Theoretical Study On Seismic Performance Of Offshore Bridge During Service Period

Since the completion of the Hangzhou Bay Bridge, more and more offshore bridges are under construction. As a result, the durability of bridge structures in the offshore environment is particularly noteworthy, which the change is reflected in the deterioration of materials, and which lead to the decline of seismic performance of bridge structures inevitably. For those problems, the seismic performance of the reinforced concrete structure in the coastal area is studied in this thesis.First of all, for the deterioration of reinforced concrete structure, looking up reference, summed up the factors of affecting the deterioration of reinforced concrete. The concrete-carbonation and steel-corrosion are detailly summarized, and the value of strength and stiffness are calculated.With doubt of a bridge pier design, by changing the reinforcement ratio and axial pressure ratio, meanwhile with the finite element software OpenSEES, the life-cycle seismic performance of bridge is analyzed. The analysis results show that the design of the original pier component is really inappropriate. However the improved bridge pier has better seismic performance, on account of deterioration of the material, the seismic behavior becomes weakened, therefore it is necessary to consolidate the pier at the late stage of bridge life (t=60-90y).The piers of Hong Kong-Zhuhai-Macao approach bridge are numerically simulated. The hysteresis curve, skeleton curve, cumulative-energy consumption are given to estimate the seismic performance of four piers in detail. The results show that the anti-seismic capacity of each pier is good during the whole service life. Also the capacity of cumulative-energy consumption of the 1# pier is the most weak, which means the pier is the most vulnerable to damage under the earthquake.A real bridge is analyzed by counting material deterioration during the whole service period under different seismic intensity,, the results show that the internal force (axial compression force& bending moment) will exceed the capacity of the bridge at late stage of service period. However, the displacement, under various conditions, generally meet the requirements, which means the structure will not collapse under strong earthquake.