الفهرس 
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Abstract
It has long been known that pier skewness exerts a significant influence on depth of scour around skewed bridge piers. In a design situation, skewness effects can control the foundation design depth, thereby emphasizing the importance of an accurate determination of this quality.
The objective of the study presented herein is a comprehensive and systematic investigation of skewness effects on maximum scour depth, ds, at
skewed bridge piers and the presentation of results in a manner consistent with current design recommendations. The aim is to propose an accurate relationship which can be confidently used to estimate the angle of attack factor, K., and, consequently, used to predict ds. To achieve this goal, a theoretical study for the problem of K\, was carried out. Also, an experimental program was conducted to measure ds at pier models of rectangular and oblong shapes skewed at different
angles of attack.
The experimental work included 120 runs conducted at both the University of Alexandria (UA), Egypt and the University of Iowa (Ul), USA. The experimental investigation was conducted to measure ds under clear-water scour with the bed surface near the condition of incipient particle motion (U/U. = 0.9).
The experiments at UA, were carried out in a 12 m long, 0.86 m wide and 0.6 m deep flume, prepared to have a 6.0 m long sediment recess. A nonuniform sand and relatively shallow flow were used. At Ul, the experiments were conducted in a 25 m long, 1.5 m wide and 0.6 m deep flume, equipped with sediment recess. A uniform sand and relatively deep flow were used. At both UA and Ul, two pier shapes, oblong and rectangular of constant width, 35 mm, were used. For each shape, five aspect ratios, Ub = 4, 6, 8, 10, 12, were investigated. For each pier, the skewness was varied in 15° steps from 0° to 90°.