In the micro model technique, in addition to the independent material properties, the interaction between those also need to be defined, such as brick-to-mortar or concrete-to-mortar interfaces. Of the noble solutions, that provided by Abaqus  was preferred in order to overcome this challenge, in which cohesive surfaces enable us to simulate compressive, tensile as well as the shear behavior of the interaction zones. This method is particularly suitable when the traction-separation kind of damage is expected on thin layer surfaces. It is capable of creating the damage models on three different directions, one to the interface normal and the other two parallel to it, as shown in Figure 6. The model requires the input of stiffness values of contact and the corresponding damage initiation-evolution parameters by means of evaluating the stress, displacement or energy values. It assumes a linear behavior until reaching the ultimate load capacity and afterwards either linear or exponential damage evolution is possible to be defined. For this study, a linear branch of damage propagation was assumed, as given in Figure 7.
Overall, it can be seen that reasonable convergence was achieved in the numerical models. In terms of the compression results, numerical analyses estimated the peak stress levels accurately for the mortar specimens, though the initial stiffness values were over-estimated. However, analyses with the flexible joints provided a good match during the ascending stiffness branch at the beginning, whereas the peak stress was calculated higher than the experimental measurements and rather sharper softening behavior was seen in the numerical analyses. Elastic stiffness values of the numerical results had good agreement with the experimental ones for the tensile tests of both stiff and flexible joint implemented specimens. Analysis of the mortar tests achieved a close match with the mean peak stress values of experimental outcomes, although PolyUrethane PM utilized numerical analysis slightly exhibited higher maximum stress capacity. Similarly, shear analyses were also able to simulate the real behavior in the initial elastic branch, however, the numerical analysis belongs to flexible joint tended to exhibit higher stress values at the ultimate levels.
Ground motion suites representing the ultimate limit state (ULS) and the serviceability limit state (SLS) as defined by Eurocode 8 were created. The ULS earthquake has a 10% probability of exceedance in 50 years. Structures are designed to withstand the ULS seismic action while retaining structural integrity after the earthquake. The SLS earthquake has a 10% probability of exceedance in 10 years. Damage at the SLS should be limited to a point that does not compromise building serviceability (CEN 2013). 1e1e36bf2d