Taking the width/depth ratio of a river channel as an independent variable, a variational analysis of basic flow relationships shows that alluvial‐channel flow adjusts channel geometry to achieve stationary equilibrium when the condition of maximum flow efficiency (MFE) is satisfied. As a test of the veracity of MFE and to examine if this theory of self‐adjusting channel morphodynamics can be practically applied to large river systems, this study examines the degree of correspondence between theoretically determined equilibrium channel geometries and actual measurements along the middle and lower Yangtze River. Using four different forms of the Meyer‐Peter and Müller bedload relation and relations of flow continuity and resistance we show that the Meyer‐Peter and Müller bedload relation modified on the basis of MFE theory predicts channel dimensions most accurately when applied to the middle and lower Yangtze River. This provides convincing evidence supporting MFE equilibrium theory. Copyright © 2014 John Wiley & Sons, Ltd.

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Sediment transport and bed morphology at channel confluences with different confluence angles and discharge ratios are analyzed through a series of flume experiments. Bed topography and sediment transport rate are measured and results are compared among different conditions. Sediment transport is intermittent and pulsating as the tributary flow mixes with the mainstream, and the sediment transport rate goes up with the increase in discharge ratio and confluence angle. With no sediment supplied from upstream of the flume, a central scour hole will form along the shear plane and develop toward the right bank, and the depth of the central scour hole increases as the confluence angle and discharge ratio increase. With heavy upstream sediment supplement, deposition will happen in the separation zone and upstream of the confluence area because of the tributary. And the deposition height is related to the discharge ratio and confluence angle. Results indicate the significant impact of confluence geometry, sediment, and flow factors on fluvial processes.

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Through and half-through arch bridges is one of the main bridge types in China, having arch ribs and simple suspended deck systems, which are connected by high-strength wire suspenders. However, due to the lack of robustness, the suspended deck systems of these types of bridges caused progressive collapse after the suspender corrosion damage. In this study, the internal structural factor of progressive collapse induced by suspender failure was revealed by comparison of five cases of suspender failure, and the robustness requirement of the suspended deck systems was proposed as redundancy to avoid transverse beam collapse when two supporting suspenders on both ends were broken at the same time. Meanwhile, a typical rigid-framed tied through concrete-filled steel tube arch bridge was investigated, and structural condition evaluation was carried out based on the Chinese standard (JTG/T H21-2011). It was found that the evaluation results of bridges with different deck systems were unreasonable, as the better the robustness was, the worse the condition of the deck system was rated, which would mislead the bridge maintenance decisions. A robustness-based evaluation method was then proposed by adopting different evaluation method according to the robustness of the suspended deck system, which is determined by qualitative classification or quantitative calculation. In addition, weight-adjusting method considering robustness was introduced in the evaluation process. The result showed that the new method could objectively reflect the condition of the bridge and thus fits the needs of bridge maintenance and management better.

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