【作者】 王玉良；

【导师】 王铁成；

【作者基本信息】 天津大学 ， 结构工程， 2007， 博士

【摘要】 预应力钢筒混凝土管(Prestressed Concrete Cylinder Pipe,简称PCCP)是一种优质复合管材,在大口径输水管线选型时,越来越具有竞争力。由于PCCP中含有混凝土、钢筒、预应力钢丝,结点构造和地下埋置工况复杂,对于PCCP的受力机理认识尚不统一。本文旨在研究PCCP受力机理,探讨预应力设计计算方法,分析PCCP的应力分布规律、管壁开裂性能、砂浆保护层的剥离性能以及PCCP抗裂可靠度。首先以完全弹性理论为基础,根据环形预应力作用机理,结合多层圆筒轴对称平面形变计算理论,建立了PCCP在使用阶段的理论计算方法。结合PCCP结构抗裂承载能力的要求,给出运行阶段PCCP预应力设计计算公式。并对受力模型与有限元分析结果进行对比,对预应力设计计算公式进行相应的修正。通过对PCCP在不同管壁厚度、埋深、内水压力和混凝土强度等级条件下PCCP最大环形应力变化特征和PCCP在内水压力作用下裂缝扩展过程以及砂浆保护层剥离性能进行数值分析,结果表明:(1)PCCP中最大环向应力随着埋深、内水压力的增大而增大,最小应力随着埋深、内水压力的增大而减小;(2)增加管壁厚度能够明显减小管道环向应力,而增加混凝土强度等级对改善混凝土的受力效果并不明显;(3)管侧砂浆较早开裂,并随着内水压力的增大向两侧扩展,外层管芯管腰较管芯其它部位较早开裂,并随着内水压力的增大向两侧扩展并向深处延伸,内层管芯管顶基本为一次裂通;(4)在发生开裂时,钢筒和预应力钢丝上在相应位置的应力会发生突变;(5)PCCP砂浆保护层剥离是预应力钢丝应力松弛、管体内外部温度差、保护层收缩共同作用的结果。最后采用改进支持向量机(SVM)响应面方法研究了PCCP抗裂可靠度,结果表明:混凝土抗拉强度和混凝土变异性,以及内压变化对抗裂可靠度影响较大,而预应力钢筋截面面积、有效预应力以及埋深的变异性对抗裂可靠度影响相对较小。更多还原

【Abstract】 Prestressed Concrete Cylinder Pipe(PCCP)is a kind of high quality composite pipe. In the field of large diameter pipes, it has been demonstrated more competitive than other pipes. The mechanical performance of PCCP is not uniform yet, because of its complicated structure and work condition. In this paper, the mechanical behavior of PCCP is researched, design method of prestressing is discussed, distributing rule of stress, cracking and peeling performance and anti-crack reliability of PCCP are also analyzed.First of all, the mechanical model is established in PCCP working stage, based on the elastic plane strain theory of axisymmetric multilayer cylinders and the mechanism of the ring-like strands action. Design method of prestressing is put forward according to the aim at the crack control and the ultimate bearing resistance, then the method is amended compared with the finite-element analysis.The distributing rule of the biggest ring-like stress in the condition of different burying depth , hydraulic pressure, thickness of pipe wall and rank of concrete, the developing of cracks and the coating delamination are analyzed by finite-element analysis. It is shown as follows: The ring-like stress of pipe wall increases with the increscent burying depth and hydraulic pressure. The biggest ring-like stress of pipe wall decrease obviously with the thickness of pipe wall rising, on the contrary, the variation of stress is not obvious with the rank of concrete rising. The mortar cracks prior at springline and the crack expands towards both sides along with increasing of the internal pressure. The outer core cracks at the springline earlier than at other parts, and the crack expands towards both sides and extends deeply as the internal pressure increasing. The inner core cracks at crown at one blow. There is a sudden change of stress at the corresponding position when crazing in pipe wall. The coating delamination is a conjunct result of the relaxation of prestressed wire, the internal and external difference in temperature and the shrinkage of the coating.At last, the anti-crack reliability is analyzed with the method of improved Support Vector Machine (SVM) response surface method. It is indicated that the concrete tensile strength and the concrete changeability, as well as the hydraulic pressure affect the anti-crack reliability obviously, otherwise, the influence of variation of section area of prestressed wire, effective prestressing and burying depth is not obvious correspondingly.更多还原