超高性能混凝土HJC本构模型参数确定及应用

在超高性能混凝土的数值模拟中,合理地确定其本构模型参数是提高计算精度和设计可靠度的基础。基于超高性能混凝土单轴压缩试验、霍普金森压杆试验和已有的三轴围压试验等,确定了超高性能混凝土的Holmquist-Johnson-Cook (HJC)本构模型参数。利用LS_DYNA软件模拟单向板爆炸试验,通过与试验中单向板的损伤程度和最大挠度进行对比,验证了已确定参数的有效性。为了进一步了解超高性能混凝土构件的抗爆机理,采用已确定的参数对单向板爆炸工况进行数值模拟,分析配筋和尺寸变化对爆炸结果的影响。结果表明,在爆炸过程中,提高纵筋配筋率可以减小单向板的跨中最大挠度,适当加密箍筋可以减小单向板侧面的斜裂缝长度。超高性能混凝土单向板具有明显的尺寸效应,其中厚度和长度变化对爆炸结果的影响最突出。

Determination and application of the HJC constitutive model parameters for ultra-high performance concrete

The parameters of the Holmquist-Johnson-Cook (HJC) constitutive model for ultra-high performance concrete (UHPC) were determined based on uniaxial compression test, split Hopkinson pressure bar (SHPB) test and existing tri-axial compression test and so on, in order to improve the calculation accuracy and design reliability. In the determination process of parameters, the parameters of the HJC constitutive model were divided into five categories. The yield-surface parameters were determined by the static failure surface equation, the parameters of state equation were determined by the p-μ relation, the damage parameters were determined according to relevant literature, the basic physical parameters were determined according to the test, and so on. LS_DYNA was used to simulate the explosion test of the one-way slab. Firstly, the finite element model of the one-way slab was established. The HJC constitutive model was used for the UHPC, and the linear reinforcement model was used for the reinforcement material. The reinforcement and UHPC were connected by common joints. The air and explosive models were established, and the fluid-solid coupling method was used for calculation. The effectiveness of the determined parameters was verified by comparing the simulation results with the damage degree and the maximum deflection of the one-way slab in the test. In order to further understand the anti-blast mechanism of the UHPC members, the determined parameters were used to conduct numerical simulation on the one-way slab explosion condition, and the influences of reinforcement and size effect on the explosion result were analyzed. Results show that during the explosion process, the maximum mid-span deflection of the one-way slab can be reduced by increasing the longitudinal reinforcement ratio, and the length of oblique cracks on the side of the one-way slab can be reduced by properly encrypted stirrups. The UHPC one-way slab has an obvious size effect, and the variation of its thickness and length has the greatest influence on the explosion result.