Calculation of bending resistance for simply-supported composite-slim beam with deep rib

In the plastic stage, the composite-slim beam with deep rib is of a complex stress distribution in its section, so the existing calculation methods of bending resistance depend greatly on engineering experiences. In order to solve this problem, a method, equivalent rectangular stress distribution, is proposed based on the experiments conducted on two simply-supported composite-slim beam specimens. A model for calculating the bending resistance of the beam is then established and the corresponding formulae are derived. Moreover, a reduction coefficient for concrete peak stress is suggested on the basis of the existing experimental results, preliminarily confirming the correctness of the proposed formulae.