Reinforced concrete shear wall structures are an important part of the construction due to their ability to withstand in large earthquakes force and deformation demands. In some of these buildings, shear walls are implemented in successive bays to create more lateral resistance, to reduce drift or to satisfy architectural requirements, and adhered walls are appeared. In Open Sees, the MVLEM and SFI_MVLEM methods do not have the ability to model the common boundary element between two shear walls adhering to each other. So, modeling of these walls in Open Sees software is difficult. In this paper, we propose a method for modelling these walls, Multiple Vertical Columns (fiber) method, and modeling results are compared with experimental results and the results of other models. The ability of this method in the modeling of the adhered shear wall is measured via the actual building modelling. The results of static posh-over analysis and nonlinear dynamic analysis show that the proposed model has a good performance for the modeling of adhered walls. The main advantages of using Multiple Vertical Columns (fiber) method are the use of multiple fiber columns to model the geometry continuity of the wall in a horizontal direction (similar to the MVLEM) and the possibility of folding the vertical elements along their longitudinal axis and using horizontal joints in the mid-points to model The geometric continuity of the wall is vertical direction.

Recent earthquakes show that masonry infill walls should be taken into account during the design and assessment process of structures, since this type of non-structural elements increase the in-plane stiffness of the structure and consequently the natural period. An overview of the past researches conducted on the modelling of masonry infilled frame issues has been done, with discussion of past analytical investigations and different modelling approaches that many authors have proposed, including micro- and macro-modelling strategies. After this, the present work presents an improved numerical model, based on the Rodrigues et al. (J Earthq Eng 14:390-416, 2010) approach, for simulating the masonry infill walls behaviour in the computer program OpenSEES. The main results of the in-plane calibration analyses obtained with one experimental test are presented and discussed. For last, two reinforced concrete regular buildings were studied and subjected to several ground motions, with and without infills’ walls.

Optimum implementation of nonlinear dynamic analysis (NDA) in progressive collapse is one of the most important issues that has not been addressed recently. Using detailed FE software like ABAQUS and ANSYS in progressive collapse analysis despite their accuracy is not appropriate because of consuming a lot of time. For this reason, many of researchers utilize the macro software such as OpenSEES. In this study, authors tried to introduce an optimum and appropriate method for element removal in open program, OpenSEES. Since nonlinear dynamic analysis shows the exact behavior of structure, this algorithm is developed for NDA. For this purpose, the developed algorithm has been compared with the other methods and it has been found that it has a high accuracy. Developed algorithm can remove one or more columns at the same or different time intervals and the effects of sequence column removals to their time durations can be seen. The application of the developed algorithm for nonlinear incremental dynamic analysis (NIDA) has been implemented and its application for an ultimate capacity of the structure has been shown. Analysis results showed that using of developed algorithm will lead to the speed and accuracy improvement of calculations in the sequence of columns removal and ultimate capacity of the structure using NIDA. At the end of this research, the application of this method has been shown for other element removal such as beams and infill walls.

In this research, dilation effect related to density and confining stresses during liquefaction on structural settlement is investigated using OpenSEES. Therefore, a sand layer with different dilation angles and surface load is considered. The numerical model presented in this research, calculated the excess pore water pressure based on fully coupled effective stress analysis during seismic loading. Model parameters were selected and verified using the results of VELACS centrifuge tests. The results show that by increasing the dilation angle, the pore water pressure decreases and the liquefaction-induced settlements decrease. The decreasing trend of settlement with increasing dilation angle tends to a constant value, so that at high densities with increasing dilation angle, little changes in settlement is observed. Also, the dilation angle is calculated based on the preshear mean effective stresses and compared with the dilation angle caused by the stresses during liquefaction. The comparison shows that for relative densities less than 60%, the dilation angle obtained from preshear effective stress is more than the confinig stress based method during liquefaction.