Seismic Performance and Nonlinear Strain Analysis of Mechanical Splices for High-Strength Reinforcement in Concrete Structures.

This study investigates the strain development in reinforcing bars within the plastic hinge regions of beams and columns, with the main objective of modifying the current acceptance criteria for mechanical bar splices to accommodate high-strength reinforcement. The investigation utilizes numerical analysis based on moment-curvature and deformation analysis of typical beam and column sections in a special moment frame. The results indicate that the use of higher grade reinforcement, such as Grade 550 or 690, results in lower strain demands in the plastic hinge regions compared to Grade 420 reinforcement. To validate the modified seismic loading protocol, over 100 samples of mechanical coupling systems were tested in Taiwan. The test results demonstrate that the majority of these systems can successfully complete the modified seismic loading protocol and are suitable for use in critical plastic hinge regions of special moment frames. However, caution is advised for slender mortar-grouted coupling sleeves, as they were unable to fulfill the seismic loading protocols. These sleeves may be conditionally used in plastic hinge regions of precast columns, provided they meet specific conditions and demonstrate seismic performance through structural testing. The findings of this study offer valuable insight into the design and application of mechanical splices in high-strength reinforcement scenarios.

Polycyclic aromatic hydrocarbons in surface sediments of the East China Sea and their relationship with carbonaceous materials.

This study measured concentrations of polycyclic aromatic hydrocarbons (PAHs) in surface sediments in the East China Sea (ECS) to investigate possible sources and fate of PAHs. Total concentration of PAHs in the sediments of the ECS ranged from 22 to 244 ng g(-1), with the highest levels in the coastal area and outer shelf. The observed PAH results showed elevated levels in both inner and outer shelf areas, a finding that is different from predictions by an ocean circulation model, suggesting that terrestrial sources are important for PAH contaminations in the ECS, while sediment resuspension, tidal changes and lateral transport may be important in affecting the distribution of PAHs in the outer shelf. The distribution of PAHs in the surface sediments of the ECS is similar to the distribution of carbonaceous materials (e.g., particulate organic carbon and black carbon), suggesting that carbonaceous materials may strongly affect the distribution of PAHs.

A long-term survey on anthropogenic impacts to the water quality of coral reefs, southern Taiwan.

Before 2001, the ecological protection area in the Kenting National Park (KTNP), southern Taiwan, was poorly described. In this study, a set of four-year data (2001-2004) of seawater qualities at 19 sampling sites around the Nanwan Bay in the KTNP was used to explore anthropogenic impacts to ecological environment, especially coral reefs. The parameters of water quality were analyzed immediately after collection. The results showed that higher values of nutrients and suspended solids were attributed to the higher run-off around Nanwan Bay. The fluxes of nutrients and suspended solids were consistently correlated to rainfall. Hence, equations were developed to calculate nutrient fluxes and suspended solids by using only rainfall data. Our results show that suspended solids and ammonia were the dominant factors leading to the drop in coral coverage. In summary, the water quality in the intertidal zone of Nanwan Bay has been degraded and required greater attention.

A model to predict total chlorine residue in the cooling seawater of a power plant using iodine colorimetric method.

A model experiment monitoring the fate of total residue oxidant (TRO) in water at a constant temperature and salinity indicated that it decayed exponentially with time, and with TRO decaying faster in seawater than in distilled water. The reduction of TRO by temperature ( degrees K) was found to fit a curvilinear relationship in distilled water (r(2) = 0.997) and a linear relationship in seawater (r(2) = 0.996). Based on the decay rate, flow rate, and the length of cooling water flowing through at a given temperature, the TRO level in the cooling water of a power plant could be estimated using the equation developed in this study. This predictive model would provide a benchmark for power plant operators to adjust the addition of chlorine to levels necessary to control bio-fouling of cooling water intake pipelines, but without irritating ambient marine organisms.