研究目的:对于主槽占河道宽度较大，边滩相对较窄的河段，当主槽中不容许设置墩台且结构高度受到 桥头路面标高和设计洪水位等多重因素控制时，如何选择合适的桥式桥跨方案，设计出经济、合理的桥梁结 构，是广大桥梁工程技术人员要研究的课题。
研究结论:本文的设计研究表明:在具有上述河道特征的河段，桥梁设计往往受到多重因素控制，此时可 以结合实际情况进行多方案比选，其中边中跨比值明显小于常规值的异形预应力混凝土连续梁桥方案有时 是一种比较好的桥型选择。对于这种桥型，关键的问题是要采取必要的措施防止边支座出现拉力，解决的办 法可以选择在边跨设置实心截面、横向加宽、竖向加厚等平衡压重措施，必要时也可以在梁底加设压重块。
Research purposes: For the river reach with broad main channel and narrow alternative bar, when the piers are not allowed to set in the main channel and the structural height is controlled by such multiple factors as pavement elevation of bridge approach and designed flood level, etc.，how to select the right bridge type and span scheme as to work out the economical and reasonable bridge structure is a subject to be studied by bridge designers.
Research conclusions: In the paper, the study shows in the river reach with above-mentioned characteristics of river reach the design of bridge is generally controlled by multiple factors. Therefore, the comparison can be made on multiple schemes in combination with practical circumstances. It is thought that the abnormal-shape prestressed concrete continuous beam bridge of which side-middle span ratio is smaller obviously than normal that is sometime a better selection of bridge type. For this bridge type, it is key to take measures for preventing bridge side bearing from occurrence of tension. It is suggested to take such a counter weight measure that the side span is solid section and widened transversely and thickened vetically, if necessary, the concrete blocks can be set at the bottom of beam for counter weight.
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