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Influence of chloride ion corrosion on the performance of reinforced concrete beam bridge in offshore environment

100%

Gao Y. H.

2020

tom Vol. 66, nr 2

253--265

Chloride ion erosion in offshore environment may damage the mechanical properties of beam bridges. In this study, the reinforced concrete specimen was designed, accelerated erosion experiments were carried out to simulate the coastal corrosion environment, and the corrosion rate, nominal strength and equivalent strength of steel bars, concrete cracks and reliability of beam bridges were calculated to understand the time-varying mechanical properties of beam bridges. The results showed that the nominal and equivalent strength of reinforcing bars decreased with the increase of corrosion rate of reinforcing bars. The change of yield strength was greater than that of equivalent strength. The change of crack width of concrete showed a slow-fast-slow trend, and the reliability of beam bridges decreased significantly in about 50 years. The experimental results show that chloride ion corrosion can significantly damage the mechanical properties of the beam bridge and affect the time-varying reliability of the beam bridge. Therefore, it is necessary to carry out timely maintenance and inspection and take effective methods to control steel corrosion to ensure the safety of the use of the beam bridge.

Warming effects on plant growth, soil nutrients, microbial biomass and soil enzymes activities of two alpine meadows in Tibetan Plateau

51%

Li N. , Wang G. X. , Gao Y. H. , Wang J. F.

nr 1

The aim of this study was to assess initial effects of warming on the plant growth, soil nutrient contents, microbial biomass and enzyme activities of two most widespread ecosystem types: swamp meadow (deep soil, high water content) and alpine meadow (poor soil, low water content), in the hinterland of the Qinghai-Tibet Plateau (altitude 4600–4800 m a.s.l.) The temperature of air and upper soil layer was passively enhanced using open-top chambers (OTCs) (50 cm high with 60 cm at opening and constructed of 6 mm thick translucent synthetic glass) from 2006 to 2008. The use of OTCs clearly raised temperature and decreased soil moisture. In warmed plots, monthly mean air temperature was increased by 2.10oC and 2.28oC, soil moisture of 20 cm soil layer was decreased by 2.5% and 3.9% in alpine meadow and swamp meadow, respectively. Plant biomass significantly increased by 31% in alpine meadow and 67% in swamp meadow. Warming also affected soil microbial biomass C and N at both meadows. In swamp meadow, warming caused the decrease of soil organic carbon and total nitrogen in 0–5 cm layer and an increase in 5–20 cm. While in alpine meadow, these soil parameters increased in 0–5 cm layer and decreased in 5–20 cm layer. The effects of warming on enzyme activities differed depending on the enzyme and the meadow ecosystem. In general, enzyme activities were higher in the upper soil layers (0–5 cm) than in the lower soil layers (5–20 cm). The experiment results exhibited that warming improved the soil biochemical and microbiological conditions in high- mountain meadows, at least in the short term.