Numerical modeling using traditional, hybrid, and multiscale finite element methods, as described in a doctoral thesis, seeks to improve our understanding of material behavior under extreme mechanical and thermal loads, such as those experienced during earthquakes and fires in buildings. The use of a hybrid approach that has shown superior performance for coupled thermo-mechanics [1] required several innovations at all stages of the finite element solution. These innovations include a regularized variational formulation, a discrete approximation that maintains gradient continuity in mechanical and thermal fields (stress and the normal component of heat flux) across finite element boundaries, and a time integration scheme that has proven stable over long durations by ensuring energy conservation or dissipation from higher-order modes. To assess the durability of these materials, the embedded discontinuity finite element method was employed, with a macro plasticity model for concrete that captures a full set of 3D failure modes, including opening, shear-in plane, and shear-out-of-plane failures. This model is compared to a novel, strongly coupled multiscale finite element model [2] that differentiates between the micro scale, composed of sets of Timoshenko beams, the macro-scale, represented by solid elements with embedded discontinuities to simulate crack opening and the Lagrange multipliers that is used to couple the scales. A series of numerical simulations and an identification procedure were performed on the proposed macro-model [3], using results from the multiscale model as a reference point. These analyses confirmed the performance of the macro-model and provided insights into the durability of these composite materials. REFERENCES [1] Suljevic S, Ibrahimbegovic A, Dolarevic S. Hybrid stress and heat-flux formulation of thermodynamics for long-term simulations in thermo-viscoplasticity. International Journal for Numerical Methods in Engineering, 2024;e7436. doi:10.1002/nme.7436 [2] Ibrahimbegovic A, Rukavina I, Suljevic S. Multiscale model with embedded discontinuity discrete approximation capable of representing full set of 3D failure modes for heterogeneous materials with no scale separation. International Journal for Multiscale Computational Engineering, 20(5):1-32, 2022. [3] Suljevic S, Ibrahimbegovic A, Karavelic E, Dolarevic S. Meso-scale based parameter identification for 3D concrete plasticity model. Coupled System Mechanics 11(1):55- 78, 202