Recalculation of arched bridges
Table of contents
Project data
| Titel | Title Nachrechnung von Gewölbebrücken | Recalculation of arched bridges Förederer | Funding |
Report from annual report 2024/25
Load tests on railroad arch bridges
Train crossing during the load test
Arch bridges are among the oldest structures in the Deutsche Bahn network and are still an important part of the railroad infrastructure today. Arch bridges are known for their durability, robustness and good-naturedness in the case of load increases and external influences. But yet they are often demolished due to calculated load-bearing capacity deficits and replaced by frame bridges made of reinforced concrete. The reason for this are the current verification concepts, which do not represent the load-bearing behavior of arch bridges realistically enough, although previous experimental investigations indicate high load-bearing reserves. In order to simplify the maintenance of these structures and thus reduce costs and emissions, a series of load tests are being carried out on vaulted bridges in a joint research project between DB InfraGO AG and TU Dresden. The aim is to gain knowledge of the load-bearing behavior in order to subsequently calibrate numerical models with measured values and derive simplified verification concepts. The basis for the selection of arched bridges for the load tests is a comprehensive evaluation of existing structures. Representative structures can thus be selected and the results transferred to the bridge stock.
Measurement setup of for the load test on a brick arch bridge
The structures are loaded by a 95-ton, six-axle diesel locomotive. Static loads as well as dynamic passages and braking tests are carried out at different speeds. The structural reactions are recorded using two independent measurement concepts: an electromechanical concept based on inductive displacement transducers and an optical measuring system with laser tracker and fine level. This allows to record the selected measured values in the relevant areas. Deformations are measured in the crests, quarter points and transoms of the structures. Further, the inclination of the abutments, crack openings and settlement of the adjacent subsoil are recorded. In the next step, the load tests are mapped numerically and realistically calibrated using the measured values. Parameter studies on decisive influences on the load-bearing behavior of arch bridges as well as comparative evaluations can provide generally valid and transferable findings.
Report from annual report 2023
Load-bearing behavior of railroad arch bridges
Load test of the arch bridge Schöninger Straße in Helmstedt
Bridges made of stone arches have been built for centuries, making them one of the oldest types of bridge construction. The comparatively high average age of arch bridges speaks for the durability of this type of construction. They still account for a large proportion of the bridges in the network of Deutsche Bahn today: around a quarter of DB’s 26,000 bridge structures are arch bridges. Although some of these structures still have a high residual load-bearing capacity, they are often replaced by reinforced concrete frame structures. The reason for this is usually poor condition due to external damage.
Even the structures were designed for much lower traffic loads, they can also meet the requirements of current and future traffic. This often requires constructive measures, such as increasing the safety space, and also static verifications of the load-bearing capacity. Due to the large number of structures, maximum preservation of the substance cannot be achieved with individual solutions for each structure. The aim of the research project is therefore to derive standardized recalculation concepts for railroad arch bridges so that the preservation of these structures can be simplified. This not only preserves building culture and reduces costs, but also contributes to climate protection.
The first step was to evaluate the existing building stock in order to identify the types of structure that occur particularly frequently. In the course of a geometric classification based on as-built plans, a strong dependence of the geometry of an arched bridge on the ratio of arch span to clear width was shown. On this basis, the structures can be divided into three clusters with associated geometric parameters. A validation based on occurring damage confirmed different damage mechanisms per cluster, which in turn indicate different load-bearing behavior.
In the next step, the load-bearing behavior of typical arch bridges will be analyzed. This involves complex finite element simulations, which can be calibrated with load tests on real structures.