Experimental investigations on the fatigue behaviour of steel standers for noise barriers along the railway line.
Execution of a new test program regarding the determination of
mechanical and physical properties of CLT and the basis material in accordance to the EAD 130005-00-0304 in order to extend for Hinoki wood species with varying strength classes.
A quarter of all heat flows between the interior and exterior of a building pass through the exterior wall. This illustrates the importance of the exterior wall on the energy demand of a building. Driven by legal regulations on "energy saving and thermal insulation", external thermal insulation composite systems have become established. Although these fulfil the required thermal insulation properties, they cause air temperatures in neighbourhoods to rise in summer, prevent the extraction of solar thermal energy during the heating season and have to be disposed of as hazardous materials at the end of their relatively short service life. The monolithic, minerally plastered brick wall, on the other hand, can meet both the sustainability requirements and the high thermal requirements of urban residential and office buildings as long as the architecture, the masonry and the brick are optimised for this purpose. The thermally optimised, highly porous bricks currently on the market are weak. They cannot be used to realise the architecture of choice, namely multi-storey housing. The project presented here does not work on improving the fired clay properties (microstructure), but pursues a macrostructural approach. The load-bearing capacity of the brick is to be increased by reducing the proportion of holes without worsening the thermal insulation properties. This seemingly paradoxical goal has already been theoretically achieved and was patented under the name TRALAM. A case study of an 8-storey residential building showed that the load-bearing capacity requirements of a 50 cm TRALAM masonry wall are met for a building height of 22 m, the heating requirement according to the U-value method corresponds to that of an ETIC system and an additional solar energy gain of 10% is achieved via the non-insulated opaque outer surface. It is obvious that an increase of the load-bearing capacity without changing the fired clay strength, more clay has to be fired and consumed. Thus, all the associated characteristic values of the ecological footprint become worse but only those of the production’s footprint. In return, the high-performance masonry requires only one third of the building ground and one third of the roof area to create the same living space, no insulation material is used in 8-storey buildings, the service life is significantly extended and it brings solar energy gains in winter and a reduction in summer overheating. In order to be able to transfer these promising results to reality, comprehensive experimental verification is necessary. The TU-Graz plans to carry out such a project in cooperation with the Austrian brick industry. One of the goals of this R&D project is to carry out a 1-year field test in one of the test houses at the TU-Graz. This test is for determining the actual total energy balance by measurement. However, the production of the necessary bricks has not yet been tested and is thus a high project risk. This should be minimised by starting the “Sondierungsprojekt” presented here as a preliminary step, focusing only on the feasibility of the production and the final optimisation of the brick design and the masonry bond. It is expected that a reduction of the air gap thickness from 8 to 4mm can be realised in terms of production technology. Laboratory tests and numerical physical simulations shall be carried out for determining the mechanical and building physics characteristics to make sure that the follow-up project can be developed in detail. Therefore, approximately 200 prototype quarter bricks shall be produced.
3D extrusion processes with cement-based mortar materials are the starting point for the present application. This technology currently offers the possibility of producing unreinforced components very precisely and automatically at high speeds with low material input. This is the first time in the history of concrete and reinforced concrete construction that the construction of a costly formwork, which is essential, is no longer necessary. Due to this characteristic of a formwork printer, the aim is to combine the technology with the standard processes used in building construction in order to make greater use of the potential for reducing concrete cubature and thereby lower CO2 equivalents for load-bearing structures in building construction. A major limitation here is the lack of standardised requirements for the design of unreinforced and reinforced printed concrete materials and the components manufactured using them. This means that the technology is far from being integrated into standard BIM-compatible planning and design processes. The application of 3D printed components as voids in the construction process leads to increased geometric complexity, which in turn increases the demands on the construction site processes. For example, the installation and placement of the 3D printed concrete components and the steel reinforcement for the cast-in-place concrete.
The aim of the project is (i) to establish a basis for numerical simulations of unreinforced and reinforced 3D printed concrete components by means of systematic development of test set-ups and test series. A further objective (ii) is the development of mass-relevant, predominantly flexurally stressed elements and therefore reinforced applications for building construction. Here, the focus is on ultralight façade panels with reinforcement integrated into the printing process and on panel- and slab-like structural elements such as ribbed ceilings that use lost formwork and 3D printed void bodies for mass reduction. Here, the focus is on issues of complementary steel reinforcement and construction logistics.
After completion of the project, (i) data and methods for the characterisation of 3D printed concrete components will be available, which will enable numerical simulation in the design and planning phase and can also provide the basis for future production monitoring. The project clarifies and evaluates (ii) on the basis of selected application examples the potentials of 3D printed concrete components for the reduction of concrete cubature and the associated CO2 equivalents in building construction. (iii) Construction processes and construction logistics (placement of 3D printed concrete components and steel reinforcement for in-situ concrete) are developed, tested and evaluated for BIM-compatible processes.
In the context of the repair and retrofitting of the 364 m long Göltzschtal bridge, a directly driven UHFB layer is to be applied for the first time in Germany. On the one hand, this will eliminate the need for conventional sealing of the existing structure, and on the other hand, the structure will be strengthened to withstand higher loads. In this context, the tasks of the Institute of Structural Concrete include the scientific consulting and supervision of the project, the detailed planning, the measurement as well as the support during the implementation of the project.
This project is an experimental study on the crakcing behaviour of concrete (with and without reinforcement) which is loaded by a concentrated ancorage force. The study covers variation in the amplitude of the ancorage force as well as in the size of the ancor head.
Tests to determine the mechanical and physical properties of CLT according to EAD 130005-00-0304 and the test program “Solid wood slab elements” (OIB-2015-015/20-TPR) respectively.
The project is part of a Comet-project, with the vision of a fully digitalized, highly performed and extremely resilient Railway system. In this project method development for quantifying the overall structural time-dependent behaviour in respect to its long-term serviceability will be investigated. This requires hybrid models for large-scale simulations based on historic and current load data of a particular assed, as basis for predictive maintenance.
Cross laminated timber (CLT) and self-tapping screws are considered to be the most important developments in timber construction of the last 30 years. Both together open up completely new possibilities for timber construction and lead it into areas which have been dominated by mineral-based building materials up to now. With a focus on solid wood construction with CLT, systematic and versatile connection solutions tailored to this product have been largely lacking to date, despite the given dynamic developments taking place worldwide. At present, for the connection / joining of CLT components connection solutions are borrowed from lightweight wood construction. However, these are not able to guarantee the high performance of the CLT product in the connection area nor the often-required amount of energy dissipation. An additional complication in the development of adequate connection solutions adapted to the CLT building product is that there is generally a high diversity in terms of joint type, construction method and requirement profile.
The aim of the research project is a systematic and fundamental investigation of the connection situations of CLT construction elements and related requirements, with a focus on load effects on the material and product behaviour in case of locally concentrated, quasi-static and cyclical loading as well as the recording and consideration of tolerances. This is to create a sound basis for the development of systematic and versatile connection solutions for solid wood construction with CLT, combined with the development of an automated, quality-proof application unit as an integral part of the joining process of CLT elements, for which corresponding control parameters and quality assurance measures are being researched. In the development of connection solutions themselves, flexibility as well as the achievement of defined failure mechanisms depending on the type of connection joint, type of stress and direction of stress on the basis of a fundamental discussion of the structural behaviour to be aimed at and the separation into a timber connection and an assembly joint are also in the foreground.
Considering the high CO2 emissions in the construction industry and the ongoing climate change, it is important to increase the resilience of buildings and cities by enhancing their adaptability, durability, energy and resource efficiency. In this context, the “Austrian Climate and Energy Strategy” and the European "Green Deal" emphasise the circular economy and the potentials of digitalisation.4 A resilient building primarily requires appropriate training of the constructive interfaces from primary structure (shell) to secondary structure (extension) and the management of tertiary structures (technology). The requirements are a separable combination of short-lived and long-lived components, ease of maintenance, accessibility and standardisation.5 In order to be able to guarantee the given requirements, a rethinking in the design and planning of the interfaces is necessary. As the exploratory study "Klett-TGA" (FFG project no.: 861664), which preceded this project, shows, the Velcro-connection meets these requirements better than conventional methods. In addition, Velcro offers simple, clean and fast assembly processes. It creates damage-free and detachable connections and a uniform connection system that can be applied to any component from any supplier. Resilience in construction also requires intelligent buildings. Corresponding sensor technology due to especially active transponders that offer possibilities of predictive modelling and predictive maintenance through AI-supported analysis and processing of data. Valuable prognoses and findings are provided, which further increase resilience and facilitate maintenance. However, the installation of the preferred sensors is complex due to the cabling or the service life is limited by the fixed battery.6 To solve these problems, the present project proposes to consider the building/building parts as energy generators and to operate by using the Velcro connection in combination with the piezoelectric effect to do “energy harvesting”. Based on the high weight loads, strains, vibrations, changes in temperature or due to air currents occurring in buildings (e.g. wind loads in facades, deformations; fluctuations in high-rise buildings, load bundling at nodes; membrane structures), energy can be generated independently. From the point of view of planning and construction (engineering performance), building parts would be designed and optimized for the piezo effect. The project goal is to investigate the hook-and-loop connection (velcro) as a joining system, as well as an energy generator, based on the exploratory study. As well as the idea to supply self-sufficient active sensor technology, to accruing data e.g. loads with regard to predictive modeling and their transmission cycles. Compared to the state of the art, the use of a fastener for energy generation, especially at the details of individual joining and intersection points, offers a very high level of innovation with a significant need for research. The desired result is a comprehensive gain of knowledge, concepts for possible applications of the proposed system and the verification of individual concepts by means of experiments.
Based on existing AVI-DS elements an investigation of a possible increase of the bearable punching shear force through the combination with shear bolts is planned. The investigation includes an experimantal test program as well as theoretical calculations.
The project “3DWelding: Additive Manufacturing of structural Steel Elements” should investigate the potential for 3D printed metals within the field of construction. The question is, is it possible to produce a building element in the correct scale which achieves the relevant static and dynamic requirements, as well as other requirements such as the surface quality and accuracy? Both topology optimised free-forms and regular forms should be investigated. Which mechanical properties can be achieved by layering weld over each other and are these constant throughout the printing process? Does the system have to be optimised so as to prevent voids and defects? Can the process be transferred from a laboratory to a building site? Is it possible to control the thickness of the layers and building elements? Which production speed is possible and can the costs be kept within a realistic budget?
The aim is to create a Centre of Know How and Development for structurally relevant 3D printed building elements (beams, slabs, plates, columns, etc) integrating the 3D printing system.
The first phase will define the degree of reinforcement, the adaption of the current facilities, preliminary tests for the first evaluation. Part of the service being offered is to search for other uses as well as the current customer needs.
Further development of Punching-Shear-Elements of the client for the use as shear elements primary in slabs.
Based on experimental and theoretical research a design concept will be developed for an easy of the shear elements.
With this project the existing knowledge gaps regarding UHPC should be closed. Thereby the practical application of UHPC can be pushed forward. A guideline for the application of UHPC will be summarized at the end of the project.
Microbial induced concrete corrosion (MICC) is accounted for ~40 % of the degradation of concrete based subsurface wastewater infrastructure globally. A further problem is the toxic outgazing, which poses a serious health hazard. In Germany a use of 450 Mil. Euro for repair measures of MICC-damaged sewer systems are documented each year. The number of unreported cases is suspected to be significantly higher.
At present there are two usual ways, how to repair such sewer constructions: Firstly by mounting inliners made from plastic and secondly by coating the inner surfaces. The latter is mostly realised by the use of organic polymer-modified mortars and synthetic resins (i.e. epoxy). A great number of such measures of repair turned out to be costly and non-durable. This is the reason why alternative materials, especially inorganic ones based on the silicate-technology, were developed and launched. These materials are used for making very thin (up to 3mm) coatings. Their long-lasting protective function has not been proven yet. Conventional sulphate attack happens via fluid transport whereas MICC progresses due to the transport and diffusion of aggressive gases such as H2S and CO2 and subsequent microbial transformations. Thin coatings from silicate-based inorganic materials are generally water-proof but permeable to gas and therefore they cannot sufficiently work as a MICC barrier for the standard concrete beyond. One of the most acid-resistant silicate-based materials are Geopolymers. However, their physical and microstructural properties vary in a wide range depending on their composition.
If Geopolymers are mixed with aggregates, one gets Geopolymer Concrete (GPC). The project consortium developed specific compositions of GPC, highly resistant against MICC. Further previous research work pointed out, that certain metallic admixtures significantly inhibit the growth of relevant bacteria steering this highly corrosive attack of concrete.
Based on these findings the outlined project BioResComp deals with the idea to use such innovative bacteriostatic Geopolymer Concrete as a more solid construction material instead of thin coating applications for both, repair measures and new construction of waste-water buildings. One can expect that constructing without any standard concrete will not be an economic future way. Therefore, the project proposes a new composite technique by combining a standard concrete part with a GPC part. The key of this technique is a very strong bond between the two materials. Main goal of the project is to study the mechanical composite behavior and the resistance of composites to MICC. A multi-disciplinary and mainly experimental research approach will help to get a comprehensive understanding of all the interdependencies between material composition, GPC-thickness, bond behavior, crack formation, bacterial growth and the corrosion mechanisms. We follow the hypothesis, that at certain thicknesses of the new bacteriostatic GPC layer (typically a few centimeters) a balance between the microbial growth (attack) and the corresponding resistance of the composite system will come into being.
Within the project longitudinal girders are tested, which were members of an old riveted steel railway bridge.
Notches are milled in at the critical girder positions and afterwards fatigue tests were done with measurements of the crack front. Numerical calculations, based on fracture mechanics, are done to verify the crack growth behaviour. With these calculations the remaining fatigue life of similar riveted railway bridges with fatigue cracks could be determined.
This project aims at the correct determination of the real restraint forces in statically indeterminate reinforced concrete structures. In contrast to a determination based on the elastic theory, the restraint forces are significantly reduced by cracking, creep and plastic deformation. In particular, the basics for the planning of integral structures will be further improved, making the project an important contribution to reducing the life cycle costs of engineering structures.
The production method for precast UHPC bridge elements is investigated by using both scale model tests and full scale concrete pouring tests. Scale model tests are used to study the deformation of the front surface of the precast components while pouring tests will verify the workability of the concrete. In conjunction a suitable concrete mixture in terms of strength and workability is developed.
The project deals with laboratory tests regarding the determination of bending, rolling shear and shear properties of cross laminated timber according to EN 408, to the EAD 130005-00-0304 and to the test program of the Technical Assessment Body OIB. The contractor needs the gained results for obtaining a CE mark for his building product.
Predictions for the remaining fatigue life of steel railway bridges, based on SN-curves, often lead to very conservative results. Based on a fracture mechanics approach the remaining fatigue life can be extended significantly. The key aspect are fatigue test on fifty years old longitudinal girders of a steel girder bridge, without any remaining fatigue life. At the critical positions notches were applied, leading to cracks. The crack front and crack growth was measured and documented. Numerical calculations in parallel, based on fracture mechanics, were carried out, to end up with simplified calculation procedures for the practical application.
In the Scope of an Europaen Technical Approval Procedure three test series are carried out:
1.) load transfer tests
2.) load trandfer tests considering a steel casing at the top end of the pile
3.) compression tests on jointed bars
The project consists of three main tests and three failure tests. The main tests have to confirm the waterpressure resistance of the waterstop at the level of servicivbility limit state.
The failure tests aim at findings on the ultimate water pressure resistance at various deformation states of the water stop.
The Hook-and-Loop fastener is omnipresent in many fields today. Its potential lies in the astonishing strength of bonds, which can in addition be loosened and re-fastened tool-free for several hundred times without compromising their strength and durability. Astonishingly it is far from utilizing its full potential in the construction industry although its properties would be intensified if transferred to the construction processes and could have a variety of positive effects.
Commonly the building installation lines (such as electricity, water or ventilation, to name just a few) are walled-in, screwed, or glued at the construction site. Would these instead be
assembled and mounted using the Hook-and-Loop similar fasteners, the following effects with corresponding consequences could arise:
‐ Simplified assembly processes: They would decisively accelerate the construction phase of a building and would additionally be less prone to performance-related
‐ Flexible mountings and adaptability: They would enable the building to react to shortnotice planning changes as well as to adapt to a new spatial program more efficiently.
‐ Damage-free mountings - both for the base and the component to be mounted: They would enable a pure separation of materials. The possibility of easy re-use of specific components could prolong the component’s in-use phase of the lifecycle, which would contribute to sustainable usage of resources.
Despite the obvious benefits, the usage of Hook-and-Loop fasteners at the moment requires an additional working stage, where the surface of the base as well as the component to be
mounted must be treated in order to achieve a Hook-and-Loop compatible skin. This additional stage usually requires the known fastening methods and is not an integral part of
the construction process.
Therefore the aim of this exploration study is to explore a possible systematic change that will allow for a more universal application of Hook-and-Loop (or similar) fasteners in the
construction industry, especially in building installation phase. It is to be investigated to what extent Hook-and-Loop compatible surfaces can be integrated into the production of components. These could serve as a base whereupon following building installation lines (but also e.g. final surfaces and thermal insulations) could be directly mounted: Either with
their own integrated Hook-and-Loop compatible components or with the aid of Velcro based measures.
In doing so, the exploration study will not be restricted to the consideration of a single material or trade, its aim is rather to establish the widest possible scope of consideration.
The evaluations will uncover potentials that could evoke further and more product-specific research projects.
High strength threade steel bars produced are investigated with respect to their ability for the use as passiv reinforcment in structural concrete. Bending tests will show the rotating capacity of plastic hinges. The bond behaviour is studied by means of direct tension tests on strain specimens as well as on pull out tests.
The Auenbachbrücke is an existing railway bridge wich will be substituted by an innovativ steel-UHPC composite bridge. The Graz University of Technolgy supports this practical project by means of specific experiments for the quality management.
For three to five typical damage scenarios of traffic structures the refurbishment and strengthening with textile reinforced concrete is developed. Therefore results of basic research in Germany are evaluated and own supplementary investigations are performed. A direct transfer of the results into practice should be enabled by concrete development with raw materials from Austria, design concepts and a production guideline. By large scale application and load-bearing capacity tests the practical applicability and effectiveness of the developed solutions can be verified.
COEBRO // Additive Fabrication of CONCRETE ELEMENTS BY ROBOTS is a foundational research project. An interdisciplinary team of architects, civil engineers, mechanical engineers and material technologists ask scientific questions about and research the resource efficiency usage of concrete with 3D printing technology within the construction industry. Industry partners that contribute knowledge along the investigated line of production expect results as basis for the development of an industrial concrete printing system in the near future.
Concrete is the most used building material in the world. Producing building elements takes a lot of effort creating forms and formwork is proportional to the costs of the material itself. 3D printing concrete could significantly reduce the amount of effort. Considering the Fields of Expertise of the TU Graz and the category Sustainable Systems the interdisciplinary team is researching the subjects Konstruktionen aus UHPC and Structural Robotics focusing on the resource efficient use of raw materials construction processes of buildings.
The project objective is the investigation and the prototypically development of a complete production line for the additive fabrication of concrete elements. Considering the dependencies between the printed prototypes and the technical components a specific framework for the whole system will be analysed and defined. Prototypes will be designed respecting typical requirements of construction industry. This vice versa requires the selected application and the necessary technology. The goal is maximum flexibility within a defined quality. As orientation for the definition of quality, typical industrial-standards, like surface quality, precision and stress capacity of concrete elements are applied. At the core the technical focus of COEBRO is the prototypical development of the whole printing system including the conveyor and nozzle technology for fabricating building elements with defined attributes.
After finishing the project it’s expected that within the next 3 to 5 years practical applications for the construction industry can be developed.
In the run-up to a mega building project the glued laminated timber structures which have been desinged, are tested experimentally. The focus of the tests is on 1.) the mechanical behaviour of steel dowel and flitch plate timber connections under diverse loads, 2.) the durability of the glulam product with its particular combination of preservation treatment and adhesive, and 3.) on its flame spread behaviour.
QUICKWAY is an integral concept of mobility for people and minor goods in large cities. This
concept is based on additional traffic area which is used by diverse driverless vehicles that
are controlled by a central electronic controlling system. The controller uses information
about the current position as well as the desired destination of all QUICKWAY users at the
same time and calculates the fastest routes with minimised stops, which finally increases the
traffic capacity by more than thousand percent. The outlined project focuses on the
necessary elevated roadways (QUICKWAYs) made of UHPC, the construction progress of
which is intended to be 400 m per week and construction site. Engineering and scientific
investigation on the structural design, the manufacture and the erection are completed by a
probabilistic quantification of lifecycle costs on the one hand and by analyses on the social
interaction between QUICKWAYs and the resident population on the other hand.
Based on the results of a feasability study, elaborated at the Graz University of Technology, an underwater method for the assembling of precast concrete elements is tested in the field. The test project is a 40m long sewer at the sewage-works Gössendorf.
The ambition of this fundamental research project is to develop the entire process for the realization of a uhpc-shell structure made of precast-elements, reaching from the design to the fabrication. All issues are dealed by an interdisciplinary team of architects, structural engineers and material scientists. In addition to that business partners from different kind of industries are supporting the intention.
One part of the project is the development of adequate casting-methods for thin-walled shell elements, considering material properties of uhpc (ultra high performance concrete). Another issue is the design of different suitable joining technologies. Furthermore is the digital parametric design of shell structures and the engineering of a flexible formwork, actuated by an industrial robot a substantial part of the project.
Optimisation of the fibre coctail design.
In the actual design code EN 1992-1-1 the estimation of minimum reinforcement for crack width control of restrained concrete members is regulated with a heuristic approach. The steel stress at taking up the cracking force of the cross section or relevant parts of it is limited. But with the simplification of a restricted view on the cross section, this approach is not able to cover the central problem of deformation impacts. Especially in cases of massive cross sections or large dimensions, where the minimum reinforcement for crack width control is often decisive, this approach provides implausible results and was therefore modified on base of empirical values to avoid uneconomic reinforcements. Altogether this pragmatic approach does not consider essential material properties or the real structural behavior. Especially in watertight constructions this leads to damages due to leakage often.
In cooperation with the German Federal Waterways Engineering and Research Institute (BAW) therefore a new design concept based on deformation compatibility is going to be developed. The design model considers real deformation impacts and the real structural behavior when it comes to the restraint condition and the geometry of the construction (see Schlicke, doctoral thesis 2014). Thereby the collaboration of material technology, structural design and on-site construction is promoted. The design model also allows the explicit superposition of restraint stresses due to hardening with restraint stresses during service life. Hence, an economical and safe approach for estimating the minimum reinforcement for crack width control in jointless concrete structures will be established.
Ultra High Performance Concrete (UHPC) has an outstanding compression strength. Thus, one of many important fields of application of UHPC is the construction of columns. However, at the present not any realisation of a classical, highly loaded column is being public. Therefore this project aims at providing the scientific basics for the practical realisation of such structures. Because UHPC allows also extra-slim designer-columns, the existing design codes have to be revised and adopted for that new application. Special focus is on the determination of the members load-carrying capacity in a way, where both is correctly considered, the physical circumstances and the aspects of the safety concept. The theoretical results are confirmed through manifold experiments known from literature. In the actually not investigated field of extra-slender columns combined with ultra high strength materials additional experiments will be performed in the scope of this project. The development of new structural details, which agree with the special demands coming from UHPC, is also part of the project work. For instance, prestressing is a very useful tool for getting improved capacity of slender high-strength columns. This bridge 1-project (FFG) is the follow up of a very close and long lasting cooperation with the Austrian construction industry, which is here presented by the SW Umelttechnik GmbH.
The significance of the durability of ultra high performance fibre concrete (UHPFRC) is well known. International efforts focus on an adequate economic exploitation by constructing new infrastructural buildings made of UHPFRC, for example bridges lasting twice as long as conventional ones. That trend is highly restrained because of the lack of appropriate, cost-effective methods for controlling the quality during construction. In order to release that situation, a non-destructive method for ascertaining the tensile carrying capacity, which depends on the direction, is developed in the scope of this project. The principle of magnetic induction is utilised for getting information about the orientation and position of the steel fibres within the hardened UHPC. In the case of success of this project, not only the aims mentioned above will have been met, but also other new products made of UHPFRC will be able to move into the market very quickly.
The excellent advantages of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) are durability, strength and ductility. Thus, various possibilities for new developments in structural concrete arise. On the one hand the outstanding mechanical properties of hardened UHPFRC allow slender and light building elements, which almost reach the aesthetic occurrence of steel structures. On the other hand its good rheological properties in the initial liquid state can easily be utilised in order to get effective bond to other materials. Hence, mixed building technologies can be developed, where each material contributes its beneficial properties. An impressive example for such developments is the glass-concrete-technology, which combines the robustness of reinforced concrete and the elegance end transparency of glass.
Mixed building technologies (Composite Structures) are generally based on adhesion between the different components. Adhesion depends on numerous parameters like chemical composition, wetability, roughness and morphology etc. which also lead to several different bond mechanisms. These complex interdependencies are not studied systematically yet. The current models only consider the roughness characterised by the mean roughness depth and the strength of the concrete.
This proposal presents a coherent multi-disciplinary approach to study these phenomena. Investigations of the interfacial zone with electron microscopy and computer tomography will give information about the chemical and the geometrical mechanisms of adhesion. Intermolecular forces will be considered by a thermo dynamical approach. Information about the amount of these forces is expected to get by experimental determination of the surface energy of both materials. The theory proposed bases on the correlation between true contact surface and adhesive power. Therefore, special attention will be given on the measuring of the geometry of the surface in a micro scale. The method of evaluation of the measured data will depend on the wetting property of the applied UHPFRC. An extensive mechanical testing program will complete the necessary data for the finding of a reliable calculation model for adhesive bond strength as well as a meaningful constitutive law.
The results of the project will provide the scientific base for safe design of innovative composite constructions with UHPFRC. Moreover, the theoretical model will be formulated by simplified but really existing phenomena, which should provide the possibility for an easy transfer to other materials.
Ultra high performance concrete shall be introduced into the manufacturing process of a precast plant. New high performance building elements are developed. The project includes theoretical and experimental investigations as well as practice orientated tests in the plant.
The pilot project in Carinthia/Austria for an UHPC-segmental-arch-bridge for traffic loads, is an example for the swivel-in-method that will be applied. The polygonal arranged UHPC-segmental-arches consist of individual 6 cm thin-walled and for this reason very light precast UHPC-segmental-box-girders made of C 165/185, which are assembled by the use of external tendons running inside of the arches. Because the actual shear force in the arches is very low, the thin-walled webs made of UHPFRC need not any shear reinforcement for carrying the loads. At the bends of the arches so called knee-elements are arranged. They work as deviator and anchor block for the external tendons and offer the base for the columns. The columns have a rigid connection to the knee as well as to the deck.
Present design codes and guidelines do not completely cover the use of UHPC in relation to the structure presented. Experimental tests answer open questions in designing and construction. In addition to many other experiments, full-scale laboratory tests within the scope of the pilot project are carried out. The focus of the full-scale test is the load carrying behaviour in the region of the springing. These elements are fixed to a massive supporting block by prestressing tendons. The external tendons are the same type of monostrands as in the real arch continuing in the inside of the box-girder. An additional prestressing is applied by Dywidag Steel Threadbars, which causes a bending moment and a further axial force. First the test is performed only by prestressing elements with force-controlled load increase. Afterwards the shear force and the further bending moment is increased path-controlled by a hydraulic jack until the failure occurs. So the total load path is performed according to the design calculation and then until failure.
Light and elegant load-bearing structures made of UHPFRC could contain extremely thin-walled webs and/or panels. As a result of the crack formation highly non-linear material effects result in fibre-reinforced thin- walled panels.
Within the scope of this project the shear carrying capacity and the stability (buckling) of thin-walled panels are investigated by means of theoretical modelling and numerical simulation as well as by experimental investigations.
The results are indispensable for the implementing of UHPFRC in the practice in the form of innovative load-bearing structures and construction methods.
In the building practice it is common to use point supported flat slabs made of insitu concrete. The use of precast elements working as a mould and as the lower structural part of the slab is not handy, because the region arround the column must always be formed by extra fitted formwork. Thus, this project aims at a pre-cast element made of UHPC which replaces the extra mould around the columns and which improves the punching shear performance of the slab.
Finite element analyses and full-scale experiments are accomplished for finding the scientific fundamentals
EU-project on the plastic capacity of semi-compact cross-sections and members made of steel. Numerical and experimental inverstigations.
Since for this specific group of rolled and welded profiles EUROCODE 3 does not allow to exploit their full capacity, the present project should eliminate this handicap. This will be based on testing, numerical simulations and the development of new design rules.
The results of the project would widen the applicability of semi-compact steel profiles due to their increased competitiveness, would reduce the material and energy consumption and would lead to a more economic design of steel structures.
An additional layer of concrete is often cast on an existing bridge deck for retrofit purposes. The condition of the interface between the concrete layers is crucial for the bearing capacity of the new deck and different surface preparations are investigated. The test specimen are designed to fit the in situ situations and are tested in the laboratory. The bearing capacity of the composite deck is tested under cyclic loading in order to detect fatigue failure under high static loads. The tests are accompanied by a detailed numerical investigation of the problem employing a nonlinear finite elements analysis. The scope of the numerical analysis is the verification of the analytical results and the investigation of the influence due to creep and shrinkage. The experimental results and the numerical results have been in agreement until now.