FORMATION AND OPENING OF TILTED CRACKS IN COMBINED FIBER REINFORCED CONCRETE BEND ELEMENTS

Visnyk LNAU: Architecture and Farm Building 2017 №18: 40-47

FORMATION AND OPENING OF TILTED CRACKS IN COMBINED FIBER REINFORCED CONCRETE BEND ELEMENTS

V. Bilozir, PhD
Lviv National Agrarian University

https://doi.org/10.31734/architecture2017.18.040

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 kf,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.

Key words

bend elements, steel fiber, tilted cross section, cracks formation, crack opening

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Link

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