The Explicit Finite Element Method is a powerful tool in nonlinear dynamic finite element analysis. Recent major developments in computational devices, in particular, General Purpose Graphical Processing Units (GPGPU's) now make it possible to increase the performance of the explicit FEM. This dissertation investigates existing explicit finite element method algorithms which are then redesigned for GPU's and implemented. The performance of these algorithms is assessed and a new asynchronous variational integrator spatial decomposition (AVISD) algorithm is developed which is flexible and encompasses all other methods and can be tuned based for a user-defined problem and the performance of the user's computer. The mesh-aware performance of the proposed explicit finite element algorithm is studied and verified by implementation. The current research also introduces the use of a Particle Swarm Optimization method to tune the performance of the proposed algorithm automatically given a finite element mesh and the performance characteristics of a user's computer. For this purpose, a time performance model is developed which depends on the finite element mesh and the machine performance. This time performance model is then used as an objective function to minimize the run-time cost. Also, based on the performance model provided in this research and predictions about the changes in GPU's in the near future, the performance of the AVISD method is predicted for future machines. Finally, suggestions and insights based on these results are proposed to help facilitate future explicit FEM development.

The experimental investigations performed on the behaviour of reinforce concrete elements subjected to blast loading have revealed that the shear mechanisms and ductility play important roles in the overall response and failure mode of such structures. The main aim of this master thesis is to study the possibility of using finite element method as a tool for predicting the dynamic response of blast loaded reinforced concrete beams and evaluation of their shear strength. In this study, the commercial software, ABAQUS/Explicit has been used by implementing appropriate constitutive material models in order to consider the material nonlinearity, stiffness degradation and strain rate effects. The results of some blast loaded tested beams have been used for verification and calibration of the model. As a secondary objective, the calibrated model used to study the influence of some important factors on the shear strength of reinforced concrete beams and investigate their effects on the failure mode. The results used as a reference and compared with the calculations according to some design codes for blast resistance design. The results of the present research show that the implemented nonlinear finite element model successfully simulates the dynamic responses including displacement/reaction force time histories and induced damage patterns of blast tested beams with reasonable accuracy. The results of performed parametric study confirm that the ductility play important role in the failure behaviour of studied beams. The numerical simulations show that dynamic response of a soft element is more ductile than the stiffer one and the shear forces are thereby limited. Thus, although a soft element fails by large deformations in flexure, a stiff element may experience a brittle shear failure mode for the same load intensity. The comparison between the results of numerical analysis and design codes calculation show that the American approach in shear design of reinforced concrete elements subjected to blast loading is relatively conservative, similar to static design approach and do not consider the effect of ductility in the shear design procedure. On the contrary, the procedure that Swedish guideline implemented somehow considers the effect of ductility on the shear strength of reinforced concrete elements subjected to impulsive loads. Further research should involve the using the developed finite element model as a tool in order to theoretically study the dynamic response of blast loaded reinforced concrete elements and their failure modes. The results of numerical simulations can be used as a reference to derive simplified computational methods for practical design purposes.

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