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Der vorliegende Aufsatz stellt ein Konzept für den Entwurf und die Herstellung von gefalteten schalenförmigen Tragstrukturen aus zementbasierten Verbundwerkstoffen vor, das in Anlehnung an die japanische Papierfaltkunst Origami entwickelt wurde. Die räumlichen Tragstrukturen werden durch Faltung von ebenen Elementen mit vorgegebenen Faltlinien hergestellt. Ziel ist die Entwicklung einer Entwurfs- und Herstellmethodik für dünnwandige Faltwerke mit einfachen oder doppelt gekrümmten Geometrien, die als segmentierbare Hüll- und Konstruktionselemente mit optimierten mechanischen Eigenschaften eingesetzt werden können. Wegen der hohen Variabilität der Formen und der großen Anzahl von Freiheitsgraden der Faltstrukturen ist eine Unterstützung mit numerischer Simulation in allen Phasen des Entwurfs und der Herstellung unabdingbar. Gegenüber der traditionellen Herstellung von Schalentragwerken mithilfe aufwendiger gekrümmter Schalungen verspricht die Methodik ein hohes Potenzial an Wirtschaftlichkeit. Insbesondere durch die Verwendung von modernen, zementbasierten Verbundwerkstoffen werden durch das Konzept neue Anwendungsfelder erschlossen, die sich durch geringen Materialverbrauch, einen hohen Ausnutzungsgrad des Werkstoffs sowie eine einfache systematische Herstellung auszeichnen. Oricrete - design and manufacturing methodology for folded plate structures made of novel cementitious composites The present paper shows an approach for the design and production of folded plate structures made out of novel cementious composite materials. The idea of the approach is derived from the Japanese art of paper folding, origami. The spatial structures are obtained by folding of planar elements provided with prescribed crease lines. The aim of the present work is the development of a design and manufacturing method for the production of free-form structural members with optimized mechanical properties applicable as façade and load bearing segments. Due to the high variability of forms and the large amount of degrees of freedom of the fold patterns, a support by numerical simulation in all phases of design and production is required. The method has a high potential to reduce the production costs compared to traditionally fabricated shell structures with complex curved formworks. New fields of application for cementious composite materials can be entered that are characterized by low material consumption, a high exploitation of the material and a systematic manufacturing process. [ABSTRACT FROM AUTHOR]

Modelling of the CUBE's TWIST shell This paper gives an overview of the main procedures prepared during the phase of the project development within the field of numerical modelling and design. The roof shell elements represent itself twisted shape that together with complicated structurally demanded inner structure forms quite complicated configuration for the concrete volumes as well as for the used reinforcement. Therefore, custom developed numerical method was required to be prepared. For that, the software solutions Rhinoceros 3D and Grasshopper 3D were used as the main algorithmic environment. The paper additionally gives an insight of important aspects required for production of the formwork components, thermal insulation, biaxially oriented carbon reinforcing grids and other parts of the load‐bearing shells. Finally, the paper gives an idea how was established a collaboration with partners of the CUBE project in particular in the field of structural analysis. [ABSTRACT FROM AUTHOR]

Nonwoven bonded pre‐applied waterproofing membranes – bond development and properties Pre‐applied bonded membranes are used as an additional waterproofing measure on waterproof concrete structures and are installed before concrete placement. They achieve a bond to the fresh concrete and often use nonwovens, which must be filled with cement paste during concrete placement. However, little is known about the separation of cement paste from fresh concrete, its properties in the nonwoven, or beneficial nonwoven characteristics. The following paper analyzes the bond of nonwovens in three parts: first, the deformation behavior of the nonwovens during concrete placement is determined using microsections. During concrete placement, the nonwovens are compressed and progressively recover during cement paste filling. As the fresh concrete is placed, filtration processes start. Excess water and a limited amount of fine solids separate into the nonwoven. A filter cake forms on top of the nonwoven and is responsible for a water‐rich cement paste within the nonwoven. Only with the onset of vibration compaction is the filter cake loosened, more solids penetrate the nonwoven, and the water‐solid ratio in the nonwoven is lowered. The bond subsequently develops proportionally to the tensile splitting strength of the concrete. Nonwovens influence the bond strength as they control the separable amount of excess water, which degrades the cement paste strength in the bonding layer. [ABSTRACT FROM AUTHOR]

Influence of transverse tensile loads on the compressive strength of carbon reinforced concrete Initial findings on the load‐bearing behaviour of carbon reinforced concrete components under uniaxial compressive stress are available, however multi‐axial stress states are of particular relevance for an application in construction practice. It is known from steel reinforced concrete constructions that transverse tensile stresses lead to a reduction in the compressive strength, although there is still no international agreement on the actual reduction. In this paper we investigate the boundary conditions under which carbon reinforced disc shaped specimens can be tested under combined compressive and tensile loading. This includes the anchoring of the carbon yarns required for the tests in limited space conditions as well as the influence of the loading regime – proportional or sequential – and the manufacturing process – laminated or casted – on the test results. Finally, an outlook on the following investigations is given. [ABSTRACT FROM AUTHOR]

Manufacture and erection – TWIST The TWIST shell structure of the CUBE Result House was built from carbon concrete using the wet spraying method. The report from the executing company's perspective provides a detailed description of the technological realization based on the plans submitted for execution. The paper deals with special aspects of production, which result from technology, building materials used, building material properties and general conditions during construction. The experience gained should serve the further development of carbon concrete constructions and shows the need for development to be ready for practice with regard to construction. [ABSTRACT FROM AUTHOR]

Image‐based quality conctrol – part 1: consistency and paste content Today, only very simple empirical test methods are available for quality conctrol of fresh concrete on the construction site or in the production plant. Corrective actions in the case of quality deviations are based on a subjective visual inspection and thus on the experience of the inspector. The standard test method in Europe is the flow table test. The consistency of the concrete is derived from the diameter of the spread out fresh concrete. In order to overcome the deficiencies of this subjective fresh concrete testing, an image‐based method for determining (fresh) concrete properties was developed and validated. In addition to the diameter, extensive information can be derived from the surface properties of fresh conrete. In this paper, the image‐based determination of the consistency and the paste content is explained. The image‐based determination of granulometric properties (part 2) and the homogeneity of fresh concrete (part 3) will be presented in planned follow‐up articles. [ABSTRACT FROM AUTHOR]

Accuracy limits of modular concrete structures – Part 2: Probabilistic evaluation of assembling with bolted connection The paper treats the assembling of modular precast concrete elements with steel‐made truss nodes. Honeycomb structures are considered, which consist of several Y‐shaped precast elements. The paper extends the direct kinematics between modules for honeycomb structures derived in Part 1, where shrinkage strains induce deformations into the modules. For the assembly, bolted connections are considered, which either have standard hole clearance or enough friction strength. In the latter case, strict alignment before fixing compensates for some of the deviations. The reliability of the assembling is checked via probabilistic methods based on Monte Carlo simulation. It is shown that connections purely based on hole bearing resistances are just suited to combine few modules. Bolted connections with enough friction strength and compensatory pre‐alignment have confidence intervals of four times the standard deviation and thus are suited to reliably assemble honeycomb structures up to approx. 60 m in height and width. [ABSTRACT FROM AUTHOR]

Position paper "Concrete without hard coal fly ash" – Change in concrete construction due to decreasing availability of hard coal fly ash and other power plant by‐products as additives for concrete Due to the gradual phase‐out of coal‐fired power generation, significantly lower volumes of hard coal fly ash produced in Germany are already available today. By 2038 at the latest, their share will fall to zero. The German Society for Concrete and Construction Technology (DBV) and the Federal Waterways Engineering and Research Institute (BAW) are pursuing the aim of this position paper to inform all those involved in construction about the resulting supply bottlenecks of hard coal fly ash and to create understanding. In addition, in this paper they show initial approaches to solutions to minimize the negative effects on concrete construction as far as possible. [ABSTRACT FROM AUTHOR]

Life Cycle Assessment in the Building Sector – Greenhouse Gas Emissions of Common Ceiling Systems In the past, life cycle assessments (LCAs) of buildings were only carried out in rare cases at the request of project initiators. Against the backdrop of social and political pressure to act more climate‐friendly and sustainably, LCAs and the available data are also becoming increasingly economically relevant. This paper therefore presents the essential principles of LCA in the building sector. In addition to a critical analysis of the scope of assessment, there is a brief presentation of available data bases, such as the national database ÖKOBAUDAT. Furthermore, the greenhouse gas balance of timber as a building material is discussed, which in some cases opens up considerable scope for assessment with the risk of false incentives. As horizontal building components, ceiling systems of multi‐storey buildings can cause almost 40 % of the structural emissions and are therefore highly relevant for a LCA. By varying the life cycle stages assessed and data sets used as possible factors influencing the results of a LCA, these building components are examined and compared in more detail in the following article. Despite some sensitive effects on the comparison of the ceiling systems, the LCA offers a decision‐making aid for the selection of ceiling systems in terms of reduced greenhouse gas emissions of a shell construction. [ABSTRACT FROM AUTHOR]

An UHPC for use in deep‐sea research The article deals with comprehensive material investigations carried out with an ultra‐high performance concrete (UHPC) intended for use in the deep sea. The tests performed include the determination of the stress‐strain behavior under uniaxial loading of the specimens, of the biaxial compressive strength of the UHPC under different stress ratios, of the tensile strength characteristics, and of the elastic modulus. Cubes, prisms and bone‐shaped test specimens were used for the investigations. From the determined material properties, conversion factors for the geometry‐dependent strengths of the concrete were calculated. In the paper, the determined biaxial compressive strength values are compared with data known from the literature. It is shown that an UHPC can have a similar increase in strength as a normal strength concrete. [ABSTRACT FROM AUTHOR]

Environmental Performance of Ceiling Systems in Building Construction – Currently used Systems and Future Optimisation Potenzial The building industry counts to the most influencing sectors regarding raw material demand, energy use and solid waste generation (≥ 38 %). The development and use of construction methods and building materials with minimal environmental impact over the entire life cycle has therefore utmost relevance. In order to quantify the environmental impact of construction methods and materials, a fact‐based life cycle assessment must be carried out. Currently, these kinds of assessments are not state of practice with a lack of objective comparisons missing on the market. When looking at building construction, ceiling systems in particular have a great influence on the environmental footprint of the entire building. Therefore, this paper is dedicated to the environmental comparison of different ceiling systems in building construction based on EN 15804 and EN 15978. The system boundaries were defined with the life cycle phases of cradle‐to‐gate and cradle‐to‐grave. A total of nine different ceiling types within different structural systems were considered and evaluated. All systems were dimensioned as efficiently as possible according to common engineering practice for the given boundary conditions with the currently valid standards (ÖNORM, Eurocode). The results show that environmental competitive systems can be implemented using all considered materials. The key is to take the materials properties into account while simultaneously optimising the structure and load‐bearing systems. [ABSTRACT FROM AUTHOR]

Tensile load‐bearing behaviour of concrete components with impregnated textile reinforcement made of natural fibres Recently, the use of natural fibres as a reinforcement in composite building materials have witnessed a growing interest amongst researchers due to their ecological, economical and mechanical properties. In civil engineering, however, they have not been considered in extensive investigations or the development of design guidelines for concrete members with textile reinforcement made of synthetic fibres. In this paper, the uniaxial tensile load‐bearing behaviour of concrete members reinforced with flax fibre textiles (impregnated leno fabrics) is investigated. Therefore, test specimens were casted and tested, varying parameters of the textiles, e. g., the spacing of the weft threads. For a reference, both test specimens reinforced with non‐impregnated textiles and without any reinforcement were investigated. The suitability of this type of reinforcement for concrete members under uniaxial tension is shown by an increase in the ultimate load compared to members without or with less reinforcement. The curves of the stress‐strain diagrams can be divided into three stages typical for reinforced tensile test specimens (state I – uncracked, state IIa – process of cracking and state IIb – completed crack pattern). The differentiation of the areas is clearer with an increasing reinforcement cross‐section. Further, a finely distributed crack pattern with uniform crack widths was observed which supports the findings of the diagrams. [ABSTRACT FROM AUTHOR]

Creep and shrinkage prediction models for concrete In autumn 2020, the revision of EN 1992‐1‐1:2004 (Eurocode 2) was completed, resulting in the current draft prEN 1992‐1‐1:2021. It provides practice with numerous improved and new design concepts. This also applies to the models for shrinkage and creep of structural concrete, some of which have undergone significant changes. This three‐part paper (Part 1 Shrinkage, Part 2a and 2b Creep) presents the new models for predicting the deformation behaviour of concrete. It also highlights the background that led to the development of the improved approaches. The Parts 1 and 2a have already been published (Beton‐ und Stahlbetonbau 116 (2021), issues 1 and 9). The article at hand (Part 2b) continues and concludes the previous treatment of concrete creep. First of all, the functions for describing the time development of creep and the implications associated with them are presented. Then, various aspects of linear and non‐linear creep are examined. The focus of the article is on the new prediction model of prEN 1992‐1‐1:2021, which is presented and justified. Statistical considerations on the reliability of the new model and the presentation of a concept for the inclusion of laboratory test data to improve the prediction of the model conclude this article and the entire paper. [ABSTRACT FROM AUTHOR]

Ductility‐increasing reinforcement systems for fabricated column elements made of UHFB In order to build faster, lighter and more precisely with concrete, a new modular construction concept based on ultra‐high performance concrete (UHPC) was investigated, which has a highly advantageous ratio of axial compression load‐bearing capacity and dead weight [1]. In order to enable proper manufacturing of this column element, which is referred to as a winding‐reinforced UHFB hybrid tube, in an automated extrusion process, a novel reinforcement concept has to be developed without the usual steel reinforcement. In an extrusion process, a supporting inner steel tube is encased with UHPC and advanced together with the UHPC. Subsequently, a ductility‐enhancing confinement reinforcement is applied to the surface of the components from the outside in a process that can be automated. As UHPC fragments damage the CFRP reinforcement in case of failure, this paper investigates which protective layer/reinforcement system can be used to achieve ductile component behavior for beam structures subjected to axial compression. For this purpose, different textile reinforcement layers were applied to UHPC specimens and their influence on the load‐bearing behavior of the components was determined with special consideration of ductility and residual load‐bearing capacity after exceeding the maximum load. A combination of aramide fabric and carbon fiber textile showed favorable load‐bearing behavior with enhanced quasi‐ductility in experimental investigations. [ABSTRACT FROM AUTHOR]

Flexural design of UHPC girders with mixed reinforcement Determining the flexural strength of cross‐sections reinforced with a combination of reinforcing bars and steel fibres requires enhancing the assumptions applicable to reinforced and prestressed concrete. To account for the load‐bearing capacity of the fibres in the flexural crack, generally, a stress‐strain curve is derived from measured stress‐crack opening or load‐deflection curves. A so‐called structural characteristic length serves as reference value for conversion. Within the scope of this paper, influences from the cross‐section height and other parameters influencing crack formation are taken into account when determining the structural characteristic length. A stress block with a limit strain, which refers to reaching a "critical" crack width, is proposed as "stress‐strain curve". The "critical" crack width marks the maximum of the load‐bearing capacity of the fibres in the flexural crack in case of cross‐sections exclusively reinforced with steel fibres and the beginning of strain localisation in case of cross‐sections with mixed reinforcement. With mixed reinforced cross‐sections, strain localisation is a further possible failure mode in addition to the well‐known failure modes flexural tensile failure and flexural compression failure. The bending capacity, the moment‐curvature relationship and the failure mode of selected tests are represented very well by the proposed design approach. A parameter study shows basic relationships that could also be observed in experiments. [ABSTRACT FROM AUTHOR]

Experimental and numerical investigations of constraining forces due to temperature differences A realistic estimation of the constraint force is of great importance for a safe and economical design of reinforced concrete members subjected to constraint. Previous work suggests that a distinction should be made as to whether concrete shrinkage or a temperature difference is the cause of the constraint forces. In the present paper, experiments are described in which reinforced concrete components held on both sides were experimentally examined under uniform temperature differences of up to 70 K. The resulting cracking and the corresponding forces are elaborated, compared with results from numerical simulations, and extended by the variation of the degree of longitudinal reinforcement, concrete tensile strength and degree of restraint. The significant differences in the load‐bearing behavior compared to members subjected to constraint forces resulting from shrinkage are confirmed. In addition, it is shown that the final state of full cracking of the respective structural member can be achieved at strains much lower than 0.8 ‰. The usual procedure for a combined loading and restraint, in which the design for both types of loading is carried out separately and then the larger of the two determined reinforcement cross sections is provided, can in part be clearly on the unsafe side. [ABSTRACT FROM AUTHOR]

Climate Compatibility as a Criterion for the Design and Performance of Concrete illustrated by the Example of an ÖBB Small Animal Passage Concrete is the world's most widely used building material and is preferred for infrastructure construction inter alia due to its high performance, versatility and durability. Its production and use, however, generates significant amounts of greenhouse gas emissions (CO2eq). Consequently, any reduction of CO2eq of the building material contributes to achieving the societal goal of CO2 neutrality. In this paper, a small animal passage of an ÖBB railway line is used as an example to show how climate compatibility or CO2‐equivalents (kg CO2eq/m3) are directly integrated into the mix design. It is also explained how the essential performance characteristics of climate‐compatible concretes – in addition to the CO2‐equivalents, in particular their early strength and durability – can be considered and optimised in their entirety. For this purpose, performance‐based concepts are applied for the optimisation of binders with combined additives and for the verification of durability. Furthermore, experiences with the realization, testing and quality assurance of CO2eq‐reduced concrete in comparison to equivalent standard concrete will be reported. [ABSTRACT FROM AUTHOR]

Creep and shrinkage prediction models for concrete In autumn 2020, the revision of EN 1992‐1‐1:2004 (Eurocode 2) was completed, resulting in the draft prEN 1992‐1‐1:2020. It provides practice with numerous improved and new design concepts. This also applies to the models for shrinkage and creep of structural concrete, some of which have undergone significant changes. This three‐part paper (Part 1 Shrinkage, Part 2a and 2b Creep) presents the new models for predicting the deformation behaviour of concrete. It also highlights the background that led to the development of the improved approaches. Part 1 has already been published (Beton‐ und Stahlbetonbau 116 (2021), issue 1). The article at hand (Part 2a) deals with the creep of concrete. In an overview, the components of creep, their characteristics and influencing parameters as well as the corresponding constitutive relationships are first presented. They are crucial for understanding the creep models. Then, the normative developments that have led to the creep model in DIN EN 1992‐1‐1:2011 valid today in the year 2021 are shown. The focus is on the analysis of the reliability and accuracy of this model. It revealed certain deficiencies, which were the reason for corrections and further developments being included in prEN 1992‐1‐1:2020. The new prediction model is presented and justified in Part 2b of this paper. Statistical considerations on the reliability of the new model and the presentation of a concept for the inclusion of laboratory test data to improve the prediction of the model conclude the entire paper. [ABSTRACT FROM AUTHOR]

Energy‐based direct calculation of reinforcement for crack width control In the literature and in many standards, crack spacing and mean strains are used to predict crack widths. To calculate the crack spacing, the average bond stress must be known. In many calculation approaches, this is simplified and assumed to be a constant value. Based on a realistic approximation of the slip curve s(x) over the length, Tue and König have shown how the mean bond stress can be determined depending on the crack width in order to improve crack width calculation. This paper describes an energy‐based approach that can be used to directly determine the reinforcement for the control of crack widths for any given relationship between local bond stress and slip (bond law). The approach is applied to the well‐known bond law with power approach and examined for agreement with experimental results. Although mean strains, crack spacing and mean bond stress do not appear explicitly in the formulas, the solution is mathematically exact within the underlying relationship of local bond stress and slip. [ABSTRACT FROM AUTHOR]

Renewal of reinforced concrete bridges by means of UHPFRC Ultra‐High‐Performance Fiber‐Reinforced Cementitious composite building material UHPFRC is a novel building material that is characterized by high mechanical strength and durability. UHPFRC is suitable for the renewal of existing reinforced concrete bridges. Based on the experience with numerous applications, the basic design concepts for the protection, rehabilitation and strengthening of reinforced concrete bridges are developed in this paper. These relate to the improvement of durability as well as the strengthening of bridge deck slabs and girders. The implementation in practice of the design concepts is illustrated by three recently completed projects. It is shown that the renewal of reinforced concrete bridges with the help of UHFB is also important with regard to the sustainability, since the material resources already installed in the reinforced concrete structure are reused. [ABSTRACT FROM AUTHOR]

Pull‐out load capacity of thin composite dowels as fasteners for reinforced concrete wall panels Increasing requirements for thermal insulation and the reduction of transmission heat losses in buildings lead to an increased demand for energy‐efficient insulation systems and technologies for the building envelope. In this paper, thin composite dowels are used to present novel fasteners for an efficient vacuum‐insulated wall element. This element consists of two concrete layers and a vacuum‐insulated core layer. The individual layers are coupled by means of thin composite dowels, which are used as fasteners for reinforced concrete wall panels. Tensile tests are performed to investigate the load‐deformation behaviour of thin puzzle‐shaped composite dowels and to highlight the influence of different parameters such as reinforcement, embedment depth and number of composite dowel bars. The experimental results are compared with an existing model from the literature for determining the tensile capacity of composite dowels and evaluated in terms of their suitability. Based on this, a modified model for describing the tensile load‐bearing capacity of thin composite dowel bars is presented and validated based on the test results. [ABSTRACT FROM AUTHOR]

Additive manufacturing of monolithic, steel‐reinforced concrete walls using CONPrint3D‐reinforced methods 3D concrete printing technology is developing rapidly and is increasingly finding practical applications. However, the integration of load‐bearing reinforcement remains a challenge. This paper presents three new methods for the construction of monolithic walls of reinforced concrete based on the CONPrint3D‐technology developed previously by the authors. In detail, these are: 1) the additive covering of reinforcement meshes, which are hung in front of a printed core wall, 2) the lateral additive filling of a reinforcement cage and 3) the fully automatic construction of a reinforcement structure with immediate subsequent layer‐by‐layer encasing by extruded concrete. In addition to the current state of research and the material challenges, mechanical engineering development approaches and the calculative evaluation of the new processes in comparison to established construction methods will be presented. [ABSTRACT FROM AUTHOR]

Development of processes for the automated planning and production of individual reinforced concrete elements Industry 4.0, digitalisation and automation are the topics of high interest for research and development in the construction industry and related institutions these days. As a result, robots and robotic machines can be found more and more frequently in production halls. Following this trend, this paper presents research and development work currently being carried out by the Max Bögl Group and the Institute of Structural Engineering of the Universität der Bundeswehr in Munich. The first declared development goals of this collaboration concern the implementation of drivers of digitalisation and Industry 4.0 in the planning and production of precast reinforced concrete elements. For this purpose, in digital planning, a process for parametric 3D modeling and path planning for robotic applications is being developed. The resulting data sets are then used in the technical implementation using industrial robots for the individual production of reinforcement cages on the one hand and for the production of alternative component geometries using a concrete 3D printing process on the other hand. [ABSTRACT FROM AUTHOR]

Statistical size effect and corresponding influence for reliability in steel structures, part 2 – reliability analysis This paper presents – as the second of two parts – research results about the statistical size effect and the corresponding reliability in steel structures. In this paper, the influence of the size effect on the reliability analysis and the design of steel structural components are discussed based on a linear failure limit state. The calculation examples for 3‐point and 4‐point bending tests are carried out applying a Gaussian load as a simplification. The results show that the statistical size effect leads directly to a size‐dependent reliability index, which in most cases can provide a reasonable estimate of the failure risk. [ABSTRACT FROM AUTHOR]

Influence of the steel fibre reinforcement type on the concrete breakout resistance of fastenings A frequent design situation for various types of structures (such as slabs on ground, industrial floors, and tunnels) is associated to connections of structural and non‐structural elements on a steel fibre reinforced concrete substrate. Consequently, strong research interest has been recently drawn to this structural application. While various research efforts have focused on normal and fibre reinforced concrete with different anchor types and fibre characteristics individually, an insight to the influence of fibres with different characteristics under otherwise comparable conditions is currently missing. This paper offers consistent conclusions on the fibre type influence as regards the concrete breakout capacity of fastenings, and it allows for a re‐examination of currently proposed design approaches. [ABSTRACT FROM AUTHOR]

Development and application of ultrasonic techniques for the quality control of concrete This paper is dedicated to Prof. Reinhardt for excellent supervision and exciting research. He was about 20 years my supervisor and mentor. On the occasion of the 80th birthday of Prof. Hans‐Wolf Reinhardt, one of the most important modern measuring techniques for concrete quality control is discussed. It was developed under his guidance and facilitates the ultrasound technique for monitoring and analyzing fresh concrete and mortar properties during setting and hardening. To stress Prof. Reinhardt's merits, the developments at the University of Stuttgart are summarized. They culminated in one of the first commercially available modern test device that was the blueprint for other devices. The paper is giving also an introduction into the capabilities of the technique along with some more recent example of applications and a brief overview about standardization activities. The author's hope is that more scientists and practitioners are stimulated to use and further develop this technique establishing it on a broader range in the area of building constructions. [ABSTRACT FROM AUTHOR]

Bond in glass‐rigid foam‐concrete sandwich elements – part 2: experimental investigations on the bond between concrete and rigid foam Sandwich elements in building envelopes with facing layer made of glass require currently mechanical or adhesive connectors. The absence of these connectors is of interest in terms of resource and energy savings both in production and in the building envelope. This paper reports on the bond behaviour between polyurethane rigid foam and float glass with different surfaces without and with the use of a bonding agent. The studies are part of the development of a glass‐rigid foam‐concrete sandwich element without additional adhesives and mechanical connectors. The results of adhesive tensile and shear tests show that a sandblasted roughened glass surface resulted in cohesive failure in the insulation layer. The production‐related different glass surfaces on atmosphere and tin side come to an adhesive failure between insulation layer and glass. Composites of glass and insulation layer without adhesion agent show no significant differences between the atmosphere and the tin side. Overall, the test specimens with bonding agents achieved higher levels of adhesive tensile and shear strengths. Light and electron microscopic studies of the fractured surface show that the bonding agent has a significant influence on the wetting and pore formation of the liquid polyurethane. The composite of the polyurethane rigid foam and concrete is described in part 1 of the paper. [ABSTRACT FROM AUTHOR]

Numerical process simulation for concrete constructions – Practical application at example of concrete dam of pumped storage power station Linth‐Limmern The power station project Linth‐Limmern in the Swiss Alps finished in 2016 is a focused location in the national power supply strategy of Switzerland. The central element is a subsurface pumped storage power station at a level of 1800 m which is supplied by the 700 m higher storage lake Muttsee. The erection of the necessary dam construction is a challenging task due to the massive dimensions of concrete works, the extreme alpine conditions and the reinforcement‐free design requiring a high level of structural safety, usability and durability. This applies in particular to a possible crack formation due to hydration heat of the concrete which has to be prevented by adequate technological methods. The paper presented here introduces the used thermomechanical simulation models and derived practical conclusions and method statements. It is also seen as a prelude for a series of similar papers reporting about the practical application of numerical material and process simulation. [ABSTRACT FROM AUTHOR]

Bond behaviour of wrapped CFRP bars in concrete The usage and availability of reinforcement made of CFRP is steadily increasing. The understanding of the bond behaviour is still not satisfactorily investigated, but mandatory for a secure application. This publication shows the broad variety of CFRP reinforcement and their surface treatments. Focusing on CFRP bars with a spiral of carbon fibres tightly wrapped around the bar, the competitiveness to other surface treatments like grooves milling into the bar is presented. In total 84 pull‐out tests were performed to evaluate the bond behaviour in four different concrete qualities. The varying parameters of the CFRP bars are the width, thickness and height of the spiral, the distance between the spirals and the diameter of the bar. The results are presented and compared using bond‐slip‐curves. A thorough discussion completes this paper. [ABSTRACT FROM AUTHOR]

European beech glued laminated timber European beech wood (Fagus sylvatica L.) is currently used only to a very limited extent for the production of glued laminated timber (glulam). Although this most widespread hardwood species in Central Europe has a very high potential in terms of strength and stiffness, besides its application to railway construction (as sleepers), it has so far been mainly used by the furniture industry and for heating purposes. One main reason for this is the lack of standards and guidelines regulating the production, quality control and specifying the mechanical properties of beech glulam. In this paper, an extensive research project aiming at determining the mechanical properties of beech glulam is presented. Based on bending, tension, compression, buckling and shear tests on beech glulam specimens of different cross sections and strength classes and taking into account previous investigations as well as the results of numerical simulations, the mechanical properties of beech glulam are determined. Furthermore, formulas to account for the effect of the member size on the bending and shear strength as well as buckling curves for the design of columns made of beech glulam are presented. [ABSTRACT FROM AUTHOR]

Models for the bond behavior of wood screws for design Wood screws are important fasteners for timber‐to‐timber or timber‐to‐steel‐connections as well as for compression reinforcement of beams. For these joints, the decisive property is the load‐bearing capacity, which is determined by the bonding mechanisms between the screw thread and the wood. For the design of wood screws, there is a lack of suitable models that describe the relationship between the thread design and the load‐bearing capacity. This paper aims to examine the models of the bond behavior of wood screws from the point of view of design. As a result, four requirements on load‐bearing models for the design are shown and a model extension is presented. The extension to the stress distribution concerning the rotation angle to the screw axis is investigated experimentally using colored crack patterns. The use of the model for design is shown on the parameter flank angle. Improved models of the bond behavior can be used by manufacturers to optimize the screw geometry as well as to enable of a safe and economic design approach. Timber engineering thus benefits from withdrawal capacities as well as higher reliability of the screw joint. [ABSTRACT FROM AUTHOR]

Evolution of creep and shrinkage models for concrete structures in Austria and Germany – Evaluation of the current models regarding the sensitivity of the input parameter Concrete is one of the most important materials in civil engineering structures and finds its application in the building of bridges, ground engineering and building construction. As widely known, concrete is a material which changes its behavior with time in dependency of the environmental conditions. Especially the long‐term deformations caused by creep and shrinkage processes are of great interest regarding the durability and sustainability of infrastructures. Early versions of design codes gave some guidelines on how to treat deformations caused by these sources. In the beginning, these deformations were taken into account by an additional temperature drop. The first sophisticated approaches on how to deal with these long‐term processes were published in the standards for prestressed concrete structures. These early models were updated and improved to today's prevailing documents such as the Eurocode 2 and the fib Model Code. The first part of this paper gives an overview of the historical development of creep and shrinkage models in Austria and Germany until today's guidelines. The second part presents a sensitivity study of the current models regarding the input parameters for some given scenarios. Lastly, the differences between the models are highlighted based on an application example taken from literature. [ABSTRACT FROM AUTHOR]

AI‐supported quality assurance for the flow production of UHFB bar elements Fast precision construction requires modular designs with lightweight, easy‐to‐handle components that can be manufactured at high repetition rates. To enable such elements to be produced continuously, quickly and economically, new manufacturing and design concepts are needed, in which the design must be highly efficient (form follows force) and which also consistently complies to the requirements for rapid series production. AI‐supported quality assurance controls in the course of flow production, which obtains its data from a variety of different sensors and sensor types, lend themselves to such new manufacturing processes. Such AI‐assisted manufacturing is implemented by an Artificial Neural Network (KNN), which, compared to conventional approaches, offers the possibility to map nonlinear relationships of heterogeneous data. In this paper, the KNN‐based form of quality assurance (QA) on flow‐produced beam elements is described as an example for the assessment of the concrete surface and geometry, which can represent a first step into process control. First investigations have shown that even small defects can be detected and localized very efficiently. [ABSTRACT FROM AUTHOR]

Modular bridge structures made of carbon fibre reinforced ultra‐high performance concrete Graph‐based design and trajectory‐sensitive manufacturing In order to enable the prefabrication of bridge structures in a continuous production line, extensive changes in design and execution are necessary. Therefore, this paper explains a holistic and end‐to‐end digital design process for a modular construction system that composes planar, additively manufactured modules. The system is computationally represented with a graph‐based data model, laying the foundation for design automation employing graph rewriting rules. Sets of rules are employed to generate modular structures according to two approaches: Either existing component geometries are segmented, or rules formalize the aggregation of structures. At this process state, predominantly geometric information is available. This information is developed into a semantically rich representation of the decomposition until a highly detailed production model for each module can be instantiated parametrically. Because of the flexible definition based on NURBS, the production model can depict a variety of possible joining situations and connections. Beyond this, the model is the basis of the printing path generation for the additive manufacturing process. The path is determined according to the principal stress directions, numerically interpolating the results of a non‐linear FE analysis. Along this printing path, the alignment of carbon fibre reinforcement is steered by custom nozzle technology, enabling outstanding material properties of the manufactured components. [ABSTRACT FROM AUTHOR]

Experiments on shrinkage reduction of high‐performance concrete components by heat treatment The paper investigates the shrinkage reduction of high‐performance concrete by heat treatment. Concretes are heat treated to accelerate hardening and to allow early stripping. Damage to the concrete structure is to be minimized by a suitable choice of maximum treatment temperature, heating and cooling rate. This leads to temperature durations of more than 24 h, which is not suitable for a serial production of precast concrete parts. For a minimally short heat treatment, a pre‐storage time and a regulated heating rate are omitted so that the heating starts directly after concreting. This shortening of the temperature duration has an influence on the shrinkage behavior. It is investigated here on prisms with and without steel fibers, as well as on beams with rebar ratios of 1.8 % and 3.1 %. All specimens are heat treated at 80 °C and 60 % relative humidity for 1, 2, 4, 6, and 24 h. Specimens without heat treatment serve as reference. The results show that the shrinkage strain is significantly reduced with increasing temperature duration. It also decreases with an increasing rebar ratio. In order to predict the shrinkage behavior as a function of temperature duration, data‐based response surfaces are derived and validated. Thereby, the prediction quality increases with increasing concrete age. [ABSTRACT FROM AUTHOR]

Punching shear behaviour of steel fibre reinforced flat slabs with punching shear reinforcement The guideline "Steel Fibre Reinforced Concrete" published by the German Committee for Reinforced Concrete (DAfStb) contains the current normative regulations for the punching shear design of steel fibre reinforced flat slabs. Due to a lack of sufficient experience and knowledge, a consideration of the combined action of steel fibres and shear reinforcement was explicitly excluded. While numerous punching shear tests on steel fibre reinforced flat slabs without shear reinforcement are available in literature, only eight tests in combination with shear reinforcement are known to the authors. These few tests used types of shear reinforcement which are not common for engineering practice in Germany, or showed bending failure, which limits the reliability of statements about the behaviour of such a combination. In this context and the expected favourable behaviour, seven tests were carried out to systematically investigate the punching shear behaviour of steel fibre reinforced flat slabs with stirrups and shear studs as shear reinforcement. The test program included one fibre reinforced test without punching shear reinforcement, two fibre‐free and four fibre reinforced tests with punching shear reinforcement. This paper describes the experimental investigations carried out and discusses the results obtained. [ABSTRACT FROM AUTHOR]

Development of innovative wood‐concrete composite floors in prefabricated construction method The use of wood in construction as a natural and sustainable building material is becoming increasingly important. New developments are moving towards the use of wood in multi‐storey residential and office buildings. In addition to the ecological advantages, the favourable room climate and the direct experience of wooden surfaces on walls and ceilings are also important for the user. In storey construction, the wood‐concrete composite construction method in particular, which makes optimum use of the static advantages of both building materials, has proven to be forward‐looking. The newly developed wood‐concrete composite floor described in this paper consists of CLT panels and precast concrete elements. The wooden element mainly absorbs the bending tensile forces and the concrete slab mainly absorbs the bending compressive forces. The necessary shear connection is made via so‐called cleats, which are milled into the wood and formed in the concrete in complementary form. The connection is also secured with an adhesion bond. In addition to the development of the design and the appropriate manufacturing method, shear tests on small bodies and several large‐scale bending tests on ceiling elements on a scale of 1 : 1 were carried out to investigate the load‐bearing behaviour. Furthermore, in order to find a suitable calculation method, the gamma method and the discrete were compared with the bending tests. [ABSTRACT FROM AUTHOR]

Design of steel fibre reinforced concrete with and without additional rebars Design of steel fibre reinforced concrete with and without additional reinforcement is defined in Germany by the approved guideline "Steel Fibre Reinforced Concrete" of the German Committee for Reinforced Concrete (DAfStb). According to the guideline, the crack‐bridging effect of steel fibres is determined on an experimental basis via standardized four‐point bending tests, idealised as residual flexural strength and quantified or classified in terms of performance classes. For concrete design in ultimate and serviceability limit state, stress‐strain curves of the steel fibre reinforced concrete in tension apply which additively add the steel fibres effect to the well‐known resistance equations for reinforced concrete. The paper illustrates how to derive design values of residual tensile strengths on the basis of residual flexural strengths and the associated stress‐strain relations. Based on this, design equations in ultimate and serviceability limit state are described. Overall, a compact overview on the mechanical principles and design approaches of steel fibre reinforced concrete is given. [ABSTRACT FROM AUTHOR]

Separation crack avoidance in water‐impermeable constructions using the example of the orange wanne® system Water‐impermeable concrete constructions require close cooperation between all those involved in the planning and execution. An essential aspect of achieving water impermeability is the limitation or avoidance of separation cracks, in addition to considering the requirements for future use, compliance with the requirements for concrete and construction. In particular, the latter objective and the associated design principle presuppose the definition and consistent implementation of constructive, concrete‐technological and implementation‐related measures. The DAfStb Guideline "Water‐impermeable constructions made of concrete" refers to the possibility of limiting the crack width by combining steel reinforcement and steel‐fibre reinforcement. The paper presents the implementation of the design principle avoidance of separation cracks by means of the orange wanne® system on a construction project completed in 2019. The requirements for steel‐fibre concrete and concrete technology instructions for the use of the building material are explained. Construction processes are described in their interaction. [ABSTRACT FROM AUTHOR]

Database for punching shear resistance of steel fibre reinforced concrete flat slabs without shear reinforcement – Verification of design approaches according to DAfStb guideline and Model Code 2010 The punching shear design of steel fibre‐reinforced flat slabs is currently carried out in Germany based on the DAfStb Guideline "Steel fibre reinforced concrete". The addition of steel fibres to the concrete allows an effective transfer of tensile forces across the crack and limits the progressive crack opening, which proves to be particularly favourable for the punching shear strength. Numerous investigations since the mid‐1970s have confirmed this and have enabled the derivation of empirical and partly mechanically based approaches for the calculation of the steel fibre contribution in the punching shear capacity of steel fibre reinforced flat slabs without punching shear reinforcement. For the evaluation and further development of these approaches, a critically reviewed database of punching shear tests on steel fibre reinforced flat slabs without punching shear reinforcement was created. Considering the practical construction requirements regarding the slab thickness, the degree of longitudinal reinforcement as well as the concrete compressive strength and the post‐cracking tensile strength, about 116 tests could be included in the punching shear database "Steel fibre reinforced concrete". This paper presents the database and discusses its evaluation about the prediction accuracy and the safety level of the design approaches according to the DAfStb guideline "Steel fibre reinforced concrete" as well as according to the Model Code 2010. [ABSTRACT FROM AUTHOR]

LCA comparison at component level The construction industry is one of the major spheres of influence for reducing climate change. In the construction sector, as in other sectors, there is an increasing demand to keep the ecological footprint as small as possible. In order to be able to define this footprint at all, the instrument of life cycle assessment is used, for example, when planning sustainable buildings. This takes into account the environmental impacts of building operation as well as the provision of the building materials used to construct a building. The latter is pursued in this paper. By means of a transparent and quantified presentation of the environmental impact of building materials at the component level, comparisons can be made with other available building systems. The entire life cycle or only parts of it can be used as a basis for subsequent assessment. A distinction is made between the models "cradle to gate", "cradle to grave" and "cradle to cradle". On the basis of a comparison of slab systems, this article shows and explains life cycle assessments for these three models and interprets the differences. [ABSTRACT FROM AUTHOR]

Rebars made of carbon fibres for the use in civil engineering: part 1: fundamental material characteristics Nowadays, the request for non‐metallic reinforcement for buildings, bridges or many other structures is increasing daily. Especially reinforcements made of carbon fibers are highly recommended for civil engineering. Those fibers are resistant against any kind of corrosion. Moreover carbon fibers offer high tensile strengths. But by designing and constructing with carbon reinforcements some crucial facts have to be considered to achieve an optimized structure. In this paper some important aspects by construction with non‐metallic rebars will be presented. The main focus is on rebars made of carbon fibers, because those rebars show a high potential for civil engineering. Therefore the principal material behavior is described. Moreover an outlook for further investigations will be obtained. Especially the tensile and the bond behavior will be pointed out in detail in following papers. [ABSTRACT FROM AUTHOR]

Abstract: Cellulose‐fibre lightweight concrete – a novel building material based on waste paper The present paper sets out a new method for the systematic formulation of lightweight concretes incorporating cellulose fibres. Lightweight concretes of this type are basically produced by mixing a cement paste with cellulose fibres won from waste paper. This is a combination of materials that can be expected to give rise to a whole range of positive interactions. Raising the fibre content, moreover, can additionally induce properties typical of insulating materials. Consideration is given to the suitability for this purpose of a variety of secondary fibrous materials as well as to the process of pulping them in concrete mixers. A viable procedure for characterising the various cellulose‐fibre sources and acquiring input values for the material volume calculation is elucidated. An algorithm for calculating the concrete composition required to achieve specific dry bulk densities in the hardened concrete is likewise presented. Adding fibres to the mix yields significantly altered rheological properties relative to conventional concrete. With regard to placing and compaction technologies, a division into three different basic types is proposed in this respect. A suitable method of consistency testing is introduced. The paper concludes by presenting the spectrum of properties of CFLC in both fresh and hardened states as achieved in the experimental investigations. [ABSTRACT FROM AUTHOR]

Strain measurement in multi‐axial compression tests on concrete using fiber optic sensors The quantification of load‐induced anisotropic damage under various multi‐axial stress conditions requires the measurement of strain inside small specimens. Therefore, quasi‐continuously measuring fiber optic sensors without a protective coating were preferred. This paper explains the challenges of strain measurement in multi‐axial tests and the potential of quasi‐continuous strain measurement with fiber optic sensors. The positioning of the measuring fibers by using a brass profile in the unreinforced test specimens is explained and the influence of this support frame on the concrete properties is described. The available measuring accuracies and special measuring requirements, especially regarding the transverse pressure‐sensitive and non‐alkali‐resistant measuring fibers, are shown. A comparison with the frequently used strain measurement via brush deformation shows that despite all existing challenges the fiber optic sensors allow strain measurement in triaxial tests in a so far not achievable accuracy. [ABSTRACT FROM AUTHOR]

Assessment of strength properties of viaducts made of prestressed concrete – Material investigations on concrete samples from the Lahntal Viaduct near Limburg In 2016 the Lahntal Viaduct was replaced by a new structure. Before the western superstructure was deconstructed, more than 250 cores and other specimens could be taken from the old structure. The present paper deals with the investigations on compressive strength and tensile splitting strength of the concrete. The test results are evaluated statistically and different populations are tested for the taken sample. The goal is to identify a reasonable subdivision of the sample. Furthermore, the design values according to DIN EN 13791 and Eurocode 0 were calculated and compared with calculated expected values. These investigations are intended to provide insights for the assessment of the strength properties of existing viaducts and to develop a safe and economical investigation methodology from them. [ABSTRACT FROM AUTHOR]

On the use of ZFSV in district heating pipeline construction Temporarily flowable self‐compacting backfill materials (ZFSV) are backfill materials made of soils and building materials that only flow into cavities under the influence of gravity and after a defined period of time exhibit the physical properties appropriate to the application. In pipeline construction, ZFSV are used to backfill the trench. Reservations regarding the transferability of existing calculation methods for pipe statics and the reliability of the ability for re‐excavation led to a problem of acceptance of this installation method in district heating pipeline construction that continues until today. As district heating pipes expand during operation after installation due to thermal loads, these pipes always interact with the bedding material. In this paper an overview of the state of the art is given and a simplified calculation approach is proposed, which stands next to much more complex models and therefore offers the possibility to overcome acceptance problems due to its simplicity. [ABSTRACT FROM AUTHOR]

Creep and shrinkage prediction models for concrete This autumn the revision of EN 1992‐1‐1:2004 (Eurocode 2) was finished and the draft of prEN 1992‐1‐1:2020 was released. Hereby the practice of design will be faced by several new and improved concepts and models. This holds also true for the models for creep and shrinkage of structural concrete, which have partially been completely revised. This article presents in two parts (part 1 Shrinkage, part 2 Creep) the new models for the deformation prediction of concrete and indicates also the related background. This paper deals with shrinkage of concrete. The different types of shrinkage and major characteristics are given at a glance. The developments in codes leading to the currently applied DIN EN 1992‐1‐1:2011 are indicated. Focus is put on the analysis of the reliability and accuracy of this model. Considerable weaknesses became evident and led to essential improvements being included in prEN 1992‐1‐1:2020. Many test data confirm the new approach, which is presented here as well. Statistical considerations on the reliability of the new model and a concept how to integrate experimental laboratory data for the improvement of the model are finally presented. [ABSTRACT FROM AUTHOR]

Flexural and bond behaviour of chemically prestressed concrete elements with textile reinforcement Chemical prestressing is a method of introducing stresses into concrete with the use of expansive admixtures instead of mechanical devices. The paper presents an approach to chemical prestressing of thin textile reinforced concrete elements. Measurements of free and restraint expansion are described, as well as experimental investigations regarding flexural and bond behaviour of thin specimens with carbon textile grids. Results of four‐point bending tests on slab members and of bond tests are presented. It was confirmed that the use of expansive concrete influences the behaviour of textile reinforced concrete specimens. The cracking load can be increased with increasing amount of expansive admixture, as well as the deflection at first cracking. Similarly, higher maximal bond stresses are achieved for specimens made of expansive concrete that of control mixture. The results are evaluated and an overview is provided. [ABSTRACT FROM AUTHOR]

Deformation behavior of concretes with high plastic compressibility For special applications, for example compressible layers in tunnel constructions, there are already initial approaches for mortars and concretes, which are characterized by a high plastic compressibility. This paper describes experiments on the compressive behavior of highly porous concretes with low compressive strength (< 5 N/mm2) under transverse strain constraint. Concretes with different compressible additives (expanded glass / EPS) and various water‐cement ratios were considered in the tests. Furthermore, the deformation behavior under both partial‐ and full‐area loading was investigated in order to cover different application‐related boundary conditions. On the basis of the determined stress‐deformation curves as well as investigations on the structure of specimens before and after the compression tests essential findings on the compressive behavior of the concretes could be gained and material‐ and test‐related parameters could be identified. [ABSTRACT FROM AUTHOR]

Conception of a real world 3D printing method for reinforced concrete (AMoRC) 3D printed plain concrete components (without reinforcement) produced through extrusion‐based 3D printing methods are rarely suitable for use in real structures because they fail brittle and have insufficient structural resistance. Therefore, new methods are needed that allow the integration of steel reinforcement into the concrete printing process and thus the additive production of the composite material reinforced concrete. The conceptual design of a practice‐oriented 3D printing process for reinforced concrete, the so‐called Additive Manufacturing of Reinforced Concrete (AMoRC), is therefore the subject of the present paper. In the AMoRC process, segmented steel reinforcing bars are joined to form a three‐dimensional reinforcement mesh using an arc stud welding process and simultaneously overprinted with a concrete extrusion process. This article describes the development of the process and preliminary investigations on its feasibility. [ABSTRACT FROM AUTHOR]