Papers by Author: Lei Zeng

Abstract: To study Steel reinforced concrete frame-reinforced concrete core wall (SRC frame-RC core wall) hybrid structure earthquake damage evolution and collapse mechanism, this paper holds the earthquake collapse mechanism, seismic collapse analysis and collapse control strategies as the mainline, establishes performance degradation and collapse criterion characterization based on structure dynamic characteristics, adopts incremental dynamic analysis (IDA) method to complete the prototype structure collapse-resistant test and quantitative assessment of seismic collapse analysis and determine the main factors that affect the structure collapse-resistant properties. Through numerical analysis to reveals the mechanism of the earthquake collapse and obtains optimal collapse model, and proposes methods and measures of collapse-resistant design for such structure, which has practical significance for enhancing the ability of high-level hybrid structure to earthquake.

Abstract: To study the effect of various types of defects on the bearing capacity of reticulated shell structures, this paper analyzes the structural nonlinear mechanics performance under physical defects and geometric defects, combining with the matrix displacement method of structure, obtains the impact law of two defects on the reticulated shell structural bearing capacity. Two reduction methods of corresponding defects are put forward which can be used as reference in engineering design and construction. Afterwards, it is pointed out and demonstrated that the safety factor should be defined by a lot corresponding experiments.

Abstract: The seismic performance and seismic damage model for steel reinforced high strength and high performance concrete (SRHSHPC) composite frame columns subjected to constant axial load and cyclically variety flexural loading was investigated experimentally. The main influencing parameters, including shear span ratio, axial compression ratio, stirrup ratio and concrete strength, on the seismic performance and seismic damage of the SRHSHPC frame columns is studied. From the test results, the failure mechanism is analyzed and damage quantization criterion is obtained. Several existing seismic damage models are comparatively analyzed. And then, the variation history of accumulated hysteretic energy of the specimens under different loading cycle indexes is figured out, and influence of different test parameters on it is also discussed. Finally, the damage index of the SRHSHPC columns is compared to the existing seismic damage models, and the double variables seismic damage model adapted for the SRHSHPC structure is established by statistical regression theory. The rule of damage evolvement for the specimens is proposed employing variation history of the damage index under different loading cycle indexes. The analytical results indicate that the seismic performance of the SRHSHPC composite column is good, and the double variables damage model could give a quantitative description for damaging process of the samples, which is a reference for seismic damage design of the SRHSHPC structure.

Abstract: Based on tests under low cyclic reversed horizontal loading, damage behaviors of steel reinforced high strength and high performance concrete (SRHSHPC) frame columns are analyzed. The strength attenuation that considered as damage variable is figured out, and the influence of axial compression ratio, shear span ratio, stirrup ratio and concrete strength on the strength attenuation is discussed. The accumulative damage model, which can reveal the effect of cyclic loading and maximum deformation, is established for the SRHSHPC frame columns. The different phases of damage growth and their features for the SRHSHPC frame columns are analyzed, and the relation of damage and displacement is ascertained. Furthermore, the influence of axial compression ratio, shear span ratio, stirrup ratio and concrete strength on the damage development is also discussed. The results show that the damage model could give a rational description for damaging process of the SRHSHPC frame columns.

Abstract: Steel reinforced concrete (SRC) structure is a kind of building structure with excellent mechanical performance, but the theory of crack width is not very clear. In recent years, the fracture energy is more and more applied to research concrete materials, which has opened up a new field for concrete materials modeling. In this paper, crack width model for SRC structure based on fracture energy concept is put forward. A uniaxial tension model is employed in the analysis for simplification. On the ground of the stress equilibrium as well as the relation among relative slip, steel strain and concrete strain, the basic equations are derived. By introducing the interfacial nonlinear bond stress versus slip constitutive relation between embedded steel and concrete, the analytical solution for distribution of slip along the interface is obtained. And based on this result, the influence of the interfacial bond-slip on tension stiffening of the steel is considered. The displacements of steel and concrete at the crack face under different load levels are computed and analyzed respectively. Finally according to the principle of work and power as well as the fracture energy concept of plain concrete, expression for fracture energy of SRC structures is obtained, and the relation of crack width and concrete fracture energy is established. The comparison shows that the fracture energy based on the model agrees with the test results well.

Abstract: Steel-concrete composite structures are widely used in high buildings for its excellent seismic behaviors, whereas faults or cracks, which have great influence on interfacial mechanical behaviors of structural members, inevitably form near the interface between steel and concrete during the process of molding. Therefore, it is necessary to study the mechanical characteristics of the crack tip near the interface. In this paper, the application scope of the path-independence of J-integral in steel-concrete composite structure with a crack is discussed. According to the conservation law of J-integral for the steel-concrete composite structure with a crack parallel to the interface, a hypothesis that the value of strain energy release rate (SERR) of the mode-$fracture is independent of the crack location when the crack is parallel and close to the interface is put forwarded. And this hypothesis is verified through finite element method (FEM). A schematic model for a skew crack near the steel-concrete interface is provided. The variation law of SERR with the Dundur’s parameters and the angle between crack direction and interface are calculated by FEM. At last, calculating method of the stress intensity factor as well as the SERR for a skew crack near the interface is suggested. All these may contribute to further investigation on interfacial mechanical behaviors for steel-concrete composite structure.