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The re-centring ability and durability of important bridges have been the main objectives in recent provisions of seismic design codes. To achieve better recoverability and durability for piers, this article presents a double-reinforced pier configuration, in which the outer layer is reinforced with fibre-reinforced polymer (FRP) rebar and the inner layer is reinforced with steel rebar. An equal flexural capacity design method was used to determine the double-reinforced configurations. The effects of the potentially influential design parameters on the seismic response of piers were studied and compared to those of conventional RC piers. The results show that the proposed design method can satisfy the ultimate capacity and durability demands. The double-reinforced piers had a better performance than conventional piers in terms of the ductility, post-yield stiffness and residual deformation. The maximum deformation and energy dissipation capacity of the double-reinforced piers were comparable to those of the conventional RC piers. The results also demonstrated that the proportion of steel reinforcement had a clear effect on the performance of double-reinforced piers. However, FRP reinforcement with a high modulus of elasticity should be avoided due to the adverse effect on ductility. [ABSTRACT FROM AUTHOR]

Lack of post-yield stiffness and corrosion resistance could inevitably result in a considerable loss of seismic performance for steel reinforced concrete (RC) piers. Fibre reinforced polymer (FRP) reinforcement can provide high tensile strength and protection from corrosion. To achieve a better post-yield stiffness and durability for piers, FRP/steel double-reinforced configurations were designed by the proposed flexural-capacity design method. A seismic fragility assessment was also conducted to investigate the effectiveness of design parameters, namely the ultimate tensile strength of FRP reinforcement, elastic modulus of FRP reinforcement, and ratio of steel reinforcement for a double-reinforced configuration to that for a steel RC configuration ( ρ steel / ρ prototype ). The results demonstrated that the FRP/steel double-reinforced piers satisfied the mentioned objectives, while the fragility of these piers was a 30.2% less than that of conventional steel RC piers. A 79.9% higher median PGA at the collapse damage state was achieved, when the elastic modulus of FRP reinforcement changed from 164 to 80.7 GPa. An increase in the median PGA of 34.8% can be achieved along with the increase of the ultimate tensile strength of FRP reinforcement. When ρ steel / ρ prototype was approximately 66%, FRP reinforcement exhibited the highest effectiveness on the seismic performance of piers. [ABSTRACT FROM AUTHOR]

Concrete exposed to the tidal zone of the Yellow Sea and bearingCrassostrea gigas(CG) with differing areal coverages was investigated for evidence of biologically induced corrosion prevention. The experimental results indicated that both the chloride ion profile and the neutralization depth of the concrete decreased with increasing CG coverage. Moreover, the water absorption rate and the chloride ion permeability of concrete with the original surface intact also declined with increasing degrees of CG coverage. However, the water absorption rates of three concrete samples with 2 mm of the surface layer removed were similar, as was their chloride ion permeability. Mercury intrusion porosimetry tests indicated that CG significantly reduced the pore structure of the concrete surface layer. SEM observation revealed that the CG cementation membrane and left valve were tightly glued to the concrete surface and had a dense structure. Concrete durability indices showed that high CG coverage greatly improved concrete durability. [ABSTRACT FROM AUTHOR]