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Recent seismic events worldwide have demonstrated the high vulnerability of existing school buildings and the urgent need to have reliable tools for the rapid seismic performance assessment and damage and loss quantification. Indeed, the significant damage observed on structural and non-structural components may have a significant impact in terms of direct and indirect losses making critical the recovery of stricken communities. Although a significant amount of work has been done in developing fragility curves for the residential building stock, only few contributions clearly refer to school buildings that significantly differ in terms of the main characteristics from the residential ones. This research work proposes fragility curves for reinforced concrete and unreinforced masonry public school buildings typical of the Italian building stock, based on the damage observed in the aftermath of the 2009 L’Aquila earthquake. A comprehensive and unique database including data on damaged and undamaged school buildings (2037 records) in the Abruzzo region was built using data from four different sources. Due to limited amount of data, the fragility curves can be very sensitive to the method adopted for their derivation, thus three different approaches (i.e. empirical, empirical-binomial, heuristic) are considered in the paper and the results are compared. Finally, a direct comparison with fragility curves available in the literature for the Italian residential building stock is presented.

As an outcome of a recent European research project, the modelling of the response of flat slab structures for seismic and cyclic loading was the object of a blind competition. No other blind tests are available in the literature on this topic. The test results concern a full-scale, two-storey, three-by two bay reinforced concrete flat slab frame. The seismic tests were carried out using a hybrid pseudo-dynamic test up to the ULS design excitation. The cyclic test reached a drift capacity of 2.5% and 6% in two concatenated tests. A synthesis of the models of three participants is provided, with one 3D NLFE (Nonlinear finite element) models and two slab and frame models. The CSCT (Critical Shear Crack Theory) model included in the fib MC2010 was adopted in the two latter to predict punching failure. The results are presented and discussed. Conclusions are drawn on research developments and practical approaches.

Post-earthquake observations have outlined the poor seismic performance of substandard reinforced concrete (RC) beam-column joints in existing buildings. They often exhibit significant cracking even under moderate intensity earthquakes, compromising the seismic performance of the entire building. This makes the quantification of their residual capacity and the definition of reliable repairability thresholds critical. Different approaches are available in the literature to establish the repairability of RC joints. However, a simple crack width-based criterion is required for practitioners during in-situ inspections. This study deals with the definition of crack width-based fragility curves relying on numerical analyses. Those are carried out by using the validated finite element (FE) models, being capable of reproducing the initiation and development of cracks in RC joints. To this end, the uncertainties in material properties, influencing the seismic performance of structural components, are accounted for different joints. In particular, experimentally validated FE models are evolved to stochastic level by generating random variables of material properties with the stratified sampling scheme. Fragility curves representing a certain level of probability of exceeding the defined crack width at the joint back, joint core, and beam-to-joint interface are developed. An application of the proposed methodology for in-situ inspections is also presented, and the results of in-situ measurements of residual crack width from real buildings damaged by recent earthquakes are used for the validation.

International audience

Recent seismic events worldwide demonstrated the high vulnerability of existing school buildings and the urgent need to have reliable tools for the rapid seismic performance assessment and damage and loss quantification. Indeed, the significant damage observed on structural and non-structural components may have a significant impact in terms of direct and indirect losses making critical the recovery of stricken communities. Although a significant amount of work was done in developing fragility curves for the residential building stock, only few contributions clearly refer to school buildings that significantly differ in terms of the main characteristics from the residential ones. This research work proposes fragility curves for reinforced concrete (RC) and unreinforced masonry (UMR) school buildings typical of the Italian construction standard, based on the damage observed in the aftermath of the 2009 L’Aquila earthquake. A comprehensive and unique database including data on damaged and undamaged school buildings (2,037 records) in the Abruzzo region was built using data from four different sources. Due to limited amount of data, the proposed curves can be very sensitive to the adopted approach, thus three different approaches (i.e. empirical, empirical-binomial, heuristic) are considered and the results are compared. Finally, a direct comparison with fragility curves available in literature for residential buildings typical of the Italian construction standards is proposed.

The existing reinforced concrete buildings typical of the Mediterranean area commonly have poor seismic performance and high vulnerability to the seismic events. As demonstrated by recent post-earthquake reconstruction processes, they commonly exhibited significant damage to structural components and to infills and partitions resulting in very high repair costs. This suggests that effective seismic strengthening interventions should aim at both improving the safety and reducing the expected annual losses. Nowadays, the seismic retrofitting of existing RC buildings by using base isolation is becoming popular because of the high effectiveness as seismic protection strategy. However, the high costs of installation are limiting the widespread in the common design practice. In this context, a unique design parameter capable of combining the increasing seismic safety, the cost of installation and the reduction of the expected losses can be useful to draw simple cost-benefits considerations. This research work proposes a PBEE-based methodology to quantify the Pay-Back Time (PBT) of seismic retrofit solutions for existing RC buildings. The non-linear response of base isolated building is assessed and a comparison with different strengthening solutions is proposed to show the applicability of the PBT as a unique design parameter to select the most effective retrofit solution. A database of 59 RC buildings retrofitted by using base isolation during the L’Aquila reconstruction process, where actual retrofit costs are available, is used for the validation. Finally, these data are used to calibrate a simple formulation of the PBT to be used in the design practice.

Existing reinforced concrete buildings were mainly designed with old code provisions. This resulted in lack of proper seismic details and, in turn, the occurrence of premature brittle failures as frequently observed in the aftermath of recent seismic events. The shear failure of the joint panel is one of the main reason limiting the seismic performance of existing structural systems. Several retrofit solutions were proposed in the recent years to improve the joint panel shear strengthening and, nowadays, composite materials are frequently used in the common design practice. The widespread use of fibre-reinforced cement composites (FRCC) and high-performance fibre-reinforced cementitious composites (HPFRCC) opened new frontiers in the design of the shear capacity of RC members. The high tensile strength, toughness, and tolerance for damage make these materials attractive for the use in earthquake-resistant structures, with emphasis on RC members with shear-dominated response. Although several experimental tests demonstrated the effectives of these materials in the seismic retrofit of existing beam-column joint a proper design formulation is still lacking. This research paper presents a novel procedure for the design of the exterior FRCC jacketing of poorly detailed on beam-column joints. A mechanical model based on the principal tensile stress approach is proposed. The model is later validated against a comprehensive database of experimental tests at global and local level. The proposed procedure allows the designers to calculate the thickness of the FRCC jacketing to avoid the joint panel shear failure and promoting a more ductile failure mode.

Base isolation applications are becoming popular in the seismic design of resilient structures and infrastructures. Even though the response of the bearings is widely studied under cyclic displacements, limited information is available for bearing response under sustained lateral loads. These types of loads can develop sustained lateral displacement in the bearing. During the holding time under sustained lateral displacement, the creep or stress relaxation may significantly change the properties of the bearings and may affect the response in the reloading stage. This research paper aims at assessing the influence of short-term lateral creep on the hysteretic response of rubber bearings, and ball rubber bearings. To this end, experimental testing on different elastomeric bearings under imposed lateral displacement is performed. For each device, the lateral response is measured, and the advantages and disadvantages are discussed in terms of strength, stiffness, energy dissipation and equivalent damping. The loss of load under sustained lateral displacement is experimentally assessed and the effects of creep in the design procedure of a base isolated system are discussed.

Recent earthquakes demonstrated that modern seismic design and retrofit of constructions should target damage containment to reduce the direct and indirect economic losses and downtime. In this context, the use of base isolation as seismic protection strategy is becoming popular. A variety of devices is available on the market. Elastomeric and metallic sliding devices are the most common type of isolators. Ball rubber bearings (BRBs) combine the practical use and the low maintenance cost of elastomeric bearings with a friction-based dissipation due to the steel balls of the inner core. Although many tests were performed to characterize the lateral response of BRBs, their stiffness, the maximum displacement capacity and the damping, further studies are needed to clearly identify the main variables and their effects on the lateral response. This research paper aims at developing a design-oriented formulation to estimate the equivalent damping, the characteristic strength and the lateral stiffness of BRBs. In order to calibrate and validate the proposed formulation, experimental tests are performed varying the axial load pressure and maximum imposed displacement. Furthermore, all the tests available in literature are collected in a unique database. Simple considerations on the influence of the different design parameters are discussed and used to calibrate reliable design formulations to be used in the design practice.

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution., Comment: Ariel Definition Study Report, 147 pages. Reviewed by ESA Science Advisory Structure in November 2020. Original document available at: https://www.cosmos.esa.int/documents/1783156/3267291/Ariel_RedBook_Nov2020.pdf/

Recent seismic events have demonstrated that the high vulnerability of existing reinforced concrete (RC) buildings is mainly due to a lack of proper seismic detailing and the employment of poor-quality concrete. The reconstruction process following the 2009 L’Aquila earthquake highlighted that strengthening these buildings using solutions based on fiber-reinforced polymers (FRPs) can be both efficient and cost-effective. Indeed, their light weight, ease of installation, and the availability of specific guidelines and standards strongly supported their use in design practices, where they were the strengthening technique employed the most. This paper analyses and discusses the data on the actual cost and effectiveness of FRP solutions for seismic strengthening of existing RC buildings. To this end, the large database relating to the L’Aquila reconstruction process was used to select 130 RC buildings strengthened with FRP systems or FRPs combined with other techniques. Details of direct costs, including at the member level, and the types and percentages of strengthened members are analysed for both local and global strategies. This study thus provides readers with valuable data for use in cost-benefit analyses of FRP systems schemes to mitigate seismic risk at large-scale.

Poor‐quality concrete and a lack of transverse reinforcement commonly characterize the reinforced concrete (RC) structures built during the past century in the Mediterranean area. However, very few experiments have investigated the performance of structural members of that kind. Moreover, the design of repair and retrofit solutions using available techniques could be challenging due to the weakness of the concrete substrate. This paper reports on the experimental response and the repair and retrofit of existing RC columns with poor‐quality concrete. In particular, it presents and discusses the outcomes of three tests on two RC columns extracted from a real building that was severely damaged by the 2009 L'Aquila earthquake and was, as a result, demolished. The concrete compressive strengths resulting from in situ and laboratory material characterization tests are used to predict the axial strength of the sampled columns. An innovative application of fiber‐reinforced cement composites (FRCC) for the repair and retrofit of damaged columns is proposed and validated experimentally. The results reveal that this material is effective when it comes to recovering and improving the axial capacity of damaged RC members. Practical suggestions to account for the confinement effect of the thin FRCC jacketing in available analytical formulations are discussed.

In order to deliver high contrast, high resolution images, a keypoint in future space telescopes is to implement a correction chain, composed by a WaveFront Sensor (WFS) and an active/deformable mirror (DM) running in closed loop. While the current baseline for WFS is mostly focused on PSF sensing, no or little attention has been paid to a crucial element: after an initial startup phase, a space telescope will be operating in quasi diffraction-limited regime, so that a WFS shall be able to stably measure nanometer-level aberrations. In this scenario, the aberration signal in the PSF is overwhelmed by the bright core and to get rid of the photon noise a long time integration is required, which is converted into a more stringent stability requirement for the DM. We propose the implementation of the pyramid WFS (PWFS), which has been already demonstrated on-sky for high contrast at large ground based observatories. In this paper we present numerical simulations of a PWFS controlling an active primary in space. We will show the signal measured by the pyramid when a offset is applied on the mirror and the closed loop performances. The results indicate that the PWFS is able to detect nanometer-level low spatial scale aberrations and drive the active mirror with an optical stability consistent with typical requirements.

Nowadays, most of the Italian existing reinforced concrete (RC) buildings have become obsolescent and not compliant with modern requirements in terms of seismic safety, energy efficiency and living comfort. Many of them require a deep renovation to comply with minimum acceptable targets. In the last decade, major economic resources have been invested for the reduction of energy consumption and polluting emissions, while neglecting structural safety. Recent Italian seismic events brought out the high seismic vulnerability of residential and school buildings, which exhibited severe damage or collapse, thereby yielding significant social and economic losses. Therefore, an effective renovation process should consider, simultaneously, both structural and energy aspects. This research work presents a novel conceptual design methodology for the integrated structural and energy retrofit of existing RC buildings. It allows the definition of incremental strategies for integrated retrofit solutions with an increasing impact while taking into account overall structural and energy performances, costs and benefits. The applicability of the proposed methodology is illustrated with reference to two case studies RC buildings. The outcomes of this study can be used to help the stakeholders for the selection of the most effective and compatible retrofit solutions for a given set of performance targets.

Substandard reinforced concrete (RC) joints often exhibited poor seismic performance even under moderate intensity earthquakes, which is due to the lack of earthquake-resistant design detailing. Premature joint cracking often compromises the seismic performance of the entire building, initiating local collapses or global failure mechanisms. The quantification of the joint repairability in terms of reduction of the structural damage as well as expected economic losses is still a challenging task. This is due to the uncertainties in the assessment of residual and maximum crack widths. This study deals with th e evaluation of crack by the increasing drift level. To this end, available numerical and experimental cyclic data on the substandard beam- column joints are collected. The variability in material properties is considered and the corre- lation between residual and maximum crack width is obtained. These data are then used to obtain residual-to-maximum crack width ratio by increasing drift level. The available repaira- bility thresholds are then compared with the residual-to-maximum crack width ratio curve.

The 2017 New Zealand Society for Earthquake Engineering (NZSEE) guidelines for seismic assessment of buildings recommends using Simple Lateral Mechanism Analysis (SLaMA) before implementing numerical analyses. The method and the NZSEE guidelines have been enhanced from the 2006 version, resulting into an efficient procedure, balancing simplicity and accuracy. This paper presents a numerical study, initiated as part of the development of the SLaMA-2017 method, to investigate the accuracy of the analytical approach via comparison with numerical 2D-pushover on 40 RC frames. SLaMA is effective in capturing the plastic mechanism of the frames, including global or soft-story mechanisms. Further-yet-simple refinements of the procedure are suggested.

The performance of as-built optical instruments strongly depends on thermal and structural loads, since these boundary conditions can affect the geometry of optical surfaces. Variations of temperature influence the volume, and the shape, of the structure proportionally to the coefficient of thermal expansion of the material, while mechanical loads, like gravity, may induce deformations on the optical elements according to the set of applied constraints. Those effects can introduce aberrations that degrade the performance of the optical system. Since software for optical and thermo-structural analysis are usually different, a coupling methodology between these two fields of physics is needed. This is a step-by-step procedure through many platforms. In this work, the procedure devised and used by the authors will be presented. At first, a thermo-mechanical analysis (depending on the loads involved) has to be performed, in order to obtain the final deformed geometry of the optical structure; COMSOL Multiphysics is the finite element solver (FEM) used for these analyses. Then an output data file, containing the coordinates of points belonging to the optical surface, can be generated. The output data are elaborated by a MATLAB routine that allows to convert the set of points into an n-th polynomial expression that best fits the surface data. The fitted polynomial surface is hence imported in ZEMAX ray-tracing software to study the optical performances of the system and the effects of thermo-mechanical loads.

Recent devastating earthquakes pointed out the high vulnerability of existing reinforced concrete (RC) buildings and the critical role of infills. The presence of stiff infills may significantly modify the lateral response of RC moment resisting frame buildings and cause severe damage on the surrounding RC members due to seismic actions transmitted at level of beam-column joints. Furthermore, due to their brittle response, they commonly exhibited severe damage often leading to high economic losses. In this context, effective seismic retrofit strategies should aim at both increasing the shear strength of RC members and reducing the damage to infills. However only few tests are available in literature addressing the seismic strengthening of existing RC frames accounting for the infill-to-structure interaction. To fill this gap a comprehensive experimental program of pseudo-dynamic tests on full-scale two-storey infilled RC frames has been designed and is currently ongoing at the full-scale laboratory testing of the University of Napoli Federico II. This paper reports the preliminary experimental results and numerical analyses carried out by using available non-linear models accounting for the infills contribution. The comparison between theoretical predictions and experimental results provides useful insights to improve the numerical models to reproduce the infill-to-strut interaction. Finally, a retrofit strategy to improve the seismic performance of the structural system and reducing the expected damage to infills is herein outlined. © 2021 COMPDYN Proceedings.

MAORY (Multi Conjugate Adaptive Optics RelaY) is one of the four instruments for the ELT (Extremely Large Telescope) approved for construction. It is an adaptive optics module able to compensate the wavefront disturbances affecting the scientific observations, achieving high strehl ratio and high sky coverage. MAORY will be installed on the straight-through port of the telescope Nasmyth platform and shall re-image the telescope focal plane to MICADO (the first light imager of the ELT) and in a future second instrument port. A general overview of the present status of the mechanical design of the Main structure is given in this paper.

ARIEL, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey mission1-3 was selected in early 2018 by the European Space Agency (ESA) as the fourth medium-class mission (M4) launch opportunity of the Cosmic Vision Program, with an expected launch in late 2028. It is the first mission dedicated to the analysis of the chemical composition and thermal structures of up to a thousand transiting exoplanets atmospheres, which will expand planetary science far beyond the limits of our current knowledge.

Experiments have demonstrated the effectiveness of fiber-reinforced polymer (FRP) materials for the seismic strengthening of deficient reinforced concrete (RC) beam-column joints. However, only a few studies have focused on the seismic response of joint subassemblies that are designed to withstand moderate seismic actions where a strong column-weak beam mechanism is expected. In these circumstances, the high strain demand on the beam's plastic hinge may be critical for existing FRP-strengthening layouts. The present work analyzes the results of three experiments on full-scale, poorly detailed RC beam-column joints, with a strong column-weak beam hierarchy tested in the as-built and FRP-strengthened configurations. The proposed FRP-strengthening layouts are designed according to the recent trend of minimizing the level of disruption caused by their application. Accordingly, light FRP-strengthening solutions that are applied to the joint panel wholly from the exterior of a building or have a minimum impact on its downtime are tested and their performance is analyzed in terms of the global and local response.

Generating the nonlinear behavior of substandard beam-column joints is challenging. Difficulties arise even more in reproducing the contribution of different nonlinear mechanisms (and their mutual effects) on the global cyclic response. This paper deals with the advanced numerical modeling of substandard reinforced concrete (RC) beam-column joints designed with structural details and material properties non-conforming to current seismic codes. Refined numerical models developed in VecTor2 and ATENA Science finite element (FE) software are investigated in detail to identify the factors affecting the global and local joint response. Two different modeling strategies are closely compared with experimental results of joint subassemblies with different failure modes in terms of hysteric response, crack pattern and its development, and local deformations at the joint panel and framing members. The advantages-disadvantages, difficulties in implementing the numerical model and their capability to reproduce the experimental behavior are discussed in detail. The comparison against experimental results in terms of local and global response is useful to assess the accuracy of the proposed models and it provides details on their applicability.

The new guidelines for the seismic assessment of existing buildings recently introduced by the New Zealand Society for Earthquake Engineering (NZSEE) recommend the Simple Lateral Mechanism Analysis (SLaMA) as an “analytical” first phase of any other numerically-based analysis. This article illustrates the development of the SLaMA method and its validation with reference to an existing RC building severely damaged during the Christchurch earthquake (2011). The capacity of the lateral resisting systems is assessed from component/subassembly to system level. The comparison of the results with observed damage and with the outcomes of refined numerical analyses confirms the effectiveness of this method

Recent seismic events are a unique opportunity to monitor and collect details of direct repair costs and the downtimes associated with massive reconstruction processes. This paper focuses on the actual repair costs of five RC buildings damaged by the 2009 L'Aquila earthquake. The repair costs for structural and nonstructural components that experienced different types of earthquake damage are discussed and then used as a benchmark for the predictions. The comparison at both the building and component levels revealed that the FEMA P-58 methodology is suitable, in general, for application to different types of building stock. Ad hoc upgrades to the FEMA fragility database for components that are typical of the Mediterranean area are required. When implementing the proposed modifications, a reasonable level of consistency is achieved in terms of actual and predicted repair costs (differences in the range of 30–48%). A discussion on the actual repair costs and the main differences with the predicted costs for infills and partitions, structural subassemblies, floor finishes, and other acceleration-sensitive nonstructural components is provided, along with suggestions for further improving.

Field surveys in the aftermath of major seismic events, laboratory tests and numerical studies outlined that existing reinforced concrete (RC) structures are likely to exhibit premature shear failures. However, a proper quantification of the shear capacity of existing members with seismic details non-conforming to current seismic code is still a challenging task. Several models based on mechanical approaches or experimental observations are available in literature, current standards and guidelines. Nevertheless, the lack of a widely accepted theory often results in the use of old formulations, mainly developed for design purposes, to assess the shear strength of non-conforming RC members. This study investigates the available shear strength formulations. Eight capacity models commonly adopted in the current practice and worldwide standards or guidelines have been assessed comparing the model predictions with a unique database of 180 experimental tests properly selected to be representative of non-conforming RC members. Members with rectangular or circular cross-section, different aspect ratio (i.e. slender or squat) and shear or flexure-shear failure mode have been investigated. Meaningful statistics have been used to quantify the accuracy and the level of safety of each formulation. Several criticisms in the use of the available formulations are herein outlined. Suggestions for the model applicability have been provided in order to drive the reader to select the most appropriate shear strength formulation for assessment purposes. Finally, corrective factors have been calibrated to allow the use of the selected models with specific levels of safety.

Recent seismic events showed the high vulnerability of the existing buildings and the need to improve their seismic performances. Nowadays different techniques for the seismic retrofit of reinforced concrete buildings are available. One of the most effective technique is the base isolation because it aims at reducing the seismic actions transmitted to the super-structure. In the framework of the seismic risk classification it aims at improving the seismic safety index and at reducing the expected annual losses containing the damage to structural and non-structural components. An efficient design of a base isolation system for existing buildings should aim at minimizing the retrofit interventions on the superstructure in order to reduce the level of disruption. This paper deals with the seismic retrofit of a case study reinforced concrete building by means of base isolation. A refined numerical models including the contribution of hollow clay brick infill wall is developed. Nonlinear dynamic analyses are carried out to assess the performance of the building in the asbuilt and base isolated configuration with and without infill walls. A direct comparison between the seismic performance is performed and the results are discussed with the reference to the reduction of the expected economic losses and needs for the intervention on the superstructure

Recent seismic events showed the high vulnerability of existing buildings and the relevant economic and social losses. Nowadays, the modern seismic engineering necessarily needs to account for expected economic losses in order to plan effective mitigation strategy at building and regional level. Different methodologies are available in literature and they are implemented in useful tools suitable for the application in the design practice. Recent seismic events have been a unique occasion for monitoring and collecting the actual reconstruction costs at a large scale. These data can be used to calibrate and validate the loss-assessment procedures. This research work focuses on the actual repair costs of a database of reinforced concrete existing buildings damaged by the 2009 L’Aquila earthquake and then repaired and strengthened. The actual repair costs derived by the quotes submitted for funding applications are analyzed and a focus on the repair cost of infills and partitions (IPs), which is majority of the total repair cost, is presented. The variability of the repair costs of these components and a correlation with observed damage is investigated. High dispersions is found when correlating the repair cost of IPs to the damage state and damage extent derived from empirical data. An in-depth analysis is performed to quantify the real extent of the damage experienced by these components. This results in a significant improvement of the correlations with actual repair costs.

The uncertainties related to the material properties may significantly affect the seismic perfor-mance of structural components. In this study, the influence of each material propertyon the global response of reinforced concrete substandard beam-column joints is evaluated by means of a sensitivity analysis. An experimentally validated finite element model (FEM) isused for probabilistic numerical simulations. The material propertiesdefined as random variablesare generated by Latin Hypercube Sampling (LHS). The existing correlation among the material parameters is also considered by the simulated annealing approach ingenerating the randomsamples. A set of load-displacement curves is obtained bythe numerical simulations with the randomized material parameters. Theinvestigated outcomes (i.e., responsevariables)are the joint shear strength at the first cracking, the joint peak strength, andjoint strength and crack width at serviceability limit state, which is considered as a repairability threshold value. The basic statistics of the response variablestogether with the probability distribution functions(PDF) are calculated at differentdrift levels. The partial correlation coefficient between mate-rial parameters and response variables is alsoevaluated to outline the parameters which mainly contributetothe joint global response.The reparabilitylevel of the joint isalsoidenti-fied stochasticallyby thecrack width distribution corresponding to the serviceability limit state.

Advanced numerical modeling for reinforced concrete structures is nowadays available. Nevertheless, reproducing the non - linear behavior of substandard beam - column joints is still a challenging task. Indeed, difficulties arise even more in capturing the con tribution of different nonlinear mechanisms (and their mutual effects) on the global cyclic response. This paper deals with the advanced numerical modeling of substandard reinfor ced concrete beam - column joints designed by reinforcement details non - conformi ng to current seismic codes. Experimental data from the different testing program s on joint subassemblies characterized by lack of transverse reinforcement in the joint, low strength concrete and plain round/deformed bars were collected from available literature studies. Refined numerical models, which were developed in VecTor2 and ATENA Science finite element method (FEM) software, are investig ated in detail to identify the factors affec ting the overall response. T wo different modeling strategies and their results are closely compared. Th e advantages - disadvantages, difficulties in implement ing the numerical model and their capability to capture the experimental behavior are discussed in detail . A focus on the influence of the modeling assumption on the joint panel shear behavior and the bond - slip of longitudinal reinforcements is provided. Practical suggestions were given to drive the structural engineers in developing efficient and reliable numerical models for substandard RC joints.

Existing RC buildings of the Mediterranean area commonly show high variability in the material mechanical properties because of the construction age and manufacturing processes. Such a variability has been confirmed by number of in-situ tests performed during the reconstruction process in the aftermath of L’Aquila 2009 earthquake. In this context, destructive and non-destructive characterization tests are useful supporting tools to estimate the actual concrete mechanical properties and to improve the accuracy of the seismic capacity assessment. The paper reports of a wide material characterization program consisting of destructive and non-destructive tests carried out on a building severely damaged by the L’Aquila 2009 earthquake. Due to poor concrete mechanical properties and seismic structural weaknesses, the building was demolished. Portions of the structural systems have been extracted before the building demolition, subjected to material characterization tests and then tested in laboratory. The comparison between the two sets of material characterization test programs and the correlation with the experimental performances of an RC column tested under compressive axial load is presented herein.

The Italian “Guidelines for the seismic risk classification of constructions” approved in February 2017 define the technical principles for exploiting tax deductions with respect to seismic strengthening interventions on existing buildings (Sismabonus). Tax deductions represent a unique opportunity to improve the seismic safety of the existing Italian building stock. The guidelines are very simple and allow practitioners to deal with the sophisticated concepts behind modern seismic design, such as expected annual losses (EAL) and repair costs (expressed as a fraction of the Reconstruction Cost: %RC). The seismic risk classes of buildings and the class upgrade due to strengthening interventions can be assessed using the principles included in the guidelines. The seismic risk class is the minimum between the class defined by the building safety index at the ultimate limit state and the one related to the EAL. The latter class depends on the area under the curve of the expected losses, which is easily obtained by computing the safety index converted in the return period (annual frequency) at different limit states and the relevant %RC. This paper illustrates the technical principles at the base of the guidelines and the procedure used to calibrate the repair costs associated with the different limit states using the actual repair costs monitored in the reconstruction process following recent Italian earthquakes. Finally, simple tools to estimate the cost of the strengthening interventions to improve the seismic capacity at the life-safety limit states are provided.

Recent seismic events demonstrated the high vulnerability of existing buildings and the significant damage experienced by structural and non - structural components. The recovery of earthquake stricken community passed through large reconstruction processes and involved massive economic and social resources . The building restoration process followed to the L’Aquila earthquake (2009) consisted in repair and retrofit or demolition and reconstruction of damaged buildings . This was also the occasion for monitorin g and collecting the actual repair/retrofit costs of private residential buildings ou tside the historical center. The s e data were later used to calibrate the new Italian seismic risk classification of constructions rating the building seismic performance c onsidering both structural safety and expected annual losses. This paper illustrates the actual repair costs of reinfo rced concrete (RC) buildings that experienced different damage levels. An in depth analysis of the building characteristics and the observed damage to structural and non - structural components is performed. The repair cost estimates submitted and a pproved for funding request of 63 RC case study buildings are analyzed in detail. The repair costs, their variabilit y and the correlation with earthquake damage is reported at component level. A focus on non - structural components (i.e. infill and partitions, acceleration or drift sensitive ), is provided. Preliminary analyses outlines that the repair cost of hollow clay brick infill and partitions ranges between the 32 % to 44 % of the total repair cost. They represents the majority of the total repair costs and this needs to be properly considered in loss - assessment procedures or in the design of resilient retrofit solutio ns

Summary The nonlinear behavior of reinforced concrete (RC) members represents a key issue in the seismic performance assessment of structures. Many structures constructed in the 1980s or earlier were designed based on force limits; thus they often exhibit brittle failure modes, strength and stiffness degradation, and severe pinching effects. Field surveys and experimental evidence have demonstrated that such inelastic responses affect the global behavior of RC structural systems. Efforts have been made to consider the degrading stiffness and strength in the simplified nonlinear static procedures commonly adopted by practitioners. This paper investigates the accuracy of such procedures for the seismic performance assessment of RC structural systems. Refined finite element models of a shear critical bridge bent and a flexure-critical bridge pier are used as reference models. The numerical models are validated against experimental results and used to evaluate the inelastic dynamic response of the structures subjected to earthquake ground motions with increasing amplitude. The maximum response from the refined numerical models is compared against the results from the simplified static procedures, namely modified capacity spectrum method and coefficient method in FEMA-440. The accuracy of the static procedures in estimating the displacement demand of a flexure-critical system and shear-critical system is discussed in detail. Copyright © 2015 John Wiley & Sons, Ltd.

A reliable estimation of the seismic performances of existing reinforced concrete building is of paramount importance to design proper retrofit solutions. Number of refined numerical models are nowadays available, nevertheless predicting the seismic performance and the earthquake damage at component level is still a challenging task. Marked nonlinear phenomena, strength and stiffness degradation and pinching affect the cyclic behavior of structural members designed with reinforcement details non-conforming with current seismic codes. This, along with the interaction between the bare frame and the stiff infills, makes complex the reproduction of the global structural behavior. This study focuses on a refined modeling procedure properly developed for existing RC frames. The modeling assumptions, the hysteresis assigned to the different building components and the modeling strategy accounting for the infill contribution are presented and discussed. The model validation at component and building level related to case-study buildings damaged by the L’Aquila (2009) earthquake is presented. A component-by-component comparison between predicted and observed damage is shown. The proposed numerical model and the in-depth discussion on the earthquake damage are useful to identify the building weaknesses, estimate the repair costs and design proper retrofit solutions.

The recent seismic events demonstrated that the high vulnerability of existing RC structures is often related to the joint subassemblies shear failure which may lead to the collapse of the entire structural system. However, most of the available computer programs do not properly account for this aspect. This paper deals with the numerical seismic assessment of RC structural systems designed without proper seismic details in the joint panel and the benefits of the FRP local strengthening. A new modelling strategy has been developed to account for the joint nonlinear behaviour and the fiber reinforced polymer (FRP) strengthening in the finite element method (FEM). Several case studies were selected for the model validation. At the subassembly level, the model predictions were compared with recent experimental tests on full-scale beam-column joints with and without FRP strengthening. At the structure level, a case study building damaged in the joints during the L'Aquila earthquake and then retrofitted with FRP systems was analyzed. The predicted structural performances and structural damages were compared with observational data. Furthermore, the benefits of the joint FRP strengthening on the global seismic performances were numerically assessed. © 2016 Elsevier Ltd.