The paper deals with the operation of continuous two- and three-span beams with damage to the middle support. For a two-span continuous beam, the dynamic coefficients for the action of concentrated forces over the middle support and span of the beam are theoretically substantiated. The results of numerical studies of double-span beams at different loads and time intervals of damage to the middle support are presented. The method of dynamic calculation, which can be used to calculate the survivability of steel structures, has been worked out. A good correspondence of the dynamic coefficients obtained numerically with theoretical values is established. Depending on the order of the formation of the design, the dynamic coefficients vary from 1 to 3. For survivability of the design, the pre-bending of the beams above the middle support is most dangerous. With the use of a well-grounded numerical technique, the dynamic coefficients for a continuous three-beam beam are investigated. For continuous beams, if the middle supports are damaged, it is recommended to use a dynamic coefficient of 2 for the load in the spans adjacent to the damaged support
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