Based on the technology analyses of strengthening reinforced concrete beams with carbon fiber sheet, and the research of calculate theory, The paper raises the technology of Relief method.

The results are in good agreement with what are found by unloading compliance method.

Experimental research on form finding of beam string structures is carried out in order to verify offload-by-steps method, and more importantly, to study the application of the method in engineering practice.

Based on fundamental principle of loading-perturbation method to shift equilibrium path,the paper presents four-step loading-unloading procedure to pinpoint the bifurcation point between the initial equilibrium path and the branching one and trace the branch paths using general FEA software.