Page 32 - ICJ Jan 2023

TECHNICAL PAPER COLLECTOR’S EDITION

Fracture of plain concrete

P. F. Walsh

The application of linear fracture mechanics to the crack propagation load of pre-
cracked concrete specimens is shown to depend upon the size of the specimen.
The results of twenty-four tests on cracked beams with depths ranging from 3-in
to 15-in (75-mm to 375-mm) are presented in support of this conclusion.

C racks do of course exist in many reinforced and prestressed concrete members,

and on a smaller scale, microcracks occur in the concrete matrix, or the aggregate matrix
interface. The significance of such cracks depends upon the type of structure and the serviceability
requirements. In some circumstances the extent to which a crack will propagate under load has
a marked effect on the adequacy of the structure. An extreme situation might be the presence of
a large crack in an unreinforced concrete dam. Crack propagation is also of interest in attempts
to represent the post-cracking behaviour of reinforced concrete by mathematical models using
such techniques as finite element analysis.

In this report, the application of linear fracture mechanics to the fracture load of plain concrete
specimens is studied. In particular, the limitations of currently available data with regard to
specimen size are examined.

LINEAR FRACTURE MECHANICS
The theory of linear fracture mechanics has been extensively treated in the literature, and so only
a brief discussion of some of the concepts relevant to this study is given here. In a linear elastic
analysis of a two dimensional, symmetrical specimen, the stressesin the region of the tip of a zero
angle crack can be expressed by equations such as

The Indian Concrete Journal | November 2018 33