Zhongxian Liu

Blast resistance of concrete slab reinforced with high performance fibre material

Abstract Concrete is now the most abundantly used material in construction. Despite good compressive strength, concrete is marked with brittleness and low tensile strength. A widely adopted method to enhance the concrete material performance especially the tensile strength and ductility is fibrous material addition. In the present study, concrete mix designs with different fibre additions have been developed, and high-performance polyethylene fibre and micro steel fibre are considered with varying volume fractions in the concrete matrix. Material static properties are obtained from laboratory tests, and further study on the dynamic performance of theses fibre reinforced concrete materials is investigated through field blast tests. Concrete slabs with high-performance polyethylene fibre reinforcement and hybrid steel and polyethylene reinforcement are casted and tested under close-in blast scenarios. Discussion on the structural damage and material performance is briefed based on the test results.

The diffraction of Rayleigh waves by a fluid-saturated alluvial valley in a poroelastic half-space modeled by MFS

Two dimensional diffraction of Rayleigh waves by a fluid-saturated poroelastic alluvial valley of arbitrary shape in a poroelastic half-space is investigated using the method of fundamental solutions (MFS). To satisfy the free surface boundary conditions exactly, Greens functions of compressional (PI and PII) and shear (SV) wave sources buried in a fluid-saturated poroelastic half-space are adopted. Next, the procedure for solving the scattering wave field is presented. It is verified that the MFS is of excellent accuracy and numerical stability. Numerical results illustrate that the dynamic response strongly depends on such factors as the incident frequency, the porosity of alluvium, the boundary drainage condition, and the valley shape. There is a significant difference between the diffraction of Rayleigh waves for the saturated soil case and for the corresponding dry soil case. The wave focusing effect both on the displacement and pore pressure can be observed inside the alluvial valley and the amplification effect seems most obvious in the case of higher porosity and lower frequency. Additionally, special attention should also be paid to the concentration of pore pressure, which is closely related to the site liquefaction in earthquakes. The diffraction of Rayleigh waves by a saturated poroelastic alluvial valley in a poroelastic half-space is accurately solved by the method of fundamental solutions (MFS).The results of dynamic displacement and pore pressure are presented both in frequency and time domain for different incident frequencies, alluvium porosities and boundary drainage conditions.It is revealed that the wave focusing effect both on the displacement and pore pressure can be observed inside the alluvial valley and the amplification effect seems more obvious for higher porosity and lower frequency.

Numerical study of ultra-high-performance steel fibre–reinforced concrete columns under monotonic push loading

A finite element model is developed to investigate the behaviour of ultra-high-performance steel fibre–reinforced concrete columns under combined axial compression and horizontal monotonic push loading. The effects of steel fibre content, axial compression ratio, reinforcement ratio (or rebar ratio), stirrup ratio and shear span ratio on the structural behaviour of ultra-high-performance steel fibre–reinforced concrete columns are investigated in detail. The numerical model shows good agreement in bond–slip behaviour of specimens based on CEB model results and numerical results, and such behaviour should be taken into consideration in engineering practice. The results indicate that the developed finite element model could predict the structural behaviour and failure mode of ultra-high-performance steel fibre–reinforced concrete columns effectively. It is found that the reinforcement ratio, axial compression ratio, shear span ratio and volume fraction of steel fibre have a great influence on both the structural behaviour and failure modes of specimens.