Study On Flexural Performance Of Concrete Beams Strengthened With Multi-supports Unbonded Prestressed CFRP Laminate

The technology of concrete beams strengthened with unbounded prestressed CFRP laminate is a new type that developed from the combination between the structural engineering of strengthening and repairing and high-new material engineering in recent years, however, due to CFRP laminate of high-strength can not be fully played and end anchorage is easily stripping damaged in practical engineering, compared with the technology of concrete beams strengthened with bounded prestressed CFRP laminate, the strength efficiency of concrete beams strengthened with unbounded prestressed CFRP laminate remains to be further improved. Based on the existing technology of concrete beams strengthened with unbounded prestressed CFRP laminate, the strengthening technology of multi-supports unbounded prestressed CFRP laminate is proposed. On the basis of previous experiment results, the study on flexural performance of concrete beams strengthened with multi-supports unbounded prestressed CFRP laminate is proceeded by numerical simulation through ABAQUS software, the main research contents and conclusions is as follows:(1) The finite element analysis model that adapted from the previous experiment study is established through ABAQUS software, the element type, constitutive relation and other parameters were determined by the properties of experimental materials such as steel, concrete and CFRP etc. Through the comparative analysis between experiment result and ABQUS calculation result, including load of different stages, midspan deflection and concrete strain in the beam cross section, the comparative result is good, and the feasibility of the finite element analysis model is verified.(2) Based on the validated finite element analysis model, the influence that various factors on bearing behavior of concrete beams strengthened with multi-supports unbounded prestressed CFRP laminate is comparative analysed, include degree of prestress, number and spacing of support etc. Besides, the variation law of bending stiffness, bearing capacity and deflection is also discussed, the results of analysis showed that: 1) within a certain range, prestress level is proportional to the flexural stiffness of concrete beam, with the improvement of prestress level, the bending deformation of concrete beam in the stage of usage is effectively restrained, and the bearing capacity is also significantly improved. 2) different number and spacing of support has a certain effect on bearing capacity, flexural stiffness and deformation of concrete beam: with the increase of multi-supports, both yield load when tensile steel yielding and ultimate load when CFRP plate failing in tension increase accordingly. The improvement of ultimate load is obviously bigger than yield load, but the ultimate load remains stable when the support increases to a certain number. When used in practical engineering, we should choose the different number and spacing of support on the basis of the practical condition of the engineering(3) The formula of concrete flexural members strengthened with unbounded prestressed CFRP laminate is put forward, including the cracking load, ultimate load and the midspan deflection, etc. The error of calculation value, compared with test value, is no more than 15%.