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
Link
- Priev B.A. Strength and crack resistance of steel-fiber-concrete thin-walled bent elements by inclined sections: Abstract for the PhD degree / B.A. Priev. Moscow, 1989. 20 p.
- Recommendations for the design and manufacture of steel fiber concrete structures. M.: NIIZHB, 1987. 148 p.
- Steel fiber concrete structures: SP 52-104-2006: Introduced on September 1, 2006. M.: FSUE SRC “Construction”, 2007. 73 p.
- Constructions of buildings and structures. Guidelines for the design and manufacture of steel-fiber reinforced concrete structures: DSTU-N B V.2.6-78: 2009. Introduced on 01.01.2010. K.: Minregionbud of Ukraine, 2009. 43 p.
- Vandewalle L. Recommendations of RILEM TC162- TDF: Test and Design Methods for Steel Fibre Reinforced Concrete: bending test (final recommendation) / L. Vandewalle // Materials and Structures. 2002. Vol. 35. P. 579-582. https://doi.org/10.1617/13884