Study On Security And Stability Of Piers Of Bay Bridge In The North Sea Region Under Freeze-thaw Action

Freeze-thaw action caused by seawater in the North Sea region of China has an important influence on safety and stability of the concrete bay bridge. Bay-Bridge of Tsingtao is the first superprojects in the freezing North Sea region of China. This paper is the study on security and stability of substructure of foundation of Bay-Bridge of Tsingtao after freeze-thaw action. Main contents and results are as follows.The decay laws of mechanical properties were obtained through a great deal of concrete freeze-thaw cycle laboratory tests, such as ultimate compressive strength, peak strain, ultimate tensile strength and elastic modulus of concrete structure of pier of Tsingtao bay-bridge. And the freeze-thaw damage constitutive equation of concrete was deduced. According to the relativities of tests between laboratory and field, the degradation laws of mechanical properties of concrete of the piers in different time were established.The finite element model of Cang-Kou Sea-route Bridge in Tsingtao was established by MIDAS. Through the numerical analysis of the finite element model the force loadings of the basic structures of the piers of Cang-Kou Sea-route Bridge were obtained. Also the finite element model of basic structures of the Bay Bridge piers of Cang-Kou Sea-route Bridge in Tsingtao was established by ANSYS. Through the numerical analysis of the finite element model based on nonlinear theory the values and location about maximum stress and maximum vertical displacement of the basic structures of the piers were obtained. Through research, some stability results were gained.The uncertainties have an important influence on the concrete pier structures. The causes of time-dependent reliability of concrete structure in the North Sea region of China were analyzed. On the basis of standards currently in effect, target reliability index of the Bay Bridge in serviceability limit states was obtained. The structure under the tower of Cang-Kou Sea-route Bridge of the Bay Bridge of Tsingtao was analyzed on structure reliability analysis theory based on response surface by ANSYS. The laws of reliability index with time were obtained. And the normal service life of structure under the tower of Cang-Kou Sea-route Bridge was gained.Through experiment research and numerical analysis, some useful results were gained, and the results could provide references for structure design and maintenance.