## 5 Verification of the Numerical Model-Examples
### Three Concrete Walls--Long-Term Testing  
The first example taken from the reference [30; 31] was chosen. In these papers, the authors showed the results of seven tests and measurement of concrete shrinkage for three walls (ST1, ST2 and ST3), as shown in Figure 12. In the cited literature, the experimental results were compared with the results of the most important and most commonly used models for predicting concrete shrinkage: Model Code 2010, Eurocode 2, Model ACI 209-R92, Model B4 and Model B4s, which served to compare the results of all models with the model developed by the computer program Precon3D. The literature describes the program of experimental testing walls, from which all the necessary material parameters and geometry of the walls were taken to simulate the above experimental test with a computer program Precon3D. An experimental study focused on shrinking concrete by drying began in 2012 at the CTU Faculty of Civil Engineering in Prague. The test was performed on three walls of different thicknesses (b), 200 mm, 400 mm and 800 mm, while the height and width of the wall were the same and amounted to 800 mm (Figure 12). Four sides of the wall are fixed (constraint of displacement), thus simulating a one-dimensional shrinkage of the concrete. Measurement of the strains in concrete began three hours after concreting at four measurement sites in the walls as follows: for two walls (ST1 and ST3) for 522 days and for the third ST3, 300 days. Due to most common use, C30/37 concrete was employed, and the basic parameters of the concrete mixture were: water-cement factor (w/c) 0.50, cement content 360 kg/m\({}^{3}\) (Portland cement 42.5 R), aggregate content 1760 kg/m\({}^{3}\) and maximum aggregate size 16 mm. The compressive strength of concrete, measured on a specimen at the age of 28 days, was 55 MPa. Ambient conditions were carefully recorded in the laboratory every five minutes, and the measured mean relative humidity was 39.1%, while the average temperature was 21.5 \({}^{\circ}\)C for the period of 552 days. In the computer program Precon3D, walls ST1 and ST2 are discretised by three-dimensional (3D) 27-node Lagrange finite elements of 100 \(\times\) 100 \(\times\) 100 mm, while wall ST3 is discretised by the same finite elements of 200 \(\times\) 200 \(\times\) 200 mm, as shown in Figure 13.  
Figure 12: The geometry of testing walls. The strains of such modelled walls with given material parameters and early defined boundary conditions were monitored during 522 days for the two of the walls and 300 days for the third wall. The results obtained by the developed computer program Precon3D were compared with those from the literature obtained by experimental testing. According to the results represented in Figure 14, it can be concluded that the numerical model Precon3D gives a very good agreement of the results with the experimental one. The biggest difference in results is obtained in the first 40 days of shrinkage, which can be attributed to the fact that the shrinkage model Fib Model Code 2010 gives a faster increase in deformation in the first days and then decreases over time. In the mentioned literature [30; 31], the experimental results were compared with the results of the commonly used models for predicting concrete shrinkage: Model Code 2010, Eurocode 2, Model ACI 209-R92, Model B4 and Model B4s. So, we used all these results for comparison with results obtained by numerical model Precon3D individually for each wall type ST1, ST2 and ST3. From the above-presented results, it is evident that the numerical model Precon3D not only gives good agreement with the experimental ones (Figure 14) but generally gives better results in predicting shrinkage deformations than other models presented in the literature [30; 31].