THERMAL RESISTANCE OF A REINFORCED CONCRETE BEAM WITH RESTRICTED MOVEMENT ON SUPPORTS

The work of a beam with partial limitation of displacements on supports under conditions of unsteady high-temperature heating up to destruction is shown. Depending on the level of limitation of the rotational stiffness, the sequence of the formation of plastic hinges on the supports and in the span was revealed, which affects the resistance time of the beam. The conditions are formulated under which restrictions on the displacement of supports lead to the formation of adaptive resistance mechanisms. The time during which the beam resists bending and the ultimate resistance time depend on the combination of the stiffness level of the axial ka and rotational kr of the anchors. An increase in the level of limitation of the rotational stiffness kr in most cases leads to an increase in both the time of resistance to bending of the beam and the limiting time of resistance. With the provision of structural measures for the stiffness levels of the support fastenings ka and kr within certain limits, it is possible to significantly increase the fire resistance of the beam due to the formation of adaptive resistance mechanisms.

flexible element, high temperature heating, plastic hinge, membrane action, catenary action, stiffness of axial and rotational restrain, large deflections, bending resistance time, ultimate resistance time

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