## 6 Conclusions  
The paper presents a developed numerical model for the analysis of spatial reinforced concrete structures with emphasis on their behaviour under long-term loads. The previously developed model for short-term loads has been extended by the possibility of simulating long-term effects in concrete: creep and shrinkage. Thus, a modified nonlinear material law using the 3D representation of [PERSON]'s material law for dominant tensile stress and a multi-surface presentation of modified Mohr-Coulomb material law for dominant compressive stresses has been extended with the phenomenological model proposed by fib Model Code 2010, with modification to include nonlinear creep. Analysis of the influence of shrinkage on reinforced concrete structures was performed using an equivalent temperature load. For the observed type of construction of appropriate material and geometric characteristics, using the adopted shrinkage model, the shrinkage deformations of concrete (without reinforcement) are calculated for the directions of main stresses. As a ratio of the deformations thus obtained and the coefficient of thermal conductivity of concrete, equivalent nodal temperature forces are obtained with which the actual system is then loaded (considering the reinforcement). The analysis of the effect of creep on the behaviour of concrete uses the model of correction of the modulus of elasticity of concrete in the direction of the main stresses. The moment of application of external load represents the starting moment for the creep coefficient calculation. The creep coefficient depends on stress level, and it is calculated according to expression (12), for each direction independently at every time step and load increment step. The stress and strain states at each Gaussian point for the direction of the principal stresses are calculated for each moment, so the modulus of elasticity of concrete is known at each observed moment. If some of the principal stresses are lower than the tensile strength of concrete, the modulus of elasticity is corrected in the direction of that stress considering the magnitude of the creep coefficient at that moment. This calculation is performed for each Gaussian point so that by correcting the modulus of elasticity, orthotropy of the material at the level of each Gaussian point is achieved. With such a corrected modulus of elasticity, the concrete stiffness matrix is entered, and a new  
Figure 26: Stresses in the reinforcement bar at midspan over time (+tension). concrete stiffness matrix is obtained. By using the stiffness matrix thus obtained, the strains caused by creep are obtained. Relating to time analysis, the magnitude of the time step does not have to be constant. However, as the increment of creep and shrinkage deformations is initially higher and decreases with time, a shorter time step is taken at the beginning of the observation, which increases in the later phase of the calculation. This interpretation of creep and shrinkage through the numerical model Precon3D resulted in a model that can conduct a time-dependent analysis of the behaviour of reinforced concrete structures. Verification of the presented model is shown through the analysis of three different examples: analysis of concrete walls, analysis of reinforced concrete slab and reinforced concrete beam. All structures were monitored and analysed for a long time with and without the influence of external load. The examples were selected to allow verification of the developed model for different structures and loads. The analysis of the first example verified the accuracy of the calculation of long-term strains in concrete. A comparison was made with experimental measurements and the results obtained by calculating other most commonly used models: Model Code 2010, Eurocode 2, Model ACI 209-R92, Model B4 and Model B4s.