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.     

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.     

Energy‐efficient masonry buildings

In line with the general trend to improved energy‐related properties of buildings in massive construction, many massive buildings have been designed and built in recent years, which have proactively observed and also helped to determine the specification of future building standards in Europe. According to [1], the first low‐energy house was built in Kassel in 1986 with an area‐related energy demand for hot water and heating of only 60 kWh/(m²a). The use of massive building materials with low thermal conductivity played a similarly important role in this case to the increasing use of thermal insulation materials and new building services technology using renewable energy sources. Keeping the constructional details simple to build by tradesmen in order to avoid thermal bridging and useless building mistakes was and is still an important practical requirement. With the help of examples, the article demonstrates that monolithic construction is suitable for compliance with current energy‐related requirements and how this is carried out.     

Design of masonry buildings of three‐layered units according to Eurocode 6 / Bemessung von Mauerwerksbauten aus Dreischichtsteinen nach Eurocode 6

In the recent past, the masonry industry has developed many different solutions for optimising the heat protection of buildings. This took place for the building materials, geometric design, but also by development of multiple layered stones in which the components masonry unit, insulation and outer shell have been integrated into a block.     

Mauerwerksbefestigungen für zweischalige Fassaden – Stand der Technik

Double‐leaf masonry façades are becoming very popular due to their outstanding thermal and sound insulation properties, their durability and their ability to maintain the climate within a building (see Figure 1). Proper fastening of the facing shell is crucial if these benefits are to be effectively exploited in the long‐term and if building owners are to be given high investment security. The following article provides detailed information and explanations on product solutions that are both technically sound and cost‐effective.     

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.     

Verification of the fire resistance of clay brick masonry – hints for efficient design

In Germany, structural fire design of masonry is carried out in a simplified way using tabulated minimum wall thicknesses depending on the loading level in fire. Against this background the procedure of structural fire design is shown briefly before two approaches for a more efficient verification of the fire resistance are explained. The first possibility is to determine the reduction factor for the design value of the actions in fire more precisely and thereby reduce the loading level. Secondly, a design methodology is presented which can be applied in case of masonry walls with low vertical load but a large load eccentricity at mid‐height of the wall. Finally, the verification of the fire resistance of masonry according to national technical approval is discussed with an explanation how to obtain the same loading level in fire if the design is based on DIN EN 1996‐3/NA as when it is based on DIN EN 1996‐1‐1/NA.     

Dry laying of masonry to build demountable,highly energy‐efficient prototype houses – First findings from a currently running research project

In recent decades, energy efficiency has been the priority for masonry buildings in order to keep up with ever more stringent requirements. For the evaluation of the sustainability of building solutions, however, the embodied energy to produce a building and finally to dispose of it at the end of its lifecycle are also important. The energy used for the disposal of a building and the processing of the residues are also important for the overall energy balance since the handling of natural resources is increasingly the centre point of thought and action. A research team at the Chair of Structural Design of TU Dresden has thus been working since 2012 on demountable solutions in masonry, which can be dismantled at the end of a building lifetime and sorted for recycling, which fully complies with the requirement for the reduction of rubbish and waste products. The high precision of block production today permits us to omit the levelling effect of mortar and to build dry buildings in the future, i.e. to do without the bonding principle. The associated strength reductions can be suffered without problems. The appropriate basics of such a dry building method have been researched in a collaboration between the ILEK in Stuttgart and the Xella Technologie‐ und Forschungsgesellschaft mbH in Emstal. In this research project with the abbreviation ”REMOMAB“, the basics of an energy‐efficient dry building method suitable for recycling were collected and made available for practical application. In a follow‐up project, these basics are being implemented and tested on an experimental building. Cost aspects are also to be taken into account and if possible, construction solutions available on the market will be used – modified if necessary. Another aim is for the first time to dismantle such a building and to rebuild it at another location. This is intended to demonstrate that a reuse is possible after dismantling and such a building method can react to changing demands in the housing market.     

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.     

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.     

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.     

Minimum reinforcement of beam‐type reinforced masonry constructions – proposals for future regulations

The minimum reinforcement of reinforced masonry under bending should according to DIN EN 1996‐1‐1:2013‐02 [N 1], Section 8.2.3(1), be not less than ρ_min = 0.05 % of the effective masonry cross‐section for building elements, in which the reinforcement makes a contribution to the loadbearing capacity of the section, with the effective masonry cross‐section being the product of the effective width (b_ef) and the usable height d of the building element. In order to limit cracking and increase the ductility of the element, the reinforcement area should according to [N 1], Section 8.2.3(3), be not less than 0.03 % of the gross cross‐sectional area (of a wall). Other regulations ([1], [N 2], [N 3], [N 4], [N 5], [N 6], [N 7]) also prescribe minimum reinforcements in order to avoid brittle behaviour of the building element when the first crack forms or to limit cracking. In this specialist article, the figures given in [N 1] for the minimum reinforcement of reinforced masonry beams, like flat lintels or prefabricated lintels, are checked. The work concentrates on avoiding brittle failure when the first crack forms. In addition to geometrical requirements, the amount of minimum reinforcement depends on the tensile strength of the masonry f_t,m. Values of ρ_min vary considerably depending on the magnitude of the tensile strength of the masonry that can be assumed. For lintels over openings in facing brickwork facades, the height of any capping or soldier courses under the reinforcement layer also has an enlarging influence on the value of ρ_min. With regard to future regulations in standards or Allgemeine bauaufsichtliche Zulassungen (national technical approvals), it is recommended not to give lump sum values for ρ_min but to undertake a calculation like for reinforced concrete, using the algorithms given in this article.     

Textile reinforcement in the bed joint of basement masonry – First findings from a current research project

The successful structural verification of basement walls under earth pressure loading with light imposed loading is often difficult. This situation is often encountered for external basement walls under terrace doors, stairs, masonry light wells etc., where the theoretically necessary imposed loading is missing. This makes it impossible to resist the acting bending forces from earth pressure using a vertical arch model. In such cases, the earth pressure has to be resisted in a horizontal direction. Since however the bending moment capacity of unreinforced masonry parallel to the bed joint is low, another possibility is to use 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 horizontal load transfer, even under a small imposed load. Textile reinforcement has the advantage above all of corrosion resistance compared to conventional steel reinforcement, and textiles can also be inserted into thin bed joints. The Chair of Structural Design in the Faculty of Architecture of the TU Dresden is currently carrying out extensive numerical and experimental studies for this purpose. The objective is to develop an optimal configuration of material and textile form for use as bed joint reinforcement. The investigations are concentrating on the tension strength, bonding and durability of the composite material ”textile mortar“. This report should give a brief overview of the state of the work in the currently running research project.     

Investigations into the improvement of the weather protection of unburnt brick masonry,part 1

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 as well as Part 2, Assessment of the results for surface treatment to unburnt bricks and the climatic chamber tests.     

Reinforced masonry beams under shear load – Proposals for future designs / Bewehrte schubbeanspruchte Mauerwerksbalken – Vorschläge für zukünftige Bemessungen

This article is written against the backdrop of the work of the European standardisation committees on the amendment of EN 1996‐1‐1 [N 4] which will also exert an influence on the design of reinforced masonry in Germany. This paper focusses on the design approaches of DIN EN 1996‐1‐1 for untensioned reinforced masonry beams under shear load in the ultimate limit state (ULS). Proposals are made to discuss their revision. The contents of E DIN 1053‐3 [N 3] and of the final draft of the guideline ”Flat Lintels” [7] are taken into account.