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A novel method for prediction of the load carrying capacity of a corroded reinforced concrete beam (CRCB) is presented in the paper. Nine reinforced concrete beams, which had been working in an aggressive environment for more than 10 years, were tested in the laboratory. Comprehensive tests, including flexural test, strength test for corroded concrete and rusty rebar, and pullout test for bond strength between concrete and rebar, were condueted. The flexural test results of CRCBs reveal that the distribution of surface cracks on the beams shows a fractal behavior. The relationship between the fractal dimensions and mechanical properties of CRCBs is then studied. A prediction model based on artificial neural network (ANN) is established by the use of the fractal dimension as the corrosion index, together with the basic intbrmation of the beam. The validity of the prediction model is demonstrated through the experimental data, and satisfactory resuits are achieved. 相似文献
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根据土力学原理 ,推导出一种在不考虑渗流力的情况下 ,确定斜坡临界滑动面和计算斜坡稳定系数的新方法。介绍了该方法在若干土石方工程中的应用实例。 相似文献
44.
本文根据1960~1994年千里岩和青岛月平均气温资料,分析了千里岩与青岛35年来气温的年、季变化特征及差别,发现35年来,千里岩和青岛的年、季平均气温均呈变暖趋势,但千里岩增温幅度较青岛小。从分析中发现,与气温变暖趋势相对应,西北太平洋副热带高压(以下简称副高)面积、强度指数的年、季变化也呈明显的增强、增大趋势。且年平均气温与冬季副高面积指数相关最显著。最后依此关系建立回归方程,并预测了1996年千里岩年平均气温的变化趋势。 相似文献
45.
Atsushi Kaneda Hidetaka Takeoka Eiji Nagaura Yoshitsugu Koizumi 《Journal of Oceanography》2002,58(4):547-556
A cold-water intrusion, called a “bottom intrusion”, occurs in the lower layer of the Bungo Channel in Japan. It is an intrusion
from the shelf slope region of the Pacific Ocean margin in the south of the channel. In order to reveal the fundamental characteristics
of the bottom intrusion, we conducted long-term observations of water temperature at the surface and bottom layers of the
channel and 15-day current observations at the bottom of the shelf-break region. The long-term water temperature data indicated
that the bottom intrusion occurs repeatedly between early summer and late autumn, and its reiteration between early and mid-summer
causes a local minimum of water temperature in the lower layer in mid-summer. Moreover, the data revealed that most of the
bottom intrusions occurred in neap tidal periods. The current meter recorded a bottom intrusion with a speed of approximately
15 cm⋅s−1. The current meter also revealed that the intruded cold water slowly retreated back to the shelf slope region after the intrusion.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
46.
Ching-Piao Tsai Hong-Bin Chen Hwung-Hweng Hwung Ming-Jen Huang 《Ocean Engineering》2005,32(3-4):469-483
Estimation of the wave height transformation of shoaling and breaking is essential for the nearshore hydrodynamics and the design of coastal structures. Many empirical formulas have been well recognized to the wave height transformation, but most of them were only applicable for gentle slopes. This paper reports the experimental results of wave shoaling and breaking over the steep slopes to examine the applicability of the previous empirical formulas. Two steep bottom slopes of 1/3 and 1/5, and one gentle slope of 1/10 were conducted in the present experiments. Experimental results show that the shoaling distance of steep slopes become short and the surface waves may be partially reflected from the steep bottom, thus the estimation of wave shoaling using the well-known previous formula did not conform completely to the experimental results. The previous empirical formulas for the wave breaking criteria were also examined, and the modified equations to the steep beaches were proposed in this work. A numerical model was finally adopted to calculate the wave height transformation in the surf zone by introducing the modified breaking index. 相似文献
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Density, biomass and community structure of macrofauna were estimated together with several sediment characteristics at seven stations ranging from 208 m to 4460 m water depth along the OMEX transect in the Goban Spur area (NE Atlantic) during three seasons (October 1993, May 1994, and August 1995). Median grain size decreased with increasing water depth and showed no differences between the seasons. The percentages of organic carbon and total nitrogen were highest at mid-slope depths (1000 to 1500 m), and were significantly higher in August at the upper part of the slope to a depth of 1500 m. The C:N ratio in the surface layer amounted to 7 to 8 in May, 10 to 12 in August and 14 to 17 in October at all stations (except the deepest at 4460 m, where it was 11 in May and August), indicating arrival of fresh phytodetritus in May, and therefore seasonality in food input to the benthos. Densities of macrofauna decreased exponentially with increasing water depth. Significantly higher densities of macrofauna were found in May at the upper part of the slope to a depth of 1500 m. These differences were mainly due to high numbers of postlarvae of echinoids at the shallowest station and ophiuroids at the deeper stations. Biomass values also decreased with increasing water depth, but biomass was relatively high at the 1000 m station and low at 1500 m, due to relatively high and low mean weights of the individual macrofaunal specimens. No significant differences in biomass were found between the seasons. Respiration was high (15 to 20 mgC·m−2·d−1) in May at the upper part of the slope to a depth of 1000 m and low (1–3 mg C·m−2·d−1) at the deeper part. At the shallowest stations to a depth of 1000 m respiration was highest in May, at the mid-slope stations (1400–2200 m) it was highest in August, whereas the deepest stations (3600 to 4500 m) did not show any differences in respiration rates. In conclusion; seasonal variation in organic input is reflected in denstiy, community structure and activity of the macrofauna along the continental slope in the NE Atlantic. 相似文献