Title: Fatigue Fracture of High-Strength Concrete and Size Effect

Author(s): Zenek P. Bazant and William F. Schell

Publication: Materials Journal

Volume: 90

Issue: 5

Appears on pages(s): 472-478

Keywords: deflection; fatigue (materials); fracture properties; high-strength concretes; Materials Research

DOI: 10.14359/3880

Date: 9/1/1993

Abstract:
Results of an experimental study of fatigue fracture of geometrically similar high-strength concrete specimens of very different sizes are reported and analyzed. Three-point-bend notched beams of depths 1.5, 4.24, and 12 in. were subjected to cyclic loading with a lower load limit of 0.07 P u and an upper limit between 0.73 and 0.84 P u, where P u = maximum load in monotonic loading. The number of cycles to failure ranged from 200 to 41,000. It is found that the Paris law for the crack length increment per cycle as a function of the stress intensity factor, which was previously verified for normal concrete, is also applicable to high-strength concrete. However, for specimens of different sizes, an adjustment for the size effect needs to be introduced, of a similar type as previously introduced for normal concrete. This size adjustment represents a gradual transition from crack growth governed by stress amplitude to crack growth governed by stress intensity factor amplitude. The structure size for which this transition occurs is found to be about an order of magnitude smaller for high-strength concrete than for normal concrete, which means that the fracture process zone under cyclic loading is much smaller and the behavior is much closer to linear elastic fracture mechanics (LEFM). A linear regression plot estimating the size adjusted parameters is derived. An LEFM-type calculation of the deflections under cyclic loading on the basis.