Critique of Critical Shear Crack Theory (CSCT) for fib model code articles on shear strength and size effect of RC beams

Abdullah Dönmez, Zdeněk P. Bažant*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The size effect of Muttoni et al.s CSCT is shown to be very close and asymptotically identical to the energetic size effect law (SEL) extensively verified experimentally and theoretically (due to appear in the 2019 ACI Code for both beam shear and punching). However, the CSCT derivation and calculation procedure obfuscates the mechanics of failure. It is shown to rest on six scientifically untenable hypotheses, which makes CSCT untrustworthy outside the testing range. It would have to be taught to students as a dogma. These conclusions are supported by experimentally calibrated finite element simulations of crack path and width, stress distributions and localizations during failure, and strain energy release. The simulations also show the CSCT to be incompatible with the ‘strut- and-tie’ model modernized to include the size effect in the compression strut. Finally, further deficiencies are pointed out for the Modified Compression Field Theory (MCFT), currently embedded in the Model Code.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Oct 26 2018

Keywords

  • Brittleness
  • Concrete fracture
  • Design codes
  • Energy criteria
  • Finite elements simulations
  • Fracture mechanics
  • Mechanics of concrete
  • Scaling
  • Shear failure
  • Structural strength

ASJC Scopus subject areas

  • General

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