strengthening technique for earthen constructions, which improves the seismic performance. The retrofitting technique is based on the application of geogrids on both sides of the earthen wall. The geogrid is comprised in the...

The Asinelli Tower in Bologna is taken as a case study to define a general methodology for the analysis of historical masonry towers. The difficulties that are typically encountered in building finite element models of increasing complexity are addressed, proposing a general procedure. A formulation accounting for masonry anisotropy due to existing...

The present paper investigates the combined effect of corrosion and fatigue at very-high number of cycles on the recently collapsed Polcevera Bridge. Since the construction, in the mid-sixties, the viaduct has experienced a dramatic increase in the heavy lorries traffic. Although the amplitude of stress oscillation in the strands was limited, it is...

The phenomenon of ultrasound vibration of cylindrical solid specimen is investigated experimentally. Vibration is induced by means of an ultrasound piezoelectric transducer with 20 kHz working frequency. Brittle Luserna stone resonant samples are considered, in addition to Schorl crystals (black tourmaline). The phenomenon is characterized from a d...

A novel concept for a factory of the future is presented, based on the integration of different needs through a multidisciplinary approach: logistics of internal spaces (interaction between directional and production areas, modularity of spaces to allow future expansions/contractions), use of a prefabricated steel structure, environmental quality f...

The paper reviews some recent numerical applications for the interpretation and exploitation of acoustic emission (AE) monitoring results obtained from historical masonry structures and materials. Among possible numerical techniques, the finite element method and the distinct method are considered. The analyzed numerical models cover the entire sca...

The authors are currently doing fatigue tests, by using sonotrodes working at 20 kHz, and compression tests on solid samples of rock materials. The specimens are monitored by laser sources focused on spots of the external surface. The main purpose is to identify in the crystal lattice mechanical oscillations in a frequency range higher than the Aco...

The paper describes an activity conducted by a multi-disciplinary research group (architecture, civil engineering, technology, geomatics) for the mechanical evaluation of a timber floor belonging to a historic residential building located in the city center of Torino. The floor was made of beams of solid wood and wooden boards and presented a mid-s...

The paper analyses a reinforcement intervention conceived by one of the authors (C. Bertolini) and performed on the historical timber roof structure of the Valentino Castle in Torino (Italy) some thirty years ago. The timber roof of the towers, dating back to 17th century, is a three-dimensional frame structure with a height of about 12 m. In the t...

In this contribution a new method for evaluating seismic risk in regional areas based on the acoustic emission (AE) technique is proposed. Most earthquakes have precursors, i.e., phenomena of changes in the Earth’s physical-chemical properties that take place prior to an earthquake. Acoustic emissions in materials and earthquakes in the Earth’s cru...

The paper describes an activity conducted by a multidisciplinary research group (architecture, civil engineering, technology, geomatics) for the mechanical evaluation of a timber floor belonging to a historic residential building located in the city center of Torino. The floor was made of trusses of solid wood and wooden boards and presented a mid...

Masonry arch structures, and, more generally, vaulted structures, are traditionally assessed using a well-established approach, such as linear elasticity or limit analysis, whereby system behaviour at the intermediate stage – which occurs when the material's tensile strength has been exceeded but the collapse mechanism has not yet formed – is disre...

The paper analyzes a series of reinforcement interventions performed on the historical timber roof structure of the Valentino Castle in Torino (Italy) some thirty years ago. It is not very common to be able to assess the durability of interventions without relying to accelerated ageing test. In this case a real structure is considered, which was co...

Piezonuclear reactions concern neutron emissions triggered by high-frequency pressure-waves in inert, non-radioactive materials. This phenomenon has recently been detected in liquid solutions and brittle solids. In the present paper, the investigation is extended to a more ductile material, as steel is, subjected to different loading conditions. Al...

A multidisciplinary concept for a factory of the future is presented, based on the integration of different needs: logistics of internal spaces (interaction between directional and production areas, modularity of spaces to allow future expansions/contractions), use of a prefabricated steel structure, environmental quality for occupants and energy s...

The 2010 Maule earthquake produced brittle compression failure of reinforce concrete (RC) walls, due to high axial load, deficient detailing of boundary elements, and the use of thin and slender walls. To prevent new failures of existing buildings, there are several techniques to improve the confinement of boundary walls. The use of carbon fiber fa...

Piezonuclear reactions concern neutron emissions triggered by high-frequency pressure-waves in inert, non-radioactive materials. This phenomenon has recently been detected in liquid solutions and brittle solids. In the present paper, the investigation is extended to a more ductile material, as steel is, subjected to different loading conditions. Al...

Acoustic Emission (AE) is a Non-Destructive Inspection Technique, widely used for monitoring of structural condition of different materials like concrete, masonry and rocks. It utilizes the transient elastic waves produced by each fracture occurrence, which are captured by sensors on the external surface. The preservation of the mural painting heri...

An innovative base isolation system has been recently proposed for the retrofitting of existing buildings, in which the isolation layer is inserted under the building foundations so that the building, along with its foundations, is isolated from the surrounding soil. The isolation layer resides in closely-spaced micro-tunnels, constructed under the...

: The former clinker warehouse, also known as the "Paraboloide" of Casale is an architectural symbol of the concrete Italian industrial heritage. The constructive technology and the structural shape of the thin concrete vault are comparable to the outstanding realizations achievements of the beginning of the XXth century, as for examples the works...

Acoustic Emission (AE) is a Non-Destructive Inspection Technique, widely used for monitoring of structural condition of different materials like concrete, masonry and rocks. It utilizes the transient elastic waves produced by each fracture occurrence, which are captured by sensors on the external surface. The preservation of the mural painting heri...

We examine an application of Acoustic Emission (AE) technique for a probabilistic analysis in time and space of earthquakes, in order to preserve the valuable Italian Renaissance Architectural Complex named "The Sacred Mountain of Varallo." Among the forty-five chapels of the Renaissance Complex, the structure of the Chapel XVII is of particular co...

The paper describes an experimental research activity on the application of a polymeric resin reinforced with carbon nanotubes on an ancient timber structures belonging to cultural heritage (Bertolini Cestari et al. in Proc. of SAHC2008. VI International Conference, pp. 941–947, 2008; Marzi in Ph.D. Thesis, 2010; Bertolini Cestari et al. in Proc. o...

Nowadays, there is an increasing demand for detailed geometrical representation of the existing cultural heritage, in particular to improve the comprehension of interactions between different phenomena and to allow a better decisional and planning process. The LiDAR technology (Light Detection and Ranging) can be adopted in different fields, rangin...

Torino, in 1861, was the first capital of the just unified Reign of Italy. In the same year, Eng. A. Mazzucchetti was charged for the design of the railway station of Porta Nuova in Torino, in correspondence of the arrival of the railway connecting Genova. The original conception resembles the bilateral scheme of the King Cross station in London, w...

We present some numerical simulations of AE due to damage propagation in disordered materials under compression and bending. To this purpose, the AE cumulative number, the time frequency analysis and the statistical properties of AE time series will be numerically simulated adopting the so-called “particle method strategy” (Cundall in Proceedings I...

Seismic upgrading of historical, industrial and other important buildings is a major challenge faced by engineers. An innovative method of base isolation was proposed by Clemente and De Stefano ("Application of seismic isolation in the retrofit of historical buildings" (2011)), requiring construction of closely spaced micro-tunnels under the entire...

A combined compression and acoustic emission (AE) test is proposed to study the scaling of fracture and AE in concrete-like specimens with different size and slenderness. The cylindrical concrete specimens were drilled from two pilasters sustaining an Italian viaduct built in the 1950s. A finite-element method model of the pure compression tests is...

We present some experimental results and numerical simulations of acoustic emissions (AE) due to damage propagation in a concrete specimen subjected to the three-point bending (TPB) test. The test is performed under Crack-mouth opening displacement control. Moreover, AE are detected by an eight sensors experimental device, which allows for signal l...

The Acoustic Emission (AE) technique was used to assess the structural stability of the Asinelli Tower, the tallest building in the city of Bologna, which, together with the nearby tower, named Garisenda, is the renowned symbol of the city. AE is a passive, non-destructive structural evaluation technique based on the spontaneous emission of pressur...

In the present paper the problem of monotonically compressed concrete columns is studied numerically, accounting for transverse steel reinforcement and concrete cracking. The positive confinement effect of the ties on the core concrete is modeled explicitly and studied in the case of distributed or concentrated vertical load. The main aim is to inv...

The main room of the Valentino Castle in Torino, the “Salone delle Feste”, was conceived and realised in the XVIIth century under the guidance of Carlo di Castellamonte. The beautiful frescos and stuccoes of the domical vault are sustained by a typical Delorne carpentry, whose span is among the largest of their kind. The dome suffered from degradat...

The Ebe schooner-brig was built in 1921 and sailed the Mediterranean Sea for almost 40 years before being dissected into 90 parts to be transported to Milan (Italy). There, the schooner was reassembled, and the naval pavilion of the National Museum of Science and Technology was built around the ship. After 45 years in the museum, the ship presents...

The main room of the Valentino Castle in Torino, the “Salone delle Feste”, was conceived and realised in the XVIIth century under the guidance of Carlo di Castellamonte. The beautiful frescos and stuccoes of the domical vault are sustained by a typical Delorne carpentry, whose span is among the largest of their kind. The dome suffered from degradat...

Acoustic Emission (AE) is a Non-Destructive Inspection Technique, widely used for monitoring of structural condition of different materials like concrete, masonry and rock. It utilizes the transient elastic waves after each fracture occurrence, which are captured by sensors on the external surface. The preservation of mural painting heritage is a c...

Piezonuclear reactions concern neutron emissions triggered by high pressure waves in inert non-radioactive materials. This phenomenon has recently been documented in liquid solutions and brittle solids. In the present paper the investigation is extended to a more ductile material, like steel, subjected to different loading conditions. Although piez...

In the present paper, a project for integrated investigation is described, using noninvasive methods, specially designed for dealing with the highly diversified historic heritage of Piedmont (Italy). The stability of the decorated surfaces will be investigated by innovative Acoustic Emission (AE) and ultrasonic methods already experimentally tested...

A scaled model of a two-span masonry arch bridge has been built in order to investigate the effect of the central pile settlement due to riverbank erosion. The bridge model has been equipped with different Non Destructive Testing (NDT) instruments and subjected to incremental settlement of the pier. The evolution of the pier scour has been investig...

The Ebe schooner-brig was built in 1921 and sailed the Mediterranean’s sea for almost forty years, before being dissected into ninety parts to be transported in Milan (Italy). There, the schooner was reassembled and the naval pavilion of the National Museum of Science and Technology was built up all around the ship. After forty years in the museum,...

In the paper some case studies of damaged towers in Italy are presented: the Tower Masserano of Palace Ferrero - La Marmora at Biella, the bell tower of the Collegiata of San Vittore at Arcisate, and three medieval towers in Alba. A methodology is put forward for combining laboratory and nondestructive testing methods with monitoring systems in ord...

  A scaled model of a two-span masonry arch bridge has been built to investigate the effect of the central pile settlement because of riverbank erosion. The bridge geometry and the structural details, included the masonry bricks and mortar joints, are realized in the scale 1 : 2. The model bridge has been equipped with different Non-Destructive Tes...

Conservation and maintenance represent strategic fields of interest in EU for their high social/economic impact. Timber structures may present degradation phenomena, that require a special attention in the intervention on cultural architectural heritage. An integrated approach for interventions on timber structures is essential for the project, by...

In the present paper the results from a recent monitoring campaign and numerical analysis performed on the ancient Cathedral of Syracuse in Sicily are presented. The acoustic emission (AE) technique is adopted to assess the damage pattern evolution. The localization of the propagating cracks is obtained using six synchronized AE sensors. A clear co...

The results obtained varying the size of the masonry prism involved in the double flat-jack test are described. In these tests, not only the deformations have been acquired, but also the acoustic emissions (AE) events, in order to get information about local cracking in the specimens. In addition, a meso-scale numerical model of the test is present...

. A combined compression and AE test is proposed, in order to study the scaling of fracture and Acoustic Emission in concrete-like specimens with different size and slenderness. The cylindrical concrete specimens were drilled from two pilasters sustaining a viaduct along an Italian highway built in the 1950s. A two-dimensional FEM numerical model o...

Acoustic Emission (AE) has recently been exploited by the authors in order to assess the safety of civil structures and to get an estimate of the residual expected time to failure. AE can be measured in compressive tests, as well as in more complex in situ tests like the single and double flat jack test. In the present paper, an attempt is made in...

The sequentially linear analysis is a robust alternative to nonlinear finite element analysis of structures when bifurcation, snap-back or divergence problems arise. The load–displacement response is captured by a series of linear analyses as a sequence of ‘events’. Every ‘event’ is a scaled critical state corresponding to the reaching of some peak...

We describe the experimental and numerical assessment of a seventeenth-century masonry vault, which was required because of a change in use of the upper floor. During the in situ load test, we recorded the acoustic emissions from the vault, as well as displacements of the vault and strains in the steel rods. We compare the experimental data with th...

In the present paper, we describe the results obtained from double flat-jack tests performed varying the size of the masonry prism involved in the test. In addition, not only the deformations have been acquired, but also the acoustic emissions (AE), in order to get information about local cracking during the test. We present a meso-scale numerical...

A numerical model based on the solution of the normal contact between elastic half-spaces and subsequent post-processing according to the Mindlin and Deresiewicz solution for cyclic tangential loading is presented. Thanks to a recent extension of the Cattaneo-Mindlin analogy to the solution of tangential contact between non-convex domains, the prop...

Over the past years techniques for non-linear analysis have been enhanced significantly via improved solution procedures, extended finite element techniques and increased robustness of constitutive models. Nevertheless, problems remain, especially for real world structures of softening materials like concrete. The softening gives negative stiffness...

In the present paper a comparative numerical and experimental study of three XIII Century masonry towers preserved in Alba (Italy) is described. The buildings have been recently analyzed and monitored because of emerging damage pattern (Carpinteri & Lacidogna, 2001), also due to some seismic events during the last few years. Nondestructive evaluati...

In this paper, an attempt is made to find some general relations for the microcutting process in brittle or quasi-brittle materials, under different hypotheses of microscopic failure behavior. Fracture beneath the indenters and sudden chip formation are the main dissipation mechanisms taken into consideration. Fracture patterns in more homogeneous...

In the present paper the case study of the eighth-century masonry tower called “Torre Sineo” (Alba, Italy) is described. The building has been recently analyzed and monitored because of an emerging damage pattern, and also due to some seismic events during the last few years. Nondestructive evaluation techniques have been adopted to assess the pres...

The correct evaluation of the shear behavior of rock joints is of fundamental impor-tance in slope stability analysis. A strong size-dependence of shear strength has been detected. The study of the force exchange mechanism at the joint interface, supported by the proper description of the fractal contact domain, represents the mean to provide a siz...

In the present paper a comparative numerical study of two XIII century masonry towers preserved in Alba (Italy) is described. The buildings have been recently analyzed and monitored because of an emerging damage pattern, also due to some seismic events during the last few years. Nondestructive evaluation techniques have been adopted to assess the p...

After a brief discussion on crack models, it is demonstrated that cracking is often accompanied by snaps and jumps in the load–displacement response which complicate the analysis. This paper provides a solution by simplifying non‐linear crack models into sequentially linear saw‐tooth models, either saw‐tooth tension‐softening for unreinforced mater...

The process of indentation of brittle and quasi-brittle materials has been investigated both from the experimental and the theoretical point of view. As far as we know, only a few studies have tried to explain the mechanics of cutting due to an indenter which penetrates inside the material. In this paper, an attempt is made to find some general rel...

A wide variety of applications, ranging from rough cutting of stone and concrete to ultra-precision machining of ceramics for electronic components, are commonly performed with the so-called super-abrasive tools. The working part of such tools is made of hard particles, typically diamonds or cubic boron nitride crystals, embedded in a resin or sint...

In the past two decades, Fractal Geometry developed as a new and powerful mathematical tool able to model a wide class of complex natural systems. Particularly, when joined with renormalization techniques, Fractal Geometry represents the natural and synthetic way to characterize the so-called self-organized processes, emphasizing their universality...

In a previous work [1] the authors showed how to acquire the meso-structural characteristics of undamaged concrete-like materials by a peculiar laser equipment [2]. In order to extend the analysis to damaged disordered materials, a new direct tension test equipment has been developed, that minimizes flexural effects by freely rotating boundary cond...

The fracture process in concrete-like materials cannot be properly modelled in an Euclidean framework, due to its complex morphology at the micro- and meso-level. The inherent flaws interact through a multi-scale process, leading to self-affine fracture surfaces. Moreover, the self-organized network of microcracks displays fractal properties prior...

The aim of the present paper is to study the variation of tensile strength of disordered materials in relation to the structural size. Griffith[1] gave an explanation to this phenomenon assuming the size of the most dangerous microdefect as proportional to the specimen size. Therefore, decreasing the specimen size, the size of this microdefect decr...

We present some numerical simulations of AE due to damage propagation in quasi-brittle materials under compression. To this purpose, the AE cumulative number, the time frequency analysis and the statistical properties of AE time series will be numerically simulated adopting the so-called “particle method strategy”. The method provides the velocity...

An experimental and numerical study on the mechanical behaviour of an innovative composite material based on the combination of a self-compacting concrete (SCC) matrix with transparent glass inclusions is proposed. The experimental tests have been monitored by an acoustic emission (AE) device. The results are interpreted by a FEM model accounting f...