体外预应力筋极限应力和有效高度计算方法

为了建立体外预应力混凝土梁抗弯承载力简化计算方法,通过系列模型试验形成体外预应力筋极限应力和有效高度的基础数据;基于试验验证的非线性有限元计算方法,分析试验加载方式与我国桥梁规范设计荷载的差异以形成相应的修正系数;根据试验结果分析体外预应力筋极限应力和有效高度随试验参数的变化规律,研究有效高度变化产生的抗弯承载力的二次效应;基于上述分析结果,采用施工方法、跨高比、体内受拉钢筋配比等参数,建立体外预应力筋极限应力和有效高度的回归计算公式,并通过试验数据进行验证;最后按照我国公路桥梁设计可靠度水平和现行规范要求对计算公式进行修正,提出体外预应力筋极限应力和有效高度计算方法。该计算方法能较有效的反映各主要因素对体外预应力筋极限应力和有效高度的影响规律。

Calculation methods for the ultimate stress and effective height of external prestressing tendons

In order to establish a simplified calculation method for the flexural bearing capacity of externally prestressed concrete beams,a series of model tests were conducted to obtain the basic data for analyzing the ultimate stress and effective height of external prestressing tendons.By using the nonlinear finite element method,as verified by the test results,the difference between test loading system and the design load in the Chinese code is compared and a corresponding modification coefficient is introduced.Based on the test results,the variations of ultimate stress and effective height of external prestressing tendons with the test parameters are analyzed,and the second-order effect of effective height variation on the flexural bearing capacity is also studied.With construction method,span-to-depth,area ratio of internal reinforcements as the parameters,the regression formulas for ultimate stress and effective height of external prestressing tendons are established and validated by using the test results.According to the requirements of the current Chinese code and its reliability level for design of highway bridges currently in effect,suitable calculation methods of ultimate stress and effective height for external prestressing tendons are proposed.Use of the proposed methods may reflect the effects of the main factors on the ultimate stress and effective height of external prestressing tendons.