About the influence of fiber on the deformation of compressed flanges at 3.6 𝒉 𝒇′ , 4.8 𝒉 𝒇′ , 8 𝒉 𝒇′ overhangs of reinforced rubber concrete t-beams with reinforcement of 2.50%

. The aim of this study is to determine the effect of fiber reinforcement on deformations arising from the applied load in the compressed flanges of reinforced rubber concrete beams of a T-section.This article presents the results of testing prototypes of rubber concrete and fiber rubber concrete beams of a T-section, tested to a pure bending. The strain curves for compressed flanges (3.6 ℎ 𝑓′ , 4.8 ℎ 𝑓′ , 8 ℎ 𝑓′ overhangs) of reinforced rubber concrete beams of T-section are obtained.


Introduction
Composite material -rubber concrete (rubcon), obtained on the basis of liquid rubbers, has a high, almost universal chemical resistance and high physical and mechanical properties. Component composition and coefficients of chemical resistance of this polymer concrete are given in tables 1 and 2.  An analysis of previous studies [9,10,12,[14][15][16] shows that based on rubcons, it is possible to create highly efficient reinforced structures for various purposes, including flexural ones of various cross sections [1 -7,11,13].
The T-section, in comparison with the rectangular, is more effective from the point of view of profitability, because from the tensile zone, poorly resilient to tension, a part of the material that was practically not involved in the work was removed.
It has been established that the type of reinforcing fiber and its amount affect the deformation-strength properties of fiber rubber concrete. The most effective is dispersed reinforcement of rubcon with fibers made from steel cord waste [8].

Methods of experimental research
In order to conduct experimental studies, T-beams of cross-section were made of rubcon and fiber rubcon. A500C class reinforcing bars were used as longitudinal reinforcement, and Вр500 with a diameter of 5 mm and a step of 50 mm as transverse reinforcement. Fiber reinforcement is represented by steel fibers with a diameter of 0.3 mm and a length of 30 mm (i.e., the ratio of the diameter to the length of the fiber is 1/100) located randomly throughout the volume of the experimental beams. Dimensions of experimental samples of the beams: Length (l) -1400 mm; web height (h-ℎ ′ ) -95 mm; web width (b)-60 mm; flange height (ℎ ′ ) -25 mm; flange width ( ′ ) -240, 300 и 460 mm; diameter of the longitudinal reinforcing bar -2Ø10; which corresponds to the percentage of longitudinal reinforcement (µ) -2,50 %. The reinforcement scheme and the location of the T-beam on the supporting elements is shown in fig. 1. Experimental studies were carried out according to the following procedure. The beams were tested for bending by two forces applied in the third span, increasing up to failure. The calculated span of the samples was 1200 mm, the length of the samples was 1400 mm, which ensured reliable anchoring of the reinforcing bar. Flange sizes were assigned for the following reasons: flange height (ℎ ′ =25 mm) was chosen in such a way as to provide, if necessary, the possibility of placing reinforcing bar in it. The width of the flange was 240, 300 and 460 mm. The arrangement of strain gauges is shown in fig. 2. The type of beam before and after the test is shown in fig. 3. The tests were carried out at the Center for Collective Use named after Professor Yu.M. Borisov of VSTU, the following devices were used: Universal floor-mounted hydraulic testing system model 600KN from INSTRON (USA), a set of equipment for monitoring the stress-strain and technical state of structures and their elements (Germany). The difference in the relative deformations for the BFRT240 and BRT240 beams of the wall and at the farthest portion from the wall at the construction stage close to critical for the BFRT is 652.10 * 10 -6 , in BRT-148.20 * 10 -6 . The difference in the relative deformations for the BFRT300 and BRT300 beams of the wall and at the farthest portion from the wall at the construction stage close to critical for the BFRT is 661.71 * 10 -6 , in BRT-421.91 * 10 -6 . The difference in the relative deformations for the BFRT460 and BRT460 beams of the wall and at the farthest portion from the wall at the construction stage close to critical for the BFRT is 652.32 * 10 -6 , in BKT-651.54 * 10 -6 . In BFRT240 mm, an increase in the strain value at the farthest portion from the wall is 4.78 times in comparison with BRT240, the value of wall deformation in BFRT240 is 1.18 times higher than in BRT240.
In BFRT300 mm there is an increase in deformations in the farthest portion from the wall by 2.33 times in comparison with BRT300, the value of wall deformation in BFRT300 is 1.15 times higher than in BKT300.
In BFRT460 mm, an increase in deformations at the farthest portion from the wall is 1.86 times in comparison with BRT460, the value of wall deformation in BFRT460 is 1.13 times higher than in BRT460.

Conclusions
1. An analysis of experimental data showed that with the addition of fiber filaments, the strain values in the compressed flange of a rubber concrete beam of T-section increase.
2. The greatest difference in deformations, when fiber is added to the walls and at the farthest portion from the wall, is observed in a beam with a flange width of 240 mm.