Study On Cracking Of Pc Continuous Rigid Frame Bridge During Construction Process Based On Strain State

PC continuous rigid frame bridge in China has been rapidly developed in the last two decades. However, a lot of problems occurred during this period and the cracking of concrete box girder is one of the serious problems.Cracking can classified as construction process cracking and service process cracking according to time. Based on a certain PC continuous rigid frame bridge, cracking occurred during the construction process was stuied in this thesis and the main research contents are as follows:1. Cracking phenomenon of PC continuous rigid frame bridge in China was summarized, especially the cracking during the construction process. On this base, cracking during the construction process was classified according to different standard.2. Strain-energy density described by the principal strain was deduced, a theory used the strain state method to analyse the security risk of structural material was proposed, what’s more, a concept of inhomogeneous strain and a theory of strain strength was put forward at the same time.The mechanics behaviors and structure crack security of the concrete was discussed and analyzed during the construction process of PC continuous rigid frame bridge.3. As the major factors which would case complex strain state during the construction process, prestressing effect, temperature effect, shrinkage and creep were stuied.The factors influencing the prestressing effect were analyzed, such as the waiting age to tension and recurvation angle of prestressing tendon.Further more, the stress state of the closure segment was discussed after stretch-draw of closure prestressing strands. Combined with the APDL parametric programming function of ANSYS, the influence of non-uniform temperature field to the stress and strain state of concrete box girder during the construction process was studied from two aspects, hydration heat and solar radiation. Besides that, the temperature effect to Concrete box girder at Cantilever construction stage was analysed by different vertical temperature gradient mode. In additional, combined with the influence of creep, shrinkage stress was analyzed which is caused by the shrinkage strain difference at the bond surface of concrete.