基于ATENA的钢筋混凝土无腹筋梁的非线性有限元分析

通过ATENA软件建模对Bresler-Scordelis梁进行非线性有限元模拟,将模拟结果与试验结果进行对比,验证了所建立的有限元模型能较好地模拟无腹筋简支梁的破坏过程和破坏形态.采用已验证的有限元模型对Kani试验的133根梁进行了计算,模型能够准确地模拟试验梁的破坏荷载.通过对Kani梁计算结果的进一步分析发现,随剪跨比的增大,"拱"作用对梁受剪承载力的贡献逐渐减小,"齿"作用对梁受剪承载力的贡献逐渐增大.无腹筋简支梁名义极限剪应力随剪跨比的增大而减小,在剪跨比为2.5处,曲线发生明显转折,剪跨比小于2.5时减小幅度较大,剪跨比大于2.5后减小幅度较小.对于其他条件相同情况下的梁,在剪跨比超过2.5后,抗剪承载力减小幅度较小甚至基本保持不变,而剪跨区段的长度增大,导致破坏弯矩增大,破坏弯矩与截面计算最大受弯承载力的比值增大,因此,Kani提出的"剪切破坏谷"在剪跨比超过2.5后出现上升段.

Nonlinear Finite Element Analysis of RC Beams without Web Reinforcement by Using ATENA

Bresler-Scordlis beam was numerically analyzed to verify a finite element model proposed by ATENA. The simulated damage process and failure mode of Bresler-Scordlis beam and the experiment result are in good agreement. Then, 133 beams of Kani test were analyzed with the verified model. The ultimate load of simulated beams agrees well with the experiment data. From the further analysis of the simulation results of Kani beams, it can be found that the shear capacity contribution of arch action grows and the shear capacity contribution of teeth action reduces as the shear-span ratio increases. The nominal ultimate shear stress of the beams decreases with the increase of shear-span ratio. The curve turns obviously at the shear-span ratio of 2.5. The degree of the reduction before the turning point is larger than that after the point. When the shear-span ratio is larger than 2.5, the shear resistance of the beams with similar factors reduces slowly or even almost remains constant. However, the length of the shear span increases due to the growth of shear-span ratio. As a result, the maximum moment at failure increases, as well as the ratio of the moment and full flexural capacity. Hence, "The valley of shear failure" proposed by Kani has a rising branch as the shear-span ratio is greater than 2.5.