## 8 Conclusions  
Implicit solvers may encounter convergence issues, especially with materials exhibiting softening behaviour. Furthermore, nonlinear dynamic analysis can be computationally demanding. Explicit solvers offer a solution to these challenges, but their application in seismic analysis, especially for URM structures, is limited. Therefore, the sensitivity analysis herein presented intends to aid users in the framework of explicit solutions. It offers insights into the parameters applicable to dynamic analysis and their impact on the results. In this work, several models were created using only plane stress elements. Subsequently, a large set of numerical analyses was conducted within the explicit solver of Abaqus. The solutions were then compared with outputs generated by the implicit solver. The findings showed that the nonlinear dynamic response is significantly affected by the element type (quadratic or linear with full or reduced integration) rather than by the specific time integration solver (explicit or implicit method) applied to solve the equations, mainly when strong nonlinearities start to rise. In the explicit method, the models with damping parameter \(\beta=0\) are conservative. A response more aligned with the implicit solution can be achieved by setting the damping to \(0.1\beta\), and by increasing the bulk viscosity value to \(1.00\). In this regard, the bulk viscosity has less impact on the time increment than the \(\beta\) damping parameter. When using elements with reduced integration for dynamic analyses, assessing the increment of artificial energy plays a key role. The tolerance range of 5-10% appears to be acceptable. For models in the explicit solver, the three hourglass controls performed better in terms of artificial energy when their scaling factor was set to \(0.01\). No notable difference was observed for simple models. However, for models with more complexity, stiffness hourglass control seemed to be more efficient than relax stiffness and combined controls. It is worth noting that these conclusions are only applicable to plane stress elements. Future works should consider a reliability analysis that includes other variables, such as seismic actions with diverse characteristics, OOP response, and 3D models built with solid elements. Furthermore, a validation of the parameters through the simulation of experimental campaigns, especially shake table tests, should be considered. With the onset of high nonlinearities (crack formation, material softening, and large displacements) all the numerical techniques started to diverge. However, a majority of these  
Figure 29: Time history results for amplitudes of 100% and 125% in the strengthened SW models (solid wall). techniques were able to simulate the damage patterns at the NC state. Explicit methods are a promising tool for studying complex buildings that require extensive nonlinear dynamic analyses. In this regard, the reduction in computational time becomes more noticeable as the size of the model increases. Conceptualization, E.N.-M. and N.M.; Data curation, E.N.-M. and N.M.; Formal analysis, E.N.-M.; Funding acquisition, N.M.; Methodology, E.N.-M. and N.M.; Project administration, N.M.; Software, V.C. and S.O. ; Supervision, N.M.; Validation, E.N.-M. and N.M.; Visualization, E.N.-M., V.C. and S.O. ; Writing--original draft, E.N.-M., V.C. and S.O. ; Writing--review & editing, N.M. All authors have read and agreed to the published version of the manuscript. This work was funded by FCT--Foundation for Science and Technology within the scope of project EXPL/ECI-EGC/0940/2021. The first author is grateful for the funding from the Mexican National Council for Science and Technology (Consejo Nacional de Ciencia y Tecnologia CONACYT), grant number 2018-000013-01 EXTF-00137. Not applicable. The data presented in this study are available on request from the corresponding author.