In general, deflection should be calculated taking into account both the bending and shear contributions. According to Eurocode 2 it is possible to ignore the shear contribution, when the shear contribution is smaller than 10% of the bending contribution. Model Code 2020 does not give any information. As shown in the literature, this limit can be overcome not only in case of deep beams, but also in case of beams whose span-to-depth ratio is smaller than 12. However, shear deformation in cracked sections is often neglected because there are no suitable models for everyday applications. In this section, in order to study shear deformation of RC beams with thin web, an experimental campaign was carried out at the Politecnico di Torino on seven RC beams with the same transversal I-section 600 mm high and 400 mm wide, width-to-web thickness ratio of 4 and span-to-depth ratio of about 12, reinforced with two reinforcement ratios (0,5% and 0,8%). Three testing schemes were considered, that means: simply supported beams, subjected to two symmetrical loads; simply supported beams, subjected to one symmetrical load; simply supported beams, subjected to one anti-symmetrical load. From the experimental observations it results that shear does not produce only a transversal deformation, as assumed in Saint-Venant theory, taken into account through the determination of the shear strain. Nevertheless, in a cracked RC beam, shear produces also longitudinal deformations of the tension and compression chords due to the truss behaviour of cracked RC beams. From this effect on the deformations of these chords, it also results the influence of shear on the mean curvature. On the basis of the experimental observations, three calculation methods are proposed, for the analysis of the effect of shear on the deformation of RC beam, presenting via via an higher level of approximation, that means refined method, simplified method, graphical method. Finally, on the basis of the above graphical method, when a greater precision is not required, in case of RC beams subjected to uniform load, a simplified application rule is proposed for a quick check of cases where the shear contribution can be ignored.
Deflections due to shear / Guiglia, Matteo; Taliano, Maurizio - In: Serviceability Limit States of Concrete Structures - Background Document of fib MC2020STAMPA. - [s.l] : FIB, Fédération Internationale du Béton, 2024. - ISBN 978-2-88394-187-8. - pp. 157-177 [10.35789/fib.BULL.0114]
Deflections due to shear
Guiglia, Matteo;Taliano, Maurizio
2024
Abstract
In general, deflection should be calculated taking into account both the bending and shear contributions. According to Eurocode 2 it is possible to ignore the shear contribution, when the shear contribution is smaller than 10% of the bending contribution. Model Code 2020 does not give any information. As shown in the literature, this limit can be overcome not only in case of deep beams, but also in case of beams whose span-to-depth ratio is smaller than 12. However, shear deformation in cracked sections is often neglected because there are no suitable models for everyday applications. In this section, in order to study shear deformation of RC beams with thin web, an experimental campaign was carried out at the Politecnico di Torino on seven RC beams with the same transversal I-section 600 mm high and 400 mm wide, width-to-web thickness ratio of 4 and span-to-depth ratio of about 12, reinforced with two reinforcement ratios (0,5% and 0,8%). Three testing schemes were considered, that means: simply supported beams, subjected to two symmetrical loads; simply supported beams, subjected to one symmetrical load; simply supported beams, subjected to one anti-symmetrical load. From the experimental observations it results that shear does not produce only a transversal deformation, as assumed in Saint-Venant theory, taken into account through the determination of the shear strain. Nevertheless, in a cracked RC beam, shear produces also longitudinal deformations of the tension and compression chords due to the truss behaviour of cracked RC beams. From this effect on the deformations of these chords, it also results the influence of shear on the mean curvature. On the basis of the experimental observations, three calculation methods are proposed, for the analysis of the effect of shear on the deformation of RC beam, presenting via via an higher level of approximation, that means refined method, simplified method, graphical method. Finally, on the basis of the above graphical method, when a greater precision is not required, in case of RC beams subjected to uniform load, a simplified application rule is proposed for a quick check of cases where the shear contribution can be ignored.File | Dimensione | Formato | |
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Chapter 3-3-3_TALIANO-GUIGLIA_rev3.pdf
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Descrizione: Section 3.3.3. Deflections due to shear
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https://hdl.handle.net/11583/2997021