Silver nanoparticles (AgNPs), potent antibiotic materials, have been found to cause cell-membrane damage and produce reactive oxygen species (ROS). The resultant structural change in the cell-membrane could cause an increase in cell permeability of silver ions and AgNPs. To address this issue further, in-vivo and in-vitro cytotoxicity testing of as-made nanomaterials was conducted to quantify and assess their nanotoxicity. Considering the behavior of AgNPs in the environment, toxicity may be reflected by differences in their physicochemical properties (size, agglomeration rate, adsorption properties on humic acid) dependency and toxicity depression. Therefore, we investigated the effect of the cellular uptake of AgNPs with the kinetics of agglomeration and adsorption. The amount of agglomerated and adsorbed AgNPs with sizes of <14 nm was higher than that for AgNPs with sizes of 90 and 140 nm. For 90 and 140 nm sized AgNPs, adsorption was more significant than agglomeration. It is noteworthy that the normal concept that smaller sized AgNPs are taken up more readily may be in error in cases of interactions of abiotic factors.

Cable-stayed bridges are infrastructure facilities of a highly public nature; therefore, it is essential to ensure operational safety and prompt response in the event of a collapse or damage caused by natural and social disasters. Among social disasters, impact accidents can occur in bridges when a vehicle collides with a pier or when crashes occur due to aircraft defects. In the case of offshore bridges, ship collisions will occur at the bottom of the pylon. In this research, a procedure to evaluate the structural behavior of a cable-stayed bridge for aircraft impact is suggested based on a numerical analysis approach, and the feasibility of the procedure is demonstrated by performing an example assessment. The suggested procedure includes 1) setting up suitable aircraft impact hazard scenarios, 2) structural modeling considering the complex behavior mechanisms of cable-stayed bridges, and 3) structural behavior evaluation of cable-stayed bridges using numerical impact simulation. It was observed that the scenario set in this study did not significantly affect the target bridge. However, if impact analysis is performed through various scenarios in the future, the load position and critical load level to cause serious damage to the bridge could be identified. The scenario-based assessment process employed in this study is expected to facilitate the evaluation of bridge structures under aircraft impact in both existing bridges and future designs.

<p>In this study, a firewall was proposed as such countermeasure against the risk of vehicle fires on a suspension bridge, and the effect of the firewall was investigated by CFD analyses considering the proposed firewall. CFD analyses results, it is observed that temperatures exceeding the regulation of PTI standards (300℃) occur in the tanker fire scenario. Thus, countermeasures are required in this case. Therefore, analyses of the cases with firewall were performed, and it was confirmed that installing a firewall reduces the maximum temperature of the cable. Finally, the optimal dimensions of the firewall were suggested through a parametric study of a series of CFD analyses. In the future, if additional CFD analyses for various scenarios and assessment of wind stability considering the firewall installation are performed, it is expected that the cable members of the actual cable- supported bridges can effectively be protected from vehicle fire.</p>

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