RESISTANCE OF STEEL FRAMES WITH RIGID AND HINGED JOINTS TO PROGRESSIVE COLLAPSE

The paper considers an important and topical aspect of improving the mechanical safety of buildings and structures with metal frames under special impacts. On the basis of experimental tests and numerical verification, the behavior of a steel frame under emergency action is studied. The rapid removal of the central frame from the design scheme was considered as such an emergency action. In order to increase the resistance of the frame to progressive failure, safety elements in the form of tie-rods, which redistribute additional loads from the emergency dynamic loading, were included in its scheme. Two types of frames were considered: with hinged beam-column connections and with similar rigid units. As a result of the experiments, the character of change of longitudinal deformations with time under dynamic loading was revealed, characteristics of vibrational processes for frames with different designs of nodes were determined. The role of tie rods in the stability of frames against progressive failure is determined. The character of displacement variation with time was determined. Satisfactory agreement with experimental data of the approach to modelling the accident situation is achieved. It is established that the frame with hinged nodes has a lower load-bearing capacity at the node connections in comparison with rigid nodes, but it has a predictable failure mechanism and a shorter duration of the transient dynamic process of the accident impact.