方德平     （华侨大学土木工程系  泉州 362011）

[提要]  推导了梁截面弯矩-轴力-曲率之间的关系，提出了分析大偏心体外预应力筋的应力增量和梁弯曲性能的通用方法。将体外筋的效应表示为作用在转向座和锚具的等效荷载，梁（不含体外筋）的内力是由外荷载和等效荷载共同引起的。根据节点位移和梁的轴力，计算出附加弯矩（P- Δ 效应），直接加在单元的杆端弯矩上，近似地考虑了该效应。比较荷载作用前后转向座和锚具的不同位置，计算出体外筋的应变和应力。因此该方法考虑了体外筋的变形协调条件，同时自动地考虑了体外筋偏心距的损失。计算结果与试验结果吻合。
[关键词]  体外筋  预应力梁  弯矩-轴力-曲率  抗弯强度  大偏心

The M-N- ф relationship of a beam section is studied. A general method for analyzing the stress increment of external tendon with large eccentricity and beam flexural behavior is presented. The action of external tendon is expressed as the equivalent loads applying at the deviators and anchorage ends. The beam not including external tendon is subjected to both external and equivalent loads. Based on the displacements of nodes and axial forces, the additional bending ruoments ( P- Δ effect) are calculated approximately, and added directly to the element ends. By comparing the different positions of deviators ancl anchorage ends before and after loading, the stress and strain of external tendon are obtained,  the deformation compatibility of the external tendon is met, and the loss of tendon's eccentricity can be considered automatically. The calculation results conform well to the experimental results.
Keywords: prestressed concrete beam; external tendon; bending moment-axial force-curvature; flexural strength; large eccentricity