Minimum Potential Energy Principle on Slip Calculation of Composite Beams

Energy method has the mathimatical convenience because it is scalar. The work potential is work done by external forces. After it is transfered to the work done by the internal force, the classical second-order differential equation of slip effects is deduced according to Minimum Potential Energy Principal. In the derivation, integration by parts is used to transfer the higher order variation into the first order according to Euler Equation. For simply-supported composite beam, the slip-induced stresses are self-equilibrium and the redistributed internal forces are significant. The slip effects is important for composite beams in service time, like the compresion stress of the top flange of steel beam may become the 11.5 times, which arises the problem of local buckling.