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Publication
Span-to-depth ratio limits for RC continuous beams and slabs based on MC2010 and EC2 ductility and deflection requirements
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Advisor(s)
Abstract(s)
In the design of reinforced concrete structures several limit states are usually verified using simplified methods
instead of using complex direct calculation. Span-to-depth ratio limits are applied for deflection control. In the
same way, a redistribution factor and the relative depth of the compression zone are applied for the required
ductility, but this is not enough. In fact, specific span-to-depth ratio limits, which are developed in this paper,
should also complement the conditions referred to here.
A numerical study is developed to compute the deflection ductility index of a wide range of continuous beams
(or one-way slabs) considering as ultimate point when the rotation capacity (given by MC2010 and EC2) is
achieved. From the boundary between fragile and ductile failures, the new span-to-depth ratio limits for the
required ductility are defined and compared with the existing similar limits for deflection control.
The results indicate that: (i) for normal strength concrete (up to 50 MPa), the ductility limit is more restrictive
than the deflection limit when the redistribution factor δ is lower than 0.9, being always more restrictive for high
strength concrete; (ii) for the current building beams, the slenderness used (10 < l/d < 20) allows ductile fail ures, while for typical building slabs (low reinforcement ratio, but high redistribution), the slenderness should be
l/d ≤ 20; (iii) the conditions of MC2010 and EC2 to use plastic analysis without any direct check of the rotation
capacity are actually incomplete and need to be revised.
The new span-to-depth ratio limits proposed in this paper, which satisfy both ductility and deflection requirements, depend on the redistribution factor, characteristic compressive strength of concrete and total mechanical reinforcement ratio
Description
Keywords
Continuous beams Continuous slabs Deflection control Deflection ductility index Eurocode 2 Model Code 2010 Pre-design Required ductility Rotation capacity Slenderness ratio . Faculdade de Ciências Exatas e da Engenharia
Citation
Santos, J., & Henriques, A. A. (2021). Span-to-depth ratio limits for RC continuous beams and slabs based on MC2010 and EC2 ductility and deflection requirements. Engineering Structures, 228, 111565. https://doi.org/10.1016/j.engstruct.2020.111565
Publisher
Elsevier