框架结构中无粘结预应力筋极限应力

为了研究各种结构形式中影响无粘结预应力钢筋(UPS)应力变化的主要设计参数,通过非线性有限元分析给出能全面准确计算各种不同结构形式中UPS极限应力的计算公式。分析了影响UPS应力变化的主要参数综合配筋力比、预应力度、配箍率、跨高比、荷载形式、结构形式对框架结构中UPS极限应力的影响。结论是:对框架结构中UPS极限应力影响较大的设计参数有综合配筋力比、配箍率、跨高比、水平荷载效应比。修正了UPS极限应力的计算公式。结果表明:现有规范ACI318-89、BS8110、JGJ/T92-93计算结果存在局限性,特别是对承受较大水平荷载的无粘结预应力混凝土框架的设计存在不安全的情况。对修正公式、规范公式与试验结果进行了对比。在承受较大水平荷载的框架结构中采用修正公式计算UPS极限应力更准确、对结构使用更安全。

Ultimate stress of unbonded prestressed steel in frame structures

The design parameters influencing stress transformations in unbonded prestressed steel in various structural forms were analyzed using the nonlinear finite element method to determine a formula for the ultimate stress of unbonded prestressed bars. The analysis also considered influences of design parameters the unbonded prestressed concrete such as the synthesis reinforcement force ratio, prestressing degree, hoop reinforcement ratio, span-depth ratio, load form, and structure form on the ultimate stress of unbonded prestressed steel bars in frame structures. The results show that the factors that significantly affect the ultimate stress of unbonded prestressed steel bars in frame structures are the synthesis reinforcement ratio, hoop reinforcement ratio, span-depth ratio, and horizontal load effect ratio. A formula is given relating the four parameters to the ultimate stress of the unbonded prestressed bars. This article also identifies possible unsafe cases when unbonded prestressed concrete frames have large horizontal loadings and the limitations of the current codes ACI318-89, BS8110 and JGJ/T92-93. The accuracy of the corrected formula has been verified by comparison with experimental results.