112 research outputs found
Vulnus Vb 4.0: Procedura automatica per analisi di vulnerabilità sismica di edifici in muratura
No full textAggiornamento ed estensione in Visual basic della procedura VULNUS, di Bernardini-Gori-Modena, 1988. A cura di M.R. Valluzzi, con contributi di Benincà G., Barbetta E., Munari M
Study on local effects of aggressive environmental conditions on masonry strengthened with FRCM
No full textAggressive environmental conditions as moisture, temperature and presence of salts, may affect the interfacial behaviour of FRCM bonded to masonry. To check the effectiveness of intervention solid clay brick samples and masonry assemblages including mortar joints were investigated. Strips of carbon fibre nets were applied with a cementitious or a lime based matrices. Specimens were exposed to salt crystallisation tests, according to a RILEM procedure, and to thermal cycles with a temperature variation ranging between -10°C and +70°C. The characteristic size of damage of the samples were monitored by visual observation and laser profilometer; the loss of bond of the composites was verified by pull-off test. Tests results showed different behaviour between the inorganic matrices applied on bricks having different strengths. Moreover, the adhesion strength was affected by the presence of bed joints. The adherence of the specimens of cement matrix depends from the type of substrate and his damage. Specimens of lime matrix do not seem to have a relation between damage of the substrate and adherence, as the failure occurred at the interface matrix/strengthening
Testing of bond solutions for UHTS steel strand composites applied to extruded bricks
No full textFibre-Reinforced Polymers (FRPs) are currently a viable and widespread solution for retrofitting masonry buildings, including those of the architectural heritage where interventions need to meet strict requirements. Nevertheless, continuous investigations on possible fibre-matrix combinations and lay-up methods are needed to find further FRP bonding solutions that are possibly more resilient and efficient. In this study an Ultra-High Tensile Strength Steel (UHTSS) fabric was considered as the reinforcement for the FRPs, while either Polyurethane (PU) or epoxy polymers were considered as the matrix. UHTSS fabrics have been introduced in the last decade to overcome some of the limits of common reinforcing fabrics (e.g. carbon, glass, etc.) like, for example, the limited shear resistance that complicates the use of mechanical anchoring for improving the bond of FRPs, especially under peeling stresses. The suitability of PU flexible polymers (Young’s modulus lower than 30 MPa) as matrices for FRPs, in place of the most commonly used epoxy resins, has been investigated in the past few years. Their key characteristic is the diffusion of bond stresses over longer adhesion lengths, with the consequent reduction of peak values. This paper presents and discusses an experimental investigation that compares the bond strength of two Steel-FRP (S-FRP) reinforcements applied to extruded solid clay bricks, made of UHTSS fabric embedded in either a PU or an epoxy matrix. Lastly, two possible lay-up solutions, with one aimed at improving the bond behaviour by inserting an additional interface, are also discussed
Probabilistic Modelling of the damage induced by salt crystallization in fiber reinforced clay brick masonry
No full textMasonry buildings suffer continuous and various attacks due to the changes induced from the surrounding environment. Those conditions also influence materials interacting with the substrate, due to intervention techniques. Nowadays, Fiber-Reinforced Cementitious Matrix (FRCM) are increasingly used to strengthen and retrofit existing structures, also belonging to historical contexts. Nevertheless, the durability of composite systems applied on existing substrates, particularly for masonry, has not been sufficiently investigated yet. In this paper, to examine durability against sulphates, a series of salt crystallization tests were carried out on small masonry assemblages reinforced with FRCM. Carbon fibers open meshes, embedded in layers of matrix based on two hydraulic binders, were used. The loss of material from the surface was assumed as parameter of damage, as well as the bulging of the material under the fibers. That loss was computed on the vertical section of the specimens through a computer code, which elaborated successive readings of the surface decay measured with a laser profilometer. The randomness affecting the damage due to the salt crystallization and the consequent loss of material layers under the fibers, suggested the adoption of a probabilistic approach, where the continuous deterioration of specimens can be assumed as a stochastic process. Preliminary results are discussed in the paper
Correction to: Understanding of historical masonry for conservation approaches: the contribution of Prof. Luigia Binda to research advancement (Materials and Structures, (2018), 51, 6, (140), 10.1617/s11527-018-1254-4)
No full textThe article ‘‘Understanding of historical masonry for conservation approaches: the contribution of Prof. Luigia Binda to research advancement’’, written by ‘‘Anna Anzani, Giuliana Cardani, Paola Condoleo, Elsa Garavaglia, Antonella Saisi, Cristina Tedeschi, Claudia Tiraboschi, Maria Rosa Valluzzi’’, was originally published electronically on the publisher’s Internet portal (currently SpringerLink) on 16 October 2018 without open access. The copyright of the article changed in December 2019 to © The Author(s) 2019, and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made
Rocking resonance of a rigid free standing block
No full textThis paper deals with the resonance conditions of a rigid free standing block in order to highlight to what extent the ground motion details and the system parameters can influence the rocking response. A sequence of instantaneous pulses causing “rocking resonance” is first explored and the natural motion occurring between two impacts is then investigated. The coefficient of restitution is assumed to be a variable of the problem to account also for other damping effects (e.g. local plastic deformations). A stabilized phase of the motion is identified for which an upper-bound of the maximum rotation angle of the block can be defined in closed form. The results are plotted in resonance spectra which point out the influence of the coefficient of restitution and the size and slenderness of the block
Knowledge-based data warehouse of interventions for the protection of masonry historical heritage
No full textThe great social, cultural and economic losses caused by seismic events on the cultural heritage assets have stimulated, in the last decades, a great research effort in the development of new integrated knowledge-based approaches and tools for their protection from earthquake-induced risk. Great amounts of data have been collected and several databases developed so far to gather information about peculiar aspects on the seismic behaviour of masonry historical buildings. The detail level of such databases is usually influ- enced by the required survey or intervention, with a generalised lack of information on the fundamental pa- rameters that affect the seismic response, i.e. boundary conditions, used materials, types of connections and constraints, etc. A global systematization is required, to take advantage from the considerable and precious amount of available data, linking all information on the basis of the relation between construction typologies and elements and failure mechanisms, including also survey and monitoring procedures and tools available in literature. A new web-based data warehouse was developed within the FP7 European research project NIKER (2010-2012) “New Integrated Knowledge-based approaches to the protection of Cultural Heritage from Earthquake-induced Risk”) to collect, systematize and analyse available data. This tool is able to link con- struction typologies and structural elements with collapse mechanisms into a matrix of interventions where end-users can easily select optimum solutions for the seismic improvement and assess the effectiveness, on the basis of pre- and post-intervention parameters. The interactive and dynamic functionalities, together with the capacity of cross-correlation of information at different knowledge levels and the sharing philosophy of a web-based system, make the data warehouse a powerful tool for a new innovative, integrated and knowledge based approach to the protection of cultural heritage, useful both to professionals and researchers
Seismic vulnerability assessment of clustered historical centers: fragility curves based on local collapse mechanisms analyses
No full textProtection and preservation of minor historical centres against earthquakes effects are
not trivial tasks, particularly in the cases, quite common, of complex aggregate buildings. The paper
aims at evaluating the seismic vulnerability of historical clustered buildings on a urban scale, through the
analysis of local collapse mechanisms, carried out with a parametric approach. This procedure is applied
to four historical centres of L’Aquila province struck by the 2009 earthquake. The identification of the
significant parameters is related to the definition of representative typologies within the city centres. Each
typology is characterized by recurring features, mainly recognizable with a survey performed outside the
buildings. After the identification of the relevant aspects, local mechanisms of collapse analyses are carried
out, by varying the parameters between defined range of values, in order to take into account possible
uncertainties in the data collection. A set of fragility curves for each identified typology is defined
and the obtained results are compared to the damage data gathered in the post-earthquake phase for the
buildings. This approach allows for possible extensions to buildings that may be included in the typology
categories here defined
MODELLING THE MECHANICAL BEHAVIOUR OF VEGETABLE FIBRE REINFORCED CONCRETE BLOCKS
No full textThe mechanical behavior of hollow blocks made of concrete and natural sisal fibers tested to failure is dealt with. First, the results of compression tests carried out on blocks, prisms and wallettes are presented; for comparison, the mechanical response of companion plain concrete specimens is also shown. Then, a numerical model is developed to simulate the nonlinear behavior of the blocks, with the aim of predicting the possible crack growth of structural masonry elements in the design phase. The parameters and the boundary conditions that define the models are calibrated to match the experimental load-displacement curves. A qualitative description of the damage evolution in the elements using the smeared crack model implemented in the commercial FE program DIANA and the XFEM implemented in Abaqus is obtained. The experimental and numerical results are critically discussed, and possible future improvements of the proposed models are outlined
FIBER-REINFORCEMENT OF MASONRY ARCHES AND BARREL VAULTS THROUGH TOPOLOGY OPTIMIZATION
No full textAn innovative approach based on topology optimization is presented to define the optimal reinforcing layout for masonry arches and barrel vaults that have to be retrofitted using a prescribed amount of unidirectional fiber-reinforced composite strips. The overall elastic energy of the strengthened element is adopted as objective function to be minimized. The negligible tensile strength of brickwork is taken into account by using a no-tension elastic model. Conversely, the strength in the reinforcing fibers is constrained to be non-negative. To ensure perfect bonding of the strengthening layer at the intrados, suitable fasteners have to be employed. Preliminary numerical simulations are presented to assess the capabilities of the proposed procedure and to investigate the optimal reinforcement patterns for arches and barrel vaults. Fiber-reinforcement is found to spontaneously arise where cracks would occur in the unreinforced element. The proposed formulation allows also the optimal location of reinforcing steel ties to be spotted out
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