Strains and strength of reinforced concrete beams manufacturing by high-strength concrete for non-coincident planes of temperature gradient and loading

The object of research is bent reinforced concrete elements of the beam type manufacturing by high-strength concrete, exposing the effects of uneven heating and loading in non-coincident planes. Method. Experimental research of beam specimens' temperature internal forces, strains, and load-bearing capacity was carried out with characteristic modes of uneven heating and loading in non-coincident planes. Theoretical research was done using the calculation’s special program based on clarified ratios of the nonlinear deformation model. Results. Data from the experimental research, which determine the changes' regularity of temperature internal forces in statical indeterminate bending elements of the beam type manufacturing by high-strength concrete, have been obtained, as well as its strains depending on the temperature and duration of uneven heating. The theoretical and experimental research's results of changes in the stress-strain state of bent beam elements under increasing bending moments until destruction and uneven heating in non-coincident planes have been presented. The temperature moments in reinforced concrete beams under the influences of temperature gradients increase proportionally to the value of the temperature changes, reach a maximum value at the first heating, and decrease after the cracks' formation. The maximum experimental values of temperature moments during one-sided heating of beams up to +90℃ amounted to about 20% of its bearing capacity. The strength of reinforced concrete beams manufactured by high-strength concrete on the bend after one-sided heating within ten days at temperatures up to 90℃ is close to the strength value of the unheated standard beam. This is due to the less sensitivity of high-strength concrete to the action of elevated temperatures in the range up to +90℃. The close accordance of the theoretical and experimental results confirms the reliability of the basic physical relations for the high-strength concrete, which has been implemented in the used option of the nonlinear deformation model of reinforced concrete.