钢管混凝土空间桁拱徐变计算的单一单元模型

Single element model for the creep of CFST spatial truss arch

采用空间杆单元模拟结构杆件,基于徐变作用下钢管与核心混凝土黏结良好因而应变协调的特点,结合徐变的时间步增量分析方法,建立适合钢管混凝土空间桁拱徐变分析的单一单元模型并开发了程序,对湖南茅草街大桥(主跨为368 m的中承式钢管混凝土拱)进行了《公路钢管混凝土拱桥设计规范》(JTG-T D65-2015)和《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG D62-2004)规定的两种徐变模式下拱肋下挠、截面应力以及杆件内力重分布的对比分析。结果表明:本研究的钢管混凝土杆件单一单元模型相对于常规的双单元模型能提高计算效率;两种徐变模式下计算的由徐变引起的拱肋下挠、截面应力重分布非常明显,杆件内力重分布不太明显;相对而言,后一种徐变模式下徐变对拱肋受力行为的影响更强些。

The three dimensional bar element was used to simulate the structural members.A single element model suitable for creep analysis of CFST spatial truss arch was established and the program was developed based on the characteristics of strain compatibility resulted from the good bond between steel tube and core concrete,and the time step incremental analysis method of creep was accommodated.The comparative analysis about the deflection of the arch rib,the section stress and the redistribution of the internal force of the member were carried out for the Maocaojie Bridge in Hunan Province(CFST arch with a main span of 368 m),in which the two creep modes specified in code for design of highway concrete filled steel tubular arch bridges(JTG-TD65-2015)and code for design of highway reinforced concrete and prestressed concrete bridges and culverts(JTG D62-2004)were used.The results show that the single element model for CFST member studied in this paper can improve the calculation efficiency compared with the conventional dual elements model.The deflection change of arch rib and the redistribution of section stress for steel tube and core concrete caused by creep are very obvious,and the redistribution of internal force of members is not obvious under the two creep modes,while the influence of creep on the behavior of arch rib is stronger under the latter creep mode.