Effect of small axial force on flexural ductility design of high-strength concrete beams

Summary Small axial forces may appear in beams in a reinforced concrete (RC) structure. The presence of compressive axial force, even at a low level, has an adverse effect on the flexural ductility of RC beams, which is a key attribute for seismic design. For example, Eurocode EN1998‐1 explicitly sp...

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Bibliographic Details
Published in:The structural design of tall and special buildings 2015-08, Vol.24 (11), p.739-756
Main Authors: Bai, Z. Z., Au, F. T. K., Chen, X. C.
Format: Article
Language:English
Subjects:
axial compression
Beams (structural)
Buildings
Concretes
curvature ductility factor
Design engineering
Ductility
flexural ductility design
RC beams
Reinforced concrete
Reinforcement
reinforcement ratio
seismic design
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Summary:Summary Small axial forces may appear in beams in a reinforced concrete (RC) structure. The presence of compressive axial force, even at a low level, has an adverse effect on the flexural ductility of RC beams, which is a key attribute for seismic design. For example, Eurocode EN1998‐1 explicitly specifies such minimum flexural ductility, whereas Chinese code GB50011 limits the depth of equivalent rectangular stress block at peak resisting moment to achieve indirectly a certain nominal flexural ductility. Therefore, ignoring the presence of compressive axial force may be risky. In this study, the effect of small compressive axial force on the flexural ductility performance of both normal‐strength and high‐strength concrete beams is evaluated on the basis of a rigorous full‐range moment–curvature analysis. An effective strategy for flexural ductility design of RC beams with small compressive axial force is identified so that various flexural ductility requirements can be satisfied. The essential control parameter proposed is the maximum difference of tension and compression reinforcement ratios. Empirical formulae and tables are developed for convenient implementation. Copyright © 2015 John Wiley & Sons, Ltd.
ISSN:1541-7794
1541-7808
DOI:10.1002/tal.1209