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This paper focuses on seismic fragility and damage scenario assessment of minor Italian historical centres through the development of urban fragility curves. With reference to the case study of Balvano, a small centre located in Basilicata Region of Italy, two hybrid models have been adopted. The first is a mechanic-based hybrid model developed by the authors to derive urban fragility curves specifically; the second is the macroseismic method, originally conceived to derive typological fragility curves for single building classes, expanded to derive urban fragility curve herein. Balvano was strongly struck by 1980 Irpinia-Basilicata earthquake (Ms = 6.90) and hence subjected to an intense reconstruction process during 1980s, where almost the 80% of the buildings were reconstructed with reinforced concrete structures in the place of unreinforced masonry ones. Seismic vulnerability and damage scenarios before and after 1980 have been assessed and compared with the purpose of validating the effectiveness of the urban scale fragility curves obtained through hybrid methodologies and quantifying the effect of the ‘new’ seismic hazard maps and first seismic codes and recommendations released by the Italian Government in the aftermath of 1980 for the construction of new buildings or for retrofitting the existing ones. A good matching between predicted and occurred damage scenario from the research outcomes emerged, confirming the effectiveness of the urban scale hybrid fragility curves to assess seismic vulnerability at urban scale. Moreover, the comparison of the damage scenarios pre and post-reconstruction highlighted the crucial role played by the code prescriptions adopted in that years for reducing the seismic vulnerability of the municipality and the importance of the ‘new’ seismic hazard maps introduced in 1980s. Finally, the differences between mechanical-based hybrid and macroseismic model have been discussed in the paper.

Existing Reinforced Concrete arch bridges represent still today an important part of transportation network. The peculiarities of such bridges make particularly complex the assessment of their behaviour under both static and dynamic actions and, therefore, their safety. This work concentrates on a specific arch bridge typology known as the "Maillart -Type Arch Bridges" or "Deck-Stiffened Arch Bridges", characterized by a very stiff deck beam and a slender and wide vault. As well as for the RC structures designed during 50s of the last century, where some important details for concrete elements were not considered, RC Deck-Stiffened Arch Bridges could be subjected to similar structural deficiencies. Moreover, the current loading conditions provide actions that were not considered in the original design or have changed over the time, such as the seismic actions or the moving loads due to the vehicular traffic.For the evaluation of the main critical issues related to the current performance of the "Maillart-Type Arch Bridges", this study, starting from a "simulated design" according to the design rules and the mandatory codes in force at the construction time, defines a large building inventory of simulated bridges (3000 samples) charac-terized by different values of the most significant geometrical parameters. Firstly, each bridge of the inventory is modelled and studied by means of a linear Response Spectrum Analysis (RSA) implemented in the software SAP2000. The large number of structural analyses allowed to investigate the seismic behaviour of such a bridge typology, assess and localize the most frequent failure modes. The results of the RSA allowed developing pre-liminary fragility functions at the Ultimate Limit State, based on shear or flexural failure of single elements of the bridges. Lastly, Non-Linear Time History Analyses (NLTHA) were carried out on two representative case studies extracted from the simulated inventory and the results were examined in terms of fragility curves obtained according to the Cloud methodology for four Damage States. Despite the different approaches (RSA on large scale and NLTHA on two prototypes), a comparison of the fragility curves for equivalent Damage States was also proposed and a good agreement was found. These fragility curves are a first step for the assessment of the seismic vulnerability of "Maillart-Type Arch Bridges" and can be useful for planning seismic risk mitigation interventions for such a bridge typology.

Several models are proposed in the scientific literature to correlate crack width and corrosion level; such relationships could be regarded as a tool for the non-destructive identification of the corrosion degradation, since they often involve easily measurable parameters, also by means of non-destructive tests. In the present paper, the reliability of literature models predicting the crack width from the corrosion level is statistically investigated by considering experimental data from naturally corroded beams.

The SPOT Project (potentially triggerable offshore seismicity and tsunamis) is aimed at helping Italian authorities to comply with the application of the Safety of Offshore Oil and Gas Operations European Directive (2013/30/EU) and the ensuing Italian codes. An extensive reconstruction of offshore geological structures is being implemented in order to assess the existence of potentially seismogenic faults in the surroundings of offshore oil and gas platforms, as a propaedeutic step for the assessment of potentially triggered seismicity connected with operations on such platforms. The descriptive parameters of the identified faults will be used to estimate their natural earthquake rates. The impact of these natural earthquakes along the coasts will then be modeled in terms of expected ground shaking and tsunamis. In turn, these models will be used to estimate potential human and economic losses in a multi-hazard approach to risk assessment. Wherever the combined earthquake and tsunami modeling indicates a relevant impact along the coasts, a more detailed analysis will be carried out, also involving the operators of the related platforms, to perform specific models which also take into account production data. The project has been conceived and funded by the Italian Ministry of Economic Development, with the technical support of the National Department of Civil Protection. The involved research institutes are the Institute of Marine Sciences of the National Research Council (ISMAR), the National Institute of Geophysics and Volcanology (INGV), the European Centre for Training and Research in Earthquake Engineering (EUCENTRE), and the Laboratories University Network of Seismic Engineering (ReLUIS).

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Reinforced concrete (RC) structural members are usually strengthened with epoxy bonded pre-cured FRP strips. An innovative strengthening technique application is based on the use of FRP strips, with enhanced bearing strength, attached to concrete substrate by using mechanical fasteners (MF-FRP) in place of epoxy adhesive. The MF-FRP method is a viable technique for strengthening concrete members, particularly where speed of installation and immediacy of use are imperative. Laboratory testing and a number of field applications have shown the effectiveness of such method. An analytical model is discussed for RC beams strengthening using MF-FRP strips. The model accounts for equilibrium, compatibility and constitutive relationships of materials, in particular, it accounts explicitly for the slip between the concrete substrate and the FRP strip due to the behavior of fasteners. The proposed flexural model, coupled with an appropriate computation algorithm, is able to predict the fundamentals of flexural behavior of RC members strengthened with MF-FRP strips in terms of serviceability limit state, such as load vs. deflection curves, strain profiles and curvatures. A comparison between the analytical predictions and the experimental results has been performed to validate the proposed model. The comparison shows a good agreement between the analytical predictions and the experimental results.

Experimental tests performed on scaled masonry buildings provide key information to improve the knowledge under seismic actions. Masonry buildings behavior is strongly influenced by their physical and mechanical parameters under dynamic actions. In fact, the actual structural behavior is very complex to predict due to the significant variability of the input parameters and the strong heterogeneity of masonry. Furthermore, the behavior of masonry buildings is often influenced by the interaction with adjacent building units. In this context, the SERA AIMS project aims to improve knowledge on the interaction between adjacent buildings. In order to assess the seismic capacity of masonry structures and their damage evolution, nonlinear models often require a numerical calibration of nonlinear parameters. Simplified Finite Element (FE) models, with some very simple assumptions, can be more suitable for complex problems like as the interaction between adjacent building aggregates. The low initial knowledge level in the SERA AIMS blind competition favored simple assumptions. The availability of simple models allowed to perform consecutive time histories including the cumulative effects of previous signals. In fact, the tested prototype was subjected to many replicas. The masonry structure and the crucial interfaces between the units have been modelled by means of nonlinear elements according to the reduced knowledge level at the blind prediction stage. The main goal was to estimate the key information of a masonry building under seismic action like as: triggering and the type of damage at the most stressed areas and therefore the load threshold at which evident damage is expected. Global FE model provides information on the global behaviour (in plane behaviour), while, according to the failure models typically found in masonry buildings, kinematic analyses have been performed to assess the out of plane (local) behaviour, too. The numerical results obtained by the preliminary analysis have been compared with the experimentally detected damages. The simplified approach, based on limited information without calibration, discussed in this paper, represents a useful support tool to design dynamic tests on full-scale or scaled masonry buildings, but also to assess the vulnerability of real masonry structures.

The structural and seismic fragility assessment of minor historical centers of the Inner Peripheries of Italy is a key phase of the preservation process of the historical and cultural features of a portion of the Italian building stock, whose reuse is crucial for the reversal of shrinking trends and the stimulation of population growth. In this framework, the opportunities offered by digital crowd-sourcing technologies with respect to performing probabilistic structural safety assessment at a large scale are investigated herein. The objective of this research was to exploit data and information available on the web such that the key building features of an area of interest are collected through virtual inspections, historical databases, maps, urban plans, etc. Thus, homogeneous clusters of buildings identified in the area of interest are catalogued and associated with specific building classes (chosen among those available in the literature), and the buildings’ levels of seismic fragility are determined through the development of fragility curves. The research outcomes show that the proposed approach provides a satisfactory initial screening of the seismic fragility level of an area, thus allowing for the identification of priority zones that require further investigations or structural interventions to mitigate seismic risk.

A diffuse and continuous monitoring of the in-service structural response of buildings can allow for the early identification of the formation of cracks and collapse mechanisms before the occurrence of severe consequences. In the case of existing masonry constructions, the implementation of tailored Structural Health Monitoring (SHM) systems appears quite significant, given their well-known susceptibility to brittle failures. Recently, a new sensing technology based on smart bricks, i.e., piezoresistive brick-like sensors, was proposed in the literature for the SHM of masonry constructions. Smart bricks can be integrated within masonry to monitor strain and detect cracks. At present, the effectiveness of smart bricks has been proven in different structural settings. This paper contributes to the research by investigating the strain-sensitivity of smart bricks of standard dimensions when inserted in masonry walls subjected to in-plane shear loading. Real-scale masonry walls instrumented with smart bricks and displacement sensors were tested under diagonal compression, and numerical simulations were conducted to interpret the experimental results. At peak condition, numerical models provided comparable strain values to those of smart bricks, i.e., approximately equal to 10−4, with similar trends. Overall, the effectiveness of smart bricks in strain monitoring and crack detection is demonstrated.

Structural safety assessment of urbanised areas exposed to seismic risk is a complex task and can be approached at different scales. Fragility functions are the most effective tool to perform an estimation of the structural risk, since they describe the exceeding probability of the limit state of interest given a level of ground shaking. The formulation of a fragility function is based on the selection of an Intensity Measure of the ground shaking, commonly represented by peak-ground or spectral parameters or by macroseismic intensity grades. In the present paper, a novel approach to estimate the seismic vulnerability at a large scale of urbanised areas is presented. The scenario earthquakes are selected according to the current formulation of the seismic hazard disaggregation provided by National and International codes, i.e. through the disaggregation in terms of magnitude (M), epicentral distance (R) and number of standard deviation from the median ground motion (ε). To this aim, a vectorial seismic Intensity Measure is assumed to compute structural safety at large scale, and a change of variables is made to turn the traditional fragility curve into a matrix. Typological fragility matrices are processed and combined to define the so-called Urban Fragility Matrices, representative of the vulnerability of selected urban sectors. The procedure is then implemented and validated referring to the city of Pozzuoli (Southern Italy) and its effectiveness validated with reference to the damage survey relative to the 4th October 1983 seismic event which struck the city, resulting a good matching between predicted and observed scenarios.

This paper investigates the role of the horizontal axial force on the in-plane shear and flexural strength of masonry spandrels subjected to seismic actions. Strength criteria included in the main national and international codes take into account for geometrical and material properties, but valuable considerations about the influence of the horizontal axial force are missing. Nevertheless, experimental programs and post-earthquake damage scenarios proved that the horizontal axial force within the spandrels can be also significant under seismic actions, especially when they are surrounded by strength and stiff vertical piers or when significantly compressed by the effect of tensile-resistant elements. As main purpose, the strength criteria proposed by the Italian code for the spandrels have been revised accounting for the effect of the horizontal axial force on its shear and flexural strength. A database containing experimental tests conducted on masonry spandrels was elaborated and used to compare experimental with theoretical results. Outcomes showed that the revised criteria match satisfactorily the experimental results when significant axial forces affect the spandrels, both in terms of strength and failure mechanism. Contrariwise, existing code formulations are representative for the spandrels subjected to low axial force such that rocking or pure shear mechanisms tend to prevail.

The paper presents the experience of a working group within the Rilem Technical Committee 223-MSC ‘Masonry Strengthening with Composite materials’, aimed at developing a standardized, reliable procedure for characterizing the bonding mechanism of masonry elements strengthened with composite materials under shear actions. Twelve laboratories from European universities and research centers were involved. Two different set-ups were compared, for single-lap and double-lap shear tests (the latter in two versions). Four kinds of fiber fabrics, i.e., glass, carbon, basalt and steel, were applied with epoxy resins (wet lay-up system) to clay brick units, for a total of 280 monotonic tests. The results provided information regarding the response of externally bonded-to-brick composites in terms of observed failure mechanisms, load capacity, effective transfer length, and bond shear stress-slip behavior. The test results of the twelve laboratories constitute a set of statistically representative data which may conveniently be used for setting appropriate design provisions and guidelines.

The increasing exposure of Mediterranean coastal regions to tsunami risk, also due to climate changes, leads to the need of tools to support disaster risk management and loss assessment. This study presents a tsunami structural vulnerability model for Italian residential buildings based on numerical analysis and Monte Carlo simulation. Starting from national building census repositories, typical building typological classes and main attributes are defined. Monte Carlo simulation is performed to simulate building stocks statistically representative of existing Italian residential buildings, and analytical models are adopted for the structural damage assessment of such buildings under tsunami inundation. The structural damage is classified according to a unified damage scale adapted for different structural typologies, and a damage index is computed to describe the structural vulnerability to tsunami hazard. Based on the analytical vulnerability curves, tsunami vulnerability classes for Italian residential buildings are finally proposed to be used for an informed definition and prioritisation of risk mitigation strategies. Results from this study can be also applicable to other Mediterranean regions with a similar construction practice.

Since the concrete cover cracking is the earliest visible manifestation of corrosion, a relationship between crack opening and corrosion level can be a useful non-destructive tool to estimate the degradation level of an existing RC member. In the present paper, the predictive formulations available in the scientific literature estimating the crack width due to a given corrosion level are accurately described and their reliability is evaluated by a statistical analysis of the error in the predictions. At this aim, an extensive dataset on crack openings of artificially corroded RC specimen reinforced with a single bar, or more bars with large spacing, has been collected. Finally, a novel relationship for the assessment of the corrosion degradation from the surface cracking is presented and validated.

Seismic vulnerability of reinforced concrete (RC) buildings is strongly influenced by beam-column joints. Horizontal and vertical structural members converge in beam-column joints, as extremely delimited areas where the internal forces in concrete core and reinforcing bars have elevated stress gradients. In order to fully understand the seismic behavior of RC buildings and the related failures of T- and X-shaped beam-column joints (external corner and internal-positioned), an analytical model of RC joint behavior is proposed in a unified and simplified way. The equilibrium equations of cracked joint portions allow the assessment of internal stresses’ evolution at increasing values of column shear forces. In this way, the strength hierarchy is evaluated in terms of capacity for the different potential failure modes. This can drive, as a useful tool for designers, the design of new efficient structures or the assessment of existing ones to occur, with subsequent interventions to move an initial undesired failure mode to a more suitable one. Nearly 500 experimental results of tests available in the literature are compared with the analytical predictions of the proposed model.