Abstract：
The steel?鄄concrete composite beam is a new type of structure on the basis of steel structure and reinforced concrete structure?郾When it is a continuous beam the steel will be pressed and the concrete will be pulled in the negative moment areas?郾This is an unfavorable tress condition?郾The deck concrete beam will be fractured due to tension and the steel and bar will be exposed and rusted，thus the bearing capacity and endurance of the structure will be affected?郾But this unfavorable stress condition can be amended by double composite beams（the lower flange reinforced concrete slabs are set in the inner brackets of traditional single composite beams in negative moment areas）?郾The cross?鄄section rigidity of a double steel?鄄concrete composite beam is calculated by the simplified calculating method in this article and together with the test values are compared and analyzed?郾
