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Image‐based quality control – part 2: granulometric properties The changes in concrete technology necessary to achieve the climate protection targets will lead to a significant change in the concrete mixtures typically used. The raw materials used are becoming more diverse and complex. The use of recycled raw materials will also significantly increase the fluctuations in the properties of the raw materials. An Accurate and time‐efficient determination of the granulometric properties of the aggregate is of crucial importance, especially for "eco‐concretes", in order to ensure consistent quality characteristics. As a natural raw material, the aggregate is subject to certain fluctuations to which such optimized concrete compositions can react relatively sensitively. In the future, it will be necessary to determine possible quality deviations of the fresh concrete resulting from fluctuations in the raw materials in a time‐efficient manner in order to be able to make appropriate adjustments in the production process as quickly as possible. This paper presents an image‐based quality control for the digital evaluation of granulometric properties of the aggregate as a part oft he flow table test. Accordingly, the range of properties of the image‐based method already presented in Part 1 of this paper is extended to a fully comprehensive digital quality control. This paper presents the image‐based determination of the granulometric properties of the aggregate as a part oft he flow table test. The determination is based on the image‐based quality control described in part 1 of this paper. [ABSTRACT FROM AUTHOR]

Free‐form reinforced concrete, prestressed concrete and composite components: Calculation of cross‐section values A resource‐efficient use of concrete as a construction material can be achieved by adapting the individual shape of a component under consideration to the stresses that occur and by arranging composite construction materials (e. g. reinforcing steel, prestressing steel or structural steel) in suitable areas of the component. Due to the advancing digitalisation in the construction industry, for example in the context of Building Information Modeling, computer‐aided 3D modelling methods are increasingly being used in the planning of structures. These allow engineers to design components in free form. In reinforced concrete, prestressed concrete and composite construction, the design of such components is currently still associated with great effort. In the context of the development of a practical method for the calculation of free‐form concrete components, this paper presents a CAD‐integrated method for the calculation of cross‐section values. Cross‐section values are required as an essential calculation basis when real, three‐dimensional structural components are treated using simplified calculation theories, such as the beam theory. In this paper, the mathematical and numerical fundamentals of a method for the calculation of cross‐section values of free‐form concrete, reinforced concrete, prestressed concrete and compound components are presented. The calculation method is based on flat geometric regions described by Non‐uniform rational B‐Spline tensor product surfaces, which can be extracted from solid models, for example. [ABSTRACT FROM AUTHOR]

Debris flow actions on concrete bridge superstructures Bridge structures in alpine areas are subject to various hazards. These also include debris flows. Debris flows events demonstrably also lead to the destruction of bridges. In order to design bridges for such hazards, information on the impact force of debris flow is necessary. For debris‐flow impacts against piers, extensive miniaturized as well as real size tests are available. So far, no such tests are known for bridge superstructures. In this paper miniaturized debris‐flow impact tests on concrete bridge cross‐sections are presented. Based on the test results, recommendations for the design of concrete bridges in exposed locations are proposed. [ABSTRACT FROM AUTHOR]

Traffic Monitoring on a Highway Bridge – Data collection on local traffic characteristics as a basis for site‐specific traffic load models Developing site‐specific traffic load models for individual bridge structures based on local traffic data represents a potentially effective tool for existing road bridges with remaining calculative deficits when assessed according to current codes (guideline for assessment of existing structures, "Nachrechnungsrichtlinie"). A robust data basis to represent the local traffic characteristics is essential for this purpose. This paper presents investigations carried out during a long‐term monitoring campaign to comprehensively describe the traffic load on a selected bridge structure along Federal Highway A 92 over a period of one year. For the campaign, a measurement unit consisting of a laser scanner and a webcam, and structural monitoring with the application of bridge weigh‐in‐motion (BWIM), are used. Suitable strategies and concepts for collecting, processing, and evaluating all available measurement data enable a comprehensive collection of all parameters relevant for traffic load modeling and thus provide a data basis for detailed and realistic modeling of local traffic characteristics. Initial evaluations of the monitoring data for selected parameters and the comparison with otherwise typical assumptions from the literature in case of missing parameter information show partly significant differences to the extreme traffic characteristics underlying the load models in codes. [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]

New perspectives on the load bearing behavior of RC‐structures without shear reinforcement The shear behavior of structural members has been an integral part of research in concrete structures for more than 100 years. In recent years, various mechanical shear models have been developed that deliver important insights into the background of shear behavior and are able to provide physical explanations for shear failure in RC members without shear reinforcement. However, these models require further experimental validation. New measurement techniques (e.g. digital image correlation or fiber‐optic strain measurement) play a decisive role in this context, allowing deeper insights into the load‐bearing behavior of reinforced concrete components subjected to shear loads. Based on experimental investigations with modern measurement techniques, software has been developed that performs an automated crack detection based on the finite element method with detailed evaluation of the kinematics and the stresses transferred in the crack. In this paper an overview of different evaluation methods of experimental investigations with modern measurement techniques is given, on the basis of which an in‐depth evaluation of new model approaches can be carried out. [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]

Fire testing of loaded carbon tension members The application of carbon tension members is motivated by extraordinary well fatigue behaviour and high tensile strength of the material. Compared to steel, cross sections can be reduced. Steel tension members used for network arch bridges shall be replaced in perspective. The loadbearing behaviour of carbon tension members in case of fire is still unknown. Therefore, fire tests were performed to investigate the failure mechanisms. Based on the derived test data the comparability to conventional steel tension members was estimated. This paper describes real scale fire testing of mechanically loaded carbon tension members, carried out as a part of the joint research project NeZuCa. The test setup consisted of four carbon tension members with circular cross sections and diameters of 36 mm and 51 mm. In absence of a prescriptive fire scenario for the application case intended in the research project and to ensure comparability, a fire exposure according to standard temperature/time curve was chosen. The elongation of the tension members as well as the temperatures of the specimen and the furnace were recorded. [ABSTRACT FROM AUTHOR]

Influence of the arrangement of the punching shear and composite reinforcement made of L steel plates on the load‐bearing capacity The CLIXS punching shear and composite reinforcement system consists of L steel plates with one or two connected stirrups made of reinforcing steel. It is possible to increase the load‐bearing capacity by more than twice the load‐bearing capacity without punching shear reinforcement. The experimental investigations described in the paper were carried out on square slab cut‐outs with a length of 2.8 m and a thickness of 18 and 25 cm. The load‐bearing capacity as a function of the number of uniform arranged L steel plates was determined based on 17 experiments. For this purpose, test specimen with 6 L steel plates up to 36 L steel plates in the first three perimeters were investigated. In addition, 10 test specimen with different sized areas without L steel plates were tested. The areas without L steel plates were between 25 % and 75 % of the area within the first three perimeters. The use of stirrups with a diameter of 8 mm instead of 6 mm was investigated using two test specimens. [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]

Shape optimisation of eccentrically loaded columns – theory and experimental verification. In shape optimisation, the external shape of the structural component is adapted to the predominant force flow. In this way, large load increases can be achieved with the same material use, or high material savings can be achieved with the same load‐bearing capacity. In this paper, a shape optimisation for eccentrically loaded columns is presented, where the bending stress results from a frame effect of the load‐bearing system. This is the case, for example, in edge columns of typical reinforced concrete skeleton structures, as they are usually used in residential and commercial buildings. The shape optimisation method presented in the article can be applied to columns with an arbitrary ratio of a moment‐normal force loading, provided that a material failure occurs. Results for shape optimisation in the case of a stability failure have already been published separately for centrically pressed columns. The optimisation itself is carried out iteratively on a column segmented over the height under the criterion of achieving a uniform stress state in the component. With the help of an experimental check on 3.3 m high columns, the selected calculation and optimisation method could be verified. In addition to the failure loads, the concrete strains and the deformation behaviour were also analysed and evaluated at selected points of the specimen. [ABSTRACT FROM AUTHOR]

Universal high‐performance columns made of high‐strength steels without welding In recent years, steel‐concrete composite columns made of normal‐strength steels are seldom used owing to the economic and technological advantages of precast reinforced concrete columns. Though, the use of high‐strength structural steels bears high potential for the efficient production of composite columns with excellent structural performance that are economically competitive to precast concrete columns, there are currently major obstacles to use of the ultra‐high‐strength steels (UHSS) in Germany. Hollow section composite columns with embedded high strength steel core without welded connections provide an opportunity to regain lost market share. A research project, funded by the AiF (Arbeitsgemeinschaft industrieller Forschungsvereinigungen), is intended to explore the potential of UHSS composite columns by experimental and theoretical investigations. The present paper demonstrates the concept of such composite columns with UHSS and gives first exciting insights into the research results. In addition to column tests under ambient and fire conditions, small scale tests are necessary to investigate various influencing factors and to create the basis for new and easy to use design and construction principles that allow efficient application. [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]

Experimental investigations on the durability of intumescent coatings Intumescent coatings are used in structural fire protection to improve the fire resistance of steel structures. Beside structural fire resistance also aesthetic demands can be fulfilled. The profile‐following application and the low dry film thickness of the products make it possible to maintain the filigree appearance of steel structures. In addition to the thermal protection effect, the durability of the coating must also be ensured. The assessment methods available at European level by EAD 350402‐00‐1106 aim to a service life of ten years. Test methods for a longer period are not described. This paper presents experimental investigations on the influence of weathering on the expansion behaviour, the thermal performance and the reactions taking place during foaming in case of fire. The tests were carried out on a water‐based and an epoxy resin‐based intumescent coating. The research results were obtained in the IGF research project 20470 N. [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]

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]

Development and testing of an urban green façade system for humans, flora and fauna This paper presents the climate‐regulating and biodiversity‐supporting potential and synergies of an innovative green façade system for humans, flora and fauna. The developed system opens up vertical habitats, especially for native plants, birds and insects, and creates climatic compensation functions for buildings and people. An interdisciplinary research methodology brings together the fields of (urban) building physics and ecology. The test results from the summer months of 2022 prove the contribution of the green surface to reducing heat input into the façade as well as into the surrounding area in comparison to a reference concrete wall. At the same time, the biodiversity (e.g. different insects) was significantly increased on the vertical by creating heterogeneous habitats and plant populations. Thus, the developed green system represents an innovative element for coping with complex requirements due to climate change, urbanization and species loss in the built environment and shows solutions for inclusive urban surfaces for humans, flora and fauna. [ABSTRACT FROM AUTHOR]

Mechanical activation of clay Known advantages of clay in building physics are moisture sorption and regulation, reduction of sound and heat storage capacity. Compared to other materials, clay has low mechanical properties. The paper focuses on mechanical activation of clay and relates to challenges in the production of clay‐based‐construction panels. It examines compressive and bending strength due to the process of milling, using a vibratory disc mill. The raw clay was sieved and for testing the fractions < 250 μm were milled. This milled clay was mixed in various compositions. Samples consisting of a mixture of milled fractions < 0,25 mm and non‐milled fractions 0,25 to 2 mm, a max. increase in compressive strength of 74 % was observed at a milling time of 60 minutes and for 20 wt.% water addition. Also, preliminary rheological tests (SAOS), which were carried out to follow the cohesion development over time of the clay pastes at different milling time, showed a max. of reactivity for samples which were milled 60 minutes. [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]

Explainable Domain‐Specific Artificial Intelligence for Bridge Engineering and Design The use of artificial intelligence (AI) is currently being discussed and evaluated across the board in research and practice in all industries. This paper first provides the necessary background knowledge on general AI and then elaborates the necessity of developing domain‐specific AI as well as explainable AI (XAI) for the calculation and design practice in civil engineering. The role of the civil engineering domain at the interface with AI in terms of data and modeling and design philosophy is discussed. The three examples of (i) computation of Kirchhoff slabs with physics‐informed neural networks, (ii) calibration of prior models for parametric bridge design from databases, and (iii) AI‐assisted conceptual design of bridges illustrate the application of domain‐specific machine and deep learning and XAI with special focus on concrete and bridge design. In particular, physics‐informed AI (piKI) represents an alternative to established numerical methods with special consideration of available simulation and experimental data and becomes explainable and comprehensible via the use of XAI. This paves the way for the use of piKI models in civil engineering as digital twins of a structure over its life cycles. [ABSTRACT FROM AUTHOR]

Automated post weld treatment for offshore wind turbines A more economical and resource‐saving construction of offshore wind energy converters (OWEC) is necessary in order to implement climate policy objectives. The increase of the fatigue resistance by using high‐strength steels and by applying post‐weld treatment methods offers great potential for reducing the use of materials and costs for monopiles. Specifically, in the automated OWEC manufacturing chain, automated processes such as deep rolling are a suitable option. Deep rolling is an established process in mechanical engineering for increasing the wear and fatigue resistance of metallic components. This paper presents results of deep rolling as a new post treatment method to increase the fatigue strength of welds. The surface and subsurface zone properties of submerged arc welded butt joints made of a structural steel grade S355MLO before and after deep rolling are shown. In order to quantify the influence of deep rolling on the weld geometry, measurements of a laser line sensor are presented. Finally, the results of fatigue tests are discussed, which show the great potential of the deep rolling process as a post weld treatment method. [ABSTRACT FROM AUTHOR]

Abstract: Dedicated to Prof. Dr.‐Ing. habil. Joachim Lindner on the occasion of his 80th birthday The aesthetical and structural advantages of tubular structural elements sustained the increase in their use in Brazil in last decades. The joints between tubular members remain a critical issue, with many studies indicating that further research is still needed, particularly for some geometries. In the past, some experiments on the influence of the chord stresses over the brace load capacity were published, but a definitive answer to this design issues was not reached. The first part of this paper presents an experimental evaluation centred on the effect of tension and compression chord stresses over RHS chord to SHS braces T‐joints. The results showed that compressive chord stresses could considerably reduce the joint resistance. In contrast, when tension chord stresses are applied the joint resistance increases but this is still not considered in the design codes. Still considering the tubular joints structural behaviour, there are cases where the ultimate resistance of the tubular joints may be enhanced by using flange plates as reinforcement, instead of replacing the chord or braces with stronger sections. Bearing this scenario in mind, the second part of this paper presents some experimental results of SHS T‐joints reinforced with flange plates to achieve a more economical design. The results showed that the joint resistance could be increased about 88 % using the reinforced plate with the same thickness of the chord profile. [ABSTRACT FROM AUTHOR]

Abstract: Practical Application of an innovative concrete shell construction method: Construction of the deer pass AM2 by use of PFHC Concrete shells are aesthetic and economic supporting structures, if properly designed. They can absorb high loads and can span large areas with little material. Unfortunately, high costs for the complicated formwork avoid a wider use in practice. A new shell construction method called Pneumatic Forming of Hardened concrete (PFHC) was developed at the Institute for Structural Engineering at TU Wien. Within a tight development process numerous material tests, tensile tests, bending tests and two large scale experiments were performed. Now, the Austrian railways (ÖBB) used the construction method to build the deer pass AM2 as concrete shell bridge over the two‐rail track Koralmbahn in Carinthia in Austria. At first a test shell, which now serves as event canopy, was built with the plan dimensions 26.5 × 19.1 m and a height of 4.2 m. Directly after that the main supporting structure, the shell bridge, was built (plan dimensions 36.2 × 38.7 m, height 8.1 m). The first part of the paper which was published in the previous issue summarizes the development process of the new building method. Furthermore, the paper describes the building process of the two shell structures and chosen experiments for the construction process. Finally, the monitoring concept is explained. [ABSTRACT FROM AUTHOR]

About the design concept for compressive fatigue loading of concrete - Structure of the fatigue design concept For building structures exposed to fatigue loading, especially for those made from high-strength concrete, the fatigue design is decisive for the structural design. Coincident, nowadays new experimental results exist which demonstrate that further developments of the fatigue design concept are expedient and necessary. The safety concept for fatigue design was assigned from the static design concept. From this approach, particularities and challenges arise for the further development of the design concept. In this paper the structure of fatigue design is described. Furthermore, the enclosed parameters are explained and their relevance in the context of safety considerations is discussed. Based on this, outstanding issues are identified for the further development of the design concept. In part 2 of this paper the safety concept of the fatigue verification is discussed and the potential of further developments is pointed out. [ABSTRACT FROM AUTHOR]

'Restless and unsettled' - Gustav Adolf Wayss, a pioneer of reinforced concrete (1851-1917) Gustav Adolf Wayss, editor of the well-known 'Monier Brochure' published in 1887 and founder of some of Germany's most renowned companies for reinforced concrete construction, has a very controversial reputation. Some contemporaries and researchers describe him as a successful engineer who laid the foundations for establishing reinforced concrete. Others characterise him as a poorly trained engineer who, due to his restless and unsettled character, was not successful in his business in the long run. So far, papers on Wayss mainly focus on the time when the Monier Brochure was published. On the occasion of the hundredth anniversary of his death, the present paper puts Wayss' entire life and work into focus in order to provide a new perspective. This case study further offers possibilities to examine how construction history is written. [ABSTRACT FROM AUTHOR]

Abstract: In‐situ tests at the bridge Hammelburg regarding the shear capacity of existing pre‐stressed bridges Part 2: Measuring concept, results of the in‐situ tests, comparison with different theoretical approaches Due to the relatively high average age of the existing bridges, a dramatic increase in traffic volume and axle loads and modified design standards, a realistic prediction of the shear capacity of existing pre‐stressed concrete bridges with little shear reinforcement has become an important topic in research. In 2017 the Chair of Concrete and Masonry Structures of the Technical University of Munich (TUM), supported by the Federal Ministry of Transport and Digital Infrastructure, was able to conduct unique field tests at the 1955 built Saalebrücke Hammelburg. According to systematic strength evaluations many concrete bridges, especially those which have been built prior to 1966, show severe (theoretical) deficits regarding the longitudinal shear capacity. Often the results of the strength evaluation cannot be verified at the real bridges though. The primary objective of the field test was therefore to determine the shear capacity of existing pre‐stressed bridges in order to contribute in closing the gap between calculations and experience for older concrete bridges. In the first part of this article the general assessment of the bridge and the original design concept as well as the conceptual approach, the execution of the in‐situ tests and the used measuring equipment were described. In the present paper the measuring concept and the results of the conducted tests are presented. Furthermore, the results of the in‐situ tests are discussed, and the measured maximum loads are compared to the results of different theoretical approaches and engineering models, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Analysis of the intrusion of de‐icing salt into concrete pavements by a novel test method In recent years the German motorway network has seen an increase in the occurrence of damage in concrete pavements. This has been caused by the use of alkali‐sensitive aggregates. Given the exposure of the concrete pavement to water and the alkaline environment caused by the use of Portland cement during concrete mixing, this environment can lead to an alkali‐silica reaction (ASR) process. This ASR‐damage process in concrete pavements is further exacerbated by the external application of de‐icing salt in winter. Against this background, the evaluation of the intrusion of de‐icing salt becomes of great importance. Until now, the analysis of the intrusion of de‐icing salt was carried out in a wet‐chemistry process on finely ground segments of drilling cores. The disadvantages of this method are the relatively arduous testing process and the limited depth resolution. The alternative application of LIBS (laser‐induced breakdown spectroscopy) offers new possibilities in this context. In this paper, the procedure for the LIBS analysis of sodium and chloride distribution on vertical cut surfaces of drilling cores taken from representative ASR‐damaged concrete pavements is presented. Because the intrusion of de‐icing salt takes place primarily in the cement matrix, the distorting effect of the sodium content in the aggregates was eliminated by an exclusion criteria (namely, the calcium content). The comparable chloride mappings by micro X‐ray fluorescence spectroscopy and wet‐chemical analysis confirm the quality of the LIBS measurements. However, additional investigations are necessary for the quantitative analysis of sodium content in concrete pavements. [ABSTRACT FROM AUTHOR]

Abstract: In‐situ tests at the bridge Hammelburg regarding the shear capacity of existing pre‐stressed bridges – Part 1: General assessment, original shear design, conceptual approach and execution of the in‐situ tests Due to the relatively high average age of the existing bridges, a dramatic increase in traffic volume and axle loads and modified design standards, a realistic prediction of the shear capacity of existing pre‐stressed concrete bridges with little shear reinforcement has become an important topic in research. In 2017 the Chair of Concrete and Masonry Structures of Technische Universität München (TUM), supported by the Federal Ministry of Transport and Digital Infrastructure, was able to conduct unique field tests at the 1955 built Saalebrücke Hammelburg. According to systematic re‐analyses many concrete bridges, especially those which have been built prior to 1966, show severe (theoretical) deficits regarding the longitudinal shear capacity. Often the results of the strength evaluation cannot be verified at the real bridges though. The primary objective of the field test was therefore to determine the shear capacity of existing pre‐stressed bridges in order to contribute in closing the gap between calculations and experience for older concrete bridges. In the present paper the general assessment of the bridge and the original design concept as well as the conceptual approach and execution of the in‐situ tests are presented. In the following part 2 of this article the results of the conducted full‐scale tests will be discussed. [ABSTRACT FROM AUTHOR]

Abstract: Reinforcement made of carbon fiber reinforced concrete In the research project C3 – Carbon Concrete Composite new reinforcement systems made of carbon for concrete construction are developed. In that case, mesh‐like and bar‐shaped reinforcements are examined. Until now, these carbon reinforcements predominantly contain a plastic matrix that combines thousands of carbon filaments into one cross section. Scientists of the HTW Dresden and the TU Dresden are currently pursuing an approach to replace this plastic matrix with a mineral matrix to further improve the properties of the carbon reinforcement. In this paper, the basic principle of this new type of reinforcement for concrete construction as well as associated tests are presented. This should give an impulse for further research in this field. [ABSTRACT FROM AUTHOR]

Abstract: Contribution concerning load bearing behaviour of CFRP confined RC columns with circular cross section Beside CFRP (Carbon Fiber Reinforced Polymer) strips, which are successfully utilized as an additional glued reinforcement in tension zones of existing reinforced concrete (RC) members, CFRP sheets gain more and more attention in terms of strengthening and retrofitting. Those sheets are capable to increase the bearing capacity of RC slaps and beams significantly. Furthermore, CFRP sheets can improve the capacity of RC columns, too. In doing so, the connection of concrete surface and CFRP sheet is enabled by an epoxy resin (CFRP confinement). Thereby, concrete's lateral expansion is efficiently restricted in cases of imposed axial compressive deformation; therefore, the elastic CFRP resisting response generates an ever increasing lateral compressive stress state on concrete, leading to structural upgrade of the member core to provide a remarkable higher concrete strength and sufficient deformability. Regarding CFRP confinement design in Germany, this paper presents a brief overview concerning the state‐of‐the‐art, and it introduces a design procedure utilized in German DAfStb‐Guideline „Strengthening of concrete structures with adhesive bonded reinforcement“. Furthermore, some recent research efforts and findings to improve the current model will be offered, too. [ABSTRACT FROM AUTHOR]

Abstract: Modern railway bridges as thick‐plate trough bridges – Optimization of fatigue design and life‐cycle analyses. Innovative improved design solutions of bridge constructions increasingly aim at maintenance reduced structures where the utilization and surrounding traffic routes are affected only in minor extent by rehabilitation and maintenance works. As part of the FOSTA‐AiF‐research project „Holistic Assessment of steel‐ and composite railway bridges according to criteria of sustainability” (P978) specific investigations were carried out in order to optimize different railway bridge types by improving single structural details and construction variants types. To assess the benefits of these optimized constructions within the life‐cycle of the bridge, the conventional and improved constructions were compared with each other by applying sustainability analyses. This paper deals with the evaluation of the trough bridges with thick track plates which was especially developed for rail traffic constructions and which is also known as thick‐plate trough bridges. It focusses on questions related to the fatigue design, uses large scale tests for verifications and provides recommendations for the construction and design. [ABSTRACT FROM AUTHOR]

Abstract: Applying the theory of structural state of stress, this paper investigates the behaviour characteristics of concrete‐filled stainless steel tubular (CFSST) short columns during their experimental working process. First, the sum of the generalized strain energy density (GSED) values (Eij) of the short column at every load value (Fj) is normalized as Ej,norm to describe the structural state of stress. Then, the state of stress jump is identified by applying the Mann‐Kendall (M‐K) criterion to the Ej,norm‐Fj curve creatively, following the rule of quantitative change to qualitative change. The investigation reveals the general state of stress mutation characteristics of short columns at specific individual loads, leading to an update of the failure load. Furthermore, it is verified that the simulative working behaviour of short columns can also reflect the state of stress characteristics revealed through the investigation into the experimental data. Hence, we formulate the relationship between the failure loads of CFSST short columns using the simulative data, and then validate it through both experimental and simulative data. In total, this study explores a new way to reveal some unseen working characteristics of structures; hopefully, it will initiate similar research on various structures, and the results achieved will lead to more rational design codes. [ABSTRACT FROM AUTHOR]

Abstract: Calculation of the deflection of reinforced concrete members – general procedures for slabs and beams This paper introduces the fundamental procedures to calculate the deflection in the cracked state taking into account creep and shrinkage. A range of different methods with various degrees of accuracy is presented for beams and one‐way slabs, based on the guidelines of EC2. For simple systems these methods can also be used for hand calculations, permitting a high degree of control over the procedure. Subsequently, the usually rather complex calculation of deflections caused by the shrinkage of the concrete is considered in more detail. For a selection of systems, diagrams containing coefficients for a more efficient estimation of shrinkage deflections can be derived. Furthermore, the cracked state deflection of concrete slabs is addressed more closely. It can be calculated with the help of suitable finite element programs or using simplified manual procedures. The basic principles can be transferred from the previously considered beam structures. However, other influence factors have to be addressed, such as the procedure to reduce the flexural stiffness and the redistribution of the internal forces caused by cracking. [ABSTRACT FROM AUTHOR]

Abstract: Fatigue strength of RC beams without transverse reinforcement under cyclic loads The shear design of RC members without transverse reinforcement (e.g. slabs, bridge decks, footings of wind energy plants) for fatigue loads is based on empirical approaches, which had been rarely validated by experiments. This paper presents theoretical, experimental and numerical studies, which aim to give a better understanding of the load transfer in RC members without web reinforcement under static as well as cyclic loads. Furthermore, the approach of Eurocode 2 will be examined. [ABSTRACT FROM AUTHOR]

Abstract: Rib shear connectors with concrete break out failure subjected to tension or compressive loads – Part 1: Finite Element Analysis The shear connectors in steel‐concrete composite structures have to provide sufficient resistance against stresses acting orthogonally to the shear connection leading either to uplift of the concrete slab or mutual penetration of the steel girder and the concrete. While the anchoring behavior of headed studs has been extensively researched in the past, investigations in the load bearing behavior of composite dowels subjected to tension and compressive loads are missing, to date. Therefore, the present paper describes finite element investigations in the load bearing behavior of composite dowels exposed to loads acting orthogonally to the shear connection. The FE‐model, validated against tests from literature, is used to investigate the transfer of stresses between steel dowel and concrete and to clarify the influence of different parameters, like the effect of transversal reinforcement in the concrete and the size effect of the anchorage depth. In the second part, the FE‐results are used to derive engineering models and design approaches for composite dowels subjected to tension or compression. [ABSTRACT FROM AUTHOR]

Abstract: Introduction of the Direct Strength Method into the design of cold formed steel members according to EN 1993‐1‐3. Cold formed steel members have a varied area of applications in steel lightweight constructions but are subject to local and global instabilities due to compressive and bending stress. The design method of the European Standard EN 1993‐1‐3 is based on the Method of Effective Widths covering local and distortional buckling. Unfortunately, an EN 1993‐1‐3 design is time‐consuming and prone to errors, furthermore the results are often conservative. This paper is going to introduce a new, practical design method for cold‐formed steel sections that combines the established European regulations of global instabilities with the Direct Strength Method (DSM) described in the North American standard AISI Standard 100 regarding local stability analysis. Based on comparative studies of mono‐symmetric cross‐sections it is possible to demonstrate that this new method offers a great potential of improving the design of cold‐formed sections, additionally improves the economic efficiency of lightweight steel sections. More theoretical and experimental investigations are needed, deeper leading questions are to answer, until this method is able to supplement the European standard. [ABSTRACT FROM AUTHOR]

Abstract: Trough girders are widely accepted in engineering on account of lowing construction depth and protection against traffic noise pollution, but most of them are used for simple‐supported girder bridges with a span of generally less than 30 m. On the railway line of Nanjing–Qidong in China a new railway bridge will be built which has a span of over 64 m but a construction depth of less than 2.4 m on which Shanghai–Nantong railway line is also passed, so the type of concrete‐filled steel tube tied‐arch bridge with trough girder was chosen. For such a new structure hardly used in engineering, there are no research results yet available about mechanical properties of the structure. This paper therefore makes for the bridge an experimental model of 1:4 geometric scale in order to test mechanical properties under operation load, cracking load, and ultimate load such as cracking diagram, load‐carrying capacity, stress distribution, and failure mechanism. According to the experimental results, when the model is subjected to longitudinal bending moment, the failure mode is similar to that of pure bending of a girder, and when the model is subjected to transverse bending moment failure mode behaves like the flexural failure mode of the traditional reinforced concrete structure. A non‐linear element analysis is also made on the model with the results in good agreement with that of the experiment. The same modeling method is applied to the finite element analysis of the real bridge, considering various load in design. In the analysis, it is finally verified that this new type of bridge meets specification requirements in strength, rigidity, and resistance to cracking. [ABSTRACT FROM AUTHOR]

Abstract: Load‐bearing capacity of unreinforced concrete compression members under biaxially eccentric loading Compression members, such as columns or walls, have to carry vertical loads primarily. Due to the rotation of the adjacent components, they are also subjected to bending moments. If the compression member is, in addition to the bending moment about the weak axis, also loaded by horizontal bracing forces in direction of the strong axis, bending moments about both axes (biaxial bending) occur. This paper deals with the load‐bearing capacity of slender, unreinforced and biaxially eccentrically loaded compression members made of concrete. Existing theoretical methods for determining the load‐bearing capacity of centrically and uniaxially eccentrically loaded compression members are shown as well as the corresponding normative regulations. On this basis, two practice‐oriented proposals for determining the load‐bearing capacity of biaxially eccentrically loaded unreinforced concrete compression members are presented. The proposals can easily be adopted into the standard and thus, the existing restricting limits of application can be neglected. [ABSTRACT FROM AUTHOR]

Abstract: Failure of a steel pallet rack in Athens. Pallet racking systems have peculiar characteristics which differ from usual steel structures that make them sensitive to stability failure modes. In the present paper a rack failure is presented where the rack has failed due to lateral torsional and distortional buckling of its most stressed uprights. The structural behavior was studied by a combination of experimental and numerical/analytical methods. The investigations included test loading, bending tests on pallet beams, compression tests on stub column and bending tests on beam end connectors. Subsequently, a global geometrical non‐linear analysis is performed on the 3‐D system. Its results indicate by comparison with the pictures of the actual structure that the collapse mode is correctly detected. Conclusions are drawn that recommend the performance of static and dynamic analyses on an obligatory basis. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on the effect of structural system and load configuration on the shear behavior of flexural reinforced concrete (RC) members without shear reinforcement. A total of ten rectangular beams with three structural systems and two load configurations were tested. With the chosen test set-up, almost all M/V-combinations commonly encountered in practice can be investigated. The test results indicate significant differences of the shear capacity of members with different M/V-combinations. The shear capacity of the simply supported beam under a uniform load is higher than that of similar beams under a concentrated load. Moreover, the shear capacity of the cantilever and continuous beams under uniform load is significantly higher than that of simply supported beams. Generally, it can be concluded that the co-existing flexural action has a positive influence on the shear resistance of a RC member without shear reinforcement. Furthermore, the flexural crack pattern plays an important role in the shear resistance of slender RC members. [ABSTRACT FROM AUTHOR]