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Concrete structures

Research into the causes of damage to noise protection walls with a facing layer of lightweight concrete (15.0687)
Noise protection walls made of concrete, which consist of a facing layer of no fines lightweight concrete (absorption layer) in a monolithic bond with a structurally sealed reinforced concrete supporting layer, are often installed on federal trunk roads. So far, these noise barriers have been characterized by a long durability. In the recent past, however, damage has become known in which the facing shell had detached from the supporting concrete after a few years of use, in some cases in the form of shells and over large areas, and had fallen down. The aim of this research project is to determine the causes of the detachment of this absorption layer from the reinforced concrete load-bearing layer through systematic investigations and to develop suitable remedial measures for the choice of materials, manufacture and installation of such wall elements. In this way, the new construction of such noise barriers should again be possible without damage and the repair of already damaged noise barriers should be technically and economically successful.

Resource-conserving concrete (R-concrete) in bridge structures: Feasibility study and necessary procedures to ensure concrete quality (15.0696)
The aim of the research project is to determine the possible applications of concrete with recycled aggregates for bridge components and civil engineering structures. The available findings are to be analyzed with regard to the use in components for engineering structures and taking into account the concerns in the federal trunk road network, and the possibilities and application limits are to be described. The determination of the necessary procedures to be applied, with which a high-quality and constant concrete quality can be guaranteed, serves as the basis for an adaptation of the existing regulations in the handling of recycled aggregates for bridge and engineering structures of the federal trunk road network. Finally, necessary criteria and essential requirements are to be formulated, which form the basis for the implementation of pilot projects.

Precast bridges made of high-strength concrete (15.0689)
Designing precast bridges with high-strength concrete makes structures with greater bending slenderness possible. Systematic studies on the effects of designing bridges with precast elements made of high-strength concrete are currently not available. The changes can affect, for example, the system response under dynamic loads or the deformation and stability behaviour and thus make additional design rules necessary. Furthermore, questions arise about the cross-sectional design when using normal-strength concrete on the construction site in combination with high-strength precast concrete elements, as well as about the structural design in the case of cross-sectional shapes that deviate from current designs. The aim of the project is to investigate the effects on the structural behaviour, the design and construction of (partial) precast bridges when using high-strength concrete and to develop supplementary rules and design parameters for the planning of road bridges.

BrAssMan (2120004)
The joint research project BrAssMan, “Brücken Asset Management für Straßenbrücken” (Bridge Asset Management for Road Bridges), aims to supplement the current practice of maintenance management of road bridges with cross-asset data analyses (forecast models, permanent measurement systems, characteristic values) in order to pave the way for an intelligent asset management. The BrAssMan project sees itself as a link on the way from inspection- and recalculation-based inventory management of bridge structures to condition- and forecast-based asset management. The essential step towards intelligent asset management is data-based condition statements that can be determined not only for one bridge but – based on unit models, standard measurement systems and comparative parameters (Key Performance Indicators KPI) – for groups of similar bridge structures.

Life cycle monitoring (2120003)
The use of life cycle management (LCM) can help to optimise the use of existing budgetary resources. For the development of a life cycle management and the derivation of measures, it is necessary to have information on the condition of the structure and its development. Monitoring offers a possibility to record the condition of a structure. A multitude of monitoring systems is available, but the knowledge about the application of the systems and the evaluation of the results is still incomplete. The project pursues 2 goals: A demonstrator on the duraBASt is to be used to show the application of new developments in measurement technology and to investigate possibilities for data processing. In addition, parameters for the LZM are to be determined and, in a second step, it is to be shown which of these parameters can be recorded by the results of monitoring.

Creation of a finite element model and calibration of the model using real measured data of a bridge on the duraBASt (89.0344)
Due to the strong increase in traffic (number and loads) and the high age, bridge structures may have load-bearing capacity deficits and limitations of the remaining service life. Since it is not possible to reinforce or replace all affected structures in the short term, a way must be found to continue to use the existing structures safely. A finite element model of the structure offers the possibility to evaluate the existing load-bearing capacity and serviceability of a structure. The aim of the project is to model the global load-bearing behaviour of an existing bridge as realistically as possible. The possibilities, challenges and chances of estimating the load bearing reserves with calibrated finite element models are to be estimated. The calibration should enable the approximation of the calculation model to the measured structural behaviour under defined load. The investigation will be carried out on an existing bridge on the duraBASt.

Validation of verification formats for the determination of shear strength and experimental evaluation of the load-bearing behaviour of old structural shapes (15.0661)
The realistic determination of the shear force bearing capacity of concrete bridges has been the subject of national and international research for many years. From this a multitude of different approaches for the calculation of the shear force bearing capacity of reinforced concrete and prestressed concrete bridges for existing and new structures have been derived. The objectives of the present project are to validate the existing lateral force design approaches for existing and new structures, to quantify any influences of high longitudinal reinforcement levels within the framework of laboratory tests carried out and to create a decision and evaluation basis for the application of internationally available verification formats (in particular CSA A23.3-04). The results serve as support for the updating of the rules and regulations for recalculation and the design of new constructions as well as a qualified basis for the evaluation of the achievable safety level when applying the verification format based on the Modified Compression Field Theory to determine the shear force bearing capacity according to the Canadian standard CSA A23.3-04 for the recalculation of existing older prestressed concrete bridges in Germany.

Pavement slabs of concrete bridges (2119001)
The aim of the project is to develop a uniform, comprehensible and clearly reproducible procedure for determining the required roadway slab thicknesses for concrete bridges that are not prestressed in the transverse direction of the structure. By defining uniform planning and design principles that guarantee a safe and at the same time economical construction and apply to the entire planning process, cost certainty for the client is to be achieved.

Measurement of the shear force of carriageway slabs – development of a uniform procedure for determining the necessary cross-sectional dimensions of carriageway slabs without shear reinforcement (15.0639)
The greatly increased tandem axle loads of the LM 1 load model for dimensioning new structures resulting from the introduction of the Eurocodes for bridge construction frequently produce problems in current design practice when verifying the shear force load capacity of carriageway slabs without shear reinforcement. Previous experiences clearly indicate that the results of calculations can vary substantially depending on the models selected and the assumptions taken into consideration. In view of this, uniform planning and design principles for the entire planning process from design through to implementation are crucial from the perspective of the awarding authority. Only with the aid of uniform contractual regulations will it be possible to achieve planning reliability and thus cost certainty. The objective is to develop a uniform and comprehensible procedure for determining stresses and resistances on the basis of the current design rules in accordance with DIN EN 1992-2/(NA). In addition, consideration should be given to the impact of the possible introduction of the shear force measurement rules currently under discussion for the future development of the EC 2.

OSIMAB (2117010)
As a consequence of increasing digitalisation, extensive data are available even now which may be used for the predictive life cycle management of road traffic infrastructures using new and innovative approaches. Additional information can be obtained for bridge structures through durable structure monitoring systems. All in all, this permits an innovative approach to recognise structural shortcomings and risks and their temporal development at an early stage and to take any counter-measures which may be necessary in good time. With the innovative approach of OSIMAB, a holistic concept is pursued to monitor and assess the condition of road bridges. In addition to recognising and evaluating the current condition, predictions are to be made for future developments from the data obtained at the structure and their temporal change in connection with prediction models. Through the directly ensuing assessment of potential risks and possible measures to maintain and restore the planned target reliability, a platform is created with OSIMAB which permits an early initiation of measures to safeguard the availability of structures using a holistic approach for the first time. In this way, restrictions to the flow of traffic can be minimised and the requisite traffic and structural measures planned and implemented directly or with an adequate run-up time.

Maximising the availability of existing bridges made of steel and concrete (2117005)
Structural maintenance measures on civil engineering structures usually require partial or complete closure and therefore traffic rerouting in most cases, which entails reduced capacities and higher risk of accidents. What is more, simultaneous construction and maintenance measures on several structures leads to a restriction to the performance of the federal trunk road network. The aim of the project is to maximise the availability of existing bridges made of steel and concrete during structural maintenance measures. For this purpose, findings, procedures and methods are provided which minimise the restriction of the availability and performance of maintenance measures. The investigations focus both on the planning and on the construction process at an object level. For typical structural measures, current construction methods and technologies are analysed in terms of the availability of existing structures and optimised under consideration of the modes of operation. Optimisation aspects through new approaches and coordinated planning of measures are also incorporated. Specific concepts in the form of handling instructions and auxiliary aids which take the entire planning and construction process into consideration are provided for practical situations.

Digital motorway test field – smart bridges – study programme (15.0615)
By way of supplement to damage-based structural inspections which have been the norm so far, an adaptive system is developed under the heading of “Smart Bridges“ for the continuous provision of relevant information for a holistic assessment of condition using suitable sensor technology combined with analytical and evaluation methods. In the “Digital Motorway Test Field”, developments of new concepts and technologies are demonstrated and made accessible. The construction of a new four-field prestressed concrete box girder bridge in Bavaria serves as a pilot project for smart bridges. Sensor-controlled measurement and analysis technology has already been installed which records and analyses the impacts and structural reactions occurring in normal traffic conditions. The structure is calibrated for traffic approval. Focus is placed on heavy-traffic data. The structure serves as a monitoring system here that captures and processes bridge-specific parameters in free-flowing traffic. The findings obtained provide the basis for the evaluation and prediction of the condition as well as the reliability of the structure and its structural components. The captured and prepared information is provided to the operator online. The system is operated as part of a five-year investigation programme in collaboration with the motorway authority for Northern Bavaria - Autobahndirektion Nordbayern. The aim is to demonstrate the functioning and use of smart bridges for a reliability-based assessment of the condition of road bridges and therefore to provide a foundation to guarantee safety in holistic and sustainable maintenance planning.

Coordination and further development of the smart bridge project cluster (2116009)
The federal highway network is facing major challenges as a result of aging structures, increasing traffic loads, effects of climate change and a limited budget. Damage to structures is frequently only discovered once it has assumed considerable proportions. Adaptive systems to provide information in real time and facilitate a holistic approach have been developed as part of the “Smart Bridge” project cluster since 2011 in order to further develop the damage-based and reactive approach to maintenance. Numerous projects on intelligent sensors, structure and damage models and reliability-based assessment methods have been conducted within the project cluster. This project aims to coordinate and further develop the subject on the path to the demonstrator (

Forecasting the serviceable life of concrete bridges (2116017)
According to the applicable regulations, bridge structures made of concrete should be capable of bearing loads, suitable for use and durable under consideration of economic aspects for around 100 years. Proof of durability against external effects is currently provided using descriptive concepts based on empirical values. Design and material-related requirements are outlined depending on the exposure classes assigned to the respective environment. A quantitative prediction of serviceable life is not possible. Computational verification or a design of durability is aspired to throughout the world and the methods are already contained in the regulations today. Concrete structures are based on physical and chemical damage models founded on experimentally determined model parameters. Models of this kind seek to provide computational verification for serviceable life under consideration of different impacts that reduce durability. However, no indications are provided for implementation in practical construction. The way in which the aspired-to serviceable life is achieved depends firstly on the design concept and secondly on considerations of economic efficiency. The aim of this project is to support procedures for durability design with bridge-specific coefficients. The results gained in this project will provide the foundation for further development and for methods which forecast the serviceable life of durable bridge structures made of concrete.

Method for the Cost-Efficient Maintenance of Bridge Parapets (89.0298)
Due to their particularly exposed position, bridge parapets are subject to increased freeze-thaw stresses. This can lead to a variety of damage profiles. The occurrence of these types of damage can be influenced by the type of cement and aggregates, production conditions, surface structure and follow-up treatment. In order to secure the fabric of these structures, it is necessary to document and/or suggest cost-efficient and highly durable maintenance methods relevant to the various damage profiles. In practice, the surface maintenance of damaged horizontal concrete surfaces which are exposed to the weather and passable for people to walk on involves a variety of methods and systems. These still contain a number of outstanding issues which must be clarified before recommendations for efficient and effective measures to protect the structures can be put forward.

Evaluation of concrete for civil engineering structures on federal highways using the XF2 CDF method (2114010)
The frost-thaw resistance is of key importance for the durability of concrete structures on federal highways. Against the background of changing bonding agents for concrete, a testing method to prove the equal value with the tried and tested bonding agents used on federal highways is of great significance. The new XF2 CDF method developed for this purpose has shown itself to be suitable for this application. This XF2 CDF method for testing concrete in the XF2 exposure class has been especially developed and validated for use on federal highways. The experience gained in the process as well as in the first round-robin trial with the new testing method has been transferred into a test specification. Before the adoption of the new CDF method in the set of regulations for bridges and civil engineering structures on federal highways, an improvement in the acceptance of the new XF2 CDF method is being sought. For this purpose, it is essential to undertake a second round-robin trial taking the new test specification into account and – complementing this – gather experience with the acceptance criteria by checking various concrete formulations.