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Partial safety factors for resistance applied in the design equation of semi‐probabilistic formats can be obtained from the evaluation of a test database. These partial safety factors are influenced by two factors, the material uncertainty and the model uncertainty. This topic is covered in a former publication [1]. It includes the determination of a partial factor for the model uncertainty of unreinforced masonry shear walls. In this study the authors examine the next step, and calculate the partial factor of resistance applying the same method, as recommended i n EN 1990 – Annex D. In addition to the Coefficient of Variation (COV) for the model uncertainty, the calculation of the resistance partial factor considers deviations in geometry, as well as loading and material properties. The influence of the material uncertainty on structural performance is considered in the calculation by means of a weighted average of all COV values for various types of material properties, based on the number of relevant failure modes in the test database. In the last step, the resistance partial factors for models defined in DIN EN 1996‐1‐1/NA and DIN EN 1996‐1‐1/NA – Annex K are calculated by applying the probabilistic methods recommended in EN 1990 – Annex D and the model bias.  相似文献   

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《Mauerwerk》2017,21(3):155-167
This article investigates the transferability of the Simplified Modified Compression Field Theory (SMCFT) [2], which is known in reinforced concrete design and included in the fib Model Code for Concrete Structures 2010 (Volume 3) [1], to reinforced or prestressed masonry beams (RM beams) with or without an additional layer of concrete. The investigation for this work is the obsolete shear design concept that has been used until now for reinforced masonry under shear loading, which does not adequately reflect the actual load‐bearing behaviour of significant areas of masonry. The fundamentals of the SMCFT are explained and the transferability of the theory to RM beams is examined, taking into account in particular the different material properties of masonry compared to reinforced concrete. A first approach for future application is represented by the equations presented here for the determination of the shear force capacity of RM beams. The verification is performed through a comparison of the shear resistances determined experimentally (exp.) and by calculation (calc.).  相似文献   

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The design/verification method in the Eurocodes is based on the partial safety concept. Eurocode 6 suggests a constant partial safety factor for the material γM for all design/verification problems, without consideration of model uncertainty in the design/verification formula. In the following, a model partial safety factor is determined for the problem of unreinforced masonry walls mainly subjected to vertical loading. For that purpose, the newly proposed formula for EC 6, annex G will be considered [1–3]. In order to cover all aspects in tests and to use the results for design purposes, several methods have been included in EN 1990 Annex D for design based on test data. In this study, the recommended methods in Annex D of EN 1990 for resistance of the material are used to extract the partial safety factors. A database including more than 119 experimental tests on unreinforced masonry shear walls is used to compare the model prediction and the test results and to determine the model partial safety factor.  相似文献   

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Stress‐strain curves of AAC at high temperatures: a first step toward the performance‐based design according to EN 1996‐1‐2 In this paper, the performance‐based approach for the design of autoclaved aerated concrete (AAC) masonry walls subjected to fire is presented. The problems associated with the calculation methods in the current version of EN 1996‐1‐2 for the assessment of AAC loadbearing walls are explained. The current version of EN 1996‐1‐2 offers only tabulated data as a reliable method for structural fire assessment. The content of current Annex C and D is generally considered as not being reliable for design because of the absence of an adequate validation by experimental tests. For this reason, a proposal is made for the improvement of the input parameters for mechanical models based on experimental tests on AAC masonry. On this basis, new stress‐strain curves as a function of temperature are proposed here and then compared with the stress‐strain curves currently included in the Annex D of EN 1996‐1‐2. The comparison results point out that the current curves do not correspond to the effective behaviour of AAC masonry under fire conditions. The proposed curves can be used as base to be implemented in the new version of EN 1996‐1‐2.  相似文献   

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Seismic verification of masonry buildings in German earthquake regions With financial support of the ”Deutsche Gesellschaft für Mauerwerks‐ und Wohnungsbau e.V.“ (DGfM) and the ”Deutsches Institut für Bautechnik“ (DIBt) in Berlin, two consecutive research projects were carried out to improve the seismic verification of masonry buildings in German earthquake regions. First, the seismic behavior of three modern unreinforced masonry buildings in the region of Emilia Romagna in Italy during the earthquake series in 2012 was investigated in detail in cooperation with the University of Pavia. Based on the results of these investigations an improved seismic design concept for unreinforced masonry buildings was developed. The paper presents the main results of the conducted research work and their transfer into standardization and engineering practice.  相似文献   

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In the national annexes of Eurocode 6, the individual European Member States can define values for nationally determined parameters in various places or add regulations which are not in contradiction to the current European provisions. Consequently – despite a harmonized Eurocode 6 – the normative regulations of the individual Member States differ more or less. However, in the sense of practicability of the standards in Europe, it should be the aim to develop a European standard which is as uniform as possible and which has not to be applied in significantly different ways due to the national regulations. In order to better understand the interests of the other Member States for future generations of standards and to derive potentials of harmonization, the values of the Nationally Determined Parameters (NDPs) of various Member States are compared in this paper. In this context, the extent of the deviations between the different national annexes is examined and on this basis a possible potential of harmonization is identified.  相似文献   

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Just as with shear stress on the edges of masonry walls, prestressing through the confinement and restraint of all four sides of the wall improves the load‐carrying capacity under lateral loads. The extra load arising from prestressing leads to increased flexural strength of the masonry. The confinement of the edges results in relatively smaller span moments. In this case, the torsional stiffness of the reinforced concrete frame is important. This is determined by the frame itself as well as by its integration within the building. As a supplement to [4], an examination of panel loading was also performed within the guidelines of a research project at the TU Dresden, Chair for Structural Design, on behalf of the Federal Office for Building and Regional Planning on the subject of “Confined Masonry as an Option for Increasing the Load‐Carrying Capacity of Stiffening Walls”[9]. The various influences are to be initially researched on the basis of various analytical observations and a small numerical study. A thorough, experimentally‐based clarification of the load‐carrying capacity of the panels was not possible within the framework of the research project.  相似文献   

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According to the German National Annex to DIN EN 1996‐3, a calculative verification of the bracing system may be omitted if, besides other requirements, an obviously sufficient number of sufficiently long shear walls is in place. If it is questionable whether a building complies with this requirement, a time‐consuming verification of the bracing system according to DIN EN 1996‐1‐1/NA is unavoidable. This article therefore presents a simplified verification method for the bracing system, which will prospectively be included in the next revision of DIN EN 1996‐3. The simplified bracing verification can already be used as a decision‐making aid to omit the calculative bracing verification according to DIN EN 1996‐1‐1/NA.  相似文献   

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《Mauerwerk》2017,21(4):253-266
For the design of unreinforced masonry walls under lateral earth pressure according to DIN EN 1996‐3 [1], the active earth pressure is used, which is less than the earth pressure at rest. For the consideration of active earth pressure, a sufficient deflection of the wall is needed. It is unknown whether the deflections in reality are large enough to justify a reduction of the active earth pressure. Therefore a numerical model has been developed which considers the load‐bearing behaviour of masonry walls, with several boundary conditions being considered to estimate the effective earth pressure.  相似文献   

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《Mauerwerk》2017,21(5):306-319
Dedicated to University Prof. Dr.‐Ing. Carl‐Alexander Graubner for his 60th birthday The simplified calculation methods for unreinforced masonry structures given in DIN EN 1996‐3/NA are an easily applicable design standard for an efficient and fast verification of the resistance of mainly vertically loaded masonry walls. However, the design rules are not based on mechanical models. Instead, they are empirical approaches for a simplified estimation of the load bearing capacity. For this reason, the range of application of DIN EN 1996‐3/NA is limited by several conditions to ensure a sufficient safety of this design procedure. With regard to extending the conditions for application, extensive comparative calculations were carried out. Thereby, considering clearly defined boundary conditions, the load bearing capacity according to DIN EN 1996‐3/NA was compared to that according to DIN EN 1996‐1‐1/NA. It was the aim of this comparison to identify load bearing reserves of the simplified calculation methods to point out potential for an extension regarding the maximum permissible clear wall height and the slab span. As a result, it can be stated, that an increase of the maximum wall height up to 6.0 m and the maximum slab span of 7.0 m is possible in certain cases.  相似文献   

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《Mauerwerk》2018,22(3):162-174
This paper deals with the design of basement walls subjected to lateral earth pressure. The current simplified calculation method according to DIN EN 1996‐3/NA only covers active earth pressure, which is the lower limiting value of the earth pressure. Designing according to DIN EN 1996‐1‐1/NA, higher coefficients of earth pressure (like earth pressure at rest) can be considered, with an additional verification of the shear resistance being necessary. This paper presents a theoretical model, which forms the basis for an analytical derivation of the loadbearing capacity, and explains the required minimum values of the acting normal force to ensure sufficient resistance to cover bending and shear. Based on these results, a simplified equation is proposed for the determination of the required minimum normal force, based on the design according to DIN EN 1996‐3/NA and providing identical values in case of an earth pressure coefficient of 1/3. The required minimum load resulting from this approach fulfils the described requirement to cover bending and shear. The presented solution is verified and the conditions for application are defined. Finally, the minimum required normal forces are evaluated and tabulated for common cases relevant to building practice.  相似文献   

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Hamidreza Salehi 《Mauerwerk》2018,22(2):103-112
Experiments in structural engineering can play an important role in the prediction and characterization of the material properties and behaviour of structural components. In order to cover all aspects in tests and use the results for design purposes, several methods have been included in EN 1990 Annex D for design based on test data. The calculation of characteristic values and design values for material resistance are the main aspects. In this study, the recommended methods in Annex D of EN 1990 for resistance of the material will be used to extract the partial safety factors for masonry structures based on the formulation of design and characteristic values. A database including more than 100 tests on unreinforced masonry shear walls will be used to evaluate the results. The resistance model for shear walls based on the recommendation in the Eurocode will be compared with the test results. The main aim will be to compare the model prediction and the test results. Deviation of the prediction from the test is caused by model error or model uncertainty. The test database includes results for three types of masonry units – fired clay, calcium silicate and autoclaved aerated concrete. The evaluation of partial factors for masonry shear models will be undertaken based on the scatter and the model bias for the whole database. Further analysis will also be performed for each type of masonry unit for classification of the outcome.  相似文献   

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