三跨变截面连续梁体外预应力筋应力增量

通过4根不同预应力度及不同配筋率的体外预应力三跨变截面连续梁静力试验，对体外预应力筋应力增长规律进行了研究．结果表明：应力增量与梁中跨跨中截面挠度呈线性关系；应力增量、跨中截面挠度与外荷载之间的关系可以梁中跨跨中截面、梁中支座截面开裂作为分界点，用三折线模型描述．据此提出了“三折线刚度折减”按弹性理论计算预应力筋应力增量的方法，计算结果与非线性数值分析结果吻合．

Stress Increment of Externally Pre-stressed Tendons of Three-Span Continuous Concrete Beams with Varying Section

Based on the experimental result of 4 three-span externally pre-stressed concrete continuous beams with different pre-stress degrees, reinforcement ratios and sections, the stress increment of externally pre-stressed tendons was investigated. The result shows that the stress increment is directly proportional to the deflection at mid-section in the middle span, and the relation among the stress increment, the deflection and the load may be described using a model of tri-broken line. In this model, crackings of the mid-section and the mid-support section are taken as its turning points. As a result, a simplified method of calculating the stress increment based on the elastic theory was proposed, the calculated result being accorded with that of a non-linear analysis.