public housing in florence seismic assessment of masonry buildings

Abstract Florence is known all over the word for its historical and monumental buildings; however, most part of residential buildings have been made in the XX century, and they present all the critical issues proper of recent housing. Florence is one of the first Italian cities to have experienced the public housing. Its public housing population consists mostly of masonry buildings, and it does not comply the requirements provided by the current seismic legislation. This work is aimed at evaluating the seismic performance of a masonry building-type belonging to the public housing population of Florence. A typical public housing intervention, consisting of 18 masonry buildings, has been assumed as case-study. The seismic input has been described according to the Italian Code prescriptions, by considering the effective soil stratigraphy, and considering the effective mechanical properties of each layer. The seismic performance of the case-studies has been checked by performing a nonlinear static analysis. The results are expressed in terms of seismic performance, defined as the ratio between the seismic capacity and the corresponding demand. The obtained results evidenced the role of the building features on the seismic assessment of the buildings

Coupled interface-based modelling approach for the numerical analysis of curved masonry specimens strengthened by CFRP

[EN] Aim of the present paper is to numerically study the bond behavior of curved masonry specimens externally strengthened by Carbon Fiber Reinforced Polymer systems (CFRP). A simple 1D-modeling approach is presented to this aim, where the coupled behavior between shear and normal stresses developing at the reinforcement/masonry interface level is specifically introduced to properly account for the role played by the curvature radius. The model is indeed enriched by the introduction of shear stress-slip laws able to account for the beneficial friction effect, when compression normal stresses develop at the interface level and the reduction of the slip strength corresponding to the de-cohesion in presence of normal stresses in tension. Considering some case studies derived from the current literature, consisting of shear-lap bond tests of curved masonry specimens characterized by different curvatures of the bonded surface and different strengthening configurations, the validation of the proposed approach is carried out. In particular, two modeling strategies are considered and critically compared: the first one, denoted as approach (A), where the presence of the mortar joints is neglected, and the second one, denoted as approach (B), where mortar joints are specifically introduced in the model. Finally, the results obtained by using the proposed simple approach are compared with those obtained from both sophisticated FE numerical models and theoretical formulas deduced from the current literature.Grande, E.; Fagone, M.; Rotunno, T.; Bertolesi, E.; Milani, G. (2018). Coupled interface-based modelling approach for the numerical analysis of curved masonry specimens strengthened by CFRP. Composite Structures. 200:498-506. https://doi.org/10.1016/j.compstruct.2018.05.118S49850620

Single lap shear tests of masonry curved pillars externally strengthened by CFRP strips

[EN] The paper presents an experimental study concerning the bond behaviour of Carbon Fiber Reinforced Polymers (CFRP) sheet reinforcements applied to curved masonry surfaces. Such strengthening technique is more and more used in structural rehabilitation and retrofitting of existing buildings. Its effectiveness has been demonstrated by several studies published in the literature, mostly devoted to flat bonded surfaces. Observing that CFRPs are extensively applied on arches and vaults but only few research activities concern curved bonded surfaces, the experimental study described in this paper is aimed to contribute to fill this gap. The experimental program was carried out on portions of masonry arches, reinforced by CFRP sheets bonded at extrados or intrados, tested by a single lap shear test. The experimental results allowed to analyse the effectiveness of such reinforcements, loaded by actions tangent to an end of the reinforcement itself, with respect to its position (intrados or extrados) and to the curvature of the bonding surface. As expected, the results highlight that the bond behaviour strongly depend on the position of the reinforcement. In particular, the capacity of reinforcements bonded at the extrados increases with the curvature, while decreases with the curvature for those bonded at intrados.The Authors gratefully acknowledge the financial support provided by the Italian Department of Civil Protection and ReLUIS (Rete dei Laboratori Universitari di Ingegneria Sismica), 2014-2016 Grant - Innovative Materials.Rotunno, T.; Fagone, M.; Bertolesi, E.; Grande, E.; Milani, G. (2018). Single lap shear tests of masonry curved pillars externally strengthened by CFRP strips. Composite Structures. 200:434-448. https://doi.org/10.1016/j.compstruct.2018.05.097S43444820

Micro-mechanical FE numerical model for masonry curved pillars reinforced with FRP strips subjected to single lap shear tests

[EN] The present paper discusses the results obtained by using a micro-mechanical FE numerical model for the study the bond behavior of some curved specimens strengthened by Fiber Reinforced Polymer (FRP) composite materials. The numerical model, implemented into the FE code Abaqus, is a sophisticated micro-modelling (heterogeneous) approach, where bricks and mortar are meshed separately by means of 4-noded plane strain elements exhibiting distinct damage in tension and compression, FRP is assumed elastic and an elastic uncoupled cohesive layer is interposed between FRP reinforcement and masonry pillar. The experimental investigation considered to benchmark the numerical approach is aimed at characterizing the influence of normal stresses induced by curved supports on the stress-transfer mechanism of FRP materials. To this scope some single lap shear tests performed at the University of Florence on FRP reinforced curved pillars with two different curvature radii (1500 and 3000 mm) are here considered. The obtained numerical results show a promising match with experimental evidences, in terms of elastic stiffness, peak loads and post-peak behavior. Indeed, the proposed approach allows to correctly account for important local effects, such as the effect of FRP-masonry interfacial normal stresses on the global delamination strength and the distribution of damage in the pillar volume. By using the proposed modelling approach, comprehensive numerical sensitivity analyses to investigate the role played by the curvature on the ultimate delamination strength, are also presented in the paper.Bertolesi, E.; Milani, G.; Fagone, M.; Rotunno, T.; Grande, E. (2018). Micro-mechanical FE numerical model for masonry curved pillars reinforced with FRP strips subjected to single lap shear tests. Composite Structures. 201:916-931. https://doi.org/10.1016/j.compstruct.2018.06.111S91693120

The influence of the joint thickness on the adhesion between CFRP reinforcements and masonry arches

Abstract The effectiveness of Carbon Fiber Reinforced Polymers (CFRP) reinforcements bonded to masonry structures is demonstrated by the several interventions made on existing buildings as well as by the numerous studies presented in the scientific literature. In practical strengthening interventions, CFRP sheets are being used to reinforce both plane and curved structural elements. Contrariwise, research in the scientific literature are mainly devoted to the analysis of the effectiveness of such reinforcements bonded on plane surfaces. For this reason, the experimental program described in this paper concerns the analysis of the mechanical behavior of portion of masonry arches reinforced by CFRP sheets. The experimental results allowed to analyze the effectiveness of such reinforcements applied at intrados or extrados, loaded by actions tangent to an end of the reinforcement itself. The influence of the mortar joints thickness on the performance of such reinforcements has been also analyzed in the experimental program

Modeling of the Tensile Behavior FRCM Systems for Repair and Strengthening Interventions of Masonry Structures

Fiber Reinforced Cementitious Matrix (FRCM) systems are an innovative solution for strengthening interventions of existing masonry and concrete constructions. The current literature provides interesting experimental and numerical studies which underline the potentialities of FRCMs and their specific features. Direct tensile tests are generally used for characterizing the behavior of FRCM strengthening systems. These tests particularly underline the occurrence of both matrix cracking and debonding of the reinforcement from the matrix, phenomena which particularly influence the performance of FRCM systems. The present paper aims at numerically analyzing the response of FRCM strengthening systems during tensile tests carried out throughout different setup configurations. To this end, a simple model carried out from literature and opportunely modified is presented in the paper and validated with reference to experimental case studies. Moreover, the obtained results are critically examined to emphasize the role of the proposed model for the interpretation of the results carried out from standard tensile tests