Studies on coral aggregate concrete(CAC)mainly focus on uniaxial stress conditions.However,concrete structures often experience complex stress conditions in practical engineering.It is essential to investigate the mec...Studies on coral aggregate concrete(CAC)mainly focus on uniaxial stress conditions.However,concrete structures often experience complex stress conditions in practical engineering.It is essential to investigate the mechanical behavior and failure mechanisms of CAC under multiaxial stress conditions.This paper employs a 3D mesoscale model that considers the actual size,shape,and spatial distribution of aggregates.The reliability of the model and material parameters is verified through comparison with existing experimental data.Subsequently,the model is used to systematically study the mechanical properties,failure modes,and failure processes of C40 CAC under the biaxial compression.The numerical results are compared with the experimental results of CAC and ordinary portland concrete(OPC).The results indicate that the failure modes of CAC under the biaxial compression are diagonal shear failure.The biaxial compressive strength and elastic modulus of CAC are greater than those under uniaxial stress and exhibit a significant intermediate principal stress effect.The biaxial compressive strength reaches its maximum value when the stress ratio is 0.5,which is consistent with the conclusions for OPC.Finally,failure criteria and strength envelopes for CAC under the biaxial compression are established in order to provide a reference for analyzing the strength characteristics and structural design of CAC.展开更多
The geometries, vibrational frequencies and bind energies are reported for the ground states of CaC 2H + 2, CaC 2D + 2 and CaC 2H + 4. CaC 2H + 2 and CaC 2H + 4 equilibrium geometries have C 2v symmetry with the metal...The geometries, vibrational frequencies and bind energies are reported for the ground states of CaC 2H + 2, CaC 2D + 2 and CaC 2H + 4. CaC 2H + 2 and CaC 2H + 4 equilibrium geometries have C 2v symmetry with the metal ion lying in the perpendicular bisector of the C-C bond. The ground state in both CaC 2H + 2 and CaC 2H + 4 molecules ia a 2A 1 state and the binding in the ground state is mainly electrostatic. For both CaC 2H + 2 and CaC 2H + 4 the ligand is only slightly distorted from its free ligand structure, the C-C distance has hardly increased and there is only a very small bending of the H atom away from the Ca atom. This is consistent with the electrostatic nature of the bonding. Two different approaches-Hartree-Fock(HF) and density functional theory methods(DFT)-are used and basis sets here used is 6-311+G(3df,2p). The DFT results are in good agreement with experiments, namely, DFT methods provide the benefits that some more expensive ab initio methods can do, but at essentially HF cost. So it is important to include electron correlation for accurate results in this study.展开更多
基金supported by the National Science Foundations of China(Nos.52078250,51878350,11832013,51678304,51508272)。
文摘Studies on coral aggregate concrete(CAC)mainly focus on uniaxial stress conditions.However,concrete structures often experience complex stress conditions in practical engineering.It is essential to investigate the mechanical behavior and failure mechanisms of CAC under multiaxial stress conditions.This paper employs a 3D mesoscale model that considers the actual size,shape,and spatial distribution of aggregates.The reliability of the model and material parameters is verified through comparison with existing experimental data.Subsequently,the model is used to systematically study the mechanical properties,failure modes,and failure processes of C40 CAC under the biaxial compression.The numerical results are compared with the experimental results of CAC and ordinary portland concrete(OPC).The results indicate that the failure modes of CAC under the biaxial compression are diagonal shear failure.The biaxial compressive strength and elastic modulus of CAC are greater than those under uniaxial stress and exhibit a significant intermediate principal stress effect.The biaxial compressive strength reaches its maximum value when the stress ratio is 0.5,which is consistent with the conclusions for OPC.Finally,failure criteria and strength envelopes for CAC under the biaxial compression are established in order to provide a reference for analyzing the strength characteristics and structural design of CAC.
文摘The geometries, vibrational frequencies and bind energies are reported for the ground states of CaC 2H + 2, CaC 2D + 2 and CaC 2H + 4. CaC 2H + 2 and CaC 2H + 4 equilibrium geometries have C 2v symmetry with the metal ion lying in the perpendicular bisector of the C-C bond. The ground state in both CaC 2H + 2 and CaC 2H + 4 molecules ia a 2A 1 state and the binding in the ground state is mainly electrostatic. For both CaC 2H + 2 and CaC 2H + 4 the ligand is only slightly distorted from its free ligand structure, the C-C distance has hardly increased and there is only a very small bending of the H atom away from the Ca atom. This is consistent with the electrostatic nature of the bonding. Two different approaches-Hartree-Fock(HF) and density functional theory methods(DFT)-are used and basis sets here used is 6-311+G(3df,2p). The DFT results are in good agreement with experiments, namely, DFT methods provide the benefits that some more expensive ab initio methods can do, but at essentially HF cost. So it is important to include electron correlation for accurate results in this study.
