Investigations into the improvement of the weather protection of unburnt brick masonry,part 2

In June 2006, the Chair of Structural Design at the Technical University of Dresden was commissioned by the Iranian cultural authority ICHHTO and the UNESCO to perform structural design services for the earthquake‐resistant repair and rebuilding of the Sistani House in the historic citadel Arg‐e‐Bam in the south of Iran. The citadel was until its almost complete destruction by an earthquake on 26 Dezember 2003 the largest building of unburnt brick masonry in the world and is listed as a World heritage Site by UNESCO because of its cultural and historical significance. Surveying and documentation work, archaeological rubble clearance and the rebuilding of the Sistani House after its destruction by the earthquake have taken the team from the department to Bam at regular intervals since 2006. In the course of the work, it became apparent that research was needed in the field of the repair of earthquake‐damaged unburnt brick masonry and into the improvement of the shear strength/earthquake resistance and the weather protection of unburnt brick masonry. The article is subdivided in Part 1, Introduction, test performance and assessment of results for additives to loam render [14] as well as Part 2, Assessment of the results for surface treatment to unburnt bricks and the climatic chamber tests.     

The reconstruction of the historic facades of the Berlin Palace

The masonry and wall building for the reconstruction of the historic facades for the rebuilding of the Berlin Palace as the Humboldt Forum represent a unique challenge for the art of masonry, structural design and detailed design. In front of the modern reinforced concrete structure of the new palace building, the massive solid brick masonry wall, separated from it by mineral insulation, leads to an overall thickness for the historically reconstructed external wall that comes near to the average thickness of the baroque palace walls. The exceptional thickness of the brick wall serves as a substrate for the facade decoration elements of sandstone and together with the internal insulation, enables the requirements of the energy‐saving regulations (EnEV) to be clearly exceeded.     

Safeguarding and retrofitting works at the UNESCO World Heritage Site Takht‐e Soleyman,Iran

This article reports on the works safeguard in 2016 to secure the UNESCO World Heritage Site at Takht‐e Soleyman in the province of West Azerbaijan in the northwest of Iran. The site includes a fire temple and dates back to the sixth century AD. The complex was transformed by the Ilkhanids in the 13th century with extensive repair and building measures. From the 15th century, the complex was abandoned and decayed. In the 1970s, the north wall of the Western Eivan was first secured with steel scaffolding. The Chair of Structural design at the TU Dresden undertook works in 2016 to stabilise the Western Eivan in collaboration with the Iranian cultural heritage organisation (ICHHTO) and with financial support from the cultural maintenance programme of the Federal Foreign Office of Germany. The preliminary investigations until now and the work to the structure planned for 2018 are described below.     

Buckling of masonry walls – A new proposal for the Eurocode 6

The buckling of masonry wall depends on the deformation behaviour and can be described with the modulus of elasticity depending on masonry strength. The reduction factor solution considering buckling is described by the Gaussian bell‐shaped curve in Eurocode 6, Part 1‐1 Annex G and was calibrated for masonry with a modulus of elasticity between 700 and 1000 f_k, which describes the masonry currently used in most European countries. In case of historic masonry or where deformability is needed in new construction, the modulus of elasticity can actually be lower. In those cases the approximation procedure according to Annex G of the Eurocode 6 delivers results which do not represent the real behaviour and leads to uneconomical results. The present paper proposes a new empirical method, which can be applied over the whole practical range of the elastic modulus of masonry. The new proposed method has been verified with experimental data and shows a very good fit.     

Zerstörungsarme Bestimmung der Steindruckfestigkeit von Bestandsmauerwerk aus Hochlochziegeln

Non‐destructive determination of the compressive strength in existing masonry made of vertically perforated bricks Urban consolidation and the conservation of listed buildings often require measures to determine the structural stability of the existing masonry. The key parameter for the static proof is the compressive strength of the masonry, which consists of the compressive strength of the bricks and the compressive strength of the mortar bed. So far, no testing methods have been developed that do not significantly interfere with the static load bearing capacity of masonry made of vertically perforated bricks and which make it possible to determine the compressive strength by analysing parts of the bricks. This article presents a non‐destructive test method to determine the compressive strength of vertically perforated bricks of existing masonry. This test method only uses small test specimens taken from parts of the bricks. As a result, the static load bearing capacity of the existing masonry is hardly affected. The results of these tests show that it is possible to establish a plausible correlation between the comprehensive strength of the brick and the compressive strength of the small test specimens. On this basis, a concept for a non‐destructive testing method which makes the determination of the compressive strength of vertically perforated bricks in existing buildings possible is presented.     

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.     

Derivation of 3D masonry properties using numerical homogenization technique

Lots of research work has been conducted on homogenization technique, which derives global homogenized properties of masonry from the behaviour of the constitutive materials (brick and mortar). Such a technique mainly focused on two‐dimensional media in the previous studies with the out‐of‐plane properties of masonry material neglected. In this paper, homogenization technique and damage mechanics theory are used to model a three‐dimensional masonry basic cell to numerically derive the equivalent elastic properties, strength envelope, and failure characteristics of masonry material. The basic cell is modelled with distinctive consideration of non‐linear material properties of mortar and brick. Various displacement boundaries are applied on the basic cell surfaces in the numerical simulation. The detailed material properties of mortar and brick are modelled in a finite element program in the numerical analysis. The stress–strain relations of masonry material under various conditions are obtained from the simulation. The homogenized elastic properties and failure characteristics of masonry material are derived from the simulation results. The homogenized 3D model is then utilized to analyse the response of a masonry panel to airblast loads. The same panel is also analysed with distinctive material modelling. The efficiency and accuracy of the homogenized model are demonstrated. The homogenized material properties and failure model can be used to model large‐scale masonry structure response. Copyright © 2006 John Wiley & Sons, Ltd.     

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.     

A non‐linear interface element for 3D mesoscale analysis of brick‐masonry structures

This paper presents a novel interface element for the geometric and material non‐linear analysis of unreinforced brick‐masonry structures. In the proposed modelling approach, the blocks are modelled using 3D continuum solid elements, whereas the mortar and brick–mortar interfaces are modelled by means of the 2D non‐linear interface element. This enables the representation of any 3D arrangement for brick‐masonry, accounting for the in‐plane stacking mode and the through‐thickness geometry, and importantly it allows the investigation of both the in‐plane and the out‐of‐plane responses of unreinforced masonry panels. A co‐rotational approach is employed for the interface element, which shifts the treatment of geometric non‐linearity to the level of discrete entities, and enables the consideration of material non‐linearity within a simplified local framework employing first‐order kinematics. In this respect, the internal interface forces are modelled by means of elasto‐plastic material laws based on work‐softening plasticity and employing multi‐surface plasticity concepts. Following the presentation of the interface element formulation details, several experimental–numerical comparisons are provided for the in‐plane and out‐of‐plane static behaviours of brick‐masonry panels. The favourable results achieved demonstrate the accuracy and the significant potential of using the developed interface element for the non‐linear analysis of brick‐masonry structures under extreme loading conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Classification of SIM infill panels / Klassifikation von SIM‐Ausfachungswänden

SIM is an innovative building system for mortar‐less walls. It utilises a special method of interlocking SIM bricks that allows relative sliding of brick courses in‐plane of a wall and prevents out‐of‐plane relative movement of bricks. One of its structural applications is in multistorey frame buildings as earthquake resistant masonry infill panels. It improves energy dissipation of frame structures during earthquakes. The energy dissipation occurs through friction between bricks as they engage in relative sliding by the frame vibrating during earthquake. This paper explains the novelty of SIM and offers classification of SIM panels based on the gap width between the frame and the top of the panel.     

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.     

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.     

Added value and employment effects of brick industry

In Germany manufacturing and distribution of bricks care for direct employment of about 10,000 persons. Procurement of preliminary work and the utilisation of the payed salaries, social security contributions, taxes, and profits secure more than further 25,000 jobs. It can be assumed that a substitution of masonry by other building materials is not possible in the near term, since the masonry has increased its market share in the past few years even slightly. Thereby the masonry participates in the added value based on the shell construction of buildings in the amount of 32.4 billion Euro, and in the employment of 480,000 working people. The expansion of these buildings leads to further added value in the amount of 39 billion Euro and further employment of 691,000 employees. In the year 2016 in total, the construction of buildings with masonry has led to an overall economic added value amounting to more than 70 billion Euro and to an employment of about 1.17 million persons. Masonry products form the basis of this added value and employment, without which the construction of the buildings would not be possible.     

Verhalten von Mauerwerksbauten unter Erdbebeneinwirkung: Auswertung der Schäden des Albstadt‐Erdbebens vom 3. September 1978

Numerische Untersuchungen zum Verhalten von Mauerwerksbauten unter Erdbebeneinwirkung führen oft zu pessimistischen Schadensprognosen, welche im Gegensatz zu den Beobachtungen stehen. Um diesen Widerspruch aufzulösen, werden erfahrungsbasierte Verletzbarkeitsfunktionen für typische Mauerwerksgebäude auf der Grundlage der durch das Erdbeben vom 3. September 1978 bei Albstadt (mit einer Lokalmagnitude M_L von 5,7 und Epizentralintensität I₀ = VII—VIII) verursachten Schäden entwickelt. Anhand des Bauwerksbestandes von 1978 erfolgt die Einordnung der beobachteten Schäden in Schadensgrade auf Basis der European Macroseismic Scale EMS‐98 [1]. Die für den Bauwerksbestand repräsentativen Bauweisen werden herausgearbeitet; für die vorherrschenden Gebäude aus unbewehrtem Mauerwerk ist eine weitere Unterscheidung nach Baualter, Geschosszahl und phänomenologischen Gesichtspunkten möglich. Vulnerability of masonry structures under seismic action: Damage analysis of the September 3, 1978 Albstadt earthquake. Numerical studies of the earthquake behavior of masonry buildings in Central Europe based on national building codes acc. to the Eurocode 8 lead to pessimistic damage prognoses, which are in contradiction to the observed behavior. In order to eliminate this discrepancy realistic experience‐based vulnerability and displacement functions for typical masonry constructions are developed. Because of the rather limited number of earthquake damage observations, the Magnitude M_L 5.7 Albstadt earthquake from September 3, 1978 (intensity VII—VIII) in South Germany also based on its excellent documentation is reconstructed with the building stock existing at that time. The prevailing building types and for these the characteristic damage cases are investigated in close cooperation with the local authorities. The presented unreinforced masonry structures are divided by year of construction, number of storeys and phenomenological aspects.     

Masonry buildings at the borderline to high‐rise – Part 2 / Mauerwerksbauten an der Hochhausgrenze – Teil 2

For the verification of framing shear walls of masonry, the decisive combination of actions derives from the interaction of vertical and horizontal actions. In this article, a method based on simple truss models is extended for the transfer of horizontal actions. It is demonstrated how the required verifications of load‐bearing safety can be performed with the results of the structural calculation. As an example, the application of the method for a seven‐storey building with calcium silicate blockwork or Poroton brick masonry is described.     

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.     

混凝土多孔砖砌体房屋抗震可靠度分析

通过对混凝土多孔砖砌体房屋结构的抗震可靠性研究,提出了基于概率地震烈度所对应的地面运动加速度峰值分布的可靠度计算公式和采用将各烈度地震对应的峰值加速度概率进行离散化处理的方法,基于作者早期的混凝土多孔砖墙片试验的结果推导出该结构水平最大位移和累积能量耗损的双参数破坏准则,分析了混凝土多孔砖砌体房屋结构在不同地震设防区的抗震安全性能及其影响因素。     

High‐rise concrete and clay block masonry building in Brazil

Brazilian structural concrete and clay block masonry construction shares many common features with construction all over the world: blocks of a similar shape are bedded in mortar, vertical and horizontal reinforcement is placed in grouted cells, engineering analysis and design follows universal principles and local design codes mimic those adopted elsewhere. However, loadbearing masonry construction in Brazil has become one of the most preferred high‐rise building systems due to its cost‐effectiveness and ease of construction compared to normal reinforced concrete solutions. This paper provides an overview of loadbearing masonry building in Brazil, including case studies on notable high‐rise masonry structures, with an overview of how Brazilian materials, codes and practices differ from the rest of the world. Finally, the paper explains how the use of high‐strength units assists the growing demand for taller and taller buildings and provides insight into why owners and general contractors often prefer to use structural masonry.     

Textile reinforcement in the bed joint of basement masonry and infill walls subjected to high wind loads

The successful structural verification of basement walls under earth pressure loading with light vertical loading is often difficult. This situation is often encountered for external basement walls under terrace doors, stairs, masonry light wells, etc., where the vertical loading that is theoretically necessary is absent. This makes it impossible to resist the acting flexural forces from earth using a vertical arch model alone. In such cases the basement wall must also resist the earth pressure in a horizontal direction. However, due to the fact the bending moment capacity of unreinforced masonry parallel to the bed joint is low you have the option here of using a textile‐reinforced bed joint with longitudinal fibres of alkali‐resistant glass or carbon fibre. With an appropriately adapted textile reinforcement in the bed joints, the masonry can fulfil the requirements for load‐bearing capacity against earth pressure with a horizontal load transfer, even under a small vertical load. The same applies to infill walls subjected to high wind loads the bending moment capacities of which are also slightly parallel to and vertically to the bed joint and cannot be provably demonstrated on large infill surfaces and strong wind loads. The load‐bearing can also be increased by improving the flexural strength parallel to the bed joint. The Chair of Structural Design in the Faculty of Architecture of the Technical University (TU) Dresden was carrying out extensive numerical and experimental studies for this purpose. In the journal Mauerwerk 01/2018 [1] first findings from small trial series have already been presented. In the meantime, a series of large‐scale tests have additionally been performed to check the promising results of the small‐scale tests with respect to their real applicability. This report should provide a combined insight into the work of the concluded research project.     

Museumsstück oder Verkehrsbauwerk – Aspekte zur Instandsetzung der Steinernen Brücke in Regensburg

Museum piece or traffic construction – aspects to the restoration of the stone bridge in Regensburg The oldest usable stone arch bridge in Germany has been carefully repaired since 2010 and has been reopened for use in June 2018. Based on preliminary investigations and model repairs, the planning had to take into account, on the one hand, the building and transport requirements for an inner‐city transport link. On the other hand, during the repair, the construction and ornamental elements had to be adequately preserved from the construction period between 1135 and 1146 to the first renovation phases to the destruction by war and traffic facilities. The article provides an overview of the preliminary investigations, the planning and their boundary conditions, as well as the resulting repair work on a still used transport structure, which is part of the monument ensemble of the historic old town. In the meantime, Regensburg is one of the UNESCO World Heritage Sites.