NONLOCAL SMEARED CRACKIN(; MOUEL FOR CONCRETE FRACTlJRE

ABSTRACT: The classical smeared cracking model widely used in finite-element analysis of concrete and rock cannot describe the size effect experimentally ob-served in brittle failures and exhibits spurious mesh sensitivity with incorrect con-vergence to zero energy dissipation at failure. The crack band model circumvents these deficiencies but has limitations with respect to mesh refinement. shear lock-ing on zig-zag crack bands. and directional bias of the mesh. It is shown that all of these problems can be avoided by a nonlocal generalization, in which the dam-age that characterizes strain softening is considered to be a function of tbe spatial average of the positive part of the maximum principal strain. Two alternatives are presented: (I) Smeared cracking whose direction is fixed when cracks start to form; and (2) smeared cracking whose orientation rotates with the maximum principal strain. Furthermore. fracture tests on specimens of various sizes arc analyzed by finite elements. It is shown that the model correctly reproduces the experimentally observed si7c effect and agrees with Ba1.anfs size effect law. Orthogonal and slanted meshes:Ire shown to yield approximately the same cracking zones and propagation dircl·tiol1s. Thl ' lIIodel is easily progralllmed anti nnlll'utationally nl<lle cllkit'llt th;, " the corrcsf"lIIding local vl'rsion