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An ITS (Intelligent Tutoring System) is a complex, integrated software system that applies the principles and methods of artificial intelligence (AI) to the problems and needs of teaching and learning. They allow searching the student level of knowledge and learning strategies used to increase or correct the students' knowledge. They are intended to support and improve the teaching and learning process in a selected area of knowledge while respecting the individuality of the learner. In the paper a review of intelligent tutoring systems (ITS) is given from the aspect of their application and usability in modern learning concepts.

Application of fracture mechanics at design of RC buildings will provide significant benefit. It will contribute that different size of premises to have the same security. In this way, the security and the cost of construction will be enhanced. There will exist a greater possibility of applying new designs and materials. Especially in large RC buildings, as well as in high-strength premises, the premises made of concrete with the steel fibers, prestressed concrete, large concrete dams, nuclear power plants, the facilities that require high safety, whose damage can cause a disaster, the application of fracture mechanics is of great significance. The impact of size, which relies on mechanical fracture can be defined as the theory of fracture which for the design of RC elements take into account resistance and energy of fracture.

In order to research the influence of the dimensions there have been used the samples of slotted beams on two supports and loaded by force capacity of P = 200 kN and the sensitivity of 100 N fractured (load cell), in the middle, deformations were measured at the point of load and the top of each slot of 50 mm with the sensitivity instrument of 100x10-6 mm LVDT (Tokyo Sokki Kenkyujo Co.SDP-50C). During load all deformations are directly stored with the data logger (30 channels Bucem) that is constantly connected to the computer. The thickness of all samples is constant t = 4 cm and the other two dimensions of height h and length L are changed proportionally. For testing are used three different sizes of the beams and from each sizes are used the three samples. To a mixture of concrete were used two aggregate fractions. A large fraction is 4.76 to 10 mm, smaller fraction is 3 to 4,76 mm. First, sand is put into a mixer, followed by gravel and cement in the dry state and this is going to be mixed for about 2 minutes, after that, the water is added and mixing is going to be carried out for about 2 minutes. From the same samples were set aside the 3 samples in the molds of cylindrical forms with a diameter of 150 mm and a height of 300 mm to determine the brand of concrete. There was used the portland cement (350).