The thesis is mainly concerned with the Finite element static and dynamic models for the behaviour of reinforced concrete using non - associated flow rule. Applications of these models to the analysis of plates and some threedimensional problems are reported. The thesis can be broadly divided into four parts. The first part describes the geometric and material nonlinearities, and the non symmetry of stiffness matrix arising from the use of non associated flow rule. Some techniques are proposed to achieve symmetry by the use of scalar measures, such as incremental work done, plastic multiplier and a non associator corrector. The performance of these techniques is illustrated by a wide range of problems ranging from granular materials such as soils and concrete, to non granular materials such as metals. The second part of the thesis gives the description of the model for static behaviour of concrete. A five parameter model is adopted for the yield criterion, while the modified Drucker Prager function describes the plastic potential function. A work hardening plasticity, reflecting the multiaxial stress state is adopted and an energy recovery strategy for unloading (during crack closure) is reflected in the model. The model is examined by a number of numerical examples. The third part gives the description of a model for the dynamic behaviour of reinforced concrete. The rate sensitivity of such material properties as the elasticity modulus, yield stress and fluidity parameter are highlighted and the parameters involved are identified using some existing experimental data. The model is implemented in a three dimensional program and used in analysing some numerical examples. The fourth part of the thesis is devoted to the study of some model response to various factors, the choice of which is user dependent. Such factors include mesh discretisation, time and load increment size, numerical integration rule etc. Some conclusions that could be beneficial to the program user are arrived at. The inclusion of such information in a user - manual may be of some help to the the program user, who may be unaware of the inherent assumptions made in the model and program development.