Abstract: In the formulas of Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(short for Code)for calculation of eccentric compression members, the stress of reinforcing steel is discontinuous, which, to a certain extent, has an influence on the depth of compression zone, judgment of large or small eccentricity and bearing capacity of members. Firstly, in order to study the uniqueness of the quadratic equation and the distribution of the depth of compression zone, theoretical analysis of formulas for eccentric compression members of large or small eccentricity was made. Then, for the purpose of proving the influence on bearing capacity of the eccentric compression member, concrete illustrations containing 3 groups of material, namely C30-HRB335, C50-HRB335 and C30-HRB400, were used for contrastive study. Results show that there is only one solution in(0，+∞)for the quadratic equation; under the circumstance of firstly assuming that it is an member of large eccentricity, there is a blank interval in the distribution of depth of compress zone; under the circumstance of firstly assuming that it is a member of small eccentricity, there are both a blank interval and a wrong judged interval, and the phenomenon of nondeterminacy wont happen when judging the eccentricity. The bearing capacity of the same eccentric compress member has error at the critical eccentricity under both hypotheses. The error of firstly assuming large eccentricity is smaller than that of firstly assuming small eccentricity. There is a positive correlation between the error and the strength of materials. Research on distribution of depth of compression zone and bearing capacity has referential value for further revision of the formulas in the Code.

Key words: bridge engineering, member, eccentric compression, judgment of large or small eccentricity, bearing capacity

摘要： 现行《公路钢筋混凝土及预应力混凝土桥涵设计规范》(简称《规范》)的偏心受压构件计算公式中，受拉钢筋的应力是不连续的，这对偏心受压构件的受 压区高度、大小偏心判别及构件的承载力会有一定的影响。首先，从理论上对大小偏心受压公式进行了分析，研究了一元三次方程解的唯一性和大、小不同偏心 假设下构件受压区高度的分布情况；然后，用C30+HRB335、C50+HRB335及C30+HRB400这3组材料组合的具体算例，对比研究了偏心受压构件承载力所受到的影响 。结果表明：一元三次方程的3个解中，只有1个解位于(0，+∞)上；先假设为大偏心的情况下，受压区高度的分布存在空白区间；先假设为小偏心的情况下，存 在空白区间和误判区间，大小偏心判别不会发生不确定性现象；针对同一偏心受压构件，在不同的偏心假设下，承载力在临界偏心距处均存在误差，且先假设为 大偏心时的误差小于先假设为小偏心时的误差，误差与材料强度呈正相关。研究结论可对《规范》偏心受压公式的修改提供参考。

关键词: 桥梁工程, 构件, 偏心受压, 大小偏心判别, 承载力