12 Pages

Ji. = _ r ! _ c + ^ e 1 _ 2ra _ c + (5)

o- c L c * J c L c

D etec t io n of f r a c t u r e l o c a l i z a t io n and d iagonal shear c racks Under blast conditions, sudden and extensive diagonal cracking occurs within a few time steps. Some recommendations on computational strategies to be adopted are now given, based on numerical results [1]. First, displaying only full cracks, i.e. cracks for which the normal strain is beyond the ultimate strain of the tensile softening branch, is necessary to reveal any fracture localization in the structure behaviour as well as to uncover the shear-type cracks in the predicted crack patterns. Second, the use of Gaussian quadrature with a reduced 2x2 order for the integration of stress fields proves to be a successful means of avoiding stress-locking phenomena associated with strain localization mechanism [1]. This results in a partial release of the continuity requirements imposed by shape functions assumed for the finite elements.