The Simulation Analysis Of Engineering Cementitious Composites

Engineered Cementitious Composite(ECC)is a kind of high-performance fiber re-inforced cementitious composite with ultra-high toughness prepared by medium fiber volume.The main performances of ECC are multiple cracks and pseudo-strain harden-ing.Through an appropriate proportion design and molding process,the ultimate tensile strain can reach more than 3%,which is 15 times over than that of normal cementitious composite.The domestic research of ECC started late in China.At present,researches are main-ly concentrated in the field of experimental research.Due to the different performance of raw materials,the foreign proportion design is not fully applicable.And most of the ECC produced in China use the fine quartz sand and the Japanese imported polyvinyl alcohol(PVA)fiber with surface-modified,which greatly increase the application cost.As a result,the actual engineering application is rare.In addition,the constitutive rela-tionship of ECC is so complicated that it is difficult to establish a simulation model of ECC.While numerical study can save much more cost in ECC researches.In view of the key issues above,the work of this paper is mainly divided into two aspects:1.Optimize the proportion ratio of ECC and prepare specimen to study its mechanical properties.Reduce the fabrication cost without the characteristic of multiple cracks and pseudo-strain hardening lost;2.Establish the meso-scale simulation model of ECC.Validate the model by experimental results and study the effects of the main parameters to the mechanical properties.(1)According to the theory of PDDA,the treated ordinary river sand is used instead of the fine quartz sand,and the domestic PVA fiber is used instead of the surface-modified Japanese imported fiber.The interface performance is improved by optimizing the pro-portion design.The fluidity(extensibility)can achieve 180mm and the ultimate tensile strain can reach over 3%.All these works successfully reduce the production cost and improve the workability of ECC,which is of great significance for practical engineering applications.(2)Use the pseudo random number method to study the random uniform distri-bution of three-dimensional linear beam element fibers in three-dimensional space.And consider the situation that the fiber should not intersect with each other.The algorith-m is implemented in MATLAB programming language,which is the foundation of the meso-scale simulation model of ECC.(3)Based on the LDPM theory,the ECC meso-scale simulation model is established.The model parameters are calibrated according to the results of uniaxial compression tests and three-point bending tests.The uniaxial tensile tests are simulated according to the calibrated parameters.The simulation results obviously show the multiple cracks and pseudo-strain hardening properties,which successfully validate the accuracy of this model.On this basis,combined with the uniaxial tensile tests of different fiber volume amount,the experimental results were predicted and verified by simulation.