Promotion Angela Schmidt

On 28.02.2022, Angela Schmidt successfully defended her scientific thesis within the framework of the doctoral procedure with the topic "Shape optimization of compression members from concrete and reinforced concrete".

Nowadays, the vast majority of (reinforced) concrete columns are designed with a rectangular or circular cross-section and a constant shape along the length of the column. However, depending on the structural boundary conditions and the actual load, there are often stronger and weaker stressed areas within a compression member. In the present work, therefore, a shape optimization of (reinforced) concrete columns is carried out and the resulting volume saving or load increase potential is shown and analyzed. For this purpose, characteristic load cases of a typical reinforced concrete skeleton structure are used. Preliminary considerations led to the fact that the investigations concentrate mainly on centrally loaded columns with buckling risk as well as on eccentrically loaded columns where the bending stress results from a frame effect of the load-bearing system.

For centrally loaded columns with buckling risk, results already exist in the literature on
shape and cross-section optimization with unbreakable and linear-elastic material behavior. The data were analyzed, verified and supplemented with investigations on the effects of elastic support, imperfection and the influence of nonlinear material behavior. The theoretical considerations showed that the optimum column shape depends on the respective buckling shape and thus varies according to the conditions of support. For verification purposes, preliminary tests were first carried out on rectangular columns with a constant shape and varying component length. These served to better estimate the stability behavior as a function of slenderness, the existing imperfection size and to determine the degree of clamping achieved for the selected test rig. Based on the results, experimental verification of the influence of shape and cross-section was carried out. In all cases, the ultimate loads determined in the tests could be compared very well with the theoretical approaches of the theory of elasticity and could be recalculated.

The shape optimization of eccentrically pressed columns was carried out for different ratios of a moment and normal force loading. In order to achieve a distinction from the considerations of stability failure, the investigations are limited to an occurring material failure. In addition to finding the shape, a material combination is also selected in accordance with the loading, in which both the steel and the concrete are utilized as much as possible. The optimization is carried out iteratively on a column segmented over its height under the criterion of achieving a uniform stress level in the component. The optimized column shapes obtained in this way are based on the bending moment curve. To verify the results, a load case was investigated experimentally. This series of tests confirmed the selected calculation and optimization method.

The doctoral committee was chaired by Prof. Dr.-Ing. habil. Ivo Herle (TU Dresden). Reviewers were Prof. Dr. Manfred Curbach (TU Dresden), Prof. Dr. Peter Mark (Ruhr-Universität Bochum) and Prof. Dr. Oliver Fischer (TU Munich). In addition, Prof. Dr. Peer Haller (TU Dresden) was involved as a further member of the doctoral committee.

We warmly congratulate Angela Schmidt on completing her doctorate and wish her all the best and every success for the future.