8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen
Filtern
Dokumenttyp
- Zeitschriftenartikel (17)
- Vortrag (17)
- Beitrag zu einem Tagungsband (13)
- Buchkapitel (4)
- Forschungsdatensatz (4)
- Posterpräsentation (3)
- Dissertation (1)
- Handbuch (1)
- Forschungsbericht (1)
Schlagworte
- NDT (11)
- Existing structures (10)
- Nachrechnung (10)
- Non-destructive testing (10)
- Reliability (10)
- Messunsicherheit (8)
- Concrete (7)
- Measurement uncertainty (7)
- Validation (7)
- Zerstörungsfreie Prüfung (7)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (17)
Relevant, abgesichert, vergleichbar – ZfP-Ergebnisse bei der Zuverlässigkeitsbewertung von Bauwerken
(2024)
Die Nachrechnung, d. h. die Zuverlässigkeitsbewertung von bestehenden Brücken, ist aufgrund der alternden Infrastruktur und sich verändernden Anforderungen an die Bauwerke eine fortwährend große Herausforderung in Wissenschaft, Praxis und Standardisierung. Ein wesentlicher Vorteil bei der Nachrechnung besteht gegenüber dem Neubauentwurf in der Möglichkeit, Informationen über den tatsächlichen Zustand der Bauwerke zu erheben – im Idealfall ohne wesentliche destruktive Eingriffe in die Bausubstanz. Deren Verwendung bei der Zuverlässigkeitsanalyse dient der Zuschärfung von Berechnungsmodellen und ermöglicht realitätsnähere Bauwerksbeurteilungen. Die Einbeziehung von Messdaten bei der Zuverlässigkeitsbewertung setzt jedoch voraus, dass die Qualität der gemessenen Informationen bekannt und deren Vergleichbarkeit sichergestellt ist. Darüber hinaus sollte die Relevanz der messbaren Informationen beziffert werden, um wirtschaftliche Inspektionen am Bauwerk gezielt durchführen zu können.
In diesem Beitrag wird am Beispiel von Ultraschall- und Radarmessungen an einer Spannbetonbrücke gezeigt, wie ZfP-Ergebnisse bei der Zuverlässigkeitsbewertung von Bestandsbauwerken mit probabilistischen Methoden genutzt werden können. Betrachtet werden innere geometrische Abmessungen wie die Lage der Bewehrung oder von Spanngliedern. Die Relevanz der messbaren Informationen wird anhand von Sensitivitätsanalysen beziffert. Messunsicherheitsbetrachtungen dienen der Bezifferung der Qualität der gemessenen Informationen und der Gewährleistung deren Vergleichbarkeit. Abschließend werden die möglichen Auswirkungen der Berücksichtigung von ZfP-Ergebnissen auf die Bauwerkszuverlässigkeit in einem Nachweis einer Spannbetonbrücke gemäß Eurocode demonstriert.
Chapter 6: Case studies
(2023)
The through-life management of our constantly ageing infrastructure is a basic requirement in order to ensure their structural safety and serviceability. Each structure experiences deterioration processes with time leading to a decrease of structural safety and serviceability. The design of new structures considers the expected deterioration for a defined period, the design service life. However, a frequent survey of structural safety controlling structural condition should be mandatory and a maintenance plan should be an integral part of the design. In addition, many structures have exceeded their design service life already or are very close to it leading to an increasing demand for condition assessment. On the one hand, assumptions made during design are not valid any more due to change of the loads, e.g., increasing traffic loads in terms of number and weights. On the other hand, design codes evolved over time in such a way that existing structures do not comply with today’s standards. In all these cases, the through-life management is an important tool to maintain the accessibility of existing structures with known reliability.
In line with the new Model Code for Concrete Structures, which includes guidance for both – design of new structures and assessment of existing structures, the Task Group 3.3 focused on the compilation of a state-of-the-art guideline for the through-life management of existing concrete structures, including:
Data acquisition by testing and monitoring techniques;
Condition assessment for the evaluation of existing structures;
Performance prediction using advanced methods;
Decision-making procedures to perform a complete assessment of existing structure.
The overall objective of the through-life management is the assessment of the current condition and the estimation of the remaining service life under consideration of all boundary conditions.
Information about an existing structure can be collected at certain costs to evaluate the reliability and condition as realistically as necessary. This information can be relevant or irrelevant, true or biased, precise or imprecise. The incorporation of relevant and quality-assessed measured information into reliability reassessment offers the chance to extend remaining lifetimes and support decision making about optimal actions or maintenance strategies. This paper shows recent developments in a national research project that aims to produce a guideline on the NDT-based, structure-specific modification of partial safety factors. The general methodology, results from recalculations according to the Eurocodes and metrologically solvable testing tasks relevant in the recalculation of the concrete bridges are shown and compared with the non-destructive testing methods applicable to concrete bridges. A case study is used to demonstrate that as-built drawings, in this case of the positions of tendons and shear reinforcement, can be verified using the radar method.
A major advantage in the reassessment of existing structures is the possibility of including measured data that describe the actual properties and the current condition of the structure to be reassessed. Currently, the incorporation of such measured information is mostly unregulated. However, the use of measurement results is vitally important, since a measured data-based improvement of the computation models level of approximation can lead at least to more meaningful results, possibly to extended remaining life times of the structure and in the best case to a saving of resources. Conversely, not appreciating well measurable and relevant information can be equated with a waste of resources. In this paper, a concept for the comparable use of non-destructively measured data as basic variables in probabilistic reliability assessments is outlined and examined using a typical prestressed concrete road bridge as a case-study. An essential requirement is the calculation of measurement uncertainties in order to evaluate the quality of the measurement results comparably. In conclusion, the example of ultrasonic and radar measurement data is used to demonstrate the effects that the incorporation of the measured information has on the reliability of the structure.
This presentation summarizes recent developments within the scope of the national pre-standardization project “ZfPStatik”, which aims to prepare a guideline about NDT-supported structural analyses. The focus is on the purposeful and explicit utilization of geometrical tendon and reinforcement bar positions measured on-site in reliability analysis — shown by means of a prestressed concrete bridge as case study.
Reliability assessment of existing concrete bridges with geometrical NDT results - Case studies
(2023)
The results of and the validity in reliability assessment of existing bridges essentially depend on the information available about the considered system. Information about the actual condition as well as structural and material characteristics can be observed on-site to refine the computation models used in assessment. Non-destructive testing (NDT) methods for concrete structures are capable of reconstructing missing, questioned, or inconsistent as-built plans. This contribution summarizes recent developments within the scope of the national pre-standardization project “ZfPStatik”, which aims to prepare a guideline about NDT-supported structural analyses. The focus is on the purposeful and explicit utilization of geometrical tendon and reinforcement bar positions (measured on-site using the ultrasound echo and ground penetrating radar (GPR) techniques) in probabilistic reliability analyses — shown by means of real case studies. The well-established first order reliability method is applied to different concrete bridges, which are typical for the German road bridge stock, to demonstrate the utility of incorporating quality-evaluated NDT-results in terms of changes in structural reliability.