Italian Code Research Articles

Possible measure of soil factors in the Italian seismic code

AbstractThe Italian seismic code provides a simplified approach to account for the effect of local seismostratigraphical configuration on the expected ground motion. This approach, common with other seismic codes, provides specific ‘soil factors’ as a function of a set of reference subsoil conditions (soil classes): these factors are considered in 1D subsoil configurations to modify the uniform probability hazard spectrum deduced from probabilistic seismic hazard at reference soil conditions. It is inferred that, to provide a coherent management of uncertainty affecting the response spectrum to be used for the design, the contribution of uncertainty affecting soil factors must be carefully considered to avoid biases in the hazard evaluation. In the present study, variability of soil factors representative of each soil class has been explored by numerical simulation relative to many seismostratigraphical configurations inferred from seismic microzonation studies available in Italy relative to 1689 municipalities. This analysis shows that variability of soil factors is of the same order of magnitude of variability affecting reference response spectra, which implies that the former cannot be neglected as presently happens in the common practice. It is also shown that neglecting this contribution can lead to underestimate the impact of subsoil configuration on the regularized response spectrum provided by the norm, in particular, in the short period range.

Shear performance and capacity of FRP reinforced concrete beams: Comprehensive review and design evaluation

To enhance the durability of concrete structures in harsh environments, replacing steel bars with FRP bars is judged a feasible method. The low elastic modulus and transverse strength of FRP bars result in the weak shear capacity of concrete beams reinforced with FRP bars. Reviewing and summarizing existing literature are important for addressing this challenge. The research progress on the shear behaviour of concrete beams reinforced with FRP bars was systematically described from two aspects in this paper. In the aspect of literature review, shear mechanisms and main influencing factors of concrete and FRP stirrups were summarized. In addition, achievements and shortcomings of existing literature were summarized, and potential research directions were pointed out. In the aspect of design method evaluation, a database containing 525 samples was established and calculation models of shear capacity of concrete beams reinforced with FRP bars in seven codes were evaluated. Evaluation parameters mainly included shear span ratio, effective height, and maximum strain of FRP stirrups. Based on the calculation model in Italian code CNR DT203-06, an optimized model was proposed to improve the accuracy in predicting concrete shear contribution. The review and evaluation in this paper had important reference significance for improving the design level of concrete structures reinforced with FRP bars and promoting the engineering application of FRP bars.

Mechanical characterisation of stone masonry of Batticaloa fortress, Sri Lanka

Historical fortresses, traditionally constructed with stone masonry, require careful preservation to uphold their cultural significance. Understanding the material and mechanical characteristics of the stone masonry assemblies used in these fortresses is crucial for their conservation. Hence, an inclusive approach was taken to analyse the mechanical attributes of stone masonry utilised in a specific historical fortress in Sri Lanka. This comprehensive method involved two main steps: (a) expert evaluation and (b) non-destructive testing (NDT) techniques. This study incorporated well-established expert evaluation methods tailored for historical masonry, such as the masonry quality index, the geometric index and mechanical characterisation based on the Italian code for construction specifications. Additionally, two NDT methods – rebound hammer and ultrasonic pulse velocity testing – were employed alongside expert evaluations to understand thoroughly the mechanical properties of the stone masonry assemblies. The investigation focused on stone walls in ten different areas of the fortress, all of which were constructed using irregular and pebble stone masonry. The results obtained through NDT methods were then cross-referenced with the expert evaluations. This integrated approach effectively outlined the properties of the stone masonry assemblies, including compressive strength, Young’s modulus and shear modulus, providing a comprehensive characterisation of the structures.

The new Italian Code of Medical Ethics

The presentation of the new Italian Code of Medical Deontology would require a broad and comparative consideration with the previous text issued by the National Federation of Medical Boards in 1978, to note the points of development in these ten years, in which new problems and new demands have emerged in the world of medical culture and science.

Integrating Sonic Pulse Velocity Tests with Masonry Classification for Heritage Conservation: An Insight from On-Site Diagnostic Campaigns

ABSTRACT The preservation of architectural heritage relies on a comprehensive understanding assisted by diagnostic procedures. Among non-destructive techniques, the Sonic Pulse Velocity Test (SPVT) qualifies the compactness of a masonry wall through elastic wave transmission. However, it does not directly estimate any mechanical parameters. This study presents findings from a database of 346 direct SPVTs carried out over thirteen years on both listed and ordinary buildings. Results were categorized based on masonry type according to the Italian building code, to derive information about construction quality and relate SPV with building features. Tests performed on 37 masonry panels strengthened by grout injections also confirmed the validity of SPVT in evaluating the effectiveness of the intervention. Furthermore, the Masonry Quality Index (MQI) method permitted to refine the masonry type definition through the judgment of the units’ arrangement. MQI and SPVT results were also combined by statistical analysis. These findings aim to increase comprehension of the different types of existing masonry capacity and contribute to engineering assessments for ensuring the structural safety of historical buildings.

Fragility and vulnerability models for poorly-detailed infilled buildings accounting for building-to-building and masonry infill variability

While in poorly-detailed masonry-infilled reinforced concrete (RC) buildings the significance of masonry infills is acknowledged, less attention has been paid to the variability surrounding their mechanical properties and its potential impact on fragility and, consequently, vulnerability models to be used in seismic risk estimation. This study addresses this gap by proposing updated fragility and vulnerability models of existing poorly-detailed masonry infilled and pilotis RC frames that consider the variability in building layout and infill properties. A large building portfolio, representative of those designed according to Italian codes between 1970 and 1980, is selected as case study, incorporating building-to-building variability through various geometrical configurations. Updated modelling uncertainty parameters, specifically derived for existing infilled RC frames, are used, including the variability surrounding the properties of different infill typologies and the occurrence of RC frame shear failure. The portfolio was analysed through multiple-stripe analyses, followed by the development of upgraded fragility models for buildings with different heights and geometrical configurations. Finally, the corresponding vulnerability models were derived using damage-to-loss models calibrated with post-earthquake observation damage data from the 2009 L'Aquila earthquake. The updated fragility and vulnerability curves can be used for more refined seismic risk estimates of large building portfolios, that account for building-to-building and infill-to-infill variability, revised modelling uncertainty estimates and a more robust intensity measure (AvgSa).

Seismic Reliability Maps of Code-Compliant Italian Reinforced-Concrete Bare and Infilled Frame Buildings

The present study illustrates the main results of an extensive campaign of numerical simulations aimed at quantifying the seismic reliability of reinforced concrete (RC) bare and masonry-infilled frames compliant with the current Italian Building Code. For this purpose, a set of different residential-use archetype structures are considered, and a prototype seismic design-assessment tool is created to quantify their performance with respect to the relevant limit states, deriving fragility curves via the execution of several non-linear time-history analyses (NLTHAs). The fragilities are subsequently combined with the hazard curves derived for each of the over 8000 Italian municipalities based on the national seismic hazard model currently in force to obtain the respective seismic mean failure rates across Italy. The seismic reliability maps obtained for the investigated code-compliant designs highlight how the current Italian Building Code fails to provide uniform seismic safety across Italy, showing—on the contrary—a strong hazard-dependency. The results are finally used to calibrate regression laws able to correlate the seismic mean failure rates with an intensity measure representative of the seismic hazard.

Extending the concepts of response spectrum analysis to nonlinear static analysis: Does it make sense?

The study presented in this paper aims to assess the recent novelties proposed by new generation building codes about the extension of some concepts at the base of linear analyses to the procedures of nonlinear static analysis. The nonlinear static analysis (pushover) is an extensively adopted approach by engineers and practitioners for purpose of assessing the seismic performance of new and existing buildings, although several drawbacks characterize this methodology, as evidenced by the existing scientific literature. In order to overcome the well-known limitations characterizing nonlinear static analysis, and to offer an alternative to nonlinear dynamic analysis, the recent upgrades of some building codes, such as the Italian one, provide different rules to employ in nonlinear static procedures. Among these new provisions, one regards the possibility to use a horizontal load profile proportional to the storey forces derived from a response spectrum analysis in all cases (i.e., also for irregular buildings). The main goal of this study is to demonstrate the reliability of this new load profile when strong irregularities arise. To this scope, the seismic behaviour of a sample of archetype buildings characterized by increasing in-height irregularity was investigated. The sample of buildings was subdivided in two subsets characterized by different design levels, one conceived by considering the prescriptions of the new Italian building code and one designed according to the oldest Italian building code (i.e., without considering anti-seismic details). The sample of buildings, simulating new and existing cases, was firstly modelled and after investigated through nonlinear static analyses by employing both traditional (i.e., inverse triangular- and uniform-like) and new (i.e., derived from response spectrum analysis) load profiles. After, nonlinear dynamic analyses were run, in order to assess the capacity of both traditional and new load profiles to capture the dynamic behaviour of the investigated archetype buildings. The performed analysis campaign demonstrated the efficiency of the new load profile proposed by the code, and the output of the work provided an answer to the main question posed by the authors: does it make sense to extend the concepts of response spectrum analysis to nonlinear static analysis?

Simulation of the Collapse Mechanism of a Minaret under the Effect of Strong Wind

In this study, the collapse mechanism of a destroyed minaret under strong wind influence was simulated to understand such structural interactions and identify potential risky regions. Wind profiles were defined according to Eurocode and Turkish Standards and were used in Computational Fluid Dynamics analyses. The pressure and suction stresses obtained with these wind analyses were applied on the minaret’s surface with Abaqus and the nonlinear finite element analyses were performed. As a result of the numerical analyses, displacements, stresses, plastic strains, and damages were obtained and results were comparatively presented. The results obtained with both standards are quite close and top displacements exceed the limit value specified in the Italian Building Code and Eurocode 8. Besides, many mesh elements in the minaret’s transition segment were damaged with tension stresses in nonlinear finite element analyses. Finally, the minaret’s failure behaviour was successfully simulated with the used methods.

Site-specific traffic modelling and simulation for a major Italian highway based on weigh-in-motion systems accounting for gross vehicle weight limitations

The present-day road traffic with the persistent change in the type and volume of vehicles needs to be specifically investigated for effective safety management of aging highway infrastructures. Actual traffic data can be implemented in refined procedures for stochastic simulation of road infrastructure performance, structural health monitoring (SHM), definition of weight limits on highways, and traffic-informed structural safety checks. While weigh-in-motion (WIM) systems had been widely used in many countries, their installation on Italian highways was mostly discussed and carried out only after the catastrophic collapse of the Polcevera bridge in 2018. This study presents a statistical data analysis, probabilistic models, and a simulation procedure for highway traffic, based on measurements of two WIM systems located along European route E45 close to Naples, Italy. Different limitations to maximum gross vehicle weight (GVW) were enforced at the locations of the two WIM systems, according to the Italian road code and the Italian guidelines for risk classification, safety assessment and monitoring of existing bridges, respectively. WIM data sets were filtered to exclude erroneous traffic data and vehicle classes defined according to the number of axles and axle distance were statistically characterised, allowing the derivation of probabilistic models for all traffic parameters of interest. A simulation methodology to generate random traffic load from the WIM data is also presented for its possible use in probabilistic performance assessment and traffic informed SHM of road infrastructures such as bridges.

Confinement effects within the seismic design of reinforced concrete frames: reliability assessment and comparison

The current Italian code “NTC2018” and Eurocode “EC8” provide specific design requirements in terms of flexural overstrength factors for reinforced concrete (RC) buildings in seismic areas. This study proposes to improve the design methodology by including explicitly the confinement effects within the seismic design of a new regular RC frame due to their influence on the capacity design principles (at structural and member level). Specifically, the seismic performance of a RC frame designed according to codes is compared, in reliability terms, with the one of the same frame designed including the concrete confinement effects. Moreover, a comparison between three constitutive models for confined concrete is performed. Selecting L’Aquila (Italy) as reference site, the two design methodologies combined with the three confinement models are numerically implemented. Scaling 30 non-frequent natural ground motions to increasing seismic intensity measures, according to the site seismic hazard, non-linear incremental dynamic analyses (IDAs) have been developed. Assuming the interstory drift indices as engineering demand parameters, the peak responses have been fitted through log-normal distributions to define IDA curves. Subsequently, appropriate limit state thresholds have been adopted to define the seismic fragility curves. Finally, through the convolution integral and Poisson model, the seismic reliability curves have been derived showing the importance of the proposed design methodology. In fact, for the frame under investigation, the seismic performance strongly improves in terms of ductility respecting all the reliability objective levels if the confinement effects are explicitly considered in the seismic design. Furthermore, the different confinement models provide similar results when the proposed seismic design is adopted, implying a reduction of the model uncertainty.

Prediction of the fundamental period of infilled RC framed structures considering the maximum inter-story drift at different design limit states

The fundamental period of vibration is a key parameter for the spectral approach to seismic design of structures, as it significantly affects the evaluation of the response spectra values. Even though infill elements can significantly increase a building's lateral stiffness, they are not always considered in the structural design process. This is particularly significant at the damage limitation states considered by the European (Eurocode 8) and Italian (NTC2018) seismic codes, where mostly elastic behaviour is expected. Non-structural elements, in fact, can influence the natural elastic period of buildings, determining spectral accelerations different from those evaluated by the simplified formulas provided by the seismic standards and related guidelines. This research aims to develop novel simplified period-height relationships to estimate the fundamental period of vibration of infilled Reinforced Concrete (RC) framed buildings more accurately at various limit states, as a function of inter-story drift value. To collect information about the fundamental period of structures in different damage conditions, several experimental campaigns involving more than 330 RC framed structures have been considered. Nonlinear numerical analyses have also been performed to integrate the database, especially for the Ultimate Limit State (ULS), considering different number of floors, infill distributions, and geometries. Collected data have been parametrized as a function of the damage level suffered by the considered structures, and different empirical period-height formulations have been defined for each limit state. The proposed relationships have been compared with those found in international, European, and national seismic codes, as well as with simplified formulations in previous literature studies. In particular, the results strongly suggested that the fundamental periods estimated according to the EC8 formulation, overestimates the experimental data, resulting in a potential underestimation of the seismic forces and therefore of damage to non-structural elements. To quantify the differences in spectral acceleration and spectral displacement at all design limit states, some examples have been proposed, considering different Italian seismic zones.

Safety Evaluation of Existing R.C. Buildings: Uncertainties Due to the Location of In Situ Tests

The paper aimed to investigate the influence, on the assessment of the structural safety level of an existing r.c building, of the different choices that the technician in charge of a structural evaluation (the “analyst”) can make regarding the structural elements to be tested to obtain a prescribed level of knowledge. To this end, the case study of a reinforced concrete framed structure built in the 1960s in Italy was investigated by means of numerical analyses. The probability distribution of the estimated safety levels was evaluated in the paper by means of a Monte Carlo approach, considering the alternative selections of elements done by a large number of analysts, and the probability of unsuccessful safety estimations is discussed for the knowledge levels considered in the Italian technical codes and the Eurocodes.

Assessment of Non-Linear Analyses of RC Buildings Retrofitted with Hysteretic Dampers According to the Italian Building Code

While the use of steel hysteretic dampers has spread in the last decade for both new and retrofitted constructions, the Italian Building Code (IBC), as well as the Eurocode 8, does not provide specific recommendations for the design and verification of structures equipped with this technology. Due to their strong non-linear behavior, the effectiveness of the design with these systems must be verified through non-linear analyses. Non-Linear Time-History analyses (NLTHAs) are the most reliable method, but they are computationally expensive. The aim of the study is to investigate the reliability of non-linear static procedures, allowed by the IBC as an alternative to NLTHAs, for the analysis of buildings equipped with hysteretic devices provided with high damping capability. A parametric study is conducted on two reinforced concrete residential buildings, typical of the Italian residential heritage, retrofitted with hysteretic braces characterized by different stiffness and ductility values. The retrofit design is verified using non-linear analyses, both static and dynamic, considering either natural or artificial accelerograms, as the IBC deems them as equivalent. Within this work, reference is made only to the IBC; however, given the significant similarity between the IBC and the European code, the outcomes are expected to have a broader impact and to be not limited to the Italian context. Therefore, although this work is a preliminary study, it is believed to offer some initial insights on the topic and serve as the foundation for a more in-depth study that could lead to a regulatory revision on the subject.

Validation of numerical results of complex seismic analysis through simple analytics

The paper analyzes the application of the numerical findings of the program, which is becoming increasingly difficult for civil and structural design. Since, as in many other countries, the verification of design using a software model is now required by current Italian codes as well. Given this, the structural engineer must provide a technical report using a licensed software tool, attached to other project documents to get the Seismic Authorization at the local Civil Engineering Department offices. Following a brief explanation of structural analysis methodologies, this study presents a criterion for assessing the applicability of numerical findings obtained using any structural software. Three case studies of this criterion are shown to demonstrate how to check them using simple manual calculations: (i) the normal stress in RC columns subjected to gravity loads; (ii) the periods of vibration, participating masses, and seismic base shear derived from dynamic modal analysis; and (iii) the main parameters characterizing the pushover curves of existing buildings. Finally, this work underlines the significance of confirming the application of numerical results obtained by software in civil and structural design. The offered criteria and scenarios exhibit realistic techniques to ensure accuracy and reliability in structural performance assessment, according to the structural requirements imposed by current codes in Italy and similar countries.

Influence of chloride-induced corrosion on the traffic vulnerability of simply supported Italian PC bridges: a preliminary study

In Italy, a large part of road bridges was built after the Second World War, mainly with Reinforced Concrete (RC) or Prestressed Concrete (PC) simply supported decks. Most of the bridges currently in service have been designed with outdated codes and could be inadequate to modern heavy traffic loads. Furthermore, their structural performance decrease over time due to ageing effects, like steel corrosion.Bridges are often exposed to chlorides from de-icing salts or marine environment; chloride diffusion in concrete can induce pitting corrosion of steel reinforcing, decreasing the structural resistance of bridge elements. As part of a broader study on the structural risk of existing bridges with respect to traffic loads, it is certainly of interest to investigate the influence of chloride-induced corrosion on the risk itself.In this preliminary study, four sets of simply supported decks made of precast PC beams and a cast in-situ RC slab were designed according to outdated Italian codes relating to different construction periods (60s, 70s, 80s, and 90s); each set is composed by bridges with different span, width, number of main girders and transverse diaphragms. The deck design took into account only the bending failure of the main girders, in order to determine the minimum amount of strands and steel reinforcements required. The vulnerability to traffic loads is evaluated with respect to the bending moment resistance of the main girders. Monte Carlo simulations were performed to evaluate the decrease over time of the resisting bending moment of the main girders, taking into account literature models for estimating the time to corrosion and corrosion propagation both in strands and in steel reinforcements.

Seismic Risk Analysis of Existing Link Slab Bridges Using Novel Fragility Functions

In this paper, a comprehensive probabilistic framework is proposed and adopted to perform seismic reliability and risk analysis of existing link slab (LS) bridges, representing a widely diffused structural typology within the infrastructural networks of many countries worldwide. Unlike classic risk analysis methods, innovative fragility functions are used in this work to retrieve more specific and detailed information on the possible failure modes, without limiting the analysis to the global failure conditions but also considering several intermediate damage scenarios (including one or more damage mechanisms), and providing insights on the numerosity of elements involved within a given damage scenario. Reliability analyses are performed on a set of LS bridges with different geometries (total lengths and pier heights) designed according to the Italian codes enforced in the 1970s. Accurate numerical models are developed in OpenSees and Multiple-Stripe nonlinear time–history analyses are carried out to build proper demand models, from which fragility functions are determined according to two limit states: damage onset and near-collapse. Mean annual rates of exceeding are thus estimated through the convolution between the hazard and the fragility. The results shed light on the main failure mechanisms characterizing this bridge typology, highlighting how different levels of risk (hence safety margins) can be associated with failure scenarios that differ in terms of elements/mechanisms involved and damage extension. Such a higher level of detail in the risk analysis may be useful to better quantify post-earthquake consequences (e.g., costs and losses) and define more tailored retrofit interventions. A comparison of the reliability levels associated with bridges of the same class with different geometries is finally presented.

On the Use of Accelerometric Data to Monitor the Seismic Performance of Non-Structural Elements in Existing Buildings: A Case Study

Monitoring of non-structural elements is not usually implemented, despite the seismic vulnerability of these components and the significant cost associated with their replacement in case of damage. By exploiting the limited cost of commercial sensors, accelerometers were installed in an existing building to compare accelerations applied to non-structural elements in case of an earthquake with critical acceleration thresholds. The exceedance of these thresholds would indicate a possible danger for the occupants and the need for a more detailed inspection of the element, guiding prioritisation strategies in the aftermath of the earthquake. Furthermore, the real-time probabilistic assessment of potential damage to non-structural elements can serve to identify escape routes and facilitate rescue operations. Critical acceleration thresholds were defined from probabilistic considerations on the expected seismic performance of each typology of non-structural element, described by appropriately selected fragility curves. The feasibility of the proposed procedure was tested by comparing the identified acceleration thresholds with the design values of floor acceleration provided by the Italian Building Code. As a further application, critical acceleration values of the different non-structural elements were compared with a set of real floor acceleration values recorded at the top level of reinforced concrete buildings, highlighting critical non-structural element typologies.

Seismic Behavior and Modeling of Ductile Composite Steel-Trussed Concrete Beam to Column Joints

This paper presents an experimental and numerical study on a ductile beam-column connection between a composite reinforced concrete truss (CRCT) beam and a reinforced concrete (RC) or concrete-filled tube (CFT) column subjected to bending and shear loads. Two experimental models with different beam-column joint testing schemes, extracted from the same prototype three-dimensional structure designed according to the rules of the capacity design provided by seismic code, were subjected to quasi-static cyclic tests by applying gravitational loads and the horizontal seismic force. The main objective of this paper is to verify the ductile behavior of both specimens experimentally and to simulate the experimental global and local responses by nonlinear static analysis, considering different modeling approaches. The comparison between the experimental and numerical results highlights, for both models considered, the ductile and dissipative capacity of the connection system, designed following the criteria of the hierarchy of resistances proposed by the current Italian code. The results of different experimental setups demonstrate that the tests can be repeated and the results can be reproduced by means of simple nonlinear models.

Reliability Estimation of the Compressive Concrete Strength Based on Non-Destructive Tests

The uncertainty in the concrete compressive strength is one of the most challenging issues in safety checking of existing reinforced concrete (RC) buildings. The concrete compressive strength used in the assessment can highly influence the vulnerability results and thus the retrofit strategies. The need to use less expensive and less invasive in situ measurements such as the non-destructive tests should be balanced with a careful check of their structural reliability. The compressive concrete strength is characterized herein based on a large database of both in situ destructive and non-destructive results measured on the same structural members. The data are obtained from existing RC buildings mainly located in the Campania region, Southern Italy. Probabilistic linear and multilinear regression models are developed for calculating the compressive concrete strength based on non-destructive tests. Furthermore, the implementation of the concrete strength based on ultrasonic test results are investigated together with the relative measurement error through a fully probabilistic workflow. Accordingly, the relative weights of non-destructive data for calculating concrete compressive strength are estimated and compared with those recommended by the Italian national code. The results demonstrate that the effective weights of the non-destructive data are very close to the code-based recommendation.