precision limits of lifetime prognoses - experimental and numerical investigation of an existent bridge structure subjected to fatigue
Final Report Abstract
One of the greatest challenges facing civil engineers today is the assessment, maintenance, and repair of engineering structures along roads and railways. Responsibilities, priorities, acceptable sequences of action in the transport network, the most common types of deficiencies, and their probable causes are now largely known. Nevertheless, despite all efforts to monitor and predict remaining service lives, those responsible must still be prepared for damage to occur unexpectedly and without much warning in advance. This applies to damage mechanisms such as stress corrosion cracking, but also to the fatigue of prestressing steel, which progresses largely unnoticed during use and can suddenly have devastating consequences. Conventional monitoring is passive. However, experience shows that active intervention can often lead to new solutions. This is precisely where the project comes in during its third funding phase, with two instruments for active influence. Firstly, the active induction of temperature gradients in bridges regulates and reduces real temperature stress. This is shown on a scaled demonstrator as well as on the reference bridge, a flyover at the Nordfriedhof in Düsseldorf. The control system considers the thermal inertia of the massive structure and is based on numerically predicted temperature distributions at the cross-section, which are compared with distributions recorded experimentally by fiber optics and thermocouples. The input remains locally limited and has been proven not to damage the structure. The second instrument is an active service life indicator in form of a replaceable monitoring element installed on site to quantify the progress of fatigue using external prestressing wires comparable to the existing ones. This can only be verified in the laboratory, as creep effects of the adhesive fixing the wires prevent time-stable prestressing. The interim goal of quantifying the remaining service life potential of installed prestressing steel using individual SN-curves with the transfer of deviating boundary conditions from the existing structure and indicator is nevertheless achieved. A concept for including such individual SN-curves, e.g., based on approval data in building documents, has been developed and brought into the discussion.
Link to the final report
https://doi.org/10.34657/26885
Publications
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Lifetime predictions of prestressed concrete bridges—Evaluating parameters of relevance using Sobol' indices. Civil Engineering Design, 4(5-6), 143-153.
Sanio, David; Ahrens, Mark Alexander & Mark, Peter
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Modification of Variance-Based Sensitivity Indices for Stochastic Evaluation of Monitoring Measures. Infrastructures, 6(11), 149.
Sanio, David; Ahrens, Mark Alexander & Mark, Peter
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Steering of continuity stresses in beam structures by temperature induction. Engineering Structures, 229, 111621.
Löschmann, Jens; Stolzuoli, Niccolò; Ahrens, Mark Alexander & Mark, Peter
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Temperaturinduktion in Betontragwerke. Beton- und Stahlbetonbau, 116(7), 539-550.
Clauß, Felix; Löschmann, Jens; Ahrens, Mark Alexander & Mark, Peter
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Temperature Induction into RC Structures. Proc. 19th MASE Int. Symp., Ed. Cvetkovska, M., Macedonian Ass. Struct. Eng., 2022, pp. 733-740.
Löschmann, J.; Sanio, D. & Mark, P.
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Shifted Experimental S-N curves for fatigue verification of structures to consider different bond conditions, In: ReConStruct: Resilient Concrete Structures: Proc. 2024 fib Symp. Henry, R.S. & Palermo, A. (Eds.), Nov. 2024, Christchurch, New Zealand, pp. 233-241.
Heußner, L.; Ahrens, M.A. & Mark, P.
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Betriebsfestigkeitsbasierter Ermüdungsnachweis mit bauwerksspezifischen Wöhlerlinien. Beton- und Stahlbetonbau, 120(4), 298-307.
Heußner, Lukas; Ahrens, Mark Alexander & Mark, Peter
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Compensation of vertical temperature gradients on bridges using temperature induction. Open Engineering Inc.
Heussner, Lukas; Sanio, David; Ahrens, Mark Alexander & Mark, Peter
