Multiscale computational first order homogenization of thick shells for the analysis of out-of-plane loaded masonry walls

This work presents a multiscale method based on computational homogenization for the analysis of general heterogeneous thick shell structures, with special focus on periodic brick-masonry walls. The proposed method is designed for the analysis of shells whose micro-structure is heterogeneous in the in-plane directions, but initially homogeneous in the shell-thickness direction, a structural topology that can be found in single-leaf brick masonry walls. Under this assumption, this work proposes an efficient homogenization scheme where both the macro-scale and the micro-scale are described by the same shell theory. The proposed method is then applied to the analysis of out-of-plane loaded brick-masonry walls, and compared to experimental and micro-modeling results.Peer ReviewedPostprint (author's final draft

Analytical and experimental shear evaluation of GFRP-reinforced concrete beams

Reinforced Concrete (RC) technology is advancing towards new frontiers enhancing its sustainability and durability through innovative materials. In particular, the application of Glass Fiber Reinforced Polymer (GFRP) bars, in lieu of steel reinforcement, shows excellent performance, especially in aggressive environments. Nevertheless, current international design guidelines and standards tend to be rather conservative, especially concerning shear reinforcement. This element hinders the technology’s competitiveness, not only in terms of material consumption but also in construction efficiency. This research aims to conduct an analytical comparison and experimental validation of the formulations found in some international standards pertaining to shear capacity in a specific case. The focus is on scenarios involving reduced shear reinforcement and cases where the number of stirrups falls below the minimum recommended by these standards. In the sample beam tests, two distinct flexural GFRP reinforcement ratios were employed to evaluate their influence on shear capacity, leading to diverse failure mechanisms: rupture of longitudinal GFRP bars and concrete crushing. The experimental results were used to compare the North American ACI, French AFGC, and Italian CNR shear capacity design approaches in the case of reduced transversal reinforced ratio. Analytical capacity expressions of the standards above are discussed with some remarks aiming at structural optimization

In-plane shear behaviour by diagonal compression testing of brick masonry walls strengthened with basalt and steel textile reinforced mortars

This paper presents an experimental study of the structural behaviour of masonry walls retrofitted with Textile Reinforced Mortar (TRM) to improve their in-plane shear strength and deformation capacity. The experimental programme consists in diagonal compression testing of ten specimens of clay brick and lime mortar masonry retrofitted with three different TRM systems: i) continuous bidirectional grids of basalt TRM, ii) discrete bands of unidirectional steel TRM and iii) continuous basalt TRM on the wall’s inner face and bed joints structural repointing with near surface mounted helical stainless steel bars on the wall’s outer face. Two of the specimens were tested two times, i.e. in the unreinforced condition and subsequently in the repaired configuration including basalt TRM retrofitting. The experimental results show that the adopted TRM solutions produce a beneficial increase of shear resistance and ductility, making them suitable for seismic retrofitting and post-earthquake repair.Peer ReviewedPostprint (author's final draft

OPTIMUM DESIGN OF A HYBRID ISOLATION DEVICE FOR SERVER RACKS USING CONSTRAINED DIFFERENTIAL EVOLUTION ALGORITHM

Nonstructural elements and contents often constitute a large fraction of the economic investment in ordinary buildings. In case of seismic events, damage to nonstructural elements not only contributes to the overall direct material costs but can also significantly impact the indirect costs. The latter are especially affected by earthquake-induced damage if production and business flows depend on proper functioning of such nonstructural components, since consequent downtime costs turn out to be very high. Within this framework, server racks' performance under seismic loading is of interest in the present work. The economic relevance of these nonstructural components requires the implementation of proper design solutions so that their performance under earthquakes can fulfill specific requirements. In this perspective, including isolation devices between server racks and building floors is deemed effective for enhancing the stability of the protected equipment, preserving the computer components' integrity and, minimizing downtime losses. Hence, the present work is meant to optimize a hybrid isolation system for server racks. Specifically, the hybrid isolation device designed for such application combines at least two elastomeric isolators and three sliders, and it is intended for the seismic protection of server racks characterized by different configurations. The objective function is formulated to minimize the accelerations transmitted to server racks and manufacturing cost

Experimental cyclic behaviour of shear masonry walls reinforced with single and double layered Steel Reinforced Grout

Recent research on the mechanical characterisation of Steel Reinforced Grout (SRG) has highlighted its excellent performance as strengthening solutions for masonry structures. Using SRG with limited fabric density ensures a good textile-matrix interlocking, preventing at the same time the failure due to slippage or debonding from the substrate. This paper presents an experimental investigation on the use of SRG as in-plane strengthening solution for shear masonry walls composed of handmade solid clay brick and hydraulic lime mortar. Cyclic shear compression tests were carried out on walls strengthened with SRG comprising low density steel sheets (LDS). The SRG was applied on both faces of the walls with a strip configuration, using one and two layers of LDS. The experimental programme aimed to study the influence of the number of textile layers on the in-plane response of strengthened masonry walls in terms of failure mechanism, load-bearing capacity, energy dissipation, and ductility.The authors gratefully acknowledge the financial support from the Ministry of Economy and Competitiveness, Spain and from the Ministry of Science, Innovation and Universities of the Spanish Government, as well as that of the ERDF (European Regional Development Fund) through the project SEVERUS (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, Ref. num. RTI2018-099589-B-I00). The reinforcement systems and construction of the specimens for the experimental programme have been funded by Kerakoll Spa through the RTD project “Seismic Strengthening of Masonry Walls” (Ref. num. A-01278). The authors wish to thank Paolo Casadei, José Luis Sanchez and José Dobón from Kerakoll Spa for their involvement and support. The support from Secretaria d’Universitats i Investigació de la Generalitat de Catalunya, Spain through a predoctoral grant awarded to the first author is also gratefully acknowledged.Peer ReviewedObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura::9.1 - Desenvolupar infraestructures fiables, sostenibles, resilients i de qualitat, incloent infraestructures regionals i transfrontereres, per tal de donar suport al desenvolupament econòmic i al benestar humà, amb especial atenció a l’accés assequible i equitatiu per a totes les personesObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.4 - Redoblar els esforços per a protegir i salvaguardar el patrimoni cultural i natural del mónObjectius de Desenvolupament Sostenible::13 - Acció per al ClimaObjectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.1 - Enfortir la resiliència i la capacitat d’adaptació als riscos relacionats amb el clima i els desastres naturals a tots els païsosPostprint (author's final draft

Cyclic shear-compression testing of brick masonry walls repaired and retrofitted with basalt textile reinforced mortar

This paper reports an experimental programme on masonry walls composed of handmade solid clay brick and hydraulic lime mortar. Reversed cyclic shear compression tests were carried out on the walls in three different configurations: unreinforced, repaired and retrofitted, and just retrofitted. Damaged walls were repaired and retrofitted with Basalt Textile Reinforced Mortar (B TRM) and tested again to investigate the recovery of strength, stiffness and the improvement in drift capacity. The repair consisted in filling the open cracks and replacing the damaged bricks by following the so-called ‘‘scuci-cuci’’ technique. The just retrofitted configuration consisted of externally bonded B-TRM on undamaged walls. The B-TRM system comprised continuous bidirectional grids of basalt fibre embedded in hydraulic lime mortar on both surfaces of the walls. The experimental results showed the suitability of the proposed solutions for seismic retrofit and post-earthquake repair of existing masonry buildings. The research results highlighted the capacity of the proposed repair technique to reinforce damaged walls and the effectiveness of the investigated B-TRM system in increasing the resistance, the ductility, and the energy dissipation of unreinforced clay brick masonry. In addition, the results allowed a better understanding of the behaviour of masonry walls subjected to cyclic horizontal displacement in terms of failure mechanism and displacement capacities.The authors gratefully acknowledge the financial support from the Ministry of Economy and Competitiveness and from the Ministry of Science, Innovation and Universities of the Spanish Government, as well as that of the ERDF (European Regional Development Fund) through the project SEVERUS (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, Ref. num. RTI2018-099589-B-I00). The reinforcement systems and construction of the specimens for the experimental programme have been funded by Kerakoll Spa through the RTD project “Seismic Strengthening of Masonry Walls” (Ref. num. A-01278). The authors wish to thank Paolo Casadei, José Luis Sanchez and José Dobón from Kerakoll Spa for their involvement and support. The support from Secretaria d’Universitats i Investigació de la Generalitat de Catalunya through a predoctoral grant awarded to the first author is also gratefully acknowledged.Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura::9.1 - Desenvolupar infraestructures fiables, sostenibles, resilients i de qualitat, incloent infraestructures regionals i transfrontereres, per tal de donar suport al desenvolupament econòmic i al benestar humà, amb especial atenció a l’accés assequible i equitatiu per a totes les personesObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.4 - Redoblar els esforços per a protegir i salvaguardar el patrimoni cultural i natural del mónObjectius de Desenvolupament Sostenible::13 - Acció per al ClimaObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.1 - Enfortir la resiliència i la capacitat d’adaptació als riscos relacionats amb el clima i els desastres naturals a tots els païsosPostprint (published version

Experimental and numerical insights on the in-plane behaviour of unreinforced and TRM/SRG retrofitted brick masonry walls by diagonal compression and shear-compression testing

The experimental determination of the parameters that characterise the in-plane shear behaviour of masonry structures is still a challenging task. Different authors have identified the key role of tensile strength in the definition of the in-plane shear behaviour of masonry, but unfortunately its direct experimental characterisation is not always feasible, and masonry’s tensile strength needs to be obtained from complex testing methodologies. As a result, tensile strength needs to be assessed from testing setups such as diagonal compression testing and shear compression testing when the failure mode of masonry is featured by tensile diagonal cracking. However, different formulations are available in the scientific literature regarding the interpretation of the experimental results derived from such tests. This work provides new insights on the interpretation of in-plane shear experimental behaviour of double-leaf historical clay brick masonry walls with low strength mortar joints, both unreinforced and retrofitted with textile reinforced mortar and steel reinforced grout. The research evaluates results derived from both testing methodologies, and investigates the potential correlation between them to fully characterise the in-plane shear behaviour of masonry walls. Finally, a numerical model is used to simulate each testing configuration and study the stress state at the centre of the walls to determine the tensile strength and its correlation with the shear strength and the maximum load attained.The authors gratefully acknowledge the financial support from the Ministry of Economy and Competitiveness and from the Ministry of Science, Innovation and Universities of the Spanish Government, as well as that of the ERDF (European Regional Development Fund) through the project SEVERUS (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, Ref. num. RTI2018-099589-B-I00). The reinforcement systems and construction of the specimens for the experimental programme have been funded by Kerakoll Spa through the RTD project “Seismic Strengthening of Masonry Walls” (Ref. num. A-01278). The authors wish to thank José Luis Sanchez and José Dobón from Kerakoll Spa and Paolo Casadei, for their involvement and support. The support from Agència de Gestió d’Ajuts Universitaris i de Recerca de la Generalitat de Catalunya through a predoctoral grant awarded to the first author is also gratefully acknowledged.Peer ReviewedObjectius de Desenvolupament Sostenible::13 - Acció per al ClimaObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.4 - Redoblar els esforços per a protegir i salvaguardar el patrimoni cultural i natural del mónObjectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.1 - Enfortir la resiliència i la capacitat d’adaptació als riscos relacionats amb el clima i els desastres naturals a tots els païsosObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura::9.1 - Desenvolupar infraestructures fiables, sostenibles, resilients i de qualitat, incloent infraestructures regionals i transfrontereres, per tal de donar suport al desenvolupament econòmic i al benestar humà, amb especial atenció a l’accés assequible i equitatiu per a totes les personesPostprint (published version

Micro-scale continuous and discrete numerical models for nonlinear analysis of masonry shear walls

A novel damage mechanics-based continuous micro-model for the analysis of masonry-walls is presented and compared with other two well-known discrete micro-models. The discrete micro-models discretize masonry micro-structure with nonlinear interfaces for mortar-joints, and continuum elements for units. The proposed continuous micro-model discretizes both units and mortar-joints with continuum elements, making use of a tension/compression damage model, here refined to properly reproduce the nonlinear response under shear and to control the dilatancy. The three investigated models are validated against experimental results. They all prove to be similarly effective, with the proposed model being less time-consuming, due to the efficient format of the damage model. Critical issues for these types of micro-models are analysed carefully, such as the accuracy in predicting the failure load and collapse mechanism, the computational efficiency and the level of approximation given by a 2D plane-stress assumption.Peer ReviewedPostprint (author's final draft

Analysis of the performance in the linear field of Equivalent-Frame Models for regular and irregular masonry walls

The Equivalent-Frame Method (EFM), a simplified procedure for structural modelling of masonry constructions, is having a great success for the good balance that it allows between the accuracy of the geometrical description and the simplicity of the mechanical calibration. Despite the widespread use of EFM in scientific and professional field, some uncertainties affect its application to the specific problem of the existing unreinforced masonry (URM) buildings. For these structures, in fact, irregular geometries, the presence of deformable diaphragms and the interaction with other structures in aggregate configurations represent hard-to-model features that limit the accuracy of EFM. The paper presents a comparative study in the linear field between EFM and the more accurate Finite Element Method (FEM), assumed as reference. The comparative analysis involves a wide set of geometrical schemes, characterized by both regular and irregular configurations, and it is aimed at providing a measure of the EFM modelling accuracy as a function of the geometry of the wall. Non-dimensional parameters allow exploring the limits of applicability of EFM for both regular and irregular walls. Based on the parametric analyses, some recommendations are given for improving the effectiveness of the method and preserving the simplicity of application that makes EFM models so popular and widely used.Peer ReviewedPostprint (author's final draft

Seismic performance of bridges during the 2016 Central Italy earthquakes

This paper focuses on the structural performance of existing masonry and reinforced concrete bridges which were surveyed in the aftermath of the 2016 Central Italy earthquakes. Typical bridge vulnerabilities are first reviewed, as they provide a reference for the response of the bridges that were damaged by the 2016 earthquake swarm. Case studies are then discussed and preliminary numerical analyses are carried out to interpret the observed failure modes. In general, all surveyed masonry bridges experienced some extent of damage, particularly when built with poor-quality materials and subjected to geotechnical-induced effects. However, they offered a robust response in terms of collapse prevention. The majority of existing reinforced concrete bridges, although designed primarily for gravity loads, exhibited acceptable performance; however, local damage due to the poor maintenance of the structural systems was observed, which affected primarily the non-structural components of the bridges