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.     

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.     

New approach for spacing of movement joints in reinforced and unreinforced masonry veneer walls. Part 1: Unreinforced masonry / Neue Bemessungsmethode für die Abstände von Dehnungsfugen in bewehrten und unbewehrten Verblendmauerwerksschalen. Teil 1: Unbewehrtes Mauerwerk

The spacing of movement joints has been subject of many discussions. The current methods for the determination of the spacing of movement joints are based on local traditions and bad experience with cracked veneer walls. This has resulted in various design rules throughout Europe with very stringent limits for spacing of movement joints. According to EC6, one of the solutions for increasing the spacing of movement joints is to introduce bed joint reinforcement, although unfortunately no specific design rules are given. Until now, most scientific research has been focused on numerical simulations without taking time‐dependent effects into account, which is a conservative approach. In this paper, a new approach is described. It is based on Peter Schubert's model and on practical experience with masonry buildings.     

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.     

Experimental determination of the load‐bearing capacity of a reinforced perforated brick facade

For a new multi‐storey car park over the Central Bus Station (ZOB) in Kiel, a perforated clinker brick veneer facade not conforming to standards was planned. The design and technical characteristics of the facade have already been described in the article by Medzech and Schrade in this issue [1]. This article deals with the experimental investigations carried out to obtain a project‐related one‐off approval (ZiE). These experiments contain in particular large tests on storey‐height wall sections, which were subjected to eccentric compressive loading and partly to horizontal loads representing wind action. Supplementary small tests on unreinforced and reinforced masonry served to determine the bending capacity, the anchoring capacity of the reinforcement and the load‐bearing capacity of the wall anchors in the masonry. Due to the special facade construction with special bricks for the project, wall anchors, reinforcement bar couplers and unique test set‐ups had to be developed for the specific project.     

Bauweise mit Zukunft: Durch und durch mineralisch —Wärmedämmendes Mauerwerk mit mineralischem Putz

Hat Mauerwerk eine Zukunft? Oder dienen Wände bald nur noch als Trägermaterial für Dämmschichten? Dabei ist gerade wärmedämmendes Mauerwerk aus gutem Grund im Wohnungsbau nach wie vor die Nummer Eins — und wird es nach Einschätzung der Fachleute auch bleiben. Dieser Beitrag schildert aktuelle Entwicklungen und beleuchtet Hintergründe. Construction with a future — theral insulating brick with mineral plaster. Does brickwork has a future? Couldn’t it be that walls will soon only serve as backing material for insulation layer? However, there are good reasons that heat insulating brickwork is still the number one in domestic constructions — according to experts this will remain so. The following article will characterize current developments und backgrounds.     

Fixing of windows with fall protection / Befestigung von absturzsichernden Fensterelementen

Glass areas in modern building are becoming ever larger and in refurbishment, window openings are sometimes enlarged. Window elements with fall protection are often used, which undertake the additional function of fall protection, for example of a handrail. Furthermore, opening casements over the entire window height are often installed and “French balconies" of metal are replaced, for example, by appropriate glass panel fillings screwed directly to the window frames. This means that the fixing of the window frame is as important as that of glazing with fall protection. The article describes the current status of this subject and explains fixing into the structure.     

Loadbearing capacity of infill masonry walls considering the deformation‐based membrane effect

According to currently valid codes, it is not possible to determine the loadbearing capacity of unreinforced infill walls considering the deformation‐based membrane effect by incorporating the exact support conditions. One reason for this is the lack of a validated calculation procedure, which in addition to the equilibrium conditions also realistically represents the compatibility conditions of these systems. In the present paper, therefore, a new non‐linear analytical calculation procedure is presented. The main focus of the analysis of walls subject to area loading is the incorporation of the support conditions and thus the consideration of the deformation‐based membrane compressive force. Through generalised formulation and a standardised notation of the determination equations, different material behaviours and various support conditions can be taken into account with few parameters. On the action side, both lighter loading like wind loads and heavier loading like explosion loads can be considered. Through the implementation of the partial factor concept, it is possible to comply with the requirements of European codes and thus ensure the applicability of the analysis model.     

Development of a clinker brick façade to exploit solar thermal energy / Entwicklung einer Klinkerfassade zur Nutzung solarer Wärmeenergie

The featured research project was intended to develop and test a specially modified brick façade, which would convert solar radiation on the façade into thermal energy for heating purposes. The main objective was to measure the energy extraction potential but all other issues concerning technical feasibility also had to be taken into account. To this end a masonry structure had to be developed, which allowed integration of the inserted pipe to dissipate the energy introduced, while allowing simple, practicable installation. Various tests were carried out on masonry walls and individual bricks. On sunny winter days, an energy extraction potential of 1.9 kWh per square metre of façade and day was measured. During summer days, an extraction potential of up to 2.6 kWh/(m²·d) could be observed. The initial findings allow the assumption that this energy could be utilized with the use of a heat pump.     

The two‐shearfield test – A suitable method for the empirical shear capacity design of masonry / Der Zweifeld‐Schubversuch – Eine praxistaugliche Methode zur versuchsgestützten Bemessung der Schubtragfähigkeit von Bestandsmauerwerk

The investigations [1] demonstrate that the two‐shearfield test is a suitable method for the determination of the shear capacity of masonry. The testing equipment is mounted directly on the wall in order to retain realistic boundary conditions like stiffness, load and prior damage. The behaviour factor q and the capacity curves of certain masonry walls can be directly obtained from the experimental results and realistic material behaviour in earthquake design can be represented. In particular, existing masonry can be assessed realistically with methods like the response spectrum, the push‐over and the capacity spectrum by using the two‐shearfield test.     

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.     

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.     

Versuche am Bau mit Injektionsankern im Mauerwerk nach Technischer Regel des DIBt

Tests on construction site for metal injection anchors for use in masonry according to the DIBt Technical Rule – Part 1: Overview On construction sites, one encounters a large number of bricks that differ in material (clay, autoclaved aerated concrete, calcium silicate, lightweight concrete or normal concrete), structure (solid bricks, perforated bricks with or without insulation filling), geometry, bulk density and compressive strength. In the context of approval procedures for plastic anchors and metal injection anchors, however, it will only ever be possible for anchor manufacturers to map part of this variety of masonry stones as a permissible base material. Tests on construction site allow the user, under certain conditions, to design and install in accordance with the approval if the base material actual available on construction site is not shown in the approval for the anchor system. This article is an excerpt from issue 4 of the series of publications of the ?Deutscher Ausschuss für Mauerwerk e.V. (DAfM)” (Dübel‐)Versuche am Bauwerk in Mauerwerk – Aktuelle Regelungen für Kunststoffdübel und Metall‐Injektionsanker zur Verankerung im Mauerwerk” and provides an overview to the existing set of rules to be observed – in particular to one of the two current Technical Rules of the Deutsches Institut für Bautechnik (DIBt) ?Durchführung und Auswertung von Versuchen am Bau für Injektionsankersysteme im Mauerwerk”.