A multi-level strategy for successively improved structural analysis of existing concrete bridges: examination using a prestressed concrete bridge tested to failure

Prestressed structures are commonly used all over the world. They might be subjected to degradation, such as corrosion of the prestressing steel. This can influence the resistance of these structures and induce early failure. Hence, prediction of the corrosion level is important in the assessment of existing prestressed structures. For this purpose, the corrosion process and the accompanying influences on the structure should be modeled. For reinforced concrete (RC) structures, a lot of research and guidelines are available to model the corrosion process. Nevertheless, this corrosion process might differ for prestressed structures, due to the different structural composition, the different geometry of the strands or tendons compared with reinforcement bars, the presence of the prestress, and so on. Moreover, for posttensioned structures, initiation and propagation of corrosion are even more different from corrosion in RC structures, due to the location of the steel in ducts and the lack of direct contact with the surrounding concrete. In this paper, a state‐of‐the‐art on the assessment of prestressed and posttensioned structures subjected to corrosion is given based on a literature review. Different models for the corrosion process and their influence on the structure are discussed. Comparison is made between reinforced, prestressed, and posttensioned structures. Furthermore, some assessment procedures are indicated and relevant topics for further research are given.

“…Bagge et al 55 investigated a PC bridge and tested it to failure. The corresponding finite element model consists of a combination of shell, beam, solid, and truss elements.…”

Section: Modeling Degradation Due To Prestress Corrosionmentioning

confidence: 99%

Assessment of corroded prestressed and posttensioned concrete structures: A review

Vereecken

Botte

Lombaert

et al. 2021

“…15 This has also been shown for Kiruna Bridge, where the shear model used for the initial structural assessment was not able to predict the shear failure of the girders accurately. 14 Enhanced analysis was therefore used in order to understand the structural behavior of the bridge better and to utilize its ultimate "hidden" capacity. Since a shear-related failure was indicated as critical, the structural model was adopted to T A B L E 3 Permitted traffic loads in the structural elements according to initial structural assessment using code and in situ tested material properties, respectively *Critical classification vehicle according to Figure 5 labeled with superscript.…”

Section: Generalmentioning

confidence: 99%

“…In lack of bridgespecific data, the tensile strength (f ctm = 2.0 MPa, V fct = 24%) and the fracture energy (G fm = 140 N/m, V Gf = 53%) were derived from previous experience, based on tests of another concrete bridge constructed around the same time. 14,63 The nonlinear concrete was represented by a 3D constitutive model (CC3DNonLinCementitious), based on the strain decomposition concept 64 where the elastic, plastic, and fracturing strains are separated to give compatibility between fracture and plasticity models; see Červenka and Papanikolaou 65 for detailed description. For concrete in tension, a smeared crack concept was used with the Rankine failure criterion.…”

Section: Constitutive Modelsmentioning

confidence: 99%

Demonstration and examination of a procedure for successively improved structural assessment of concrete bridges

Bagge

2019

Self Cite

Assessing the load‐carrying capacity of existing bridges is an important infrastructure management task. In order to support the structural assessment of concrete bridges better, a procedure has been proposed, based on successively improving the bridge analysis. A multilevel strategy for structural analysis has been combined with concepts for verification of the desired safety margin, thus providing tools for engineers to model the structural behavior of bridges more accurately when necessary. This paper describes the procedure as applied to a prestressed concrete girder bridge, with use of experiences from the previous failure tests and associated evaluations of the bridge. Initial structural assessment indicated the critical failure mode to be due to shear in one of the girders; however, the enhanced analysis showed a complex failure involving both the girder and the bridge deck slab. Improving the structural analysis using nonlinear FE analysis for the loading initially identified as critical, increased the permitted axle loads on the bridge to 12 to 14 times those given by traditional and standardized assessment methods, depending on the concept used for safety verification. The model uncertainty was crucial for the verification of the structural safety and has to be properly taken into account. However, there are few recommendations, with regard to model uncertainties, on the application of nonlinear FE analysis, and detailed guidelines should be used for the modeling procedure in order to reduce analyst‐dependent variability in the results. The presented study demonstrates the applicability and the advantages of using the proposed procedure for successively improved analysis for bridge assessment.

“…A better approach for estimating general prestress losses is the one applied in Sousa et al 10 , where prestress losses are updated based on measured displacements. Literature on destructive assessment of prestressed structures can be found in Bagge et al 11 ; Huber et al 1 ; Strauss et al 12 . Nevertheless, these works do not account for relevant uncertainties and lack a probabilistic approach.…”

Section: Introductionmentioning

confidence: 99%

Assessment of posttensioned concrete beams from the 1940s: Large‐scale load testing, numerical analysis and Bayesian assessment of prestressing losses

Botte

Vereecken

Taerwe

et al. 2021

The UCO textile factory was built in Ghent (Belgium) in the period 1947–1948. The roof structure covered an area of about 35,000 m2 and consisted of 100 primary beams and 600 secondary beams. These post‐tensioned beams were designed by prof. Gustave Magnel, who was a world‐leading expert in the field of prestressed concrete. This project was one of the first important large‐scale applications of prestressed concrete in industrial buildings in the world and also the first large scale application of on site prefabrication. Recently, part of the factory building was demolished and a primary beam and secondary beam of the roof structure were transferred to the Magnel‐Vandepitte Laboratory for Building Materials and Structures for testing at an age of approximately 70 years. The primary beams have a span of 20.5 m and a maximum depth of 1.7 m. The secondary beams have a span of 13.7 m and a depth of 1 m. Only prestressing tendons (Blaton–Magnel system with Ø 5 mm wires) were present in the beams but no passive reinforcement nor stirrups are present except for the reinforcement in the corbels and the end blocks. This article describes the results of the loading tests up to failure on the beams. The experimental results are compared with results from analytical calculations. Furthermore, a nonlinear finite element model was developed and validated. Subsequently, this numerical model was used for a Bayesian‐based assessment of the prestressing losses in these beams. As such, the article presents novel information related to time‐dependent prestress losses after 70 years in service as well as the structural performance of such existing post‐tensioned concrete structures dating from that pioneering period.