an orthotropic continuum model for the analysis of masonry structures

52 1995 TNO-95-NM-R0712is approximately the same as in the former cases. Note that the inconvenience of using the expansion/compressionmechanism, de Borst(1991), for a basically plane stress yield criterion is againevident. In a plane stress algorithm global convergence would be found in one step because all thedisplacements are prescribed whereas, with the expansion/compression mechanism, a non-zero outof-planenormal stress component must be reduced to zero.Table A.8 - Number of local iterations per global iteration for the apex algorithmPlastic steps Av erage Maximum100 3.40 410 4.32 5Table A.9 - Number of global iterations for the apex algorithmPlastic steps Av erage Maximum100 2.01 310 2.10 3Table A.10 - Convergence for selected steps (apex algorithm)100 plastic steps10 plastic stepsPlastic step1Force norm0. 515 × 10 00. 480 × 10 −50. 210 × 10 −11Plastic step1Force norm0. 516 × 10 00. 491 × 10 −40. 557 × 10 −1250100A.2 COMPRESSION REGIME0. 529 × 10 −50. 168 × 10 −120. 101 × 10 −50. 139 × 10 −135100. 693 × 10 −30. 500 × 10 −110. 120 × 10 −30. 112 × 10 −13The material properties given in Table A.11 are assumed, in which the material strength andYoungÕs modulus in they-direction are penalized by a factor 2. Three different fracture energiesare considered for the y-direction: 0. 3G fcx ,G fcx / 2 (isotropic softening) and 500 × G fcx (almostideally plastic behaviour).Table A.11 - Material properties (β = -1.0, γ = 3.0 and κ p = 0.0005)Material propertiesE x 10000 N/mm 2 E y 5000 N/mm 2ν xy 0.2 G xy 3000 N/mm 2f mx 10.0 N/mm 2 f ty 5.0 N/mm 2G fcx 0.05 N.mm/mm 2 G fcy 7.5 N.mm/mm 2A.2.1 Uniaxial compressionThe element is subjected to uniaxial compression along the x axis as shown in Fig. A.7. The resultsare illustrated in Fig. A.8.