Formulation of a consistent crack width calculation method for reinforced concrete members
Doctoral thesis
Published version
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https://hdl.handle.net/11250/3130253Utgivelsesdato
2024Metadata
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Terjesen, O. (2024). Formulation of a consistent crack width calculation method for reinforced concrete members. [Doctoral dissertation]. University of Agder.Sammendrag
Predicting crack widths in reinforced concrete structures is essential for Serviceability Limit State (SLS) Design. Crack widths that exceed a certain limit may impair the functionality of a structure, limit its use and reduce the service life. Cracking usually occurs with irregular distribution and different crack widths along the members. Despite a century of research, predicting them accurately and consistently is still difficult, as shown by Terjesen et al. [1]. On the other hand, the consequences of cracks related to functionality, durability, aesthetics, and economy are significant, and discussions in the research environments are ongoing [2, 3]. This thesis focuses on different calculation methods to predict crack widths in standard and large-scale concrete structures subjected to uniaxial loading conditions. Large-scale concrete structures are, in this thesis, synonymous with RC structures, which have member dimensions that can be up to several meters in height, sections with large reinforcing bar diameters, and large covers. The investigated calculation methods range from computer-based simulations using Nonlinear Finite Element Analysis (NLFEA) to design code formulations, i.e., Eurocode 2 (EC2, FprEC2, DIN) [4-6], fib Model Code (MC2010, MC2020) [7, 8] in addition to the Modified Tension Chord Model (MTCM) [9] and the simplified version of MTCM (SMTCM) developed in this thesis. Evaluation of the semi-empirical formulas recommended by Eurocode 2, fib Model Codes, and the German National Annex (DIN) to EC2 showed that they may predict crack widths inconsistently. The assumption of a constant mean bondstress distribution over the transfer length independent of the load level can perhaps explain the reasons for continuously calibrating the formulas, among others: i) using a lower bound for the difference in mean strains for steel and concrete to differentiate between a crack formation and a stabilized crack stage and ii) the cover addition in the crack spacing formulas. The simplified version of the MTCM denoted SMTCM was formulated by using the basic principles in solid mechanics applying the closed form solution of a Comparatively Lightly Loaded Members (CLLM) to predict a certain mean behaviour of the Comparitively Heavily Loaded Member (CHLM) as a simplification (SCHLM). The SMTCM was shown to predict the crack width to an excellent extent for RC beams and slabs in bending and RC ties in tension. Due to the mechanical formulation of the model, there might be significant advantages to apply in cases where there are particular risks of large cracks, e.g. i) at changes of sections, ii) near concentrated load, iii) positions where rebars are curtailed and iv) areas of high bond stress, particularly at the end of laps v) multilayered reinforcement combined with large covers.
Består av
Paper Ia: Larsen, I. L., Terjesen, O., Thorstensen, R. T., & Kanstad, T. (2019). Use of Concrete for Road Infrastructure: A SWOT Analysis Related to the three Catchwords Sustainability, Industrialisation and Digitalisation. Nordic Concrete Research, 60(1), 31-50. doi: 10.2478/ncr-2019-0007. Published version. Full-text is available in AURA as a separate file: https://hdl.handle.net/11250/2994363.Paper Ib: Terjesen, O., Kanstad, T., and Tan, R. (2022). Application of NLFEA for crack width calculations in SLS. Computational Modelling of Concrete and Concrete Structures. In Meschke, Pichler & Rots (Eds), Proceedings of the 9th EURO-C 2022 conference on computational methods and numerical models for the analysis of concrete and concrete structures. doi: 10.1201/9781003316404-30. Published version. Full-text is not available in AURA as a separate file.
Paper II: Terjesen, O., Kanstad, T., and Tan, R. (2024). Performance study of crack width calculation methods according to Eurocodes, fib model codes and the modified tension chord model. Structural Concrete, 1-25. doi: 10.1002/suco.202300367. Published version. Full-text is not available in AURA as a separate file.
Paper III: Terjesen, O., Kanstad, T., and Tan, R. (Forthcomming). Simplified Modified Tension Chord Model – an alternative crack width calculation model to Eurocode 2 and fib Model Codes. Submitted version. Full-text is not available in AURA as a separate file.