Study On Hazard Evaluation Methods Of Concrete Dam Cracks

In combination with program of Failure Mechanism and Safety Evaluation of High Arch Dam under Complicated Conditions supported by National Natural Science Major Fund and Yalong River Hydropower Development Jointed Fund (50539030) and National Natural Science funded key program of Fracture Mechanism and Control of the Modern Massive Hydraulic concrete cracks , the paper focuses on hazard evaluation methods of concrete dam cracks by using extenics theory, catastrophe theory, wavelet theory and numerical calculation methods. The main contents are as follows:(1) The features, influencing factors and hazard properties of concrete dam cracks are studied, and the evaluation system is developed according to its engineering classification standards and the influence on strength, stability, durability, and safety of dams. Then the crack hazard is divided into four classes of slight, general, serious and the most serious. Extenics theory is introduced to establish the multi-parameter matter element model, and then levels and extends of hazard are exactly displayed by correlation function and correlation.(2) With the wavelet decomposition of time series data of measured cracks, components of time-dependent deformation is extracted, crack propagation criteria is developed by the application of catastrophe theory and calculation of stress intensity factors.(3) Based on Ottosen four-parameter failure criterion, a second development is undertaken with UMAT interface provided by ABAQUS/Standard program. By using multi-node element and contact model, the influence of crack on load-bearing capability is studied by comparing with four models respectively without crack, with horizontal cracks, with vertical cracks and with horizontal and vertical models.(4) Based on intensive hazard analysis of concrete dam damages, natural-frequency based method is discussed to evaluate structural stiffness and dam integrity. With the application of subspace iteration method for natural frequency extraction provided by ABAQUS, natural frequency is extracted with four dam models mentioned above; sensitivity is analyzed under different cracks features, and influence on dam integrity is analyzed comparing to changes in total deformation energy and displacement at measuring points.