Abstract:Freeze-thaw action caused by seawater in the North Sea region of China has an important influence on the safety and stability of concrete bay bridge.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 and damage constitutive equation of concrete of the pier in different time were established. The finite element model was established for basic structures of the Bay Bridge pier of Cang-Kou Sea-route Bridge in Tsingtao. Through the numerical analysis of the finite element model based on nonlinear theory the location and variation trends about maximum stress and maximum vertical displacement of the basic structures of the pier in different times were obtained. The results could provide references for structure design and maintenance of Tsingtao concrete bridge.