The article draws attention to certain aspects of calculating the width of cracks and stresses in composite elements under bending, in which the slab is located in the tension zone. If semi-rigid joints are used in the element, in which the beam is attached to the column by bolts, two types of areas should be distinct in which the reinforcement stresses will be calculated in a different way. The method of calculating stresses in reinforcement will depend on the type of a used joint or on the distance of the considered cross-section from the semi-rigid joint. In order to distinguish the method of calculating stresses in the paper, two areas were introduced: specifically area B and area D. Area B will be the area where the principle of flat sections can be applied, and stresses in the reinforcement are determined using the classical theory by adding the component responsible for the tension stiffening phenomenon. Area D is the area in the vicinity of the semi-rigid joint, where the principle of flat sections cannot be applied. To calculate stresses, consider the balance of joints using the available models of the semi-rigid joint, in particular the spring model. The paper presents the formulas for calculating stresses in the D area for two types semi-rigid joints: joint with a flush end-plate with 2 rows of bolts are used and joint with an extended end-plate with 3 rows of bolts are used.