基于XFEM的RC梁静态破碎研究

Research on static cracking of RC beam based on XFEM

建筑基坑内支撑的拆除是影响施工进度的重要因素之一。为提高施工效率,提出一种在钢筋混凝土支撑梁内部沿着梁轴线预埋大直径孔道进行静态破碎的拆除方案。在此基础上,通过扩展有限元方法(ExtendedFiniteElementMethod,XFEM)建立含预埋静态破碎孔(孔径为90mm)的钢筋混凝土梁(截面尺寸为500mm ×500mm)模型,并对其在静态膨胀压力作用下的破碎及裂缝扩展过程进行了模拟分析。模拟结果表明:内支撑梁的静态破碎过程可分为弹性变形、裂缝稳定扩展和裂缝失稳扩展3个阶段;基于虚拟闭合技术,进一步计算得到了复合开裂模式下的应变能释放率,计算结果显示:裂缝扩展以Ⅰ型裂缝为主,当膨胀压力达到19.4MPa时,可实现破碎钢筋混凝土内支撑梁的目的。

Demolition of strut for building excavation is the main concerns of engineering construction.In order to improve efficiency of demolition,we introduce a static cracking scheme for strut with a large diameter hole embedded along its axis.Based on extended finite element method,the process of fracture and crack propagation of reinforced concrete beam(500 mm×500 mm in section size)with an embedded hole(90 mm in diameter)under static expansion pressure is simulated.The simulation results show that the static fracture process of the internal braced beam can be divided into three stages:elastic deformation,stable crack propagation and unstable crack propagation.The strain energy release rate of the composite crack mode is further calculated by virtual closure technology.The calculated strain energy release rate show that the crack propagation is mainly type I crack,and the static cracking of strut could be achieved under expansione pressure of 19.4 MPa.