The group has been developing beam finite elements of the highest quality. The elements have been applied in design practice. We developed a new generation of 2D and 3D kinematically exact beam finite elements, which are based on strain invariants and the consistent equilibrium of internal forces at the cross-section. 2D and 3D elements have been extended to the geometrically and materially non-linear analysis of reinforced concrete structures loaded to the ultimate load. 2D elements have been modified in such a way that they are capable of considering the softening of material which triggers the strain localization and the global softening response of the structure (i.e. the post-critical response of a reinforced concrete structure). This 2D formulation has been employed in the mechanical analysis of the response of reinforced concrete planar frames in fire. In a fire analysis, the consideration of the strain softening has been found essential. The formulation has also been applied in the analysis of steel frames. The studies of concrete and steel frames have indicated an important effect of creep in steel and reinforcement on the resistance time, whenever temperature rises over 400C. 2D elements have been employed for the analysis of layered beams, in which an interlayer slip occurs. Numerous examples of such beams can been found in practice (steel-concrete beams, wood-concrete beams, concrete beams reinforced by FRP, a new layer of concrete placed on an existing concrete beam, layered glulam beams). We have considered large deformations and the non-linearity of both material and the slip law. We have developed a mathematical model for estimating the effect of humidity and temperature on the mechanical response of layered glulam wooden beams and made comparisons with experiments performed at ZAG Ljubljana. The model considers both shrinkage and bulging of wood. We have proven mathematically that 2D beam elements are convergent. We have took part in the development of neural network methods for the determination of material parameters of soils, subsidence of the surface above a coal mine and the geoid surface. The results of our studies were published in peer-reviewed international journals.