Study on shear creep, relaxation and long term strength of serrate structure surface

Abstract:

To comprehensively analyze the creep, relaxation, long-term strength of serrate structure surface, the creep and stress relaxation tests of dentate discontinuity poured by cement mortar were carried out using biaxial creep machine under step load. Firstly, the similarities and differences between creep and relaxation were analyzed, and the differences of shear stress-displacement curves in creep process and relaxation process were compared. Secondly, a new stress relaxation model was presented based on the creep rate equation and the relations between creep and relaxation. Finally, the long term strength was determined separately by creep test and relaxation test, and contrastive analyses were made. The results show that the creep curve has similar shape with stress relaxation curve, but the trend of the creep curve is opposite to that of the stress relaxation curve. The creep deformation and stress relaxation amount increase with the increase of slope angles. The shear stress-displacement curve during creep test process and relaxation test process reveal the stress-strain path of creep differently from relaxation, which indicates the energy change in creep test different from relaxation test, so it cannot be simply considered to be equivalent between creep and relaxation due to the irreversibility of work. Though the stress relaxation model can fits the experimental data better, the differences among the orders of magnitude of the the parameter in creep equation and relaxation equation are 1 series. Based on the same mechanism, the long term strength of creep test is similar to that of relaxation test, in which the difference rate is about 9%. The long term strength is very close to yield strength in the shear stress-displacement curve of creep test and relaxation test.