Annotation

The test program presented in the table provides for the production and testing of samples reinforced with Ø5Bp-1 reinforcement and anchor fibers of Ukrainian production of 50 x 1 mm, according to the scheme of a single-pass beam with a cross-section of 100 x 50 mm loaded by lumped forces in a run equal to 900 mm. The distance from the extreme stretched fibers to the center of the weight of the rod - 15 mm. The controlled parameters during the tests were deflection, deformation of the concrete, the width of the opening of sloping cracks.

Parameters of experimental models

Sample sizes	Class of concrete	Сut-off run a, mm	Percentage of fiber reinforcement µfv, %
			0	0,7	1,25	1,8
1200х100х50	С 16/20	110	Б 1.1	F 2.1	F 3.1	F 4.1
		220	Б 1.2	F2.2	F 3.2	F 4.2

The measured widths of the opening of sloping cracks depended on the amount of fiber reinforcement and the size of the cut-off run. It has been experimentally discovered that, with an increase in cut-off run, the width of the opening of sloping cracks increased by an average of almost two-fold. It was characteristic that during the cut-off run a = 2,2d the cracks developed quite intensively, according to our experiments, the cracking forces were not much smaller than the destructive ones. When cut-off run a = 1,1d cracks developed less intensively, compared with the beams, in which the cut-off run was equal to a = 2,2d.

Experimental and theoretical studies of features combined fiber-reinforced beams on the fiber of Ukrainian production in the area of the transverse forces lead to the following conclusions:

• the fiber positively affects the crack resistance of inclined beams;
• the formation of inclined cracks should be checked according to the formula SNiP 03.01-84 *, taking into account the coefficient k_f,cr  as determined by us;
• width of crack opening advisable to determine given us an improved coefficient k₁;
• the theoretical parameters of crack resistance, as determined by us, are 1 ... 4% less than experimentally obtained, which is acceptable for design practice.