Durability damage of reinforced concrete bridges in an offshore environment often occurs in varying degrees with the extension of service life. Meanwhile, statistical data on earthquake damage show that most of the main earthquakes are accompanied by strong aftershocks, and the seismic response of bridges under the main shock and main aftershock is different. To analyze the effects of the main aftershock sequence and durability damage on the seismic performance of concrete bridges, this study establishes a nonlinear dynamic analysis model of an offshore bridge with a continuous rigid-frame girder based on the OpenSEES platform. Moreover, this work constructs the main aftershock sequence considering the degradation of the mechanical properties of materials after durability damage repair under normal maintenance conditions and the time-varying seismic effect of shortening the subsequent service period, and investigates the time-varying seismic fragility of offshore bridges under the main aftershock sequence. Results show that the seismic response of bridge structures considering the main aftershock sequence is significantly larger than that considering the main shock only. Material deterioration will lead to the increase in the seismic response of bridge components under earthquake. The seismic time-varying fragility of offshore bridges considering material deterioration and seismic time-varying effects is analyzed based on time-varying seismic action in the entire life cycle. The influences of the two factors should be considered comprehensively when evaluating the seismic performance of bridges throughout their entire life.

In this study, recycled fine aggregate (RFA), also known as recycled brick micro-powder (RBM), was used to completely replace quartz sand for the preparation of green, low-cost ecological engineered cementitious composites (ECO-ECC). RFA was used to replace ultrafine silica sand in the range of 0–100%. Firstly, the optimal replacement rate of RFA was determined, and the test results showed that the ECO-ECC prepared by fully replacing quartz sand with RFA as fine aggregate had strain hardening and multiple cracks, and the tensile strain of the specimens could reach 3%. Then the effects of fiber volume fraction and size effect on the mechanical properties of ECO-ECC were systematically investigated. The results showed that the fiber volume fraction has some influence on the mechanical properties of ECO-ECC. With the increase of fiber volume fraction, the ultimate deflection of the material keeps increasing up to 44.87 mm and the ultimate strain up to 3.46%, with good ductility and toughness. In addition, the compressive strength of the material has a good size effect, and there is a good linear relationship between different specimen sizes and standard sizes. It provides a good basis for engineering applications. Microscopic experimental results also showed that fibers play an important bridging role in the material, and the fiber pull-out and pull-break damage effects are significant.