宋泰宇, 李国平, 邓青儿. 关于抗扭空间桁架模型斜压杆倾角的探讨[J]. 工程力学. DOI: 10.6052/j.issn.1000-4750.2023.02.0108
引用本文: 宋泰宇, 李国平, 邓青儿. 关于抗扭空间桁架模型斜压杆倾角的探讨[J]. 工程力学. DOI: 10.6052/j.issn.1000-4750.2023.02.0108
SONG Tai-yu, LI Guo-ping, DENG Qing-er. A DISCUSSION ON THE ANGLE OF COMPRESSION DIAGONALS IN SPACE TRUSS MODEL FOR TORSIONAL RESISTANCE[J]. Engineering Mechanics. DOI: 10.6052/j.issn.1000-4750.2023.02.0108
Citation: SONG Tai-yu, LI Guo-ping, DENG Qing-er. A DISCUSSION ON THE ANGLE OF COMPRESSION DIAGONALS IN SPACE TRUSS MODEL FOR TORSIONAL RESISTANCE[J]. Engineering Mechanics. DOI: 10.6052/j.issn.1000-4750.2023.02.0108

关于抗扭空间桁架模型斜压杆倾角的探讨

A DISCUSSION ON THE ANGLE OF COMPRESSION DIAGONALS IN SPACE TRUSS MODEL FOR TORSIONAL RESISTANCE

  • 摘要: RC箱梁抗扭承载力计算方法基于变角度空间桁架模型建立,混凝土斜压杆倾角是模型中的关键参数、对抗扭承载力计算结果有显著影响,但不同研究和各国规范中斜压杆倾角的计算方法并不相同。为了探究纯扭RC箱梁壁板的真实主方向及其与斜压杆倾角规范值的异同,首先,基于非线性分层壳单元和修正压力场本构建立了适用于RC混凝土箱梁的非线性有限元分析程式,并通过一系列纯剪RC平板试验验证,证明了该分析程式可准确模拟平板的全过程变形发展及破坏模式。基于已验证的数值计算结果,对比分析了平板的真实桁架角、塑性桁架角、单元主应变角、混凝土单元主应力角、RC单元主应力角的全过程变化规律和极限值。分析结果表明:主应变角(代表平板真实主方向)在平板开裂后逐渐向刚度较大的方向旋转,在接近屈服荷载时开始加速旋转直至破坏;真实桁架角在加载开始时与主应变角差距最大,随荷载增加逐渐向主应变角趋近;达到极限破坏时,真实桁架角、混凝土单元主应力角和主应变角基本一致,而塑性桁架角较主应变角明显偏小。最后,对基于不同斜压杆倾角极限值的抗扭承载力进行了评价,中国规范基于塑性桁架角的计算方法偏于不安全,偏差的程度和构件配筋强度比相关。

     

    Abstract: The calculation method of the torsional resistance of reinforced concrete (RC) box girders is based on the variable angle space truss model. The angle of concrete compression diagonals is the critical parameter in the model, which has a significant influence on the calculation results of the torsional resistance. However, the calculation methods of the angle of compression diagonals are different in various research and national codes. To investigate the actual principal direction of the slab in an RC box girder under pure torsion and compare it with the angles of compression diagonals calculated using different code methods, a nonlinear finite element analysis program for RC box girders was established based on the nonlinear layered shell elements and the modified compression field constitutive models. The program was validated by a series of RC panel tests under pure shear, which showed that the numerical program accurately simulated the whole-process deformation developments and the failure modes of the panels. Based on the validated numerical results, the whole-process variations and the ultimate values of the actual truss angle of compression diagonals, plastic truss angle of compression diagonals, principal strain angle of elements, principal stress angle of concrete elements and principal stress angle of RC elements of the panels were compared and analyzed. The analysis results indicated that the principal strain angle (representing the actual principal direction of the panel) gradually rotated towards the stiffer direction after the cracking and began to rotate at a faster speed when the applied load approached the yield load. The actual truss angle of compression diagonals had the largest difference with the principal strain angle at the beginning and approached the principal strain angle with increasing load. At ultimate state, the actual truss angle of compression diagonals and the principal stress angle of concrete elements agreed well with the principal strain angle, while the plastic truss angle of compression diagonals was significantly smaller than the principal strain angles. Finally, the torsional resistances calculated based on different ultimate angles of compression diagonals, were evaluated. The calculation method in Chinese code, which uses the plastic truss angle of compression diagonals, is on the unsafe side, and the degree of unsafety depends on the reinforcement strength ratio.

     

/

返回文章
返回