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    方德平     （華僑大學(xué)土木工程系  泉州 362011）

[提要]  推導(dǎo)了梁截面彎矩-軸力-曲率之間的關(guān)系，提出了分析大偏心體外預(yù)應(yīng)力筋的應(yīng)力增量和梁彎曲性能的通用方法。將體外筋的效應(yīng)表示為作用在轉(zhuǎn)向座和錨具的等效荷載，梁（不含體外筋）的內(nèi)力是由外荷載和等效荷載共同引起的。根據(jù)節(jié)點(diǎn)位移和梁的軸力，計(jì)算出附加彎矩（P- Δ 效應(yīng)），直接加在單元的桿端彎矩上，近似地考慮了該效應(yīng)。比較荷載作用前后轉(zhuǎn)向座和錨具的不同位置，計(jì)算出體外筋的應(yīng)變和應(yīng)力。因此該方法考慮了體外筋的變形協(xié)調(diào)條件，同時(shí)自動(dòng)地考慮了體外筋偏心距的損失。計(jì)算結(jié)果與試驗(yàn)結(jié)果吻合。
[關(guān)鍵詞]  體外筋  預(yù)應(yīng)力梁  彎矩-軸力-曲率  抗彎強(qiáng)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