预应力砼梁截面的配筋与延性分析

Reinforcement and Ductility Analysis at the Section of Prestressed Concrete Beam

讨论合理配筋的方法，使部分预应力砼梁既满足裂缝控制和承载能力的要求，又具有接近普通砼梁的延性．提出适用于钢筋砼或预应力砼的梁或柱矩形截面的弯矩－轴力－曲率的计算方法；又提出适用于钢筋砼、部分预应力砼、预应力砼截面曲率延性的统一计算方法．分析与预应力砼梁截面延性相关的主要因素并计算了两个最重要因素的预应力度（ＰＰＲ）和配筋指数（ω）对延性的影响．计算结果表明，延性随ＰＰＲ和ω的增大而降低，当ω降低时，ＰＰＲ对延性的影响更为敏感，与预应力梁的试验结果相符．兼顾延性和抗裂的要求，一级抗震ω≤０．２５，ＰＰＲ≤０．５；二级抗震ω≤０．３５，ＰＰＲ≤０．７．

A discussion is devoted to the method of reinforcement which enables beam of partially prestressed concrete(PPC) to meet the requirement of crack control and load bearing capacity and to have ductlity close to that of common concrete beam.Then,the authors present a method applicable to calculating bending moment axial force curvature at the rectangular section of reinforced concrete (RC) or prestressed concrete (PC) beam or column;and present a unified formula for calculating curvature ductility at RC,PPC and PC beam section;and analyse main factors relevant to ductility at PC beam section;and calculate the effect of prestressed degree (PPR) and reinforcement index ( ω ) as two most important factors on ductility.The results from calculation reveal that the ductility decreases with the increase of PPR and ω, and the effect of PPR is even more sensitive at a low ω ,which coincides with the results in literature To give attention to the requirement of both ductility and crack resistance,the values of ω and PPR for earthquake resistance are chosen as follows: ω ≤0 25,PPR≤0 5 for 1st grade earthquake resistance; ω ≤0 35,PPR≤0 7 for 2nd grade one