abgeschlossene Arbeiten

Due to their advantages in manufacturing and assembly, bolted end plate connections are now increasingly used in structures subject to fatigue loads, which means that these connections—and especially the high-strength, preloaded bolts—must also be designed for fatigue. In contrast to the design of end plates under load-bearing conditions as specified in the GZT, there are currently no suitable calculation models available for end plates under service loads that can be used to determine the fatigue stresses in the bolts. This master’s thesis therefore addresses the question of how the fatigue stresses in prestressed, high-strength bolts under service loads can be determined in a realistic manner.

To the handout

This master's thesis focused on the numerical analysis of screw stress in end-plate connections under service loads. The results of the numerical analysis highlight, in particular, the influence of geometric imperfections on the load-bearing behavior and form the basis for the development of a semi-empirical calculation model that enables practical engineering applications for the design of bolted connections in end plates under service loads.

Assessing the load-bearing capacity of historic cast-iron columns often presents significant challenges due to the manufacturing process and the nonlinear and inhomogeneous material behavior. As part of this master’s thesis, the load-bearing capacity of the cast-iron column was determined using the Abaqus FEA program and the simplified design method according to Käpplein, and the results were compared. The load-bearing capacity of the cast-iron column was verified for the repurposing of the floors above it.

This master's thesis focuses on the design and structural analysis of a steel pedestrian bridge over the Wahlebach. The new structural design of the bridge consists of two longitudinal girders made of rolled sections, which are connected at regular intervals by cross-beams. As part of this work, structural analyses were performed for the main structural system as well as for the relevant details. Subsequently, the bridge was analyzed for susceptibility to vibrations caused by pedestrian traffic.

This master's thesis examines the fatigue damage that has occurred in the round steel hangers of the Kassel Wire Bridge. The bridge was modeled using FEA software and analyzed through dynamic calculations. It was found that the bridge’s natural frequencies lie within the range of the excitation frequencies generated by pedestrians, and that excitation of the torsional mode, in particular, leads to twisting in the round hangers. Due to the design of the round hangers, this twisting cannot occur freely, resulting in alternating moment stresses in the round hangers, which were identified as the cause of the fatigue damage.

This master’s thesis examines the remaining service life of the Weser Bridge in Rinteln. For this purpose, the suspension rods and the tension cable were identified as components highly susceptible to fatigue, and their remaining service life was determined using fracture mechanics analysis. The results show that the tension cable, in particular, is subject to high stresses and that the calculated remaining service life, using the simplified method according to Eurocode, would be zero. This highlights the need for further investigations as well as possible reinforcement measures.

As part of this master’s thesis, a small-scale test specimen of a flange-web connection was developed using an equivalent stress field and equivalent notch stresses, similar to the large-scale test specimen from the master’s thesis “Fatigue of Flange-Web Connections.” To this end, an engineering model was developed as a preliminary analysis, and based on this, a numerical study was conducted using the Abaqus FEA program and the notched stress concept.

This master’s thesis examines the suitability of two methods for predicting vortex-induced transverse vibrations. These are vibrations that can arise from the alternating detachment of vortices from angular structures. To evaluate the computational results of these methods, a wind tunnel test was designed and conducted to observe the vortex-induced transverse vibrations. Subsequently, the predicted amplitudes were compared with the calculated amplitudes, and the differences were identified.

As part of this master’s thesis, a small-scale test specimen of a flange-web connection was developed using an equivalent stress field and equivalent notch stresses, similar to the large-scale test specimen from the master’s thesis “Fatigue of Flange-Web Connections.” To this end, an engineering model was developed as a preliminary analysis, and based on this, a numerical study was conducted using the Abaqus FEA program and the notched stress concept.

This master's thesis deals with the design and sizing of a replacement road bridge over the Ahne River. The focus was on developing a cost-effective composite bridge structure, examining various design options, and verifying the structural capacity and serviceability of the bridge.

As part of this study, block shear failure in bolted steel structural connections was investigated experimentally and numerically. The results highlight the influence of unsupported connections on block shear resistance and indicate a need for further development of the current design rules in Eurocode 3.

My master's thesis focused on the numerical analysis of the Saumblech web-to-flange connection in non-accessible, fully welded box girders used in bridge construction. To this end, the fatigue strength was determined using the notched stress concept in the Abaqus FEM program and compared with the simplified RE-ING method. A significant difference was observed in the utilization of the fatigue analysis capacity between the two methods.

This master’s thesis investigates the evidence for shear failure in bolted steel connections as described in Eurocode 3. The results show that the current Eurocode provisions sometimes conservatively estimate the load-carrying capacity of connections and that shear failure can become a dominant factor in certain bolt configurations. Furthermore, the hypothesis is proposed that this failure mechanism was already partially taken into account in earlier empirical verifications under DIN 18800 and should be investigated through further testing as part of a subsequent master’s thesis.

This thesis investigates the determination of effective notch stresses in welded steel components using the finite element software Abaqus, in accordance with IIW guidelines. The substructure method is employed to reduce computation times and is evaluated for its applicability. The results show that notches lead to a significant increase in stress and that the substructure method is an efficient and reliable approach for determining notch stresses.

The master's thesis focused on modeling a guyed wind measurement tower in a specified FEM software environment to investigate its dynamic behavior. To reduce the computational load, the truss structure was simplified to an equivalent beam. For verification, the model was compared with previous studies, and good agreement regarding the dynamic behavior was achieved.

The bachelor’s thesis focused on the design and construction of an aluminum pedestrian bridge over the Ahna River. The new structural design of the bridge consists of two longitudinal girders arranged in a truss configuration, connected at regular intervals by cross-beams. As part of the thesis, structural analyses were performed for the main structural system as well as for the relevant details. Subsequently, the bridge was also analyzed for susceptibility to vibrations caused by pedestrian traffic.