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RC bridge substructures exposed to chloride environments inevitably suffer from corrosion of reinforcement embodied in concrete. This deterioration issue leads to the loss of reinforcement areas and a reduction in seismic capacity of reinforced concrete (RC) bridge substructures. To quantify the effect of steel corrosion on seismic fragility estimates, this paper proposes an improved time-dependent seismic fragility framework by taking into account the increase in the corrosion rate after concrete cracking and the reduction in seismic capacity of RC bridge substructures during the service life. Additionally, an analytical method based on a back propagation artificial neural network (BP-ANN) is proposed to provide probabilistic capacity estimates of deteriorating RC substructures. A three-span T-shaped girder bridge is selected as a case study bridge to provide improved time-dependent seismic fragility estimates that consider uncertainties in the material properties, geometric parameters, deterioration process and ground motions. The obtained fragility curves show that there is a nonlinear increase in the exceedance probability of deteriorating RC bridge substructures for different damage states during the service life. In addition, time-dependent seismic fragility analysis shows that the cases of considering only the effect of an increase in seismic demand or the reduction in seismic capacity as well as neither of them may lead to a significant underestimation of the seismic vulnerability of deteriorating RC bridge substructures.

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This study introduces a method to obtain accurate results regarding bridge seismic cost and reduce structural seismic losses. A three-span reinforced concrete (RC) continuous bridges model consistent with the reality was established, and seismic vulnerability of the RC bridge was calculated via incremental dynamic analysis combined with local earthquake disaster data. Direct losses from earthquakes are calculated based on local earthquake damage condition, specific maintenance reinforcement methods, and analysis of seismic vulnerability. The indirect economic losses caused by inspection and maintenance are calculated based on local traffic volume. To reduce the effects of bridge aging and deterioration, this paper examines periodic inspection of bridges after earthquakes. By calculating the life cycle cost of structure under different inspection frequencies, the optimal time interval was determined. The results presented for this study can serve as references for the calculation of structural seismic loss and thereby provide the basis for strategies of reducing seismic loss.

Well-defined carbonated hydroxyapatite microspheres assembled from nanosheets were synthesized by a Na2EDTA-assisted hydrothermal homogeneous precipitation route.

The morphology, nanostructures, and crystallinity of hydroxyapatite (HA) materials have significant effects on their physicochemical properties and biomedical applications. However, the controllable synthesis of HA nanomaterials with various size and morphology using the same synthesis system, though desirable, has remained a challenge. In this work, we successfully synthesized HA nanomaterials with different morphologies via a one-step solvothermal route in the same reaction system. By using (NaPO3)3, Na3PO4·12H2O and NaH2PO4·2H2O as phosphorus sources, the growth of HA crystals was regulated, resulting in the transformation of HA nanomaterials morphology from nanorods to nanowires. Different concentrations of PO43− and OH− ions in the reaction environments regulated by different phosphates lead to different nanostructures of HA crystals. Our work provides an instructive way to controllably fabricate HA nanomaterials with various morphologies and will widen the biomedical applications of HA materials.

The experiment study on the air-entrained concrete of 100 mm cubes under triaxial compression with different intermediate stress ratioα2=σ2D : σ3Dwas carried out using a hydraulic-servo testing system. The influence of rapid freeze-thaw cycles and intermediate stress ratio on the triaxial compressive strengthσ3Dwas analyzed according to the experimental results, respectively. The experimental results of air-entrained concrete obtained from the study in this paper and the triaxial compression experimental results of plain concrete got through the same triaxial-testing-system were compared and analyzed. The conclusion was that the triaxial compressive strength is greater than the biaxial and uniaxial compressive strength after the same rapid freeze-thaw cycles, and the increased percentage of triaxial compressive strength over biaxial compressive strength or uniaxial compressive strength is dependent on the middle stress. The experimental data is useful for precise analysis of concrete member or concrete structure under the action complex stress state.