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This paper deals with the structural behaviour and the damage assessment of Italian “modern” masonry buildings during seismic events. “Modern” masonry buildings are characterized by a box-like structural behaviour, due to the presence of effective connections between horizontal floors and vertical load-bearing walls, which prevents local mechanisms such as the overturning of external facades during earthquakes. “Modern” masonry buildings were built in Italy since the first decades of XX century in those regions classified as seismic zone and since 1937 in the whole country, following the Italian code prescriptions that implicitly interdicted the erection of “ancient” masonry buildings. Starting from an in deep historical analysis of the Italian seismic codes’ prescriptions for the design of “modern” masonry buildings, the typical characteristics of the most frequent structural typologies of unreinforced masonry buildings are outlined. Then, the typical damage mechanisms observed in “modern” masonry buildings damaged after the L’Aquila earthquake (2009) are reported in relation with both the global and local behaviour of the whole building and its structural elements. The analysis demonstrated that “modern” masonry buildings experienced a good box-like seismic performance, which avoided global or local collapses, but shown severe damage to piers and spandrels related to their reduced in-plane shear capacity. Given the lack of data on such kind of structural typology, this study is fundamental for understanding and modelling the seismic behaviour of “modern” masonry buildings designed before ‘80s according to different seismic design prescriptions and for defining effective strengthening solutions for reducing their seismic vulnerability.

Supplementary data: The following is the Supplementary data to this article: Acrobat PDF file (2MB) available at: https://ars.els-cdn.com/content/image/1-s2.0-S2212420921007329-mmc1.pdf Copyright © 2022 The Authors. Very large tsunamis are associated with low probabilities of occurrence. In many parts of the world, these events have usually occurred in a distant time in the past. As a result, there is low risk perception and a lack of collective memories, making tsunami risk communication both challenging and complex. Furthermore, immense challenges lie ahead as population and risk exposure continue to increase in coastal areas. Through the last decades, tsunamis have caught coastal populations off-guard, providing evidence of lack of preparedness. Recent tsunamis, such as the Indian Ocean Tsunami in 2004, 2011 Tohoku and 2018 Palu, have shaped the way tsunami risk is perceived and acted upon. Based on lessons learned from a selection of past tsunami events, this paper aims to review the existing body of knowledge and the current challenges in tsunami risk communication, and to identify the gaps in the tsunami risk management methodologies. The important lessons provided by the past events call for strengthening community resilience and improvement in risk-informed actions and policy measures. This paper shows that research efforts related to tsunami risk communication remain fragmented. The analysis of tsunami risk together with a thorough understanding of risk communication gaps and challenges is indispensable towards developing and deploying comprehensive disaster risk reduction measures. Moving from a broad and interdisciplinary perspective, the paper suggests that probabilistic hazard and risk assessments could potentially contribute towards better science communication and improved planning and implementation of risk mitigation measures. COST (European Cooperation in Science and Technology); Royal Society, UK (grant number CHL\R1\180173); Severo Ochoa Centers of Excellence Program (CEX 2018-000797-S) funded by MCIN/ AEI /10.13039/501100011033; Lloyd's Tercentenary Research Foundation, the Lighthill Risk Network, and the Lloyd's Register Foundation-Data Centric Engineering Programme of the Alan Turing Institute.

The study presents a simple mechanics-based method to develop analytical fragility functions for the risk assessment of Reinforced Concrete (RC) frame buildings subjected to tsunami or other flow-type hazards (i.e., flood, mud flows, flow-type landslides, etc.). A harmonized framework for the analysis of building portfolios to flow-type hazards is first illustrated. The mechanics-based method for the performance assessment of RC frames with breakaway infill walls subjected to tsunami and flow-type loads, called SAFETI (Structural Assessment to Flows and Extreme Tsunami Inundation), is then presented. For the large-scale risk analysis, a damage levels classification is adopted for both structural and non-structural (i.e., infill walls) components, based on the HAZUS approach. The flow depth is assumed as Intensity Measure. Damage levels computed through SAFETI are validated with ones obtained from a refined finite-element modelling in OpenSees for three case-study RC frames subjected to tsunami. Finally, an application of the SAFETI method is presented to show the feasibility of the mechanics-based procedure to derive analytical fragility curves for a simulated case-study building portfolio subjected to tsunami, flow-type landslides, and flood. The SAFETI method appears a robust solution to perform a consistent fragility assessment at regional scale for tsunami and flow-type hazards, explicitly accounting for the building-to-building variability with limited modelling and computational efforts.

Currently available performance-based methodologies for assessing the fragility of structures subjected to tsunami neglect the effects of tsunami-induced vertical loads due to internal buoyancy. This paper adopts a generalized methodology for the performance assessment of structures that integrates the effects of buoyancy loads on slabs during a tsunami inundation. The methodology is applied in the fragility assessment of three case-study frames (low, mid and high-rise), representative of existing masonry-infilled reinforced concrete (RC) buildings typical of Mediterranean region. The paper shows the effect of modelling buoyancy loads on damage evolution, structural performance and fragility curves associated with different structural damage mechanisms for RC frames with breakaway infill walls including consideration of blow-out slabs. The outcomes attest that the predominant failure mechanism of selected case-study is the brittle shear failure of seaward columns, which is slightly affected by buoyancy loads. When brittle failure is avoided, buoyancy loads significantly affect the damage evolution during a tsunami, especially in the case of structures with blow-out slabs. The rate of occurrence of slabs uplift failure increases with the number of stories of the building but only slightly affects the fragility curves of investigated structures. However, it can significantly increase their vulnerability, affecting both direct and indirect costs deriving from the repair of the damaged interior slabs.

The effectiveness of Fibre Reinforced Cementitious Mortar (FRCM) as strengthening technique of masonry structures under seismic actions has been widely investigated by means of diagonal compression tests in the last decade. The results showed that the effectiveness of FCRM solution, based on the use of FRP grid embedded in mortar matrix, to increase the masonry walls shear capacity strongly depends on the axial stiffness of mesh reinforcement and on the mechanical properties of the matrix. The paper presents preliminary experimental results of tests carried out on specimens strengthened with a new strengthening solution based on the use of Fibre Reinforced Mortar (FRM) without the use of FRP grid. In particular, the strengthening system consists of an innovative high performance and high ductility mortar made by a mix of fibres spread in lime-based powder. The experimental program aims at investigating the soundness of such technique to increase the shear capacity of different masonry panels. In particular, the system was applied over limestone masonry walls with irregular texture, typical of existing buildings in Central Italy, and old-type clay brick masonry panels with regular texture, typical of existing buildings in the Northern Italy

Fiber Reinforced Polymer (FRP) composites have been widely used in past decades for the seismic upgrading of sub-standard reinforced concrete (RC) members and their effectiveness as a suitable strengthening technique for such kind of structural components has largely been proved. However, some concerns still arise with the effectiveness of such composite materials at high temperature, such as in the case of fire exposure. Furthermore, the use of FRPs requires a min- imum quality for the concrete substrate to avoid undesirable premature failure mechanisms. Usually, the replacement of the poor quality or damaged concrete cover of existing members with a new one is needed before the strengthening intervention. Current research is now moving towards the adoption of inorganic composite materials, such as Fiber Reinforced Cementitious Composite (FRCC), for repairing existing RC buildings and infrastructures as a replacement of the original concrete cover, due to its good durability properties and resistance to high temperature. The present study discusses the possibility of adopting such FRCC jacketing also for the seismic upgrading of existing shear critical RC columns. The experimental performance of RC columns strengthened with FRCC jacket- ing subjected to cyclic lateral loading and different axial load ratios is analyzed herein, and the experimental performance of FRCC and FRP jacketed columns is compared to point out the effectiveness of both retrofit solutions.

Fabric Reinforced Cementitious Matrix and Composite Reinforced Mortar, are amongst relatively new type of inorganic composites. Several precedent research programs have investigated the effectiveness of inorganic composite materials to enhance in-plane shear capacity of unreinforced masonry (URM) walls. A database consisting of 406 diagonal compression test results was prepared using experimental results reported in literature with the aim of investigating the role of strengthening parameters on the effectiveness of solutions for enhancing the in-plane shear capacity of masonry panels. The experimental results were analysed for different masonry typologies and effects of masonry texture, mesh reinforcement, matrix properties and strengthening configurations were investigated to provide useful indication for the design of such systems. Furthermore, the accuracy of current design equations for FRCM was evaluated based on experimental data. Shear stress amplification factors were also proposed. The results showed that both the axial stiffness of mesh reinforcement and the mechanical properties of the matrix affected the shear capacity of strengthened panels. Furthermore, based on obtained results, topics for future research are also recommended.

The increasing attention of governments and insurance companies toward the evaluation of tsunamis' impacts on coastal communities led to a renewed interest in assessing the behavior of existing buildings under onshore tsunami flows. Codes and standards regulating assessment procedures for existing structures under tsunami loading are currently missing, and only a few design codes for vertical evacuation shelters can be found. Furthermore, structural analysis methods currently assume watertight buildings for the assessment of their performance under tsunami inundation. In this work, a methodology for assessing the performance of reinforced concrete (RC) buildings that considers explicitly the progressive failure of exterior breakaway infill walls hit by tsunami flows is proposed. The effects of the progressive failure of breakaway infill walls on the overall performance of RC buildings have been highlighted on case-study buildings representative of low-, mid- and high-rise buildings built before the 1980s in the Mediterranean area, characterized by masonry infill walls with low out-of-plane (OOP) capacity. In the absence of specific guidelines for assessment, load models provided by existing tsunami design codes for evacuation buildings were adopted and opportunely modified for the case of buildings with breakaway infill walls. The explicit consideration of the failure of exterior breakaway infill walls completely changed the distributions of loads inside the structure, leading to different structural capacity and damage evolution with respect to watertight buildings. The height of the building affected the global capacity but did not influence the damage evolution. The proposed methodology can represent a suitable solution for a realistic performance assessment of frame structures with breakaway claddings.

One of the main issues in civil engineering is to estimate the level of damage for existing buildings subjected both to decay due to natural ageing and to additional loads that could affect their serviceability during lifetime. This paper looks at the process of Structural Health Monitoring (SHM) in the context of seismic damage detection and quantification. The aim of the paper is to define ranges of variation for parameters commonly monitored as structural damage indicators, like fundamental periods, residual drift ratios and lateral stiffness, in relation with seismic damage levels. For this purpose, a methodology is proposed for simulating the seismic damage of existing reinforced concrete (RC) columns and assessing the correlation between the variation of such parameters with increasing damage levels. Seismic damage levels are defined based on the Park and Ang damage index, and preliminary ranges of variation of damage indicators are derived for the seismic damage quantification in existing RC columns.

A new jacketing technique consisting in a thin layer of Fibre Reinforced Cementitious Composites (light FRCC jacketing) in replacement of the original cover has been recently proposed for increasing durability and load bearing capacity of existing reinforced concrete (RC) structures. Although the advantages in terms of durability have been widely investigated, the behaviour of retrofitted columns under cyclic loading still deserves attention. This paper deals with the seismic response of RC columns retrofitted with a light FRCC jacketing. To this scope, flexural and shear critical RC columns were retrofitted and tested under load reversal. The resulting damage pattern was analysed by means of the Digital Image Correlation (DIC) technique. The cyclic response of the FRCC jacketed columns was compared with that of bare columns, to assess the suitability and effectiveness of the FRCC jacketing as a seismic retrofit technique. The experimental results demonstrated that the FRCC jacketing can represent a valid strengthening solution for shear critical members. In the case of flexural columns, the FRCC jacketing was able to provide an increase in ductility but induced a rocking behaviour. Preliminary modelling considerations for assessing the seismic response of FRCC jacketed columns have been finally provided, based on experimental evidences.

In a probabilistic tsunami risk assessment framework, the definition of vulnerability of the physical assets of coastal communities plays a fundamental role. Therefore, current research is moving towards the definition of a general methodology for developing analytical tsunami fragility functions for the physical assets to be used in loss-assessment frameworks at community scale. Herein a methodology is proposed for developing analytical tsunami fragility functions and its application on an inventory of RC buildings representative of the Mediterranean coastal communities is illustrated. Simple mechanics-based models are defined for the damage assessment of reinforced concrete (RC) buildings with breakaway infills under tsunami lateral loads. A simulated design procedure is adopted for the definition of the buildings inventory, relying on Monte Carlo simulation to account for geometrical and mechanical uncertainties. One key feature of the approach is that intermediate damage states prior to collapse are defined to account for light/moderate damage to both structural and non-structural components subjected to tsunami onshore flows.

Inorganic composites for enhancing the in-plane shear capacity of masonry walls with irregular texture were investigated on twenty-one panels under diagonal compression tests. Three specimens were used as control and twelve specimens were strengthened with two Fibre Reinforced Mortars (FRM-A and FRM-B), characterized by a different content of fibres embedded in the lime-based matrix. The remaining six specimens were strengthened with Fabric Reinforced Cementitious Mortars (FRCM), consisting in a GFRP grid embedded in a fibre reinforced matrix (the same used for FRM-A). The influence of single-side and double-side strengthening configurations on the capacity of strengthened panels was also investigated, to point out the reduction in strengthening effectiveness in case of single-sided applications. The results showed that all the inorganic composites adopted for the strengthening techniques provided a substantial increase of shear capacity. The grid in FRCM strengthened panels played an important role in both strength and deformation capacity at peak. The different fibres content (lower than 50% in weight) in FRM systems slightly affected the overall performance of panels. Finally, analytical predictions of experimental results were reported and discussed and a preliminary analytical model for estimating the FRM shear contribution was proposed, obtaining a good agreement with test results.

The high vulnerability of existing Reinforced Concrete (RC) structures, even to moderate seismic events, has been confirmed from recent post-earthquake surveys. Short and wall-like RC columns are particularly prone to brittle failures, governed by concrete crushing. To reduce the vulnerability of existing RC columns, the use of externally bonded Fibre Reinforced Polymer (FRP) reinforcement has been recognized as an effective method for preventing the aforementioned brittle failure and, hence, increasing members' lateral capacity and ductility. In the first part of this study, the results of an observational analysis on columns shear failures in RC buildings severely damaged after the L'Aquila earthquake are presented. The second part of the study presents and discusses the results of an experimental program carried out on seven short RC columns governed by shear failure under load reversal and compressive axial load. Both columns in “as built” configuration and strengthened in shear with discontinuous carbon FRP (CFRP) strips have been tested. Two classes of concrete have been used, in order to simulate structures with medium or poor material quality, and different external reinforcement ratios have been investigated. The specimens' responses have been analysed in terms of failure modes, strength/deformation capacity and strain distribution in CFRP strips.

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.

Unreinforced masonry (URM) buildings, largely found in Euroasian regions, are particularly vulnerable to in-plane shear failures during seismic events due to the poor shear capacity of masonry walls. In the case of historical masonry buildings, the use of strengthening solutions with polymeric and polymer-modified matrices composites is not recommended since the breathability of the masonry could be reduced, leading to a fast and undesired degradation. In this paper, an innovative fiber-reinforced cementitious mortar (i.e., FRCM) system was used to improve the shear capacity of old-type solid clay brick masonry walls. An experimental program on 24 masonry panels subjected to diagonal compression tests was carried out. The innovative FRCM system consisted of a basalt grid embedded in an improved inorganic matrix, made of lime-based mortar reinforced with short glass fibers (i.e., Fiber-reinforced mortar, FRM). Two sets of specimens were tested, single-leaf masonry panels and double-leaf masonry panels, to investigate the typical configurations of load-bearing walls and partition walls. The effectiveness of the innovative FRCM system was investigated for both a conventional symmetric strengthening configuration and an asymmetric strengthening configuration with anchors, a solution often adopted in the case of internal/external interventions only. Furthermore, the response of masonry panels strengthened with only symmetric FRM with a slightly greater amount of short glass fibers embedded in the matrix was also investigated. The experimental outcomes outlined that panels reinforced with symmetric FRM achieved similar effectiveness in the shear strength increase to panels reinforced with symmetrical FRCM. Conversely, a reduced deformability was observed in FRM panels with respect to those strengthened with FRCM. The experimental results also allowed the quantification of the effectiveness of FRCMs in the case of asymmetric strengthening configurations. Finally, a comparison between experimental results and American Code provisions for FRCM-strengthened systems was reported.

The effectiveness of reinforced plasters and Composite Reinforced Mortars (CRM) for increasing the in-plane shear capacity of masonry walls was investigated on a series of 32 single-leaf tuff masonry panels subjected to diagonal compression tests. Six specimens were used as control and two specimens were strengthened with reinforced plaster (steel grid 100 × 100 mm and cementitious matrix) with a thickness of 40 mm. The remaining specimens were strengthened with two different fibre reinforced lime-based mortars, characterized by different cement content ratios, and coupled with three different grids (steel grid 100 × 100 mm, GFRP grid 30 × 30 mm and GFRP grid 40 × 40 mm). Both single-sided and double-sided strengthening configurations were adopted for all strengthening solutions, to investigate the reduction in strengthening effectiveness in case of single-sided applications. The results showed that strengthening in single-sided configuration increased the shear capacity from 42% to 85% with respect to the unreinforced masonry panels (URM) average shear capacity. Conversely, strengthening in double-sided configuration led to a shear capacity increase from 138% up to 288%. Based on experimental results, reducing the matrix cement content ratios in strengthened system led to a reduction in shear capacity and energy dissipation, independently from the grid properties. Furthermore, specimens strengthened with GFRP 40 × 40 grid, although characterized by a large spacing with respect to GFRP 30 × 30, achieved an increase in the shear capacity and energy dissipation greater than other strengthened specimens clearly evidencing that the grid spacing and the interlock between grid and micro-fibres embedded in the mortar are crucial aspects for the strengthening system effectiveness.

Existing RC buildings may suffer of brittle failure due to the limited shear capacity of non-conforming columns. To reduce the vulnerability of such members, several retrofit techniques based on composite materials can be successfully adopted for enhancing the shear capacity of RC columns. The use of FiberReinforced CementComposite (FRCC) jacketing has been re-cently recognized as an effective solution for improving the durability of RC members and some experimentaltests have been carried out for investigatingthe role of FRCC jacketing on the shear capacity of RC members.However, poor indicationsare availableregarding the modelling of strengthened members capacity and the design of the strengthening solution. In this work, an in deep analysis about the available analytical modelsfor assessing the shear capacity of membersis reported and thendifferent methods are proposed for assessing the shear capacity of RC members with FRCC jacketing.

Unreinforced masonry buildings are particularly vulnerable to brittle failures during seismic events due to the poor in-plane shear capacity of masonry walls. The use of strengthening solutions with polymeric matrices is not often recommended for masonry buildings, due to breathability issues, and the adoption of inorganic matrices is sometimes considered preferable. In this paper, the use of inorganic composite materials for improving the in-plane shear capacity of tuff masonry walls is investigated. The experimental data from 83 diagonal compression tests carried out at the University of Naples Federico II in recent years have been collected and the main results are herein discussed to outline the main features of different strengthening techniques with inorganic composite materials such as Reinforced Plaster (RP), Composite Reinforced Mortar (CRM) and Fabric Reinforced Cementitious Matrix (FRCM).

A new repair technique consisting on a light jacketing with Fibre Reinforced Cementitious Composites (FRCC) for existing reinforced concrete (RC) buildings has been recently proposed to reduce durability problems of RC members and enhance their capacity. In this work, the effects of FRCC jacketing on the flexural capacity of existing RC columns, with and without a pre-damage, has been evaluated of full-scale specimens under cyclic loading. Digital Imagine Correlation (DIC) was also adopted for understanding the strain distribution in the FRCC jacket. The results shown that the FRCC jacket without a proper anchorage slightly enhanced the flexural capacity of the column. The strengthened column experienced a low damage with respect to control column, but occurrence of premature failures did not allow the achievement of high levels of deformation capacity and ductility.

In a performance based approach, the knowledge of ultimate capacity of reinforced concrete (r.c.) columns subjected to simultaneous compressive axial load and biaxial bending becomes essential to correctly assess the seismic capacity of existing structures. In the present work, the reduction of ultimate deformation (i.e. rotational) capacity of r.c. members due to the two components of bending moment is analysed by using a specific simplified numerical model. The influence of axial load, geometry, amount of longitudinal reinforcement and mechanical properties on the ultimate chord rotation of r.c. columns is investigated on a dataset of 780 numerical tests on non-conforming columns with plain bars governed by flexural mode. Then, a practice-oriented formulation for the ultimate rotation domain, based on the Load Contour method extended to the chord rotations, is proposed and discussed. © 2016 Elsevier Ltd

After Northridge Earthquake in 1994 and Kobe Earthquake in 1995, urban earthquakes have been warning us the importance of resilient building structures. Resilience of building structures possess quick recovery capability of building functions. In order to achieve resilient building structures, it is important to develop low damage structural systems in a broader sense and propose a design procedure to utilize them. This study presents a seismic performance of eight reinforced concrete beams using high strength (SD685) transverse steel reinforcement focusing on mode of peak load deterioration and crack performance so that the results of this study will be utilized in cost evaluation of reinforced concrete members to achieve most economical resilient structural system. Load carrying capacity assessment on flexure, shear and bond was computed based on the 1999 AIJ design guidelines and compared with the experimental results for its accuracy. The experimental load carrying capacity was 1.1 times larger than the computed results in average. Modes of peak load deterioration, such as shear tension, shear compression, flexure failures, were also well simulated. Then, residual shear crack width were evaluated for reparability of members. The crack data were used to evaluate the crack assessment procedure of the 2004 AIJ design guidelines and it was found that shear drift component can be correlated to the summation of horizontal crack gaps of positive and negative cracks. The paper describes the work as part of the current research efforts on resilient reinforced concrete structures in Japan.

Although recent efforts have been made to understand the behavior of RC members subjected to cyclic biaxial bending, the experimental data available in the literature are still limited for making conclusions about the influence of biaxial actions on the inelastic response of RC columns. To analyze the effects of biaxial bending on the seismic behavior of existing RC columns with design characteristics nonconforming to modern seismic codes, the results of an experimental program on RC columns under constant axial load and cyclic uniaxial/biaxial bending are presented in this paper. The experimental data set consists of ten tests (seven new tests and three previously published by the authors) on full-scale columns reinforced with deformed bars: six square columns and four rectangular columns. The square columns are tested with diagonal cyclic displacement paths with inclination angles of 0°, 30°, and 45° with respect to the cross section principal axes and axial load ratios of 0.1 and 0.2. Rectangular columns are subjected to horizontal displacements with inclination angles of 0°, 30°, 45°, and 90° with respect to the cross section principal axes and an axial load ratio 0.1. The effects of different horizontal displacement orientations on column performance is investigated and discussed in terms of strength, deformation capacity, and damage at failure.

Glazed curtain walls are facade systems frequently chosen in modern architecture for mid and high-rise buildings. From recent earthquakes surveys it is observed the large occurrence of non-structural components failure, such as storefronts and curtain walls, which causes sensitive economic losses and represents an hazard for occupants and pedestrians safety. In the present study, the behavior of curtain wall stick systems under seismic actions has been investigated through experimental in-plane racking tests conducted at the laboratory of the Construction Technologies Institute (ITC) of the Italian National Research Council (CNR) on two full-scale aluminium/glass curtain wall test units. A finite element model has been calibrated according to experimental results in order to simulate the behavior of such components under seismic excitation. The numerical model investigates the influence of the interaction between glass panels and aluminium frame, the gasket friction and the stiffness degradation of aluminium-to-glass connections due to the high deformation level on the curtain walls behavior. This study aims to give a practical support to researchers and/or professionals who intend to numerically predict the lateral behavior of similar facade systems, so as to avoid or reduce the need of performing expensive experimental tests.

Reinforced concrete (RC) columns typical of existing structures often exhibit premature failures during seismic events (i.e., longitudinal bars buckling and shear interaction mechanisms) due to the poor quality concrete and the absence of proper seismic details in the potential plastic hinge region. The Fiber Reinforced Polymers (FRP) externally bonded reinforcement is known to be a valid technique to improve the shear capacity or the ductility of existing RC columns. However, few experimental tests have proven its effectiveness in the case of columns affected by shear interaction mechanisms. In this work, the behavior of existing RC columns with border line behavior between flexure and shear have been investigated in the case of poor quality concrete and light FRP strengthening with local jacketing and medium quality concrete and strong FRP strengthening with local jacketing, in order to highlight the effect of concrete strength on the effectiveness of the retrofit intervention. As an alternative to FRP jacketing; the effectiveness of the Fiber Reinforced Cementitious Composite (FRCC) jacketing for the seismic strengthening of columns with highly deteriorated concrete cover or columns already damaged by an earthquake is also evaluated. Six full-scale RC columns have been tested under cyclic loading: one was used as a control specimen; four were strengthened in the potential plastic hinge region with carbon FRP (CFRP); and one was fully jacketed with FRCC. The comparison between poor and medium quality concrete columns showed that the CFRP local jacketing is more effective in the case of poor quality concrete. The FRCC jacketing appears to be a sound repair strategy and a suitable alternative to the FRP jacketing in case of poor quality; however, more experimental research is needed for improving this retrofit technique.

Under seismic actions, the structures undergo two simultaneous horizontal compo-nents of the ground motion, which cause a structural response in an oblique direction and biaxial bending in the columns. The current approach to the seismic design of new structures or the assessment of existing ones points out the need of taking into account the contempora-neous presence of the two components of ground motion, in order to make a good prediction of the real structural behaviour, both in terms of strength and deformation capacity. The pa-per analyses the influence of the two components of bending moment on the deformation ca-pacity of reinforced concrete (r.c.) cross-sections and r.c. members (i.e. columns) by using a specific fibre model. The behaviour of the generic member is expressed in terms of ulti-mate/yielding curvature domain for the cross-section and ultimate/yielding rotational capaci-ty domain for the column. The study underlines the influence of the two components of biaxial bending on the deformation capacity of r.c. cross-sections and r.c. members.