The results of tests for drawing anchor fibers with a length of 50 mm and a diameter of 1 mm, laid at the end of concrete prisms 50x50x100 mm made of fine-grained concrete of classes C 20/25, C25/30 and C 30/35 are presented. From the tests of 50 fibers, the average value of tensile strength was determined, which is equal to 1242 MPa with a coefficient of variation of 2.1%. Prisms were made of fine-grained concrete, which included cement with an activity of 41.2 MPa for concrete class C 20/25 and an activity of 50.8 MPa for concrete classes C 25/30 and C 30/35. Sand with a modulus of size 2.1 was used as a filler. The concrete mixture was prepared in a forced concrete mixer, and the concrete was compacted on a vibrating platform. Simultaneously with these prisms, cubes with dimensions of 150x150x150 mm and prisms with dimensions of 100x100x400 mm were made to determine the bottom and prism strength of concrete. The length of laying fibers into concrete was 10,15 and 25 mm. It is shown that the forces perceived by the end anchors and the smooth part of the fibers rise with increasing strength of concrete. The results of tests for drawing fibers from concrete prisms are given in tables 1 - 3. For the length of laying fiber 10 mm into prisms with strength fcm,cube = 29.31MPa and fcm,prism = 23.15MPa the maximum stresses during drawing were 515.30 - 549.04 MPa (average value - 532.10 MPa). At the same length of laying fiber into concrete prisms with strength fcm,cube = 34.76MPa and fcm,prism = 27.11MPa, these stresses were equal to 554.47 - 588.54 MPa (average value - 569.70 MPa). For the length of laying the fiber 10 mm into prisms with strength fcm,cube = 38.96MPa and fcm,prism = 31.14MPa, the maximum tensile stresses were 590.51 - 621.72 MPa (average value - 606.81MPa). At the specified strengths of the prism concrete, the maximum values of the average stresses for fiber drawing were on average 13.37 MPa for concrete of class C20/25, 14.34 MPa for concrete of class C25/30 and 15.27 MPa for concrete of class C30/35. With a fiber laying length of 15 mm into prisms with concrete strength corresponding to class C20/25, the maximum tensile stresses were 575.80 - 607.64 MPa (average value - 587.10 MPa). With such a length of laying fiber into prisms made of concrete class C25/30, these stresses were equal to 614.44 - 680.25 MPa (average value - 638.95 MPa). At the length of laying the fiber 15 mm into the prisms of concrete class C30/35, the maximum stresses during drawing were 681.14 - 692.99 MPa (average value - 685.44 MPa). The maximum values of average stresses for fiber drawing were on average 9.87 MPa for concrete of class C20/25, 10.70 MPa for concrete of class C25/30 and 11.52 MPa for concrete of class C30/35. At a fiber laying length of 25 mm into prisms with concrete strength corresponding to class C20/25, the maximum tensile stresses were 645.44 - 735.03 MPa (average value - 692.76 MPa). With such a length of laying fiber into prisms made of concrete class C25/30, these stresses were equal to 736.58 - 773.25 MPa (average value - 752.37 MPa). With the length of laying fiber 25 mm into prisms made of concrete class C30/35, maximum stresses during drawing were equal to 780.27 - 839.49 MPa (average value - 809.12 MPa). The maximum values of the average stresses during fiber drawing were on average 6.97 MPa for concrete of class C20/25, 7.57 MPa for concrete of class C25/30 and 8.12 MPa for concrete of class C30/35. The coefficient of anchoring capacity η, which under Ukrainian standards of fibroconcrete structures designing is equal to 0.9, as shown by the data of our experiments, is not constant, so it is necessary to take this into account in the formula for determining the tensile strength of fibroconcrete.

Ukrainian enterprises of PET (Polyethylene Terephthalate) waste recycling are still capable of processing only 1 thousand tons, and more than 10 thousand tons of PET granulate are imported to Ukraine every month. Therefore, the issue of reuse and disposal of used polyethylene terephthalate, especially in construction, is one of paramount importance. The aim of the research is experimental-theoretical study of the strength of bending of prisms, reinforced with fibers and strip reinforcement of used PET bottles. Objectives of the research: the study of the percentage of reinforcing fibers in volume (1% and 1.5%) influence on the flexural strength of concrete reinforced prisms, and the possibility of using ribbon reinforcement from used PET bottles for bending concrete elements, elaboration of proposals for the deformation method of calculation of PET fibrobone bent elements. In this research the experimental methods for determining the bending strength of prisms, reinforced by fibrous, trips and PET waste tapes; methods of materials resistance theory have been used. During the research, two concrete prisms of 400x100x10 mm were constructed and tested for compression together with two concrete prisms of three-point bend for a run of 350 mm, two PET-fibrous concrete prisms for bending with percentages of reinforcement in volume of 1% and 1, 5% and two prisms for bending, reinforced with glued PET strips, with 1% reinforcement per section area. As a disperse reinforcement, pre-fabricated PET bottles of 50x3x0.2 mm were used, designed in way that the required length of sealing in the concrete is no longer than half the length of the fibers. Strip fittings are made of 4 fragments of PET bottles of 200x80x0.25 mm in size, glued with cyanacrylate adhesive with each other, and 2 fragments of 120x80x0.2 mm in size, which glued on both ends to 4 glued sheets with a length of 30 mm. Thus, the total length of the reinforcing strip is equal to 380 mm. At the final sections of the tapes, 6 openings with a diameter of 5 mm were punched to improve the anchoring. The reinforcing strips were placed in the forms located 10 mm from the lower edge. According to the results of the tests, the average cubic strength of concrete is 31.21 MPa, of prisms - 23.23 MPa, the initial module of deformation - 28.02·103 MPa. The flexural strength of prisms without a fibre is 58.54 kN·cm, with 1% fibers in volume - 64.31 kN·cm, with 1.5% fibers in volume - 71.84 kN·cm, and of prisms, reinforced with glued PET ribbons – 79.80 kN·cm. As a result of the tests, it was demonstrated that the strength of the tapes was not used properly, and the fracture was fragile due to the loss of adhesion to concrete. Analysis of the results of experimental studies allowed us to develop a deformation methodology of calculating PET-fiber-concrete bending elements.

No abstract

In 2013, the Lviv National Agrarian University patented the construction of a steel-fiber concrete beam, additionally reinforced with an external steel ribbon armature with end anchors. This technical solution allows reducing the cost of the structure by reducing the complexity of its manufacture, due to the absence of a reinforcing frame in the structure. The purpose of this work is to develop proposals for a refined calculation method of deflections of steel-fiber concrete beams with tape reinforcement on the basis of our experimental studies. 3 beams with dimensions 1500x150x60 mm were manufactured. Beam B-1, reinforced with steel tape 1500x60x3 mm with end stops, did not contain fiber. Beams BF-2 and BF-3 in addition to the specified reinforcement contained fiber, corresponding the coefficient of fiber reinforcement by volume, ρfν = 1,5% i 2% respectively. Compressed prisms of 400x100x100 mm and stretched samples of 700x100x60 mm were also tested to determine the mechanical characteristics of concrete and steel-fiber concrete. Loose beams with a working run of 1400 mm were tested with concentrated force applied along the middle of the length. Mass production fiber produced both in Ukraine and abroad with bent ends HE 1050 1 mm in diameter and 50 mm in length was used for reinforcement. The percentage of fiber reinforcement by volume of concrete beams was taken ρfν = 1.5% and 2% to provide enough bearing capacity of the inclined sections. The cement of grade 400 (activity 42.3 MPa) of the Ivano-Frankivsk plant was used to obtain C20 /25 concrete. The test samples were made of fine-grained concrete containing sand from the Yasinets quarry with a fineness modulus of not more than 2.5. Mixtures for beams were made in a forced mixer. The composition of the mixture was chosen so that the settling of the cone did not exceed 4-6 cm and that the fiber did not settle to the bottom of the form. The composition of the mixture per 1 m3 of the mixture was as follows: cement - 549 kg, sand - 1647 kg, water - 285,5 l. The deflections of the steel-concrete beams were smaller than the steel-concrete beams at equal moments. For example, at the moment of 210 kN·cm the experimental deflection values of beams B-1, BF-2 and BF-3 were equal to 0.116; 0.081 and 0.064 cm, and at the moment 420 kN·cm - 0.380; 0.213 and 0.140 cm, respectively. In this paper, it is proposed to determine deflections using the Mora integral and taking into account the results of the calculation of beams by deformation method. The ratio of theoretical and experimental values of deflections was equal to 0.93 … 1.14.

Vivat A. Research of accuracy normal elevations determination by GNSS method GNSS observation is carried out on 4 points of the leveling network I-II class, which are located on the territory of the lviv region at a distance of 2-10 km. The spatial coordinates of the points in the ETRS89 system are determined, followed by geodetic excesses. An accurate method for determining the antenna heights using geometric leveling is proposed. The equality of geodesic and normal excesses at the same geoid height at the investigated territory is established.