不同密度泡沫混凝土梁断裂特性及数值模拟

Fracture Characteristics and Numerical Simulation of Foamed Concrete Beams of Different Densities

为探究泡沫混凝土(Foamed concrete,FC)梁的断裂特性和裂缝扩展过程,采用不同密度和不同初始缝高比的试件,开展不同加载速率下的三点弯断裂试验。结果表明,FC梁的抗弯承载力具有加载速率效应,其峰值荷载随加载速率的上升而增大。但加载速率效应随FC密度的增长逐渐减弱,且初始缝高比越大,加载速率效应越不明显。FC梁抗弯承载力随密度的减小而下降,但其抵抗变形的能力增强。利用ABAQUS建立FC梁的有限元模型,借助扩展有限元方法(Extended finite element method,XFEM)模拟FC梁的裂缝扩展过程,得到其断裂过程的荷载-裂缝张口位移(P-CMOD)曲线。结果表明,数值模拟的结果与试验结果吻合良好,验证了XFEM的合理性和精确性。FC梁在达到峰值荷载前的裂缝开展形式主要为拉伸裂缝,达到峰值荷载后,裂缝进入失稳扩展阶段,剪切裂缝逐渐增多。

To investigate the fracture characteristics and crack propagation of foamed concrete(FC)beams,three-point bending fracture tests under different loading rates were carried out on specimens with different densities and initial crack-depth ratios.The results indicate the flexural bea-ring capacity of FC beams has a loading rate effect,which increases with the enhancement of loading rate.However,the loading rate effect decreases with the rise of density,and the larger the initial crack-depth ratio,the less significant the loading rate effect.The flexural bearing capacity declines with the decrease of density,but its ability to resist deformation is enhanced.The finite element models of FC beams were established with ABAQUS.The extended finite element method(XFEM)was used to simulate the crack propagation of FC beams,and the load-crack mouth opening displacement(P-CMOD)curves of the fracture process were obtained.The results indicate the numerical simulation agrees well with the experimental data,which verifies the rationality and accuracy of XFEM.The crack development patterns of FC beams before reaching the peak load are mainly tensile cracks.After reaching the peak load,cracks enter the instability development stage,and shear cracks gradually increase.