1,720,971 research outputs found
Determination of Masonry Compressive Strength Properties by Testing Cores
No full textDealing with the seismic vulnerability assessment of existing masonry constructions is not an easy task, especially concerning the difficulties in determining the masonry mechanical properties. Experimental tests, classifiable, depending on their invasiveness, as non-destructive, slightly-destructive or destructive, may be performed directly on-site or in laboratory on materials extracted on-site. Existing buildings with an historical, architectural or artistic value cannot be severely damaged by testing; therefore, there is the need of assessing the reliability of non-destructive and slightly-destructive testing methodologies for the determination of the material parameters. The goal of the present research is to evaluate the suitability of testing cores for the determination of the masonry compressive strength. Testing a masonry core in compression is not a standardized procedure and it implies the casting of high-strength mortar caps at the top and at the bottom of the samples to obtain regular surfaces on which applying the compressive load and to simulate the confinement given, on site, by the surrounding masonry. In this research, a solid clay brick masonry typology is considered, for which the compressive strength is estimated by testing cores and standard wallets. To investigate the reliability of the testing method, both single-wythe and double-wythe cores are subject to uniaxial compression tests, also considering variations in the dimensions of the high-strength mortar cap. Correlations between the results obtained by testing cores and wallets are presented in the paper, in terms of compressive strength and evolution of the crack pattern
FRCM strengthening systems efficiency on the shear behavior of pre-damaged masonry panels: an experimental study
No full textExisting masonry constructions are highly vulnerable to seismic actions, as demonstrated by the severe earthquakes which stroke the Italian territory in recent years, causing great damages, especially in old masonry buildings. Therefore, restoring damaged buildings, with the aim to recover or improve their structural capacity, is a key aspect in the post-seismic interventions. Fiber reinforced composite materials could be effectively used to this purpose. One aspect which is worth to investigate is the application of these reinforcement typologies on damaged structural elements. Even though many experimental campaigns are available concerning the mechanical improvement given by composite materials applied on undamaged structural elements, only few can be found considering strengthening of already damaged masonry walls. The objective of the work here presented is to evaluate the shear response of damaged masonry panels strengthened using fiber reinforced cementitious matrix (FRCM). Two unreinforced brick masonry walls were subjected to diagonal compression tests, producing an extended state of damage. Afterwards, the same walls were strengthened with FRCM and diagonal compression tests were again performed. Comparisons were done between the results of the unreinforced samples and the pre-damaged strengthened ones, in terms of shear strength and post-peak behavior. The FRCM retrofitting system was also used to strengthen an undamaged masonry panel, which was tested in order to analyze similarities and differences with respect to results obtained for pre-damaged samples. The experimental campaign allowed to study the sole contribution of the reinforcement to the shear capacity of the wall panels. Results showed that the presence of FRCM reinforcements on damaged masonry panels influenced the shear behavior of the samples, which experienced a more ductile failure
An innovative ductile mortar to improve the seismic response of masonry structures
No full textThe proposed work presents some selected results on a wide experimental campaign devoted to evaluate
the mechanical response of unreinforced masonry (URM) systems realized with an innovative mortar,
characterized by a ductile behavior. The improved response of the mortar induces higher resistance of
masonry panels subjected to shear actions, thus improving their earthquake-resistant performances.
The experimental campaign described in the paper is part of the research project called “Zero
Environmental Risks in Our buildings” (ZERO), funded by the PORFESR 2014-2020 call of Emilia-
Romagna region (North Italy). The final objective of the project is to introduce in the market a new class
of construction and decorative materials, characterized by a high environmental-compatible profile
(VOC-free) and improved chemical and mechanical properties.
One of the objectives of ZERO has been the improvement of the ductile behavior of URM systems. To
this aim, a wide experimental campaign has been carried out at the CIRI Building & Constructions at
University of Bologna. The experimental tests have been devoted to characterize the material properties
through specimens of the innovative mortar, as well as the coupled structural response of masonry
systems realized by means of the innovative mortar and different clay blocks. In the present work, the
preliminary results of the characterization of mortar specimens is described. In detail, three-point
bending tests and centered compression tests have been performed to derive the flexural and
compressive strength of the innovative mortar, as well as quantify the ductile response of the material.
From the results, the innovative mortar is found to have improved resistance towards tensile action, and
superior ductility values with respect to the specimens realized with traditional mortar commonly
available in the market
Uni-axial Compressive Tests on Masonry Columns Confined by FRP and FRCM
Full text linkMany old masonry buildings, particularly in seismic regions without any provision for earthquake loading, are particularly vulnerable. This makes brick masonry structures unsafe and requires economical, safe and fast refurbishment measures. Traditional techniques, that were largely used and investigated in the past, may be inadequate in seismic areas where the added mass could generate a significant extra weight that induce an increase of the seismic actions. Moreover, when it is necessary to preserve the historical value of architectural heritage, the reversibility, compatibility and sustainability of the intervention could become critical for the selection of the most appropriate strengthening technique. Several investigations have shown that the use of Fiber Reinforced Polymers (FRP) materials on masonry structures can be effective for different purposes. On the other hand, few studies on masonry columns confined with Fiber Reinforced Cementitious Matrix (FRCM) are available in literature. In the present paper an experimental campaign devoted to analyse the effectiveness of different reinforcement typologies on square masonry columns built with clay bricks and cementitious mortar, in particular FRP and FRCM, will be reported. Two different configurations of the reinforcing system will be investigated: carbon or glass fibers, with organic or inorganic matrix, applied as external reinforcement along the perimeter of the masonry columns in the form of continuous and discontinuous wrap. The specimens were subjected to uni-axial compressive test until failure. The obtained experimental results showed an increment in the load bearing capacity of reinforced columns
Effectiveness of FRCM Reinforcement Applied to Masonry Walls Subject to Axial Force and Out-Of-Plane Loads Evaluated by Experimental and Numerical Studies
Full text linkAn experimental campaign and a numerical analysis devoted to the investigation of the out-of-plane behavior of masonry walls reinforced with Fiber Reinforced Cementitious Matrix (FRCM) are presented here. The main goal of this study is to analyze and evaluate the effectiveness of the strengthening system, by discussing failure modes and capacity of strengthened masonry walls, in order to assess their behavior under out-of-plane horizontal actions, such as, for example, seismic actions. A purposely designed experimental set-up, able to separately and independently apply an axial force and out-of-plane horizontal actions on masonry walls, was used. Experimental results are discussed and compared with the outcomes of nonlinear analyses performed on simplified finite element models of the walls. A proper evaluation of the flexural capacity of FRCM strengthened walls is the first step of the ongoing process of drawing reliable code guidelines leading to a safe design of strengthened masonry structures
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Out-of-plane strengthening of masonry walls with FRCM composite materials
No full textStructural strengthening by using composite materials proved to be one of the most suitable solutions for reinforcing masonry buildings. In this framework, the focus point of the presented experimental study is to evaluate the out-of-plane behaviour of masonry walls strengthened with Fiber Reinforced Cementitious Matrix (FRCM) composites when subjected to horizontal actions, by analyzing and discussing failure modes and their out-of-plane capacity. To this purpose, a new experimental set-up was developed, capable of applying an axial force and out-of-plane horizontal actions on full-scale masonry panels, placed in vertical position and subjected to a stress state similar to that present on a real masonry wall. Experimental results, obtained by using traditional and innovative techniques (such as Digital Image Correlation), will be compared with those coming from more conventional tensile and bond tests performed on FRCM coupons applied on masonry substrates, making use of simple theoretical models
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