Experimental Study And Theoretic Analysis On Strengthening Beam By External-prestressed-cable-offloading Method

This thesis puts forward a new external-prestressed strengthening beam method, extemal-prestressed-cable-sharing-load strengthening method, which adopts the structure idea of cable bridge. In order to search the feasibility and concrete strengthening construction method of the above strengthening method, three testing beams were made to do experimental research. Besides, farther theoretic analysis and calculation was made.The experimental research shows that the extemal-prestressed-cable-sharing-load strengthening method is a positive strengthening method, which improves strain difference between new strengthening material and old concrete beam. After the testing beams were strengthened, the cracks in them were almost close and bending deflection obviously reduced. After strengthened, the combined structure made up of concrete beam and strengthening system put up the following characteristic: the ability to resist deformation clearly improved, the rigidity distinctly enhanced and the utmost bearing capacity strongly increased. The experiment results showed the strengthening effect by the external-prestressed-cable-sharing-load was very perfect.This thesis offers the typical characteristic curves of the testing beams according to experimental data and analyzes the characteristic of strengthened beam.At the base of the experimental research, this thesis sets forth the strengthening mechanism of the external-prestressed-cable-sharing-load strengthening method and the second bearing-load performance of strengthened beam, deduces the relation between stress increment of external prestressed cable and structure deformation and calculates internal force, deformation and crack width of strengthened beam. Moreover, according to the relation between moment and curvature, nonlinear analysis is made out.