Limit load calculation method for double-span and multi-span floor system side column failure in fire

The invention discloses a limit load calculation method for double-span and multi-span floor system side column failure in a fire disaster, which comprises the following steps: S1, carrying out arc-shaped infinitesimal division on a plate, and carrying out stress assumption on three adjacent beams of a failed side column; s2, on the basis of conservative estimation, the distribution condition of force on the beam is determined; s3, calculating a deflection curve equation of the beam at normal temperature according to the deflection definition of the beam; s4, determining a deflection curve equation caused by the thermal gradient, and substituting the deflection curve equation into the deflection curve equation at the normal temperature to calculate the deflection curve equation caused by the thermal gradient of the beam top and the beam bottom; s5, based on a plate balance method and a principle of additional moment caused by a plastic hinge line, calculating the change of unit bearing capacity of the fan-sha