Shear capacity of honeycombed reinforced concrete beams

During the earthquake of 7 September 1999 in Athens, many reinforced concrete (RC) structures (particularly those with an asymmetric in-plan skeleton and a ‘soft ’ ground-floor storey) suffered localised damage that cannot be attributed to defective work. Typical of such damage is the localised failure suffered by vertical structural members at the location of the point of inflection usually situated within their mid-height region. This type of failure, although compatible with the truss analogy, is not predicted by the methods adopted by the codes of practice through which the truss model is applied in structural-concrete design. As a result, the likelihood of the occurrence of this type of failure is expected to increase with the denser link spacing specified by the earthquake-resistant design clauses of new codes of practice for the critical lengths of linear structural concrete members. This article describes an attempt to identify the causes for this deviation of the real behaviour of structural-concrete members from the code predictions. Prof. M. D. Kotsovos, Dip Ing, DIC, PhD, DSc Director Laboratory of Concrete Structures, Department of Civil Engineering, National Technical University of Athens Prof. M. N. Pavlovic, BEng, MEngSc, PhD, ScD, FIStructE, FICE Head Concrete Structures, Section,Department of Civil Engineering, Imperial College of Science, Technology and Medicine