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Typical failure modes for lightweight concrete masonry walls: (a) unreinforced; (b) lightly horizontally reinforced; (c) confined unreinforced; (d) confined and horizontally reinforced

Typical failure modes for lightweight concrete masonry walls: (a) unreinforced; (b) lightly horizontally reinforced; (c) confined unreinforced; (d) confined and horizontally reinforced

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Article
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The paper presents and describes the main issues related to two building systems for modern masonry structures using truss reinforcement, currently under development at University of Minho, one based on lightweight concrete blocks and another based on reinforced concrete block masonry. Details of the experimental and numerical work carried out are...

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Context 1
... selected tests, the analysis of the contribution of the reinforcement to the global response and the evaluation of the bond strength was carried through strain gauges. Results for Lightweight Concrete Masonry Walls Figure 6 illustrates typical failure modes obtained for the walls tested. In the walls without bed joint reinforcement, initially flexural behavior dominates with horizontal cracks appear-ing at the bottom and top of the walls. ...
Context 2
... selected tests, the analysis of the contribution of the reinforcement to the global response and the evaluation of the bond strength was carried through strain gauges. Results for Lightweight Concrete Masonry Walls Figure 6 illustrates typical failure modes obtained for the walls tested. In the walls without bed joint reinforcement, initially flexural behavior dominates with horizontal cracks appear-ing at the bottom and top of the walls. ...

Citations

... According to Cohn and Bartlett [55], a ductility coefficient can be calculated using the strain on the post-peak side at 85 % of the load-bearing capacity and the strain of the first yield behaviour of the specimen (Fig. 13). The ductility coefficient of Wallet 1 is 1.47, which is identical to the ductility coefficient of 1.45 presented by Dong [56] for a wall based on recycled concrete and higher than the ductility coefficient (0.91-1.23) of a wall based on lightweight concrete masonry blocks analysed by Lourenço et al. [57]. In general, it can be stated that the higher this coefficient, the higher the plastic deformation. ...
Article
This paper aims to verify the suitability of masonry blocks based on Miscanthus concrete to be used in dry-stacked walls. Therefore, the load-bearing capacity of single Miscanthus concrete masonry blocks as well as of dry-stacked wallets based on these blocks is analysed in function of geometrical imperfections, such as possible height differences between adjacent blocks due to the production process or/and surface roughness of the dry bed joint. For the study on the load-bearing capacity of single masonry blocks the mixture composition was varied and optimised leading to a maximum ultimate load of 5.42 MPa. With the optimised mixture composition masonry blocks were produced to create small wallets, which achieved a maximum load-bearing capacity of 4.84 MPa. The Miscanthus masonry blocks presented a low Young’s Modulus leading to a very ductile behaviour of the wallet without sudden failure. Furthermore, the variation of the contact area as a consequence of geometrical imperfections was studied and an exponential relation between the contact area and the applied load could be established.
... [5][6][7]) or within confined masonry walls (e.g. [8][9][10][11][12][13]). ...
... On the other hand, the amount of experimental data from tests on masonry walls with bed-joint reinforcement only, which is the focus of the present work, is rather limited (e.g. [4,7,11,12,[14][15][16][17][18][19][20]). Most of the available tests were carried out on scaled wallettes and only three of these works included specimens with truss-type reinforcement [11,12,19]. ...
... [4,7,11,12,[14][15][16][17][18][19][20]). Most of the available tests were carried out on scaled wallettes and only three of these works included specimens with truss-type reinforcement [11,12,19]. In particular, only one of the specimens of the experimental campaign performed at EUCENTRE in Pavia [12] would fall within the scope of the current study (e.g. ...
Article
Experimental campaigns carried out in the past showed that the presence of truss bed-joint reinforcement provides a general improvement to the performance of masonry panels subjected to horizontal actions. The truss-like elements are effective in improving resistance and reducing damage and, therefore, they enhance the displacement capacity. The experimental tests available in the literature, performed on prototypes in different scale or in small number compared to the possible combinations of slenderness, axial load and boundary conditions, hardly allow drawing quantitative conclusions on the real benefit of the presence of horizontal reinforcement to the performance improvement for a specific masonry type. The experimental campaign presented in this paper includes a set of in-plane cyclic tests on Autoclaved Aerated Concrete (AAC) masonry panels with thin horizontal and vertical joints filled with thin layer mortar, made both in unreinforced and bed-joint reinforced masonry with flat-truss bed-joint reinforcement. The direct comparison of the results, along with specific tests performed on wallettes made with the two different construction technologies, allows the assessment of the effectiveness of the horizontal reinforcement in enhancing the in-plane seismic performance of AAC masonry.
... without vertical flexural steel) could be an appropriate practical solution for low-moderate seismic regions. Truss or ladder type bed-joint reinforcement in horizontally RM is known to confer increased deformation ductility capacity of the RM wall (Lourenço et al., 2008;Penna et al., 2008;Penna et al., 2010). With the introduction of bed-joint reinforcement, the already labour-intensive construction process should not be further lengthened, as steel is being placed only in the bed joints, which nonetheless have to be prepared. ...
Conference Paper
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Introduction: As per the Indian housing census data (2011), nearly 85.4% of the building stock belongs to the category of non-engineered and semi-engineered masonry structures, of which 47.5% are with solid burnt brick walls, up from 44.9% of census 2001. Most of these structures lack simple seismic-resistant features, even in moderate to severe seismic zones. Bed-joint reinforcement could be an appropriate solution to improve the seismic performance of masonry buildings in low-moderate seismic regions. Due to the lack of a national code on design and construction of reinforced masonry so far, experimental investigations on bed-joint reinforced shear walls, to quantify the effect of reinforcement on deformation capacity, gain significance. Past international literature indicates that bed-joint reinforcement provides only marginal improvement of in-plane shear capacity, but satisfactory improvement in ductility capacity. However, almost no research on solid brick masonry walls is available. Developments: The current paper focuses on the use of ladder type bed-joint reinforcement in solid clay brick masonry, on which no full scale experimental tests are available in the literature, other than the extensive tests on scaled masonry walls, reinforced with smooth mild steel bars (Tomaževič and Žarnić, 1984). IS 4326 (1993), the code for earthquake resistance design and construction of buildings, prescribes methods for improving seismic resistance by providing vertical and horizontal RC tie columns and bands, depending on the category of masonry building (based on seismic zone and importance factor). The provision of corner reinforcement within grout columns (forming RC tie columns) assists in resisting larger lateral forces due to increased lateral stiffness. However, the role of these elements in increasing the lateral deformation capacity and displacement ductility is debatable, as no significant experimental verification has been carried out for these code provisions. The use of bed-joint reinforcement could also provide necessary deformation capacity to URM walls provided with horizontal RC bands and vertical RC ties. Remarks and Conclusions: Bed joint reinforcement substantially enhanced performance parameters of squat wall when compared to slender wall. Presence of the ladder-type horizontal bed-joint reinforcement delayed crack propagation and led to distributed shear crack formation. Effectiveness of horizontal reinforcement materialised in the presence of the end RC tie columns (as the horizontal reinforcement was anchored to the vertical reinforcement and grouted column), which provided necessary anchorage at ends and forced the horizontal reinforcement to behave as stirrups. Horizontal reinforcement provided the necessary deformation capacity to the masonry panels in the presence of the end RC tie columns.
... To simplify these envelopes, a common method used is the bilinear idealization for which some observations and results from the experimental tests are used in the calculations. Fig. 16 illustrates the idealization which is determined from the calculations that follow [15][16][17]. ...
... Although only a single specimen of each type was tested, it is quite unusual in full scale testing of structural elements for multiple specimens to be tested. Results of other experimental work have also shown improvements in lateral capacity from as low as 10% to upwards of three times the capacity of unreinforced masonry for various strengthening methods including external application of FRPs, near surface mounted FRPs, as well as bed joint reinforcement [8,10,15,[17][18][19][20][21]. In particular, when steel truss shaped BJR was used every second course, capacity was increased by 10% up to 60% [15,17,18], comparable to the 13.3% obtained in this study for ladder shaped BJR. ...
... Results of other experimental work have also shown improvements in lateral capacity from as low as 10% to upwards of three times the capacity of unreinforced masonry for various strengthening methods including external application of FRPs, near surface mounted FRPs, as well as bed joint reinforcement [8,10,15,[17][18][19][20][21]. In particular, when steel truss shaped BJR was used every second course, capacity was increased by 10% up to 60% [15,17,18], comparable to the 13.3% obtained in this study for ladder shaped BJR. ...
... Priestley and Bridgeman, 1974; Schultz et al., 1998; Mosele et al., 2009) or within confined masonry walls (e.g. Ganz and Thürlimann, 1984; Aguilar et al.,1996; Alcocer and Zepeda, 1999; Lourenço et al., 2008; Penna et al., 2008). Nevertheless, the amount of data from tests on masonry walls with bed-joint reinforcement only, which is the focus of the present work, is rather limited (e.g. ...
... Nevertheless, the amount of data from tests on masonry walls with bed-joint reinforcement only, which is the focus of the present work, is rather limited (e.g. Žarnić, 1984,1985; Lourenço et al., 2008; Penna et al., 2008; Mosele et al., 2009). Also, most of these tests were carried out on scaled wallettes and only two of these works included specimens with truss-type reinforcement (Lourenço et al., 2008; Penna et al., 2008). ...
... Žarnić, 1984,1985; Lourenço et al., 2008; Penna et al., 2008; Mosele et al., 2009). Also, most of these tests were carried out on scaled wallettes and only two of these works included specimens with truss-type reinforcement (Lourenço et al., 2008; Penna et al., 2008). In particular, only one of the test specimens of the experimental campaign performed at EUCENTRE in Pavia (Penna et al., 2008) would fall within the scope of the current study (e.g. ...
... Priestley and Bridgeman, 1974;Schultz et al., 1998;Mosele et al., 2009) or within confined masonry walls (e.g. Ganz and Thürlimann, 1984;Aguilar et al.,1996;Alcocer and Zepeda, 1999;Lourenço et al., 2008;Penna et al., 2008). Nevertheless, the amount of data from tests on masonry walls with bed-joint reinforcement only, which is the focus of the present work, is rather limited (e.g. ...
... Nevertheless, the amount of data from tests on masonry walls with bed-joint reinforcement only, which is the focus of the present work, is rather limited (e.g. Žarnić, 1984,1985;Lourenço et al., 2008;Penna et al., 2008;Mosele et al., 2009). Also, most of these tests were carried out on scaled wallettes and only two of these works included specimens with trusstype reinforcement Penna et al., 2008). ...
... A quantitative or systematic assessment of the contribution of the horizontal reinforcement in the bed-joints in improving the global seismic response of a masonry structure in absence of vertical reinforcement is not available in the open literature. It is believed that an increase in the deformation 8 th Priestley and Bridgeman [1] concluded from experimental work that shear steel (horizontal reinforcement) is effective in improving the ultimate shear capacity of masonry, provided sufficient shear steel is present to carry the full ultimate flexural load. The horizontal steel is three times as efficient as the vertical steel in carrying the shear forces across a diagonal crack (vertical steel carries shear by dowel action, while horizontal steel carries shear by tension; see Fig. 2). ...
... [1]; [2]; [3]; [4]) or within confined masonry walls (e.g. [5] (flanged walls); [6]; [7]; [8]; [9]) is assessed, is available from the literature. The quantum of data from tests on masonry walls with bed-joint reinforcement alone, which is the focus of the present work, is rather limited. ...
... The largest database encountered in the current review (summarised in Table 1) is from the experimental programme at Ljubljana where 32 masonry walls were tested in early 1980s [10][11][12]. These tests were carried out on scaled specimens (1:3) with smooth mild steel bars as horizontal Improving the seismic performance of masonry buildings by flat-truss bed-joint reinforcement 8 Masonry wall specimens from the different experimental programmes use different types of masonry units (e.g. concrete blocks, AAC blocks, and perforated clay blocks). ...
Article
Full-text available
The paper discusses behaviour of masonry walls constructed with small-sized elements under the effects of mining activity. It presents some mechanisms of damage occurring in such structures, its forms in real life and the behaviour of large fragments of masonry walls subjected to specific loads in FEM computational models. It offers a constitutive material model, which enables numerical analyses and monitoring of the behaviour of numerical models as regards elastic-plastic performance of the material, with consideration of its degradation. Results from the numerical analyses are discussed for isolated fragments of the wall subjected to horizontal shear, with consideration of degradation, impact of imposed vertical load as well as the effect of weakening of the wall, which was achieved by introducing openings in it, on the performance and deformation of the wall.