Consequences of fracture mechanics for size effect, crack spacing and crack width in concrete pavements

Christian Hoover, Z. P. Bažant

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The ASTM standard C 78 for determining the modulus of rupture fr (or flexural strength) provides a constant value of a measure of tensile strength which is currently used for designing pavements of all thicknesses, as well as concrete structural members, of all sizes. However, accumulated test data on fr, as well as analytical studies and numerical simulations, clearly indicate that fr is not constant but significantly decreases as the structure size increases. This evidence of size effect has so far been ignored. The consequence for thick pavements is increased cracking and thus poorer durability and serviceability, and for large structures even a significant increase of failure probability. The size dependence determined from test data follows a simple equation, which represents a gradual transition between a deterministic (energetic) size effect caused by stress redistribution at small sizes, and the power-law size effect of the classical Weibull statistical theory of strength, which is approached for large sizes. The transition is explained and modeled by the non-local Weibull theory. In this paper, modifications to the current standards that incorporate a simple procedure to obtain the size dependence fr are proposed. Furthermore, the cohesive fracture mechanics, which is a more fundamental way to predict the effect of pavement thickness, resting on a given subsoil, is described. The energy release calculated according to cohesive fracture mechanics is shown to give the initial crack spacing, which may later increase due to instability of interacting parallel cracks. This is and important design consideration, since crack spacing controls the crack opening, and thus the ingress of water and corrosive agents, as well as transmission of shear stresses. Discussion and examples are limited to the formation of secondary cracks in between stress-relieving notches. This summary paper presents a general apercu of the problem, explains the fracture mechanics approach, and concludes by comparisons with test data.

Original languageEnglish (US)
Title of host publicationPavement Cracking: Mechanisms, Modeling, Detection, Testing and Case Histories
Pages137-144
Number of pages8
StatePublished - 2008
Externally publishedYes
Event6th RILEM International Conference on Cracking in Pavements - Chicago, IL, United States
Duration: Jun 16 2008Jun 18 2008

Other

Other6th RILEM International Conference on Cracking in Pavements
CountryUnited States
CityChicago, IL
Period6/16/086/18/08

Fingerprint

Concrete pavements
Fracture mechanics
Cracks
Pavements
Stress relief
Structural members
Bending strength
Shear stress
Durability
Tensile strength
Concretes
Computer simulation
Water

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Architecture

Cite this

Hoover, C., & Bažant, Z. P. (2008). Consequences of fracture mechanics for size effect, crack spacing and crack width in concrete pavements. In Pavement Cracking: Mechanisms, Modeling, Detection, Testing and Case Histories (pp. 137-144)

Consequences of fracture mechanics for size effect, crack spacing and crack width in concrete pavements. / Hoover, Christian; Bažant, Z. P.

Pavement Cracking: Mechanisms, Modeling, Detection, Testing and Case Histories. 2008. p. 137-144.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Hoover, C & Bažant, ZP 2008, Consequences of fracture mechanics for size effect, crack spacing and crack width in concrete pavements. in Pavement Cracking: Mechanisms, Modeling, Detection, Testing and Case Histories. pp. 137-144, 6th RILEM International Conference on Cracking in Pavements, Chicago, IL, United States, 6/16/08.
Hoover C, Bažant ZP. Consequences of fracture mechanics for size effect, crack spacing and crack width in concrete pavements. In Pavement Cracking: Mechanisms, Modeling, Detection, Testing and Case Histories. 2008. p. 137-144
Hoover, Christian ; Bažant, Z. P. / Consequences of fracture mechanics for size effect, crack spacing and crack width in concrete pavements. Pavement Cracking: Mechanisms, Modeling, Detection, Testing and Case Histories. 2008. pp. 137-144
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