Quality Of Masonry Research Articles

Emergency condition of loggies in buildings with supporting brick walls

This article is devoted to the problems of the existing residential buildings of 70-80 years of construction of the last century, which have been in operation for about 50 years and are subject to immediate technical inspection. The most important factor for the safe operation of such buildings is the quality of construction, as in this period the construction was performed with many shortcomings that are manifested today. The article describes the problem of joints of loggias with the building in the design and construction of multi-storey buildings with load-bearing brick walls. Poor ligation of bricks in the masonry, as well as the lack of quality ligation of the transverse walls of loggias with load-bearing longitudinal walls of the building leads to the formation of cracks on the entire height of the loggias, which completely cut them at the abutment, which creates an emergency collapse of building structures. A real example of such a problem in the existing 9-storey building with brick load-bearing walls, where the shortcomings of construction were manifested, namely the poor quality of masonry at the junction of loggias to the load-bearing walls of the building. The structural scheme is also described, as well as the main structures of the building. The main damages and defects are shown. Using the PC "LIRA-SAPR" created a calculation model and compared the results of calculations with the existing condition of the considered area of the building. Recommendations for strengthening the emergency section of the building are given.

Factors determining the quality of masonry – differentiation of resistance and reliability

A house or any other building without walls is truly hard to imagine. The first thing usually associated with walls is, of course, masonry. Today, masonry walls perform a load-bearing function in buildings up to four above-ground floors, in the higher parts of the buildings they perform a protective and stiffening function. However, there is a widespread opinion that the designer does not have to check the bearing capacity of masonry structures because masonry are were stand, are standing and will stand. Not everyone, however, currently works the wall as it should. The problem is that a lot of emphasis is now placed on reducing construction times. Therefore, there are a number of factors affecting the quality of the masonry structure, which overall reduce their safety. The article presents the influence of the quality of masonry on the differentiation of bearing capacity and reliability of an example masonry structure. The analyses included various values γm of the partial factor, recommended in the national annex PN-EN 1996-1, depending on the category of masonry units, class execution of works and type of mortar. In addition, a decrease in load capacity and reliability caused by the increase of the initial eccentric resulting from the inaccuracy of the masonry wall was examined.

AHP-based methodology integrating modern information technologies for historical masonry churches diagnosis

Surveys conducted in the aftermath of recent earthquakes have shown that the structural and anti-seismic performances of historical masonry churches are related not only to structural damages and masonry quality but also to other key features such as effectiveness of connections, damages of wooden elements or criticalities related to humidity. Technical and scientific communities are interested in developing or improving existing procedures for the fast-visual survey and diagnostics in order to measure and analyze all the parameters affecting the building performance. In this paper a new procedure, that can be implemented in a Decision Support System (DSS) based on the Analytic Hierarchy Processes (AHP), is developed to perform a rapid visual survey and diagnostics of masonry building through a set of condition ratings. The originality of the presented work is fourfold: 1) the AHP allows to include in the analysis qualitative and quantitative data such as the quality of masonry and connections effectiveness; 2) the proposed survey and diagnostics performed by suitable condition ratings allow an extensive application in order to identify the most damaged buildings that require more detailed structural investigations; 3) the proposed AHP-based approach is integrated in a DSS to provide a powerful computerized tool, useful to large scale data acquisition; 4) the comparison with a standard diagnostics is performed to validate the procedure and emphasize the advantages of the novel diagnostics.

Anisotropy Effect of Masonry on the Behaviour and Bearing Capacity of Masonry Walls

Firstly, an updated numerical model for the numerical analysis of planar unreinforced and confined masonry walls is presented. The model can simulate the main nonlinear material effects of masonry and reinforced concrete. A simplified anisotropic constitutive model for masonry is developed and presented. The criteria for the limit bearing capacity and collapse of masonry are separately defined for normal stresses only and for normal and shear stresses. The presented numerical model is verified and used to analyse the anisotropy effect of masonry on the behaviour of unreinforced and confined two‐story anisotropic masonry walls with different coefficients of anisotropy, wall lengths, and quality of masonry under horizontal static forces. The influence of the anisotropy coefficient of the masonry on the response of the walls is discussed in detail, and the main conclusions are given.

Shear effect on seismic behaviour of masonry walls

AbstractFirstly, a finite element numerical model for nonlinear dynamic analysis of masonry walls is briefly presented. The model can simulate the main nonlinear effects of masonry and reinforced concrete. It is simple and intended to the engineering application. A macro model of masonry is adopted for simulation its behaviour in compression and for cracks modelling in tension. Two constitutive models are implemented to describe the shear resistance of the masonry wall: One that does not take the effect of the shear failure of masonry (Model 1), and second which takes into account shear failure of masonry (Model 2). By using the numerical model, the shear effect of masonry on the behaviour of two‐storey unreinforced and confined masonry walls exposed to harmonic base acceleration was investigated. The height to length ratio of the walls and the quality of masonry are varied. Analysis results for Model 1 and Model 2 are significantly different. Model 1 gives a significantly higher load bearing capacities of masonry. It was concluded that the shear effect of masonry significantly depends on the type of the masonry walls (unreinforced, confined), the quality of the masonry and height to length ratio of masonry walls.

Damage patterns in the town of Amatrice after August 24th 2016 Central Italy earthquakes

The impact of the two seismic events of August 24th 2016 on the municipality of Amatrice was highly destructive. There were 298 victims, 386 injured, about 5000 homeless, and the historical center of the town suffered a great number of partial and total collapses. The 260 strong motion records obtained for the first event were analyzed and plotted in a shakemap, comparing them with the macroseismic damage surveys made in 305 localities. On the basis of an inspection survey made in September 2016, a map of the damage patterns of the buildings in the historical center was elaborated according to the EMS 98 classification. The damage level resulted very high with more than 60% of the inspected buildings showing partial or total collapse. The elevated level of destruction was mainly caused by the high vulnerability of the masonry buildings, mostly due to specific vulnerability factors such as the poor quality of masonry, the lack of connections between walls and the poor connection between external walls and floors.

Building damage assessment after the 2009 Abruzzi earthquake

Soon after the earthquake that damaged L’Aquila municipality and its Province in the Abruzzi Region, Italy, on the 6th of April 2009, a widespread damage and usability assessment of buildings was launched. In 3 months, about 70,000 buildings were inspected, with the AeDES form, by public servants and professionals coordinated by the Italian Civil Protection Department. The paper, after describing the procedures and the form that were used for the assessment, discusses the time evolution of the inspections and analyses the data on building type and seismic damage. The empirical damage distribution conditional upon seismic intensity and building type is provided and the role of several vulnerability factors, such as the quality of masonry, the construction year, the number of stories, and the pre-existing damage, is highlighted. Lastly the damage consequences, such as the immediate occupancy conditional upon building damage and building type, are reported.

Effect of horizontal ring beams on the ultimate bearing capacity of masonry walls

AbstractThis paper presents the results of numerical tests on the effect of horizontal ring beams on the behaviour of masonry walls under static and dynamic load. Two‐storey walls without and with openings were analyzed, with good and poor quality of masonry, with different boundary conditions at the foundation‐base interface. The effect of the longitudinal bars profiles of horizontal ring beams on the behaviour of walls under horizontal static load, as well as under harmonic and seismic base acceleration was studied. Previously developed numerical model by the authors for static and dynamic analysis of planar masonry structures was used. It was concluted that walls without horizontal ring beams had a significantly smaller strength capacity than equal walls with horizontal ring beams, and that greater longitudinal bars profiles of horizontal ring beams contributes to a higher limit strength capacity of masonry walls.

Assessment and analysis of damage in L’Aquila historic city centre after 6th April 2009

The paper describes the output of a survey carried out in the district of L’Aquila, Italy, in May 2009 after the April earthquake and later in January 2010, and the consequent vulnerability assessment completed by the authors. Observations collected on site regard masonry buildings of the historic centre of L’Aquila and the towns of Paganica and Onna; particular focus was given to a number of buildings of interest, which better represent two locally recurrent building typologies: the mansion and the common dwelling. A description of the main structural features and their influence on damage mechanism is provided, stressing the importance of elements such as wall lay-out, quality of masonry and strengthening interventions. The gathered information is used as input for the application of the FaMIVE method (D’Ayala and Speranza in Earthq Spectra 19(3):479–509, 2003), whereby feasible collapse mechanisms and the associate failure load factors can be identified. The procedure is briefly outlined and results are discussed from the point of view of the performance point: push-over curves produced by statistical elaboration of FaMIVE’s output are compared both with the demand spectra obtained from EC8 and the response spectrum for the main shock as recorded by the closest station to the town. Conclusions are drawn on the reliability of the FaMIVE method with respect to its capability of predicting the damage mechanism identified on site.

Flexural bond strength of natural hydraulic lime mortar and clay brick

This paper measures the bond strength of natural hydraulic-lime (NHL) mortars, to further characterise their properties and enhance their use in building. An additional objective is to correlate bond strength with mortar hydraulicity, water content, workability and water retention, to develop mortars of high bond strength that would improve the quality of masonry. To this aim, the flexural bond strength of masonry, built with mortars of three hydraulic strengths-each including the water amount required to attain three specific flows (165, 185 and 195 mm), was measured with the bond wrench test. The results suggest that NHL mortars possess high water retention, and this enables a strong bond that compares well to that of Portland cement and cement/lime mortars. The results also indicate that bond strength is not determined by the binder’s hydraulic strength, but it increases proportionally to the mortar’s water retention. The paper concludes that for the NHL5 mortars, the 185 mm flow results in the strongest bond, simultaneously providing the highest water retention and best workability. However, for the lower strengths (NHL 2 and NHL 3.5 mortars), the water content required to attain the flows that provide an optimum workability (165 and 165–185 mm, respectively) does not lead to the strongest bond, but it is the highest flow values that provide the NHL2 and NHL3.5 mortars with the strongest bond and, in most instances, the highest water retention.