1,721,093 research outputs found
The Role of the Adhesive on the Bond Behavior of SRPs Applied on Masonry Supports: Experimental and Numerical Study
No full textSteel Reinforced Polymers (SRP) have been recently introduced and adopted as strengthening systems for existing constructions. Although the interest for this kind of strengthening materials is increasing also for masonry structures, in particular for historic constructions, only few studies specifically pertained to masonry elements strengthened with SRPs are available in the literature. In this context, a twofold purpose is at the basis of the present paper. The first one consists of experimentally investigating the bond behavior of masonry elements strengthened with SRPs using different types of adhesives and strips density. The second purpose aims at developing simple formulations for evaluating the bond resistance of masonry elements strengthened with SRPs applied with different types of adhesive systems
Nuove tendenze nella progettazione sismica di edifici a controventi concentrici
No full textLe metodologie progettuali introdotte dalle recenti normative sismiche hanno modificato sostanzialmente il processo progettuale dei controventi. Le limitazioni imposte sulla snellezza delle diagonali nonché le richieste di sovraresistenza a travi, colonne e collegamenti, condizionano fortemente il dimensionamento degli elementi strutturali del controvento, conducendo in alcuni casi verso soluzioni sovradimensionate o non progettabili. In questo lavoro, a valle di un’approfondita analisi critica delle recenti normative sismiche italiana (OPCM), europea (EC8) ed americana (AISC), viene presentato il progetto di edifici controventati a 3 e 6 piani, al variare di alcuni parametri geometrico/strutturali che identificano diverse scelte progettuali. Tali casi di studio consentono di valutare l’incidenza delle prescrizioni normative su progettabilità e peso strutturale dei controventi
Proposal of a scissor-based model for the non-linear analysis of RC beam-column joints strengthened by FRP
No full textThe paper presents a new simple modeling approach for studying the monotonic response of RC beam-column joints externally strengthened by Fiber Reinforced Polymer (FRP) materials. The approach assumes a parallel combination of the behavior of the joint in the unstrengthened configuration and the contribution of strengthening system. To achieve this, the common scissor model, where the behavior of joint shear panel is modeled through a rotational spring, is here modified by introducing an additional spring, arranged parallel to the concrete spring, to account for the contribution of strengthening system. Regarding the behavior of the additional spring, the authors proposed a multilinear simplified constitutive law by appropriately combining analytical models available from the literature with specific guidelines provided by Italian technical standards. The proposed model, implemented in the computer code OpenSees and validated against experimental case studies from the literature, demonstrates its strong capability to capture the contribution of the strengthening system on both the strength and ductility of joints
Micro-mechanical FE numerical model for masonry curved pillars reinforced with FRP strips subjected to single lap shear tests
Full text linkThe 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
Full 3D FE micro-modelling for single lap shear tests on FRCM reinforcing systems
No full textA novel advanced full 3D heterogeneous FE numerical model for the analysis of specimens made by a fragile material (e.g. concrete or masonry), reinforced with FRCM and subjected to standard debonding tests is discussed. The numerical approach relies into a micro-mechanical full 3D discretization of the FRCM reinforcing system. For the two cementitious matrix layers (external and internal) 8-noded brick elements exhibiting distinct damage and softening behavior in tension and compression are utilized, whereas for PBO elastic 3D elements are used, introducing an inelastic cohesive interface layer placed between the two layers of cementitious mortar and the PBO grid. In this way, all possible failure modes in FRCM strengthening systems can be properly reproduced, exception made for PBO tensile rupture, which is unlike in the majority of the existing experimental tests available. The model is preliminarily benchmarked utilizing some experimental results available in the technical literature, and relying into single lap shear testes performed on FRCM strengthening systems applied to a concrete substrate. Excellent agreement between the results obtained with the micro-mechanical numerical model proposed and experimental outcomes is observed, especially in the prediction of the initial stiffness, peak strength and post peak behavior
The influence of the joint thickness on the adhesion between CFRP reinforcements and masonry arches
No full textThe 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
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