空腹式连续刚构桥跨径与根部梁高的经济取值研究

Study of Economic Span Length and Pier-Top Girder Depth for Open-Web Continuous Rigid-Frame Bridge

为了优化空腹式连续刚构桥的关键设计参数,提高经济效益,以贵州水盘高速北盘江大桥为背景,根据上部结构混凝土、普通钢筋和预应力钢束的工程量及其造价提出延米经济指标的概念,从工程造价的经济性角度研究了空腹式连续刚构桥跨径和根部梁高这2个关键结构设计参数的取值范围。采用有限元参数分析法研究了在桥梁主跨L=210,250,290,330,370m,且根部梁高分别为L/5、L/6、L/7、L/8、L/9、L/10、L/11等工况下,上部结构延米经济指标的变化规律。研究表明:混凝土造价的比重随着根部梁高的减小和主跨的增大而不断降低,预应力钢束造价的比重与混凝土刚好相反;上部结构的延米经济指标随根部梁高的减小先降后增,根部梁高在L/8~L/7范围内取值时,延米经济指标最低;空腹式连续刚构桥的经济跨径约为210~290m,超过300m以后,上部结构的经济性将显著降低。

To optimize the key parametric design of the open-web continuous rigid-frame bridge and improve the economic performance of the project, the Beipanjiang Bridge on the Shuipan Ex-pressway in Guizhou Province was cited as an example for the study. Based on the material used and construction costs of the concrete in superstructure, common reinforcement and prestressing tendons, an economic index of linear meter is proposed, by which the ranges of the two key struc-tural design parameters of span length and pier-top girder depth of the open-web continuous rigid- frame bridge were studied from aspect of engineering costs. The finite element parametric analysis method was used to study the variation law of the economic index of linear meter of the superstruc-ture when the main span length was set at 210 m, 250 m, 290 m, 330 m and 370 m, and the pier- top girder depth was set tobeL/5, L/6, L/7, L/8, L/9, L/10, and L/11 , respectively. The re-sults of the study indicate that the decrease of the pier-top girder depth and the increase of the man span length cause the declining of the proportion of costs of concrete but the rising of the propor-tion of costs of prestressing tendons. As the decrease of the pier-top girder depth, the economic in-dex of linear meter of the superstructure shows sign of declining first, and then rising, when the pier-top girder depth is within the range of L/8？L/7, the economic index of linear meter is the lowest. The span lengths within the range of 210-290 m are regarded as the economic values for the open-web continuous rigid-frame bridge, when the span length excesses 300 m , the economic performance of the superstructure will distinctively decline.