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Guo Yang,Xudong Chen,Shengshan Guo,Weihong Xuan 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.8
The parameters of dynamic mechanical performance at high strain rates are of significant importance in the structural designs and numerical simulations. The aim of this paper is to study the strain rate sensitivity of self-compacting rubberized concrete (SCRC) in the dynamic compressive, splitting tensile and bending tests by using the split Hopkinson pressure bar (SHPB) technique. The failure modes, stress-strain curves and dynamic strength changes of SCRC under various loading conditions were also observed. The specific energy absorption, dynamic tensile-compressive strength ratios, and dynamic constitutive model of SCRC with different rubber content were also analyzed. The results indicate that SCRC can exhibit stronger strain rate sensitivity compared to SCC when strain rate is enough high, while the strain rate sensitivity of SCRC is lower than that of SCC at when strain rate is less than a critical value. To understand the strain rate sensitivity of SCRC, dynamic constitutive model (ZWT model) based on nonlinear viscoelastic theory was proposed. For impact toughness, although the specific energy absorption decreases with increasing rubber content, the ratios of tensile strength to compressive strength of SCRC have an increasing tendency when rubber content increases.
Shengtao Li,Xudong Chen,Shengshan Guo 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.8
In the present paper, a digital image correlation (DIC) method is used to study the development of fracture process zones (FPZ) of different concrete materials in three-point bending test. Different concrete materials including original concrete, rubber concrete, self-compacting rubber concrete and pervious concrete are investigated. Firstly, the image of the FPZ and the crack opening displacement (COD) in FPZ is obtained by acquiring strain field and displacement field information. The relationship between the development of FPZ and the mechanical properties is further studied. It is found that there is a strong correlation between the FPZ and the post-peak strength reduction of concrete. The development characteristics of FPZ of different concrete materials are analyzed. The addition of rubber will result in stronger strain concentration in pre-peak stage compared to original concrete, and the FPZ will emerges at the earlier loading stage, but it can enhance the crack resistance of concrete in the post-peak stage. Self-compacting rubber concrete was observed to have higher bearing capacity and cracking resistance during fracture than that of the others. Pervious concrete has weak resistance to fracture, and there is almost no decline of the FPZ development rate in fracture process.
Xudong Chen,Dandan Shi,Shengshan Guo 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.3
High temperatures impose a negative effect on the mechanical properties of concrete. An experimental setup designed by the theory of nonlinear resonance vibration, the method of mercury intrusion porosimetry (MIP) and split Hopkinson pressure bar (SHPB) were used to test damage, porosity and mechanical properties of the pre-heated Brazilian discs of 10-year-old concrete respectively. According to the nondestructive test, the hysteretic nonlinearity parameters βh became larger as the temperature went up. The damage calculated by βh, which was 0, 0.57, 0.88 and 0.95 at 20 °C, 200 °C, 400 °C and 600 °C respectively, could be fitted by a power function. Based on MIP, the compound lognormal distribution model was used to simulate the pore size distributions. The quantitative relationship between porosity and damage was established by a power function, with the porosities of 13.96% at 20 °C, 15.77% at 200 °C, 19.17% at 400 °C and 20.22% at 600 °C. Finally, by the method of impact splitting tensile tests under gas pressures of 0.3 MPa, 0.4 MPa and 0.5 MPa, which represented impact velocity of 7.11 m/s, 10.26 m/s and 13.02 m/s respectively, the dynamic tensile strengths were obtained and the quantitative relationship between damage and macroscopic splitting tensile strength was established and the average value of exponential parameter b was 0.281.
Jiajia Wang,Xudong Chen,Jingwu Bu,Shengshan Guo 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.4
The limited availability of raw materials and increasing service demands for pavements pose a unique challenge in terms of pavement design and concrete material selection. The self-compacting rubberized concrete (SCRC) can be used in pavement design. The SCRC pavement slab has advantages of excellent toughness, anti-fatigue and convenient construction. On the premise of satisfying the strength, the SCRC can increase the ductility of pavement slab. The aim of this investigation is proposing a new method to predict the crack growth and flexural capacity of large-scale SCRC slabs. The mechanical properties of SCRC are obtained from experiments on small-scale SCRC specimens. With the increasing of the specimen depth, the bearing capacity of SCRC beams decreases at the same initial crack-depth ratio. By constructing extended finite element method (XFEM) models, crack growth and flexural capacity of large-scale SCRC slabs with different fracture types and force conditions can be predicted. Considering the diversity of fracture types and force conditions of the concrete pavement slab, the corresponding test was used to verify the reliability of the prediction model. The crack growth and flexural capacity of SCRC slabs can be obtained from XFEM models. It is convenient to conduct the experiment and can save cost.