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Nowadays retrofitting and strengthening of masonry buildings are important challenges for structural engineering to ensure the structural safety under seismic or exceptional loads. This paper aims to clarify the effects of strengthening systems on out-of-plane mechanisms activation, such as horizontal and vertical bending mechanisms, by analyzing P-M interaction diagrams according to available international design guidelines. They enable the assessment of structural behavior of strengthened masonry walls under different external loads. Dimensionless equations of maximum bending moment capacity of masonry cross sections retrofitted with composite strengthening systems are derived, assuming different failure modes such as crushing of masonry and rupture of the strengthening system. Parametric analyses are performed to assess the impact of the mechanical parameters of the strengthening systems in terms of strength. The results show that the strengthening systems play a fundamental role in terms of cross section capacity and, if not well designed, the strengthening systems may be ineffective or deleterious in cultural heritage.

Scientific community showed particular interest in tsunami risk assessment in the last years due to several worldwide tsunami events where high damages and human casualties were recorded during post-event surveys. This paper investigates the behaviour of Italian coastal residential masonry buildings under tsunami loads. Main fragility curves available in literature are based on empirical databases and consequentially, the structural behaviour is strictly related to local building typologies of other countries. For masonry buildings, it is complex to predict global response due to high material inhomogeneity, especially in the case of regional scale analysis; a critical review on local mechanisms activation of masonry walls under tsunami loads is briefly performed. Therefore, local mechanisms activation for masonry walls are investigated depending on out-of-plane and in-plane mechanisms assuming flexural and shear failure. Structures designed for gravity or seismic loads are generated based on several building classes depending on number of storeys and age of construction. Monte Carlo analyses generated building models for each identified building class to simulate the behaviour of Italian masonry buildings. Preliminary analytical tsunami fragility curves are developed in order to assess the vulnerability of Italian coastal residential masonry buildings under tsunami loads. A critical review is proposed on developed fragility curves.

In the last decades, several tsunamis hit international coasts and engaged scientific awareness to the retrofit of coastal buildings against tsunami loads. Structural design under tsunami loads is difficult due to the high uncertainties of the phenomenon. Local collapse mechanisms of masonry walls, like as out of plane mechanisms, have an high probability due to flexural actions; a higher flexural capacity can be reached using specific retrofit systems; in particular, this paper aims to deepen the behavior of masonry walls retrofitted with innovative retrofit systems like as natural fibers applied with inorganic mortar matrices. The retrofit of structures under tsunami actions could be an innovative research topic for international research community dealing with coastal buildings located in areas characterized by a high tsunami risk. Recent engineering applications demonstrated the innovative strengthening systems to be effective for the retrofit of existing masonry buildings. These strengthening systems are of great interest in the practical applications due to the low costs and their sustainability. In fact, the lower costs compared to the synthetic fibers allow their diffusion in emerging countries. In a first part the impact of constituents on the structural capacity of masonry elements strengthened with natural systems has been discussed. Important results have been provided in order to improve the knowledge and encourage the development of these systems in many engineering applications. Finally, the effects of retrofit systems on masonry walls under tsunami loads will be discussed in terms of critical inundation depth variations before and after the interventions.

Retrofit of existing structures is one of the most demanding and challenging tasks for practitioners. The research community is providing newer solutions and systems improving the compatibility and sustainability both in environmental and conservation fields. Textile reinforced mortars (TRMs) represent a good balance between strength provided by fibres and compatibility of mortars by the matrix. The main aim of the paper is to provide fast assessment tools for the effects of tsunami actions on masonry structures, assuming as main parameter the inundation depth, and to provide a comparably fast tool to design retrofit interventions with innovative strengthening systems. The peculiar multilinear behaviour of systems, like as TRM, is accounted for and some design equations and charts are provided, discussing the peculiarities of the material property variability to orient the designer to coherent and effective decisions; potential uncertainty and variability of substrate masonry are taken into account, too.

In the last years, several catastrophic tsunami events engaged scientific awareness to assess the tsunami risk. Fragility curves are required to analyse the vulnerability of masonry buildings and analytical fragility curves should be based on local buildings typologies. This paper aims to assess the vulnerability of masonry buildings under tsunami loads by means of the minimum inundation depth triggering a failure mechanism coherently with a large scale approach and consequentially, a low knowledge level achieved on properties of structures. Furthermore, out-of-plane and in-plane mechanisms activation is investigated by modelling an external tsunami load pattern with simplified assumptions. Shear and flexural failure are analysed as main in-plane failure modes while horizontal and vertical bending mechanisms are considered as main out-of-plane failure modes. Masonry walls are modelled as frame elements and masonry is modelled as a nonlinear material. Japanese guidelines are assumed to model tsunami loads instead of more refined models, such as ASCE 7-16 and FEMA P-646 proposals, due to reduced achievable knowledge level. Proposed mechanical models provide important information about vulnerability of masonry buildings under tsunami loads and they represent a basic step to provide vulnerability information on masonry buildings at a regional scale level.

The aim of the proposed work is to clarify the dynamic behaviour of asymmetric bodies in the case of rocking behaviour. The proposed algorithm is based on Housner theory and the integration of the equations of motion is evaluated with the Runge-Kutta-Fehlberg (RKF45) method. The significant accumulation of numerical errors is evaluated during the integration between two consecutive acceleration points where the rotation sign changes owing to the adoption of an equation that is wrong. An iterative calculation is developed to reduce numerical error depending on a specific tolerance and, therefore, the algorithm accuracy is investigated. In addition, the reduction of energy due to the impact at the point of change of the sign of rotation is analysed by means of a restitution coefficient. It is important to note that this is highly dependent on the rigid block properties, and experimental programmes are required to calibrate the restitution coefficient properly. Sensitivity analyses are performed in order to clarify the effects of convergence parameters and tolerances on the results, due to high numerical instabilities. Furthermore, fragility curves are retrieved based on far-field and near-field sets of accelerograms proposed by the Applied Technology Council in 2008, ATC-63, and a critical discussion is provided concerning the most efficient intensity measure parameters.