大跨度双线铁路混凝土桥极限跨径的研究

混凝土桥是我国大跨度铁路桥梁广泛应用的结构形式,但长期以来缺少对不同桥型跨越能力和适用范围的系统研究。大跨度混凝土桥的设计实践表明,支点截面混凝土的抗剪通常是控制其跨越能力的主要因素,以荷载作用下的剪应力达到混凝土容许剪应力为标准,分析得到了双线预应力混凝土连续梁(刚构)桥的理论极限跨径。在此基础上,通过分析主梁与加劲拱、拉索的荷载分配关系,进一步研究得到了连续梁(刚构)-拱桥、部分斜拉桥的理论极限跨径,分析结论与实际工程基本相符。同时在理论值基础上,结合设计经验给出工程实用极限跨径的建议值,对大跨度混凝土桥的桥式方案选择和投资控制具有一定价值。

Research on Ultimate Span of Concrete Railway Bridges on Double-track Railways

Pre-stressed concrete bridges are widely used in the construction of long span railway bridges in China,but few researches have been conducted on the spanning capacity and reasonable application range of different bridge types. According to design practices, the spanning capacity is generally controlled by the shear strength of the section near the pier. The theoretical ultimate span of railway PC girder bridges is analyzed when the shear stress generated by load is equal to the allowable shear stress of concrete. Based on the analysis results of girder bridges and load distribution between the girder and the stiffen structure,the theoretical ultimate span of girder-arch hybrid bridges and extradosed bridges are obtained. The results are approximately conformed to the actual engineering. Practical engineering ultimate spans are proposed according to the theoretical values,and the results are applicable for the technical and economic comparison of different bridge types.