钢筋混凝土框架结构屈服前阶段损伤程度模型分析

Analysis of pre-yield damage degree model for reinforced concrete frame structure

由于作用使既有结构产生的损伤,直接影响结构抗震性能及加固方案,结构损伤程度的适用计算方法即成为急需解决的科学问题。分析钢筋混凝土框架损伤机理,将其开始承受荷载至结构破坏定义为三大阶段:框架完好至截面出现裂缝为微损伤、截面开裂至框架一个截面屈服为轻中度损伤(若裂缝宽度不超过《混凝土结构设计规范》(GB 50010—2010)规定的正常使用极限状态最大裂缝宽度可为轻度损伤、至屈服为中度损伤)、框架屈服至形成机构体系为严重损伤。采用相对刚度作为损伤参数,基于框架在水平低周反复荷载作用下试验结果,拟合出相对刚度和相对荷载的关系;对钢筋混凝土单榀框架微损伤至中度损伤阶段(框架一个截面屈服)进行有限元数值模拟分析,提出了钢筋混凝土框架微损伤程度和轻中度损伤程度的理论计算模型,与已进行的框架试验和有限元分析结果符合良好。

Damages produced in the existing structures due to various actions may directly affect the seismic performance and strengthening of the structures. Hence, appropriate calculation methods for the damage degree of the structures have become the key unresolved problems. To study the damage mechanism of reinforced concrete frame, the entire process from loading to structural failure may be defined into frame changes from the intact state to cracking state, frame changes from cracking to section yielding （ i. e. three stages： the first stage is a microdamage stage in which the the second stage is a mild-to-moderate damage stage in which the according to the code for design of concrete structures, if the crack width is less than the maximum crack width stipulated for the serviceability limit state, this state is defined as the mild damage state, while the appearance of section yielding indicates the occurrence of moderate damage）, and the last stage is a serious damage stage in which the frame yields to be a mechanism system. The relationship between relative stiffness which is taken as damage parameter and relative load is fitted based on the experimental results of the reinforced concrete frame structure under horizontal low-cycle repeated loads. The process from micro damage to moderate damage of the reinforced concrete for single frame structure was studied based on the finite element simulations. A calculation model of the micro damage stage and the mild-moderate damage frame. The experimental results agree well with the finite element analysis. damage degree stage is proposed for the reinforced concrete