DETERMINATION OF THE CALCULATED VALUES OF STRENGTH AND RIGIDITY OF GLUED WOODEN BEAM DURING A FIRE

Abstract

The article deals with the calculation of load-bearing structures made of glued timber in accordance with the requirements of DBN V.2.6-161 "Wooden truss structures. Basic provisions" for the first limiting state, especially at the time of a fire. Calculated values of strength and stiffness of glued timber at normal temperatures and at the time of a fire have been determined. It is shown that centrally compressed glued laminated timber with dimensions 50x270x3000 mm on a hinged support at normal temperatures is characterized by compressive strength along the fibers from a constant load to 12.48 MPa, from a snow load to 16.64 MPa, is characterized by flexibility relative to the y-axis - 207.61. Testing the strength and stability of laminated veneer lumber according to the first limit state meets the requirements of the standard. At the moment of a standard fire of 60 minutes duration, the strength characteristics of laminated veneer lumber sharply decrease due to carbonization and a decrease in the cross-section. The calculated stresses in compression along the fibers from a constant load are 6.2 MPa, from a temporary one - 4.2 MPa. Strength test is carried out. Flexibility about the y-axis is increased by a factor of 1.42 compared to normal temperatures. The fire protection of the timber with an intuitive paint 0.9 mm thick helps to reduce the rate and depth of charring. The check is not performed, the stability of the laminated veneer lumber, taking into account the residual section in case of fire for 60 minutes. not provided. Since it is impossible to change the geometrical dimensions of laminated veneer lumber, the stability of its section in the event of a fire can be limited to 45 minutes, or the thickness of the intumescent fire-retardant paint can be increased from 0.9 mm to 1.5 mm.