Impact on structures subjected to normal force
Table of contents
Project data
| Titel | Title Promotionsprojekt A6/III: Verstärkung normalkraftbeanspruchter Strukturen gegen eine Stoßbelastung quer zur Bauteilachse als Teilprojekt des GRK 2250 | Doctoral project A6/III: Strengthening of structures subjected to normal forces against an impact load transverse to the normal force as part of the RTG 2250 Förderer | Funding Deutsche Forschungsgemeinschaft (DFG) / GRK 2250 Zeitraum | Period 05/2023 – 04/2026 (3. Kohorte | 3rd cohort) |
Report in the year book 2024/25
Columns under impact
In the doctoral project A6/III of the Research Training Group (RTG) 2250, the focus is on axially loaded reinforced concrete components—such as columns—subjected to transverse impact loading. The primary objective of this project is to experimentally investigate the structural dynamic behavior of these elements under such loading conditions, and propose different strengthening methods and materials to enhance their resilience against such loads. Understanding the response of axially loaded structures is of critical importance, as significant damage to columns or walls can result from events such as vehicle collisions or rockfalls.
Damage of the axially-loaded specimen after impact loading in the drop tower of TU Dresden
The initial steps of this project involve studying the existing methodologies for combining impact and axial load test setups used by other researchers and selecting an appropriate approach for the drop tower at the Otto Mohr Laboratory. Due to certain constraints, such as the specimen dimensions having to fit in the drop tower, the optimal solution is the internal post-tensioning of concrete columns. For this purpose, two unbounded prestressing bars were placed in the center height of the column section and were post-tensioned using two hydraulic cylinders.
Using sandbags in front of the prestressing bars to ensure safety
The next step of this project included selecting effective materials for strengthening axially loaded concrete members. Three strengthening systems were selected to wrap the column specimens: TRC (textile-reinforced concrete, consisting of L-shaped carbon textiles combined with Pagel TF10), SHCC (strain-hardening cementitious composite), and TR-SHCC (a hybrid system combining L-shaped carbon textiles with SHCC). Due to the unavailability of fully deformable textiles in the market, four L-shaped textiles were used to cover all sides of the column specimens, forming two layers of textile reinforcement. The TRC-strengthened specimens were prepared using the lamination method, while the SHCC- and TR-SHCC-strengthened specimens were applied via robotic shotcreting. Both unstrengthened and strengthened specimens were tested under impact loading in the drop tower located at the Otto Mohr Laboratory. The results demonstrated that the strengthened specimens exhibited significantly higher resistance to impact loads, whereas the unstrengthened specimens experienced severe concrete crushing, even under low-velocity impact events.
Report in the year book 2023
Transverse impact on concrete columns
Principle of an axial load application setup for a column to be tested under impact
The doctoral project A6/III is part of the third cohort of the RTG 2250 program, in which one post-doctoral and twelve doctoral candidates working together in different institutes of TU Dresden and at IPF Dresden synergically. RTG 2250 is a Research Training Group that focuses on developing innovative mineral-bonded composite-based strengthening methods for structures subjected to impact loading. The goal of the A6/III project is to experimentally evaluate the structural behavior of axially loaded reinforced concrete members under impact loading. Investigating axially loaded structures is important as there are various real-life examples of severe column or wall damage after a vehicle collision or rock fall.
The first steps of this project include studying the previous combinations of impact and axial load test setups used by other researchers and choosing an appropriate one to use in the drop tower located at the Otto Mohr Laboratory. There are some limitations regarding the dimension of the specimen and the high-speed camera view on the specimen in the drop tower, therefore we decided to use a hydraulic jack (which needs less space compared to other methods like external rebars and a mass or using disc springs in addition to the hydraulic jack) for axial load application. The next step is to select suitable materials for strengthening axially-loaded concrete members (such as textile-reinforced concrete, strain-hardening cementitious composite (SHCC), and damping materials) and to test specimens with and without layers of these strengthening materials under different impact energies to provide the best strengthening method that has appropriate strengthening and energy-absorbing properties. Finally, the results will be evaluated and an engineering model will be presented for such concrete members under impact loading.
The Reserach Training Group 2250 is not only about science but also an opportunity to develop our soft skills as well as hard skills. Participating in annual summer schools and winter workshops in which we need to present our current research state and find probable collaborations in the team is a good example of the combination of hard and soft skills development.