Burglary resistance of thermal insulating clay unit masonry (RC 3)

In 2017 the Austrian Clay Masonry Industry carried out a test of burglary resistance according to ÖNORM EN 1627 for the first time. A window was fixed in a highly insulated clay masonry wall (with declared compressive strength of the clay units 7.5 N/mm²). Resistance class RC 3 was verified for the window, the fixing to the wall and the wall itself.     

Burglary resistance of thermal insulating clay unit masonry / Einbruchwiderstand von wärmedämmendem Ziegelmauerwerk

The number of burglaries in Germany has increased during the last 10 years. The weak points in external walls are windows and doors. One important aspect is the fixing of these elements in the external masonry walls. The German Clay Masonry Industry has carried out a number of tests verifying the resistance class RC2 of windows fixed in external thermal insulating clay masonry walls.     

Monolithic lightweight concrete masonry for multi‐storey apartment buildings

Affordable living space has become one of the main talking points in Germany next to the threat of climate change. The SMEs of the German lightweight concrete industry offer regional masonry solutions for detached, semi‐detached, and terraced houses as well as multi‐storey apartment buildings. Particularly in densely populated urban centres, the need for multi‐storey apartment buildings arises constantly. In the following the performance of monolithic lightweight concrete masonry will be described and compared with the relevant requirements for multi‐storey apartment buildings. It will be demonstrated that masonry with supposedly low compressive strength can still fulfil all requirements. Of particular significance here are the external wall‐slab junctions.     

Shear tests on highly thermal insulating clay unit masonry walls with thin layer mortar

The paper presents the results of a series of 6 shear tests on full scale highly thermal insulating clay unit masonry walls. The walls consisted of units with large voids filled with mineral wool with a thermal conductivity of λ = 0,07 W/(m · K). The aim of the investigations was the verification of the in‐plane‐shear resistance of this type of thermal insulating clay unit masonry in addition to the tests reported in [1]. The current design rules for clay unit masonry in DIN EN 1996‐1‐1/NA are rather conservative compared to the test results for thermal insulating units.     

Autoclaved aerated concrete (AAC) rubble for new recycling building products: In dry premixed mortars for masonry,in masonry blocks and in lightweight blocks

In cooperation of Bremen Institute for Materials Testing (MPA Bremen), a Department of Leibniz Institute for Materials Engineering IWT, Bremen University of Applied Sciences and the Research Association RWB Bremen building products for masonry structures were developed on the basis of AAC rubble from C&D wastes. Granulates from processed AAC rubble were introduced as aggregates in dry premixed masonry mortars, in masonry blocks and lightweight building blocks and elements to replace completely natural aggregates. These recycling products exhibit beneficial technical properties, at the same time large volumes of AAC wastes may be re‐used. On the basis of the achieved R&D‐results from laboratory experiments, trial batches of dry premixed mortar and masonry blocks were produced in the building materials industry on their available industrial equipment, minor adjustments in the mix composition were necessary. After a sufficient amount of dry premixed mortar and masonry blocks were produced, the recycling products were used to erect indoor masonry walls in a building project in Bremen.     

Flexural tensile tests with vertically perforated clay unit masonry with thin layer mortar / Biegezugversuche an Planziegelmauerwerk

As part of the EU project, INSYSME – INnovative SYStems for earthquake resistant Masonry Enclosures in reinforced concrete buildings – to optimise infill masonry the German project partners carried out an initial part of the project on flexural strength testing of high‐tech clay block masonry in accordance with DIN EN 1052‐2. In this a wide range of modern products was considered which at present is regulated in Germany by means of general building authority approvals. The test results show that the specifications for flexural tensile strength of high‐tech clay block masonry in DIN EN 1996 are very conservative in most cases.     

Shear tests on external clay unit masonry walls / Monolithische Ziegelaußenwände unter Schubbeanspruchung

Monolithic external walls are commonly made of thermally insulated clay blocks that do not require any additional external thermal insulation such as an external thermally insulated composite system (ETICS). To reduce thermal bridge losses, the support length (a) of the slab on the wall is shorter than the wall thickness (t): a < t. The influence on the shear capacity of the respective masonry walls has not yet been tested and analysed. The paper presents the results of shear tests on monolithic external walls with a reduced support length under static‐cyclic and pseudo‐dynamic loading. The test results will be compared with the shear resistance calculated according to DIN EN 1996 with consideration of the German National Annex and the results according to the relevant Technical Approval.     

Reinforced bending load‐stressed masonry – Suggestions for future designs / Bewehrtes biegedruckbeanspruchtes Mauerwerk – Vorschläge für zukünftige Bemessungen

European standardization bodies are currently working on the amendment to EN 1996‐1‐1, which will also affect the evaluation of reinforced masonry in Germany. For that reason, discussion suggestions are being made here for revisions to lay the groundwork for building materials evaluations and especially, evaluations of bending load‐stressed masonry walls or beams at their serviceability limit state (SLS) for load‐bearing capacities. Information already presented in E DIN 1053‐3:2008‐03 [N3] is being incorporated as well. Characteristic values for the compressive strength of the masonry parallel to the bed joints f_k,∥ are essential for the design of reinforced masonry, although they are currently not included in national application documents for Germany. For the time being, they can be mathematically calculated using conversion factors for the characteristic compressive strength values vertical to the bed joints f_k or by using the declared axial compressive strengths of the masonry units. The ultimate strains for masonry in general should be set consistently at ?_mu = ∣–0.002∣ as several masonry types do not exhibit higher compressive strain values. The use of steel strains higher than ?_su = 0.005 does not change any measurement results. Varying stress‐strain curves of the constitutive equations on masonry under compressive strain (parabolic, parabolic‐rectangular, tension block) lead to differing values of recordable bending moments despite having the same mechanical reinforcement percentage at higher normal forces. Therefore, clear guidelines should be made for the type of applicable constitutive equation for masonry walls under compressive strain. With the introduction of a tension block, the number values of the reduction factors λ for the compression zone height x, which is dependent on limit strains, and where applicable, reduced compressive strength, need to be determined, as with reinforced concrete construction. A modification of the bending moment based on the second order theory according to [N4] is presented for the calculation of reinforced masonry walls in danger of buckling. The use of reduction factors for the load capacity of the masonry cross section, such as for unreinforced masonry, does not appear to be appropriate as buckling safety evidence because here, the design task is the determination of a required reinforcement cross section.     

Shear tests on full scale storey‐height specimens constructed with thermally insulating clay unit masonry with thin‐layer mortar

The paper presents results of a series of 6 in‐plane shear tests on storey‐height clay unit masonry panels [1] with thin‐layer mortar, carried out in addition to previous test campaigns [2], [3], and [4]. The walls were constructed with unfilled thermally insulating clay units with a thermal conductivity of λ = 0.09 W/(m · K). The current design rules for clay unit masonry according to DIN EN 1996‐1‐1/NA [5] are conservative compared to the presented test results for thermally insulating clay unit masonry.     

Lessons learned from the testing of RC frames with masonry infills and proposals for new solutions / Untersuchungen an mit Mauerwerk ausgefachten Stahlbetonrahmen und neue Lösungsvorschläge

Past experience has shown that inadequate design of unreinforced masonry walls (URM) or inadequate selection of materials can lead to significant economic losses and fatalities in the case of a strong earthquake. In this context, this paper presents the experimental research that has been carried out with the aim of gaining a better insight into the traditional masonry infill walls commonly built in Portugal. The experimental research includes: (1) shaking table tests on reduced‐scale reinforced concrete (RC) buildings with masonry infills with distinct typologies, from traditional solutions to those with enhanced properties and solutions to improve the seismic behaviour; (2) in‐plane static cyclic tests on a representative one‐storey, one‐bay RC frame with masonry infills with distinct typologies but similar to the ones tested in the RC building models. It was concluded that the typology of masonry walls influences the global behaviour of RC buildings, particularly when there is no connection between masonry infill and RC frame. An appropriate design is necessary to prevent an unforeseen failure mechanism due to shear stresses in the RC columns induced by the infill. The in‐plane cyclic tests showed that render plays a central role in the lateral strength and stiffness. Additionally, it was observed that bed joint reinforcement and reinforced render are important measures for controlling damage but do not significantly influence the in‐plane lateral strength and stiffness.     

Experimental‐numerical research on the seismic performance of URM buildings made of lightweight AAC blocks / Experimentell‐numerische Untersuchung zum seismischen Verhalten von unbewehrten Mauerwerksgebäuden aus Porenbetonblöcken

Masonry walls constructed with lightweight AAC blocks and thin‐layer mortar meet the increasingly strict requirements of energy efficiency and sustainability. In this sense, they represent an excellent solution for modern buildings, not only for external cladding but also as loadbearing elements. Despite the possible advantages of using lightweight AAC masonry, a specific assessment of its seismic performance is mandatory in order to set design recommendations allowing to reach safety levels consistent with those required for other masonry types complying with EN 1998 standard requirements. A comprehensive study on the seismic performance of unreinforced masonry buildings made of lightweight AAC was carried out in an integrated experimental‐numerical approach. The experimental campaign provided the necessary information to setup a reliable numerical model to be extensively used to assess the seismic performance of a number of prototype AAC masonry buildings with different characteristics, by means of both linear and nonlinear static (pushover) analysis. The results of this systematic numerical assessment were eventually used to draft design recommendations, to set parameters (behaviour factors) to be used in linear analysis and to calibrate rules for simple buildings.     

Massive versus lightweight construction in residential building

Masonry as the primary form of construction is currently the most economic option for the building of multi‐storey apartment blocks in Germany in order to provide affordable housing. It can however also be stated that there is definitely further rationalisation potential in masonry construction, in contrast to lightweight construction. In comparison to masonry construction, lightweight building methods show no apparent economic advantages, the ecological balance is objectively equivalent and the fire protection and sound insulation properties have to be provided technically and constructively at high cost in order to comply with the same requirements. Under consideration of a realistic and objective assessment, there is therefore no reason to promote the use of lightweight building methods, such as timber‐frame, from their current status as niche products, especially for residential building.     

Tragfähigkeitserhöhung bei Mauerwerk durch textilglasgitterverstärkte Mörtelfugen

Increase of the vertical load carrying capacity of masonry due to mortar bed joints with textile glass mesh reinforcement From a structural point of view, one of the most important material parameters in the construction sector is the vertical compressive strength of masonry, which consists of the compressive strength of the bricks as well as of the mortar bed. The interaction between the bricks and the mortar beds is the main reason for compression failures of masonry walls. A close analysis of the deformation behavior of the two components shows that different transverse strains in the contact surface between the bricks and the mortar are the main cause for compression failures. However, the load‐bearing capacity of masonry walls can be increased by using some reinforcement in the mortar beds which counteracts lateral expansion. The impact of textile glass mesh reinforcement on the load‐bearing capacity of masonry was analyzed in a test program on masonry columns with different numbers of textile glass mesh reinforced mortar beds. The results of the analyses show that the load‐bearing capacity of the columns rises with an increased ratio of reinforcement, regardless of the type of bricks used. From the ratio of the height of the reinforcement layers to the thickness of the wall it can be deduced that a higher degree of reinforcement has a positive effect on the load‐bearing capacity of the masonry. On this basis, an increase of the strength and load‐bearing capacity of masonry walls is formulated to be on the safe side.     

Bauakustische Bemessung von Mehrgeschossbauten mit monolithischen Ziegelaußenwänden

Acoustic design of multi‐storey buildings with external walls of monolithic clay masonry For masonry buildings with monolithic, highly insulated walls of clay units, no acoustic design according to standard was practically possible under Supplement 1 to DIN 4109:1989. Therefore a design procedure regulated by approvals was introduced in 2010, with which acoustic calculations for a building could be performed with a high security of forecasting. This procedure has been taken up in the completely revised series of standards DIN 4109:2016/2018 “Sound insulation in buildings”. The basis for the application of this method is knowledge of the individual sound insulation quantities and joint sound insulation quantities for the relevant clay masonry products or product combinations. In order to simplify performance of the verification for clay masonry buildings, the clay masonry industry provides the program “Modul Schall 4.0” (Acoustic module 4.0), in which the decisive acoustic parameters of external wall products from numerous clay masonry unit producers are stored in a database. In this report, experience of application of the design procedure for clay masonry buildings is presented. There is good agreement between forecasts and tests on completed buildings.     

Monolithisches Mauerwerk aus Leichtbetonsteinen erfüllt die Anforderungen der Energieeinsparverordnung 2009

Die Energieeinsparverordnung (EnEV) 2009 beinhaltet verschärfte Anforderungen an den Jahresprimärenergiebedarf und den Transmissionswärmeverlust von Gebäuden. Damit sinkt der durchschnittliche U‐Wert von Außenwänden auf 0,28 W/(m²K). Mauersteine aus haufwerksporigem Leichtbeton wurden in den letzten Jahren wärmetechnisch so verbessert, dass sich diese Anforderungen mit Mauerwerksdicken von 36,5 cm problemlos erfüllen lassen. Selbst die Kriterien für ein KfW‐Effizienzhaus 70 oder 55 lassen sich auf diese Weise mit monolithischem Mauerwerk ohne zusätzliche Dämmung noch einhalten. Monolithic masonry made of lightweight concrete blocks meets demands of energy saving regulations. The Decree for Saving Energy (Energieeinsparverordnung, EnEV — regulation for energy saving in buildings and building systems) 2009 consists stronger regulations for the yearly demand of energy and the loss of transmission heat of buildings. Therefore the average U‐Value for enclosure walls decreases to 0.28 W/(m²K). Blocks made of aggregate lightweight concrete have been improved by the industry concerning their thermal conductivity in the last years, so these demands can be fulfilled with masonry in 36,5 cm thickness. Even the criteria of a KfW Efficiency House 70 or 55 can be fulfilled in this way with monolithic masonry without an additional thermal insulation.     

Bond behaviour of a textile‐reinforced mortar for AAC masonry

The bond behaviour of a textile reinforced mortar (TRM) applied to autoclaved aerated concrete (AAC) masonry has been evaluated experimentally. The TRM is composed of a glass‐fibre mesh combined with a cementitious mortar and is intended to strengthen AAC masonry walls subjected to out‐of‐plane bending during an earthquake. The main components have been characterized with preliminary tests. Then, pull‐off and shear bond tests have been performed to determine the bonding properties of the TRM applied to the AAC substrate. Three types of AAC blocks have been used, which differ in the bulk density and compressive strength, to evaluate possible variation in the bond strength. The results of the experimental campaign have shown a good performance of the strengthening system. In most cases, the bonding between TRM and masonry was maintained up to tensile failure of the dry textile. As expected, the masonry samples realized using AAC blocks with a higher bulk density showed better performances. The paper presents and discusses main test results, providing background data for future recommendations for the use of the analysed strengthening system in AAC masonry structures.     

Non‐loadbearing partitions of unfired clay masonry – Fire behaviour tests

Unfired clay masonry is the most frequently used construction type for residential buildings worldwide, but the long tradition of building with unfired clay masonry in Germany came to an end with the onset of industrialization. The research project EGsL ”Unfired clay masonry: design and construction principles for a widespread use in residential building taking into account climatic conditions in temperate zones with Germany as example location“ is devoted to the preparation of basic principles based on the current state of knowledge about unfired clay as a building material in order to filter out design and construction principles for residential buildings of modern unfired clay masonry. It is assumed that unfired clay has a much better performance capability than is currently expected from the material. The greatest suspicion about the structural safety of unfired clay buildings is based on the water susceptibility of unfired clay, since unfired clay loses its strength under the action of water. In order to improve confidence in the structural stability of residential buildings of unfired clay masonry, a display at the trade fair BAU 2017 showed the basis for an example application of important constructional joints of a theoretical building of unfired clay masonry. As a follow‐up to this, the EGsL research project now intends to demonstrate the fire protection behaviour of unfired clay internal walls in order to ensure the structural stability of unfired clay buildings. The article reports on a first fire test on non‐loadbearing clay masonry walls and describes an example application of non‐loadbearing clay walls in the new Zinzendorf Gymnasium in Herrnhut.     

Spannungs‐Dehnungs‐Linien von Porenbeton bei hohen Temperaturen: ein erster Schritt zur versuchsbasierten Bemessung gemäß EN 1996‐1‐2

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.     

Tragfähigkeitstafeln für unbewehrtes Mauerwerk nach DIN EN 1996‐3/NA:2019‐12

Load‐bearing capacity tables for unreinforced masonry according to DIN EN 1996‐3/NA:2019‐12 Practical design aids are important tools in the day‐to‐day business of structural design. The design of primarily vertically loaded masonry walls in usual building construction can be carried out with the help of so‐called load‐bearing capacity tables. A table value is read off exclusively as a function of the geometric conditions, which – multiplied by the masonry compressive strength – results in the load‐bearing capacity of the wall for cold design and in case of fire. By comparing the acting and resisting force, the verification of structural design can be provided in a simple and yet economical form. The bearing capacity tables based on the simplified calculation methods according to DIN EN 1996‐3/NA:2019‐12 [1], [2] and DIN EN 1996‐1‐2/NA:2013‐06 [3], [4] are presented in this paper. Compared to the previous edition of Part 3 of Eurocode 6, the extended scope of application is taken into account, as well as the normative changes to the construction method with partially supported slabs.