Bridge building

Table of contents

1. 1. 1. A - 54 Rebound strain measurements
      2. A - 53 Monitoring the pretensioning process
      3. A - 52 Material model UHFB
      4. A - 51 Load tests on arched bridges
      5. A - 50 Design of a pedestrian and cycle bridge
      6. A - 49 Influence of the plain bearings on the service life extension of the Nibelungen Bridge in Worms
      7. A - 48 Influence of guide rails on rail stresses
      8. A - 47 Numerical simulation of train crossings
      9. A - 46 Force determination in bridge hangers by vibration measurement
      10. A - 44 Bridge design with parametric BIM models
      11. A - 43 Data-based planning of bridges
      12. A - 42 Public participation in bridge design
      13. A - 41 Segmented structures under torsional loading
      14. A - 40 Segmental construction in bridge and civil engineering (literature research)
      15. A - 38 Reuse of concrete components from the dismantling of viaducts
      16. A - 36 Prestressed concrete in the high modern age
      17. A - 34 Orthotropic roadway slab
      18. A - 33 Conversion of a historic railroad bridge
      19. A - 32 Recalculation of vaulted bridges
      20. A - 31 Refurbishment and repair of listed historic railroad bridges
      21. A - 30 Creep of old concrete
      22. A - 29 Reduction of partial safety factors in existing structures
      23. A - 28 Shape memory alloys for bridge reinforcement
      24. A - 27 Optimized placement of DB frame structures
      25. A - 26 Extending the service life of damaged steel components with CFRP
      26. A - 25 Monitoring with fiber optic sensors
      27. A - 24 Measurement-based verification in the digital bridge twin
      28. A - 20 Production-dependent design parameters for bridges
      29. A - 19 Type statics for frame bridges using parameterization and AI
      30. A - 7 Replacement construction of a crossing structure
      31. A - 6 Investigation of variants of a railroad overpass
      32. A - 5 Investigation of variants of a double-track arch bridge
      33. A - 4 Study for a complete or partial new construction of a viaduct
      34. A - 1 Bridge construction

A - 54 Rebound strain measurements

The realistic assessment of prestressed concrete bridges poses major challenges for the engineers carrying out the assessment. Non-destructive testing methods and the taking of material samples are part of structural examinations. When taking prestressing wire samples, the in-situ prestressing of the respective prestressing wire is often measured. For this purpose, the back-strain of the wire is recorded using a strain gauge and then converted back into a stress.

In the course of the student's work, existing back-strain measurements are to be evaluated and assessed. After consultation, there is the possibility to participate in structural investigations.

The task is structured as follows:

• Research and presentation of prestressing methods of the GDR
• Comparison of metrological possibilities for recording the back strain
• Identification and evaluation of influencing variables on the actual and measured prestressing (extraction point, prestressing force losses, wire diameter, cracks, ...)
• Measurement data analysis and plausibility check: curve progressions, fracture surface analysis (data will be provided by MKP)
• Further laboratory tests if necessary

The work is supervised by David Czeschka and Chris Voigt.

Contact person:
David Czeschka

+49 (151) 67251786

Chris Voigt

+49 3643 439651

A - 53 Monitoring the pretensioning process

Detailed title: Monitoring the prestressing process of prestressed components with fiber optic sensors

Fiber optic sensors are suitable for quasi-continuous strain measurement due to their high local resolution. The integration of fiber optic sensors in prestressing strands opens up new possibilities for investigating prestressing processes. This means that elongation can be determined not only in its entirety at the press pull-out, but also at any point on the strand. This provides valuable information on the prestressing process, for example on losses due to friction or wedge slip.

As part of a final thesis (project and/or dissertation/master's thesis), measurement data from a prestressing process is to be evaluated. The aim is to verify the design assumptions based on measured values.

The thesis consists of the following work packages:

• Presentation of the current state of knowledge on distributed fiber optic sensors and intelligent prestressing systems
• Determination of prestressing force from strain measurement data of distributed fiber optic sensors
• Comparison of the measured prestressing force with the prestressing force applied in the statics
• Development of a method to determine the coefficient of friction µ and the unplanned deflection angle k from distributed strain data
• Investigation of the parameters during pretensioning and release

Details of the task will be specified before the start of work and during the work period. Processing in English is possible.

Contact person:
Dipl.-Ing. Bertram Richter
0351 463 32822

A - 52 Material model UHFB

Detailed title: Implementation of a material model for ultra-high performance fiber reinforced concrete (UHPC) in Sofistik

The material UHPC (ultra-high performance fiber reinforced concrete) is increasingly being used in bridge construction, e.g. for the renewal of roadway slabs on arched bridges. In order to make the best possible use of the construction material, it is necessary to be able to dimension and design the component as quickly as possible in an FE program, e.g. Sofistik.

Within the scope of the work, the common material models for the calculation of concrete and steel fiber reinforced concrete are to be compared. Once a suitable material model has been selected, it is to be incorporated into Sofistik.

The newly incorporated material model is to be used for dimensioning using a real example. For this purpose, a new roadway slab for an arched bridge is to be dimensioned. Here it is crucial that the component thickness is as minimal as possible, as the distance between the top edge of the vault and the sleeper is very small. This raises the question of which component thickness can still be realized with which slab size.

Details of the task will be specified in the run-up to processing.

Contact person:
Dr.-Ing. Karoline Holz
+49 351 315864 - 111

A - 51 Load tests on arched bridges

Detailed title: Load tests on arched bridges for the development of simplified verification concepts

The preservation of existing structures is becoming increasingly important in the infrastructure sector. Although vaulted bridges are among the oldest bridge structures in Germany, their robustness and durability mean that they still make up a large proportion of the existing bridge stock. When recalculating these structures, difficulties often arise due to conservative assumptions, which then leads to demolition. To preserve vaulted bridges, a series of load tests are currently being carried out to determine the real load-bearing behavior and to calibrate numerical models. Defined loads are applied to the structures and the reactions are measured using various concepts. Optical measurement methods such as laser trackers or levels are used, as well as inductive displacement transducers and inclination sensors and fiber optic sensors. If you are interested in a practical research project, possible tasks are available, e.g:

• Literature research on load tests already carried out on arched bridges
• Comparison of the measurement methods used and creation of an optimized measurement concept
• Comparison of the load-bearing behavior of different arch bridges based on the results of load tests
• Investigation of various models for the recalculation of arch bridges and comparison with measured values
• Investigation of soil-structure interaction

Contact person:
Dipl.-Ing. Jenny Keßler
+49 351 463 39004

A - 50 Design of a pedestrian and cycle bridge

Detailed title: Design of a resource-efficient pedestrian and cycle bridge at Südpark in Dresden

For the winter semester 2024/2025, the Institute of Concrete Structures and the Collaborative Research Center/Transregio 280, under the patronage of the City of Dresden, are holding a student competition to design a resource-efficient pedestrian and cycle bridge at Südpark in Dresden.

The pedestrian and cycle bridge to be designed is to be built as part of the Dresden Federal Garden Show (BUGA) 2033 and will span Bergstraße. The crossing is intended to create a link between the planned BUGA exhibition areas and improve connections to the surrounding urban districts. The focus of the competition task lies in the development of a structurally interesting and sensible design. The supporting structure should be designed to be as efficient and resource-minimizing as possible. The choice of materials and the construction method are open, whereby material-appropriate and realistic design approaches are assumed.

The aim of the work is to develop a contribution for the student competition "Design of a resource-efficient pedestrian and cycle bridge at Südpark in Dresden" . The following aspects are to be dealt with in this context:

• Analysis of the general boundary conditions and local circumstances,
• Development of at least three preliminary designs that differ in terms of supporting structure, materiality and design,
• Reasoned selection of a preferred variant,
• Detailing of the preferred variant by optimizing the load-bearing concept, an approximate preliminary design of the main load-bearing elements and the creation of an overview plan with floor plan, longitudinal section and cross-section.

The task was announced on 14.10.2024.

Contact person:
Dipl.-Ing. Cedric Eisermann
+49 351 463 - 39814

A - 49 Influence of the plain bearings on the service life extension of the Nibelungen Bridge in Worms

Digital methods for extending the remaining service life of the entire structure are currently being designed and implemented on the Nibelungen Bridge in Worms. A wide range of information from different data sources is being brought together in a digital twin of the structure. The data is processed in such a way that those responsible for the structure always receive information on the current condition of the structure. For example, data from continuous condition monitoring is aggregated with the help of structural health monitoring and displayed as condition indicators. A condition indicator can, for example, address a specific structural design issue.

A new deck slab was built on the approach bridges of the Nibelungen Bridge as part of a repair project. The deck slab is supported in a linear manner and thus transfers its loads to the vaults below. Horizontal loads are transferred via fixed points. Outside the fixed points, the slab is mounted on sliding bearings. In order to enable sliding, a design solution was implemented at the time, the permanent functionality of which cannot currently be precisely determined.

As part of the work, this design solution and its influence on the global load-bearing behavior of the arched bridges is to be investigated numerically, among other things. A proposal is to be developed as to how metrological monitoring of the bearing conditions can be designed in order to detect changes in condition at an early stage. Based on this, an evaluation concept with recommendations for action is to be developed.

Contact persons:
Chris Voigt, M. Eng.
+49 3643 4396 - 51

Dipl.-Ing. Cedric Eisermann
+49 351 463 - 39814

A - 48 Influence of guide rails on rail stresses

Detailed title: Influence of guide rails on the rail stresses of the guide rail - design options for optimization

On long railroad bridges, the rail, which is laid without gaps, interacts with the structure, so that forces and deformations occur when the temperature of the bridge itself changes or when it is stressed by train traffic. The calculation of the interaction effects is regulated in DB Guideline 804. All previous calculation assumptions assume a "standard track", i.e. a sleeper with 2 rails. However, some structures still have so-called guide rails installed in the track, which also have an influence on the interaction behavior.

The aim of the work is to numerically investigate the effects of this guide rail: how does the rail affect the forces in the running rail, what is the influence of the position of the butt joint, how does the guide rail affect the safety against distortion of the track, etc.? It is also possible in the thesis to compare the theoretical results with existing measurement data.

The thesis is aimed at students who are interested in numerical modeling, who want to work on a practical and relevant topic and who would like to compare theory and reality.

Contact person:
Elias Will M. Eng.
+49 351 463-35467

Dr.-Ing. Sebastian Schneider
+49 511 515154 - 256

A - 47 Numerical simulation of train crossings

Detailed title: Accurate modeling of a train crossing and influence on rail stresses (incremental investigation) and comparison with measurement results

On long railroad bridges, the continuous rail interacts with the structure so that forces and deformations occur when the temperature of the bridge itself changes or when it is stressed by train traffic. The calculation of the interaction effects is regulated in DB Guideline 804. Currently, the 3 load cases (1/ temperature, 2/ vertical load due to train traffic, 3/ braking and approach force) are calculated and superimposed. However, the vertical load of the train does not occur all at once, but is introduced by a moving load (wheel on rail).

The aim of the work is to model and calculate this load case as realistically as possible by applying the load incrementally to the model. A comparison is to be made between the realistic and conventional modeling in order to derive conclusions for interpreting the results from the standard. It is also possible in the thesis to compare the theoretical results with existing measurement data.

The thesis is aimed at students who are interested in numerical modeling, who want to work on a practical and relevant topic and who would like to compare theory and reality.

Contact person:
Elias Will M. Eng.
+49 351 463-35467

Dr.-Ing. Marc Wenner
+49 3643 43 96 0

A - 46 Force determination in bridge hangers by vibration measurement

Detailed title: Determination of the normal force in bridge hangers under different boundary conditions by means of vibration measurement

The actual normal forces in hangers of tied-arch bridges or cable-stayed bridges often deviate from the assumptions made in the design, as it is difficult to achieve the planned prestressing condition during their installation. However, the hanger normal force influences both the load-bearing behavior of the hanger itself and the bending stress of the bridge girder. Therefore, the measurement of the actual hanger force is an important task in the realization and assessment of structures.

A simple and common method is to determine the forces via their relationship with the natural frequencies of the hanger. Depending on the type of hanger (strand or flat steel hanger), different theories are used to describe the swing-out behavior. These theories assume known boundary conditions such as the free oscillation length and the anchoring, which are not fulfilled in reality depending on the type of hanger.

Within the scope of the work, the relationship between the normal force and the natural frequencies of the hanger is to be investigated experimentally using a laser vibrometer under various boundary conditions (hanger type, articulated/rigid anchorage). The investigation is intended to determine how much the normal forces determined under different boundary conditions differ and to what extent it is possible to determine the normal force of the hanger with unknown boundary conditions. Knowledge of programming (Python or Matlab) is advantageous for data processing.

Contact person:
Dipl.-Ing. Ronghua Xu
0351 463 33776

A - 44 Bridge design with parametric BIM models

Detailed title: Design planning of plate girder bridges with parametric BIM models

The design phases LPH 2 and LPH 3 for new road bridges are a complex process with diverse boundary conditions and design parameters and require a great deal of experience and knowledge in determining the bridge typology and dimensions. As a rule, the design process is characterized by manual work and is therefore individual, error-prone and time-consuming. The conventional design process can be optimized in times of high demand for new construction and a simultaneous shortage of skilled workers, increasingly complex construction measures, growing demands on sustainability and shorter construction times.

The focus of this work is on plate girder bridges as a bridge typology. The bridge parameters of plate girder bridges are numerous and are partly finalized at the end of the design planning (LPH 3) (e.g. external geometry with, among other things support positions and number of girders, materiality, construction method). The correct configuration of the bridge parameters is largely dependent on the boundary conditions of the individual design task and is determined by individual knowledge and experience. Determining the bridge parameters is a manual task that is often supported by individual reference structures. There is no structured reference database adapted for the design phase. It could significantly support the design process and function as a basis for ideas. The basis of ideas using the reference database allows the planning team to subsequently pursue specific ideas for the new building.

The aim of the work is to accelerate the design of plate girder bridges for road construction by developing a parametric BIM model that enables both the subsequent verification of existing bridges and the definition of the main dimensions for new construction. This method is to be tested using a case study. The focus is on overpass structures for railroad lines. The tasks can be in detail

• Researching and categorizing plate girder bridges based on technical literature, regulations and reference examples from the Road Administration's holdings
• Development of an improved design process for plate girder bridges using a reference database and a parametric BIM model
• Conceptualization, development and construction of a reference database for plate girder bridges (software: SQL, MS Access), which contains relevant boundary conditions and bridge parameters
• Conceptual design and development of a parametric BIM model (software: Excel, Sofistik, Grasshopper or Allplan Bridge)
• Application and evaluation of the developed design process using a case study
• Evaluation of the developed design process for practical application
• Documentation of the parametric calculation model in the form of a manual

The work is part of the research project mFUND-HyBridGen - Hybrid Bridge Generator: AI-based bridge generator with knowledge and experience data and early citizen participation. Support can be provided jointly with the planning and software company A+S Consult GmbH.

Contact person:
Jakob Grave, M.Sc.
030 220 777 74

A - 43 Data-based planning of bridges

Detailed title: Data-based planning of bridges using DB InfraGO AG reference structures

The preliminary planning phase LPH 2 according to HOAI for new bridges for railroad construction is a complex process and requires a lot of experience and knowledge in determining the bridge typology and dimensions. The selection of an optimal bridge typology and construction technology in LPH 2 as the preferred variant is of paramount importance for the overall success of the project. The associated determination of the bridge parameters in bridge design is a multifaceted process that takes into account different boundary conditions. The actual design process is often dependent on individual experience. The conventional design process can be optimized in times of high demand for new construction and a simultaneous shortage of skilled workers.

The aim of the work is to qualitatively improve the preliminary planning (LPH 2) of a bridge structure (typology: e.g. thick plate, trough or frame bridge; span: < 20 m) by identifying stumbling blocks in the early planning phase and designing robust construction methods for the individual project parameters. To this end, the data and expert knowledge on the existing bridges are to be professionally processed for the planners using a reference database of existing bridges and analyzed using statistical methods and - depending on the type of study work - also using simple artificial intelligence methods. The overall objective is to ultimately enable a prediction model of bridge typology, parameters and associated construction technology for new bridges with given boundary conditions. The practical application is also to be assessed.

Previous theses that have already identified important and design-decisive boundary conditions for bridge design in the construction and final state and compiled them in an "Overview of boundary conditions" serve as the basis for the present work. The task will be detailed and structured with the student before work begins, depending on individual interests. The tasks can be in detail

• Researching and documenting a bridge typology and its design-determining parameters and construction technologies as well as design-decisive boundary conditions
• Researching and conceptualizing statistical and AI methods for recording correlations between the same
• Further development of a reference database of existing bridges on bridge typologies and their design-determining bridge parameters and construction technologies as well as design-determining boundary conditions by means of expert discussions and evaluation of existing data
• Determination of design-determining bridge parameters and design-determining boundary conditions
• Application of statistical methods to investigate the relationships between these parameters using the reference database
• Application of AI methods to develop prediction models for new construction bridges using ready-made algorithms
• Assessment of practical applicability based on the results of the prediction models and verification

The work is part of the research project mFUND-HyBridGen - Hybrid Bridge Generator: AI-based bridge generator with knowledge and experience data and early citizen participation. Supervision is carried out jointly with DB InfraGO AG, Head Office (specialist planning for structural engineering).

Contact person:
Jakob Grave, M.Sc.
030 220 777 74

Marcus Krug (DB InfraGO AG, Principles of Construction and Technical Planning, Program and Resource Management, I.IIG 2, Advisor for Technical Planning of Structural Engineering)

A - 42 Public participation in bridge design

Detailed title: Guidelines for public participation in the semi-automated bridge design process

In principle, citizens and various interest groups (e.g. nature conservation and bicycle traffic) should be more closely involved in the design and decision-making process for bridge structures as part of infrastructure projects. At present, however, most fully developed design solutions are shown to citizens as specialist plans that are incomprehensible to laypeople, which can generate criticism and, in the absence of approval for the project, deadline and cost risks for infrastructure projects. However, a reliable design decision at an early stage can significantly increase the approval speed of a bridge project. A digital citizen participation assistant with digital visualizations and additional explanations in a dashboard, for example, could provide a remedy. Semi-automated design generation (design generator) can enable a fast, resource-efficient solution for infrastructure construction projects that is acceptable to society as a whole.

The aim of the work is to develop a guideline for the applicability of the design generator based on the results of an earlier student research project in the winter semester 2023/24.

• Research, categorization and evaluation of digital citizen participation formats that already exist (urban, building and bridge construction); also by means of expert interviews
• Research into design generators for bridges using parametric processes
• Analysis and evaluation of integrated processes for semi-automated design generation of the researched digital citizen participation formats
• Conceptualization and development of a structured process model for a digital citizen participation assistant in the context of a semi-automated design generation of bridges
• Development of a methodology for a structured process model
• Investigation of the possible applications in bridge construction
• Documentation of the results in a written guideline for public participation in bridge planning with a design generator

The work is part of the research project mFUND-HyBridGen - Hybrid Bridge Generator: AI-based bridge generator with knowledge and experience data and early citizen participation. Support is provided jointly with the planning and software company A+S Consult GmbH or the Bundesstiftung Baukultur.

Contact persons:
Jakob Grave, M.Sc.
030 220 777 74

Co-supervising practice partner: A+S Consult GmbH or Bundesstiftung Baukultur (to be determined by arrangement)

A - 41 Segmented structures under torsional loading

Detailed title: Load-bearing behavior of segmented structures in bridge and civil engineering with dry, ground joints under torsional loading

Within the next 20 years, more than 50 % of the existing bridges in the German highway network are expected to be replaced by new structures. In order to achieve the expansion targets in the field of renewable energies, it is essential to erect an increasing number of more powerful wind turbines. In order to achieve the targets set, the use of new, innovative design solutions is required in addition to tried and tested construction methods. Prefabricated segmental structures, in which the supporting structures are divided into individual segments, represent a promising solution. These segments are manufactured in a precast concrete plant, assembled on the construction site and connected to each other by subsequent, often external, prestressing. The minimization of production steps on the construction site enables extremely economical and fast construction processes, which is why this construction method is now being used more and more worldwide. In Germany, on the other hand, this construction method has not yet been able to fully establish itself due to concerns about the durability of the structure as a result of the joints created. The ecological awareness of the construction industry and the further development of automation and digitalization in precast concrete production are opening up new possibilities for modular segmental construction.

The construction method is characterized by the joints that inevitably occur. A further development in this area is the design of dry segment joints without interlocking. The load transfer of the shear stresses acting in the joint takes place exclusively via friction. The joint shear resistance depends on the level of the external prestressing force in combination with the friction coefficient of the surface. When the cross-section is loaded by torsion, additional normal stresses arise in addition to the typical shear stresses according to St. Venant, which interact with the normal stresses due to prestressing and thus have a direct influence on the load-bearing capacity of the dry joints.

The following subtasks are to be carried out as part of this work:

• Literature research on the segmental design of reinforced concrete and prestressed concrete structures
• Initial examination of the theory of warping torsion
• Parameter studies on selected typical cross-section shapes to determine the level of additional normal stresses
• Linking the calculation results with the joint resistance
• Evaluation and assessment of the calculation results

Contact person:
Max Götze, M.Sc.
0351 463 35606

A - 40 Segmental construction in bridge and civil engineering (literature research)

Detailed title: Literature research on the current state of knowledge of segmental construction of reinforced concrete and prestressed concrete structures in bridge and civil engineering

* only as project work *

In the next 20 years, more than 50 % of the existing bridges of the German highway network will have to be replaced by new constructions. In order to achieve the expansion targets in the field of renewable energies, the construction of an increasing number of more powerful wind turbines is essential. In order to achieve the targets set, the use of new, innovative design solutions is required in addition to tried and tested construction methods. Prefabricated segmental structures, in which the supporting structures are divided into individual segments, represent a promising solution. These segments are manufactured in a precast concrete plant, assembled on the construction site and connected to each other by subsequent, often external, prestressing. The minimization of production steps on the construction site enables extremely economical and fast construction processes, which is why this construction method is now being used more and more worldwide. In Germany, on the other hand, this construction method has not yet been able to fully establish itself due to concerns about the durability of the structure as a result of the resulting joints.

The ecological awareness of the construction industry is opening up new possibilities for modular segmental construction. This construction method can be used to achieve ambitious goals such as increasing resource efficiency, minimizing greenhouse gases and promoting a circular economy. One particular potential that has yet to be fully exploited is the circular use of construction as a whole or individual segments. In the future, it could therefore be possible to replace or dismantle parts of a structure and reuse them elsewhere. The further development of the construction industry, in particular the automation and digitalization of precast concrete production and the use of high-strength and high-performance concretes, also favours the use of modular structures.

The following subtasks are to be completed as part of this thesis:

• Literature research on the segmental construction of reinforced concrete and prestressed concrete structures
• Literature research on topics such as joint formation, prestressing and local effects
• Classification of segmental constructions according to selected criteria (such as cross-sections, joints, construction sequence, circularity, etc.)
• Presentation of the load-bearing principle of such constructions
• Research on the circularity capacity of segmented structures
• Summary of the state of research in this field

Contact person:
Max Götze, M.Sc.
0351 463 35606

A - 38 Reuse of concrete components from the dismantling of viaducts

Germany's bridges are in a dilapidated state. Over 4,000 bridges in the German highway network urgently need to be renovated or rebuilt by 2032. For example, all 60 bridges on the Sauerland line are due to be demolished. In addition to the research required to maintain, strengthen and extend the service life of bridge structures, the focus today is on how to reduce the environmental impact of bridge demolition. In view of the fact that the construction industry is responsible for 60% of the world's waste, the reuse and recycling of components from demolition in the sense of bridge mining is a promising approach.

The aim of the work is to derive a reuse cycle for concrete components from the dismantling of valley bridges, taking into account dismantling procedures, logistics, evaluation methods and recycling potential. The work thus makes a valuable contribution to the avoidance of construction waste and the conservation of resources.

Details of the task will be specified in advance.

Contact person:
Raúl Enrique Beltrán Gutiérrez, M.Sc.
0351 463 33675

A - 36 Prestressed concrete in the high modern age

Detailed title: Investigation of prestressed concrete bridges of the high modernism as a basis for the valorization by the monument preservation

Like no other construction method, prestressed concrete stands for bridge building in the post-war period. Over 9,700 prestressed concrete bridges built between 1937 and 1980 are recorded in the federal highway network alone. This corresponds to a share of around 41%. The high proportion of prestressed concrete bridges shows the advantages of the then new construction method compared to building with reinforced concrete and steel. Numerous construction types, prestressing methods and construction methods, such as the incremental launching method, were developed and are still used today. Prestressed concrete construction can therefore look back on a rich and varied history of development, which is reflected in today's (bridge) structures. Unfortunately, these bridges have reached the end of their useful life and are being demolished. They have yet to undergo a comprehensive conservation appraisal, as was the case, for example, with the formative bridges of the Middle Ages, meaning that a piece of important structural engineering history is gradually being irretrievably lost.

During the long development period of prestressed concrete, faults, damage and shortcomings have occurred that have not yet been examined in detail. From today's perspective, these faults can be assessed and classified. At the same time, these errors can be used as an indicator of the innovative capacity of prestressed concrete construction. Mistakes were corrected, approaches discarded and "correct" procedures discussed, failures turned into successes, only in this way could the result - the prestressed concrete of today - be achieved. It is precisely these innovations that are to be used for a holistic appraisal of prestressed concrete structures.

The detailed task will be agreed with the student. Possible tasks are, for example

• Research on the prestressing methods of the high modernity and special features of the training and application as well as the advantages and disadvantages
• Analysis of the typical damage of the various tensioning methods
• Evaluation and typification of the bridge stock with regard to tensioning methods

For diploma theses, the scope of the task is adapted or extended, e.g. by

• Recalculation of historical prestressed concrete bridges taking into account current standards and load approaches and evaluation of the problems of the original construction and the damage that has occurred

The underlying research project is part of the DFG priority program 2255 "Cultural Heritage Construction".

Contact person:
Dipl.-Ing. Jakob Vogt
0351 463 45610

A - 34 Orthotropic roadway slab

Since the 1950s, the orthotropic deck slab has been a widespread construction method for the deck slab of box girder or plate girder cross-sections as deck girders of suspension bridges or cable-stayed bridges in Germany. Due to structural deficits and increased traffic loads, these bridges today exhibit considerable fatigue damage. As part of the work, various reinforcement options are to be researched and evaluated. Using a concrete example, a promising reinforcement option is to be planned and recalculated.

A concretization, detailing and structuring of the task will take place before the start of the work with the student.

Contact person:
Dr.-Ing. Oliver Mosig (MKP GmbH, Dresden)
0351 315 864 106

A - 33 Conversion of a historic railroad bridge

Detailed title: Conversion of a historic railroad bridge into a pedestrian/cycle bridge

Due to line closures, historic bridges have lost their function in many places and have already been partially dismantled. Some of these bridges are characteristic of the town and are listed buildings. Using the example of a steel truss bridge, a concept for converting it into a pedestrian and cycle bridge is to be developed. In addition to static verifications of the load-bearing capacity and serviceability of the existing structure, various designs for access to the bridge in line with requirements (e.g. ramp structures) are to be developed.

A concretization, detailing and structuring of the task will take place with the student before the start of work, depending on individual interests and the scope.

Contact person:
Dr.-Ing. Oliver Mosig (MKP GmbH, Dresden)
0351 315 864 106

A - 32 Recalculation of vaulted bridges

Arch bridges made of masonry are among the oldest and most resistant load-bearing structures and account for a significant proportion of the bridge stock in Germany. The mathematical verifications of the load-bearing capacity can often not be provided with conservative assumptions and modeling approaches. The aim of this thesis is to investigate the extent to which the calculated load-bearing capacity of a vaulted arch can be increased by using different modeling approaches (trusses, surface structure, volume elements). By varying different geometric parameters (e.g. span, stub height, arch shape), influencing parameters are to be identified and evaluated. The calculations are to be carried out using the FE program SOFiSTiK. If required, an introduction to the program can be given.

A concretization, detailing and structuring of the task takes place before the start of the work with the student depending on individual interests and the scope.

Contact person:
Dr.-Ing. Oliver Mosig (MKP GmbH, Dresden)
0351 315 864 106

A - 31 Refurbishment and repair of listed historic railroad bridges

Detailed title: Refurbishment and repair concepts for historic railroad bridges in consideration of monument protection

There are almost 10,000 bridges in the DB network that are more than 100 years old and have therefore reached their calculated service life. Due to increased traffic loads and structural defects, these bridges sometimes show deficits. Due to limited financial and human resources alone, it will not be possible to replace all of these structures; instead, reinforcement and repair concepts must be developed to upgrade these bridges. In addition, these structures are also evidence of architectural development and are often listed buildings.

The work involves developing repair and upgrading concepts for historic bridge structures, taking into account monument protection. This can be done either on certain typical construction methods/types or on a specific individual example. The conservation and architectural value of the structure type or specific structure is to be identified and evaluated. Various restoration concepts are to be developed on the basis of this assessment. Depending on the student's area of interest, vaulted, steel or reinforced concrete/prestressed concrete bridges can be examined, for example.

Details of the task will be specified in advance.

Contact person:
Dr.-Ing. Oliver Mosig (MKP GmbH, Dresden)
0351 315 864 106

A - 30 Creep of old concrete

There are no reliable calculation models or experience for the creep of old concrete that has been subjected to permanent compressive stress. However, these are of essential importance if existing prestressed concrete bridges are to be subsequently reinforced by external prestressing.

The existing prediction models for the creep of concrete (Model Code, Eurocode, ACI, etc.) sometimes result in significant differences in the amount and progression of the predicted creep deformations. In our own tactile tests on 57-year-old concrete samples from the Lahntal bridge in Limburg, quite significant creep deformations were found, which are well above the current creep models.

In further investigations, these results are to be verified or refuted with tests on specimens from the Unterrieden viaduct. A database is to be generated on the basis of which a reliable statement on the creep behavior of old concrete is to be derived.

Details of the task will be specified in advance.

Contact person:
Dr.-Ing. Gregor Schacht (MKP GmbH, Dresden)
0351 315 864 101

A - 29 Reduction of partial safety factors in existing structures

When assessing existing structures, (im)safety factors that must be taken into account when planning new buildings can be assessed more accurately and therefore often excluded. This can mean that, for example, safety elements to be taken into account on the action or resistance side can be reduced. According to the recalculation guideline, this is possible for the partial safety factor of the dead loads, for example, if the existing structure is sufficiently pre-examined. This includes a comparison of the target geometry according to the as-built documents and the actual structure geometry as well as a check of the structure weights to be applied.

Today, it is possible to digitally record existing structures in three dimensions and thus to check the geometry very precisely or even to use the actual geometry in the verification process. This means that considerable reserves can be created in existing structures.

Using the example of the Siegtal bridge, a 1000 m long and approx. 105 m high viaduct on the A45, the potentials of a precise as-built survey are to be investigated and the possible reduction of the partial safety factor of the dead loads assessed. For the existing structure, 3D survey data and a 3D as-built model are available as a basis for the assessment as well as the results of concrete investigations, which are to be taken into account in the work.

Details of the task will be specified in advance of the work.

Contact person:
Dr.-Ing. Gregor Schacht (MKP GmbH, Dresden)
0351 315 864 101

A - 28 Shape memory alloys for bridge reinforcement

Detailed title: Use of shape memory alloys for the subsequent reinforcement of bridge structures

* preferably in English *

In concrete construction, externally bonded CFRP lamellae (lamellae made of carbon fiber-reinforced plastic) are primarily used for subsequent reinforcement. The effectiveness of the reinforcement measure can be significantly increased by prestressing the lamellae. Due to the limited working space and the required prestressing technology (hydraulic presses, anchoring), prestressing of the reinforcing lamellae is often not possible. The solution can be a self-tensioning reinforcement system made from a shape memory alloy.

This is where the work comes in. Within the scope of the work, a novel reinforcement method for concrete components based on an iron-based shape memory alloy is to be investigated in the form of a pilot application. The effects on load-bearing capacity, stiffness and crack width of a selected concrete component are to be analyzed and compared with established reinforcement methods (in this case CFRP). The aim of the work is to assess the feasibility and practicability of subsequent reinforcement with shape memory alloys.

The work is offered in cooperation with the Leibniz University of Hanover, Institute of Steel Construction. Details of the task will be specified in advance of the work.

Contact person:
Dr.-Ing. Harald Michler
0351 463 32550

A - 27 Optimized placement of DB frame structures

Detailed title: Investigations into the optimization of the placement of Deutsche Bahn frame structures

Replacement construction of small and medium-sized railroad bridges in inner-city areas is often subject to severe time constraints. The reliability of the restoration of traffic on and under the structures is sometimes of supra-regional importance.

The task includes the creation of an overview of the various installation methods for half-frame structures in inner-city areas with reference to the applicable Deutsche Bahn guideline. On the basis of the DS804 guideline and the specifications of the Deutsche Bahn guideline, a design is to be developed for a typical double-track half-frame cross-section for bridging two carriageways and two footpaths and cycle paths that is load-bearing in all construction stages, which is constructed approx. 15 m to the side of the final position at road level and whose installation can significantly reduce the installation time compared to conventional methods.

Daebritz Baukonzept GmbH from Leipzig will support you with experience in such transportation concepts. The work is to be carried out in German.

Contact person:
Max Herbers, M.Sc.
0351 463 39620

A - 26 Extending the service life of damaged steel components with CFRP

Detailed title: Meta-analysis on extending the service life of fatigue-damaged steel components with CFRP reinforcements

The combination of increasing loads from heavy haulage, increasing axle loads and insufficient understanding of fatigue behavior during construction in the 1960s to 1980s, manifests itself today in significant fatigue damage to steel bridges. Repairing such fatigue cracks using established methods such as repair welding, drilling the crack tip and applying additional strengthening measures is associated with significant disadvantages and can lead to the formation of new fatigue cracks after a short time. The disadvantages can be avoided with the help of bonded laminates made of carbon fiber reinforced plastic (CFRP). The great potential of this innovative repair method has already been investigated in extensive studies with different boundary conditions. However, the range of material combinations, load scenarios, test specimen geometries and other boundary conditions is so extensive that a generally valid statement on the efficiency of the repair method does not seem possible at first glance. This is where the work comes in.

As part of the work, extensive research is to be carried out on experimental and numerical investigations on steel components subjected to cyclic loads and reinforced with the aid of CFRP. Based on the knowledge gained, the sensitivity parameters are to be identified and their influence evaluated. The objectives of the work are the creation of a research database for the aforementioned investigations, the categorization of the sensitivity parameters and the quantification of the reinforcement efficiency with the help of suitable parameters.

Details of the task will be specified in advance.

Contact person:
Dipl.-Ing. Clara Schramm
0351 463 41117

A - 25 Monitoring with fiber optic sensors

Detailed title: Monitoring of prestressed concrete components at risk of stress corrosion cracking with fiber optic sensors

Due to the lack of announcement behavior, the majority of bridges at risk of stress corrosion cracking are taken out of service, even if they otherwise show no structural damage. The closure and subsequent replacement construction cause high economic and ecological costs. With their spatially high-resolution, quasi-continuous strain measurement, fiber optic sensors are predestined for holistic structural monitoring. By monitoring with fiber optic sensors, prestressing wire breaks could be detected, thereby creating an announcement behavior and thus extending the safe use of such bridges.

The possibilities of distributed fiber optic sensors for monitoring prestressed concrete components at risk of stress corrosion cracking are therefore to be investigated as part of a final thesis (project and/or diploma/master's thesis). The aim is to develop a monitoring concept for the detection, localization and quantification of prestressing wire fractures using fiber optic sensors. Therefore, this work contributes to sustainability in civil engineering.

The work consists of the following work packages:

• Literature research on distributed fiber optic sensors and stress corrosion cracking
• Development of a monitoring concept based on the results of static calculations
• Development of evaluation approaches for the detection, localization and quantification of prestressing wire fractures
• Implementation of the approaches in an existing Python software framework

Details of the task will be specified before the start of the project and during the project period. It is possible to work in English.

Contact person:
Dipl.-Ing. Bertram Richter
0351 463 32822

A - 24 Measurement-based verification in the digital bridge twin

Detailed title: Integration of measurement-based verification management in the digital bridge twin

* Editing only possible in German *

The digitalization of the construction industry is also changing the tasks of a civil engineer. Nowadays, a three-dimensional BIM model must be created as standard for the planning of new bridges, which contains all the planned information in great detail. Digital twins are a further development of this digitization concept. In digital twins of bridges, all relevant structural information is made available in real time over the entire service life of the structure. At the same time, the day-to-day tasks of the structural engineer, i.e. the verification of components, remain the same. The use of measurement data for the verification of structural components is an area of application that is increasingly becoming the focus of structural engineers. This so-called measurement-based verification management represents a possible application of the digital bridge twin. To do this, data of different types and origins must first be identified in order to determine which data is relevant for the verification process. This data must be prepared in a form that is suitable for integration into the digital twin.

The key point of the work is to formulate requirements for the measurement data, its meta information and the way in which it is structured. The correct definition of these requirements is of great importance for the subsequent integration with other information in the digital twin. The following subtasks can be dealt with in the work:

• Identification of relevant building data (from recalculations, diagnostic reports, inspection logs, monitoring data, etc.) for the verification process
• Researching the options for integrating measurement data into BIM and deriving the requirements for the "Monitoring" technical model
• Definition of the requirements for the structure, integration and processing of monitoring data in the digital twin for measurement-based verification management
• Development of a concept for the documentation and localization of the verification results in the digital twin

The specific task will be worked out individually after consultation.

Contact person:
Dipl.-Ing. Maria Walker
0351 463 39820

A - 20 Production-dependent design parameters for bridges

Detailed title: Design parameters from production for new bridge replacements in the parameterized design process

The bridge design for new replacement structures is a creative process with diverse requirements and boundary conditions and is supported by many project participants. The design process is often characterized by manual work and is therefore error-prone and time-consuming. The conventional design process can be optimized in times of high demand for new buildings and a simultaneous shortage of skilled workers, increasingly complex construction measures due to replacement buildings, growing demands on sustainability and shorter production times.

The aim of this work is to improve the design process from production and assembly through parameterization. Firstly, the typical planning process of a bridge structure is to be recorded and documented in the form of a flow chart. Secondly, the relevant design boundary conditions are to be recorded in tabular form in the form of parameters for database-based work. Thirdly, the design boundary conditions are to be transferred to a parameterized model (software: Grasshopper3D) and documented in a model manual. Fourthly, a bridge structure is to be (conceptually) designed for an example of design boundary conditions.

The details and structure of the task will be discussed with the student before the start of the course, depending on individual interests.

Contact person:
Jakob Grave, M.Sc.
030 220 777 74

A - 19 Type statics for frame bridges using parameterization and AI

Detailed title: Development of type statics for superstructures of frame bridges using parameterization and artificial intelligence

The majority of bridges in Germany are unique structures. While this is beneficial for building culture and sustainability in terms of material savings, it always results in a high planning effort. Nowadays, complex, semi-automated design and construction methods are increasingly being used to speed up planning. Automation (e.g. parameterization) is complex to implement. Before the widespread use of computer-aided calculation methods, so-called "type statics" were common (e.g. in the GDR). These enabled quick dimensioning and construction using diagrams and reference drawings.

The aim of this work is to explore the potential of type statics for superstructures of frame bridges using artificial intelligence methods in order to improve the design process. Firstly, previous and current type statics are to be researched and compared. Secondly, a parametric design of different abutment dimensions is to be carried out in order to generate an own type statics of a superstructure of frame bridges (software: Grasshopper3D, Sofistik, Python). Thirdly, the design results of different bridge superstructures are to be analyzed using AI methods. Fourthly, if necessary, the results are to be converted into user-friendly type statics and exemplary guide drawings are to be generated.

The task will be specified, detailed and structured with the student before work begins, depending on individual interests and scope.

Contact person:
Jakob Grave, M.Sc.
030 220 777 74

A - 7 Replacement construction of a crossing structure

In order to guarantee full availability, avoid further expensive repair measures and maintain the standard of the route, the replacement of the crossing structure is to be planned. The client wants a reinforced concrete solution. The traffic on the three-track line below is to be largely maintained. Only short track closures are possible.

In the course of the work, in-depth considerations of the construction technology and the development of the assembly technology for the elevated construction of the bridge and a final lowering into the final position are to be investigated. The construction conditions are to be statically verified. Further topics will be added as required.

Contact person:
Dr.-Ing. Jens Tusche (freelance lecturer)
0351 461 7840

A - 6 Investigation of variants of a railroad overpass

Detailed title: Investigation of variants of a railroad overpass in the course of a double-track line over Stauffen-Allee

In the north of D-Stadt, in the course of the double-track railroad line Gö-Stadt - D-Stadt, there was a steel bridge structure dating from 1914. Due to the poor condition of the bridge structure, two partial superstructures had already been replaced by temporary bridges. A new replacement structure is planned, taking into account the requirements of the railroad (platform in the bridge area) and the requirements of the city (clearance height 4.50 m). In the course of the work, technical and technological variants for the replacement construction are to be developed and compared. Further topics will be added as required.

Contact person:
Dr.-Ing. Jens Tusche (freelance lecturer)
0351 461 7840

A - 5 Investigation of variants of a double-track arch bridge

Detailed title: Investigation of variants of a double-track arch bridge using the example of the "Rö-Tal Viaduct" railroad overpass

The replacement or partial replacement of the "Rö-Tal Viaduct" railroad overpass is to be planned in order to ensure full availability, to avoid further expensive repair measures and in the interest of maintaining the line standard. The arched bridge carries a double-track railroad line over a waterway/valley. In the course of the work, technical and technological variants are to be developed and compared. Further topics will be added as required.

Contact person:
Dr.-Ing. Jens Tusche (freelance lecturer)
0351 461 7840

A - 4 Study for a complete or partial new construction of a viaduct

Detailed title: Current railroad bridge construction projects - project study on possible variants for a complete or partial new construction of the existing viaduct

You can't miss it when driving through O-Stadt: the viaduct - a monstrous structure, gray, dirty, unsightly. Many citizens see the viaduct (built in 1877) as an eyesore in the cityscape. The fact that the viaduct looks like this today is also due to the town's past, which was heavily influenced by mining. The subsidence caused by mining caused enormous problems. For example, in the early 1950s, the viaduct suffered arch subsidence, which could ultimately only be repaired by concreting over the arches. The surface of the earth had sunk up to 17 m in some places between the districts.

The structure, colloquially known as the "dam wall", has been the subject of discussion for years. The town would like to see it demolished and rebuilt. In the course of the work, technical and technological solutions are to be developed and compared. Further topics will be added as required.

Contact person:
Dr.-Ing. Jens Tusche (freelance lecturer)
0351 461 7840

A - 1 Bridge construction

SRP Schneider + Partner Ingenieur-Consult GmbH is an independent engineering company with approx. 100 employees. Our head office is located in Kronach/Upper Franconia. We advise, plan and supervise in all areas of Civil Engineering, both in Germany and abroad.

We offer interested students the opportunity to supervise their project or dissertation in the field of bridge construction. Together with you and the TU Dresden, we would select a topic from the field. Experienced engineers are available to answer your questions. Perhaps this will lead to a professional career at SRP.

Contact person:
Christian Neubauer (SRP Schneider + Partner Ingenieur-Consult GmbH, Kronach)