Showing papers by "Zdenek P. Bazant published in 2005"
TL;DR: In this paper, a simple dimensional analysis of the size effect of reinforced concrete beams was performed and the authors showed that the failure is caused by cohesive (or quasibrittle) fracture propagation and the maximum load is attained only after large fracture growth.
Abstract: The shear failure of reinforced concrete beams is a very complex fracture phenomenon for which a purely mathematical approach is not possible at present. However, detailed modeling of the fracture mechanism is not necessary for establishing the general form of the size effect. The first part of this paper shows that the general approximate mathematical form of the size effect law to be calibrated by experimental data can be deduced from two facts: (1) the failure is caused by cohesive (or quasibrittle) fracture propagation; and (2) the maximum load is attained only after large fracture growth (rather than at fracture initiation). Simple dimensional analysis yields the asymptotic properties of size effect, which are characterized by: (1) a constant beam shear strength vc (i.e., absence of size effect) for sufficiently small beam depths; and (2) the linear elastic fracture mechanics size effect vc ∼ d−1∕2 for very large beam depths d . Together with the recently established small- and large-size second-orde...
134 citations
TL;DR: In this article, empirical prediction formulas for the size effect parameters, consisting of the asymptotic small-size strength v0 and the transitional size d0, are calibrated by least-square regression of a recent American Concrete Institute database with 398 data points, and a combination of this database with large-scale Japanese tests and Northwestern reduced-scale model tests.
Abstract: After theoretical derivation of the general form of the size effect formula for beam shear in the preceding Part I, this Part II presents experimental verification by least-square fitting of those existing individual data sets that have a broad size range. Subsequently, empirical prediction formulas for the size effect parameters, consisting of the asymptotic small-size strength v0 and the transitional size d0 , are calibrated by least-square regression of (1) a recent American Concrete Institute database with 398 data points, and (2) a combination of this database with large-scale Japanese tests and Northwestern reduced-scale model tests. Previous alternative proposals for dealing with the size effect in beam shear are also discussed.
73 citations
TL;DR: In this article, the problems of computational algorithm and convergence of iterations are addressed and typical numerical responses are demonstrated and the parameters of the model are calibrated by test data from the literature.
Abstract: Following the formulation of the constitutive model in the preceding Part I in this issue, the present Part II addresses the problems of computational algorithm and convergence of iterations. Typical numerical responses are demonstrated and the parameters of the model are calibrated by test data from the literature.
71 citations
01 Dec 2005
5 citations
01 Dec 2005
TL;DR: In this paper, the effect of structure size and structural geometry on quasibrittleness of concrete and other quasibittle structures has been studied in the context of structural failure.
Abstract: During the last two decades, researches on quasibrittlc failure have led to major advances in the understanding and modeling of the energetic and statistical size effects in the mean statistical sense •2• Computational approaches and simple design code formulas giving better mean predictions have becn developed. It now appears, however, that the existing design codes• and standard practice for concrete and other quasibrittle structures also necessitate major revisions with regard to the effect of structure size and, more generally, degrec of brittleness, which depend not only on the size of the structure but also on its structure geometry.
1 citations