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Triplet Test on Rubble Stone Masonry: Numerical Assessment of the Shear Mechanical Parameters
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Simulating shear-compression mechanical behavior of historical masonry panels: sensitivity of 3D numerical models to input parameters
No full textSimulating the Nonlinear Mechanical Behavior of FRCM-strengthened Irregular Stone Masonry Walls
No full textEarthquakes constitute a significant cause of degradation and damage for masonry heritages, such as churches, palaces, castles, and entirely historical centers. This work aims to investigate numerically the Fiber Reinforced Cementitious Matrix (FRCM) system applied as coating- reinforcement to existing stone masonry walls. Indeed, despite the FRCM is, nowadays, one of the most widely adopted systems for the consolidation of masonry structures, the knowledge on its mechanical behavior is still incomplete. In this work, diagonal compression tests performed on reinforced stone masonry panels are simulated and interpreted by adopting a sophisticated numerical framework, based on the Lattice Discrete Particle Model (LDPM), which simulates, at the length scales of the masonry stones and coating mortar grains, the fracture and failure behavior of the quasi-brittle heterogeneous materials by modeling the interaction among irregular particles. Different assumptions on the FRCM features (bond behavior and thickness of the coating mortar, and the presence or not of the fiber grid therein the coating mortar) were investigated to better understand their effect. The computational effort of using that method was rewarded from the possibility of capturing the main aspects of the material heterogeneity on the fracture propagation and damage evolution in the reinforced masonry walls
Lime-based mortar reinforced by randomly oriented short fibers for the retrofitting of the historical masonry structure
Full text linkRecent seismic events prompted research to develop innovative materials for strengthening and repair of both modern and historic masonry constructions (buildings, bridges, towers) and structural components (walls, arches and vaults, pillars, and columns). Strengthening solutions based on composite materials, such as the Fiber Reinforced Polymers (FRP) or the Fiber Reinforced Cementitious Matrix (FRCM), have been increasingly considered in the last two decades. Despite reinforcement made of short-fibers being a topic that has been studied for several years from different researchers, it is not yet fully considered for the restoration of the masonry construction. This work aims to experimentally investigate the enhancement of the mechanical properties of lime-based mortar reinforced by introducing short glass fibers in the mortar matrix with several contents and aspect ratios. Beams with dimensions of 160 mm × 40 mm × 40 mm with a central notch were tested in three-point bending configuration aiming to evaluate both the flexural strength and energy fracture of the composite material. Then, the end pieces of the broken beams were tested in Brazilian and compressive tests. All the tests were performed by a hydraulic displacement-controlled testing machine. Results highlight that the new composite material ensures excellent ductility capacity and it can be considered a promising alternative to the classic fiber-reinforcing systems
Fragility curves of masonry buildings in aggregate accounting for local mechanisms and site effects
No full textThe seismic evaluation of masonry buildings in aggregate, largely diffused within the existing Italian and European building stock, represents a difficult and open task that has not been exhaustively investigated so far. The study proposes a procedure aimed at evaluating the potential impact of the combination of local mechanisms and site-amplification in terms of fragility curves on an existing unreinforced masonry (URM) aggregate which is made of five adjacent structural units mutually interacting with each other during seismic sequences. The case study is inspired by built heritage of the historic centre of Visso struck by the Central Italy 2016/2017 earthquakes. The in-plane (IP) response of URM buildings was simulated through nonlinear dynamic analyses performed on a 3D equivalent frame model of the structure, whereas out-of-plane (OOP) mechanisms were analysed by adopting the rigid-block assumption but assuming, as seismic input, the floor accelerations derived from the post-processing of data derived from the global 3D model. An innovative procedure considering the pounding effect to the global response of the building is also presented. Two soil conditions were assumed with (freefield) and without (bedrock) site amplification. The results showed that site effects strongly affected the seismic vulnerability of the aggregate, also altering the combination between IP and OOP mechanisms. In fact, for bedrock condition, especially for medium-high damage levels, local mechanisms were prevailing with respect to the IP response. Conversely, for freefield condition, IP mainly governed the overall behaviour for all the damage levels, consistently with the field evidence
Performance of Fiber Reinforced Mortar coating for irregular stone masonry: Experimental and analytical investigations
No full textNowadays, the application of Fiber Reinforced Mortar (FRM) is widely used for the consolidation and rehabilitation of masonry structures because represents an effective solution in terms of reversibility and applicability. The paper illustrates the results of cyclic diagonal compression tests performed in situ on stone masonry specimens isolated from the walls of a historic building of L'Aquila (Italy). The tested stone masonry is representative of existing structures of the territories of the central Apennines in Italy. Only two of four panels were strengthened by FRM to provide also the reference value of the unreinforced masonry. The FRM comprised a glass-fiber grid embedded in a natural hydraulic lime (NHL)-based mortar applied as a coating to the masonry surfaces as well as carbon shear connectors. The tests were analyzed to derive the shear strength and the shear modulus of the masonry, as well as their evolution during the tests. Moreover, these tests were compared and integrated with a consistent number of experimental data collected in the current literature aiming to validate a new analytical equation for the estimation of the shear strength of the reinforced masonry, merely based on the properties of the unreinforced masonry and the FRM mortar
Assessment of the FRCM in-plane behavior in masonry retrofit applications
Full text linkBecause of its well-documented effectiveness in enhancing the strength and ductility of unreinforced masonry (URM) construction, Fiber Reinforced Mortar (FRCM) is now widely used for the consolidation of heritages, such as churches, palaces, castles, and entirely historical centers. The main purpose of this work is to provide the authors' principal outcomes in the FRCM application to masonry after performing extensive experimental campaigns and numerical simulations over the previous few years. The recent findings have already been appreciated by the research community but have yet to be considered in existing standard codes/recommendations, leaving the contribution of fiber mesh (i) and features of both coating mortar and URM wall (ii) to the improvement of the shear strength of reinforced masonry panels unclear. In fact, unlike FRP, fibers embedded in the mortar coating of the FRCM do not affect the shear strength of the reinforced panel, "limiting" its effect in enhancing the load-bearing capacity of the wall and, therefore, the structure's ductility. This important recent experimental/numerical evidence should be incorporated into the code's recommendation to avoid overestimating the FRCM performance during design phases. Furthermore, the Italian codes suggest simplified amplification factors for estimating the improvement of shear strength owing to the strengthening system that ignores the fact that the greater the thickness of the masonry wall, the lower the FRCM's efficiency, and vice versa. A practice-oriented analytical formulation has been provided to validate such mechanisms by confirming a consistent data set of masonry panels strengthened by FRCM tested under diagonal compression. In this work, a numerical investigation is provided to highlight the importance of considering the effective thickness- and tensile strength-ratio between the FRCM mortar coating and the URM panel to accurately predict the enhancement in the mechanical behaviour of the FRCM-reinforced masonry. (c) 2023 The Authors. Published by Elsevier B.V
Fiber Reinforced Cementitious Matrix (FRCM) for strengthening historical stone masonry structures: experiments and computations
No full textSeismic fragility assessment of existing masonry buildings in aggregate
No full textThe paper describes the derivation of fragility curves useful for the seismic risk analyses of existing unreinforced masonry buildings inserted in aggregate. The L-shaped examined aggregate consists of three adjacent structural units that may mutually interact during seismic events. The seismic assessment is focused on the corner unit. The effects of different connection types between the adjacent units on the structural response were investigated. The seismic vulnerability of the masonry aggregate was assessed through nonlinear dynamic analyses (NDA) performed according to the multi-stripes approach. Both the in-plane and out-of-plane mechanisms were analyzed. The in-plane response of the corner unit is assessed through a 3D equivalent frame model of the entire aggregate, while the evaluation of its out-of-plane response makes use of the rigid-block assumption. Although evaluated in a separate way, the NDAs performed on the latter are based on the time histories derived from the global 3D model. The results are then processed in order to derive fragility curves, firstly, of the single failure mechanisms and, then, of the overall combined behavior. To this aim, various performance conditions are examined. For the reference building, the damage limit state is mainly governed by the in-plane behavior, while the collapse limit state by out-of-plane mechanisms. Moreover, the higher the connection level between adjacent structural units, the higher the interaction between in-plane and out-of-plane mechanisms at the collapse limit state
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