大型混凝土底板温度与收缩裂缝分布特征计算  

Distribution Characteristics Calculation of Temperature and Shrinkage Cracks in Large Concrete Floor

作　　者：徐兆全 苏成[1] 范学明[1] XU Zhaoquan;SU Cheng;FAN Xueming(School of Civil Eng.and Transportation,South China Univ.of Technol.,Guangzhou 510640,China)

机构地区：[1]华南理工大学土木与交通学院

出　　处：《工程科学与技术》2019年第6期146-151,共6页Advanced Engineering Sciences

基　　金：国家自然科学基金面上项目(51378009);国家自然科学基金面上项目(11602087);华南理工大学亚热带建筑科学国家重点实验室开放基金项目(2017ZB32)

摘　　要：大型地下结构物的渗漏问题一直以来都较难解决,作为主要构件的混凝土底板其裂缝宽度和数量直接决定整个地下结构的渗漏严重程度,目前关于底板开裂后的裂缝分布特征研究还较少。作者以解析方法得出不断增大的温度及收缩效应下混凝土底板的裂缝出现位置、宽度及间距表达式,实现对裂缝分布特征的描述。假定滑脱钢筋表面受均匀摩擦力(为混凝土抗拉强度),滑脱临界处混凝土为极限拉应变(约100×10^–6)的情况下,求解出钢筋拉力、滑脱长度、钢筋变形量等参数之间关系式。把滑脱钢筋作为边界条件,带入通解,计算第一条裂缝的宽度及新底板块体内位移和应力分布。在已发生裂缝位置和滑脱钢筋刚度恒定的情况下,从坐标原点和端部的块体向某裂缝处叠加计算,得出该处底板块体的新组合刚度和自由位移值,进而求解应力重分布后的裂缝宽度。持续增加温度与收缩应变,计算新裂缝出现后的底板块体组合刚度、最大拉应力值,存储已有裂缝位置和滑脱钢筋刚度,用于下步计算。循环计算过程,直至应变的上限值,得出整块底板的多条裂缝宽度和间距,建立大型混凝土底板温度与收缩裂缝分布特征的计算方法。最后以尺寸80 m×20 m×0.4 m的混凝土底板为例,持续施加0~350×10^–6的温度或收缩应变,实现裂缝5次出现时分布特征的计算。It is difficult to solve the leakage problem of large underground structures,in which the width and quantity of cracks on concrete floor directly determine the leakage severity of the whole underground structure,but there are few studies on the distribution characteristics of cracks after cracking.In this paper,the expressions of crack location,width,and spacing of concrete floor under increasing temperature and shrinkage effect were obtained by analytic method,and the distribution characteristics of cracks were described.Under the condition that the surface of the slipping steel bar was subjected to approximately uniform friction(concrete tensile strength)and the concrete at the slipping critical point was the ultimate 100×10^–6 tensile strain,the relationship among the parameters of the steel bar tension,the slipping length and the deformation of the steel bar was obtained,and then the width of the first crack and the displacement and stress distribution in the new floor plate were calculated.When the location of cracks and the stiffness of slipping reinforcement were constant,the new combination stiffness and free displacement value of the floor body were obtained from the calculation of the coordinate origin and the end block to a crack,and then the crack width after stress redistribution was solved.Under the continuous increase of temperature or shrinkage strain,the assembly block stiffness and maximum tensile stress after the emergence of new cracks were calculated,and the position of existing cracks and the stiffness of slipping bar for the next step were stored.Up to the strain maximum,the final crack width and spacing of the whole block were obtained.The method of describing cracks character of concrete floor was established.Finally,0~350×10^–6 temperature or shrinkage strain was continuously applied to a concrete floor with a size of80 m×20 m×0.4 m,and the cracks distribution characteristics calculation was finished in five time cracking process.

关 键 词：混凝土底板 温度与收缩 滑脱钢筋 裂缝 

分 类 号：TU311.41[建筑科学—结构工程]