Research Of Overall Structural Safety And Numerical Simulation Of Reinforcing Construction For Long-term Operating Gravity Dam

More and more serious aging problems have appeared in early constructed concrete dams with their age increasing, so the theoretical research and engineering treatments for solving aging problems of the dam have become more and more important and emergent. Aging phenomena and their origins must be studied in detail and the relative theoretical work can form a theory system. In this dissertation, the main subject is about the mechanical behavior analysis of a long-term operating concrete gravity dam with longitudinal joints and numerical simulation of its reinforcing and regenerating construction using Finite Element Method (FEM). The major contributions are summarized as follows:A typical characteristic of the longitudinal joints of the long-term operating dam is that many deposits and sediments are in the joints caused by early worse construction and aging of the dam concrete. Based on analyzing of the normal and shear characteristics of the longitudinal joints of the dam, the constitutive model of this type of longitudinal joint is provided, especially a new normal constitutive function is developed reasonably for contact surface elements with thickness simulating such joints, and then all of the ideas are written in a nonlinear finite element code, Joint₂D, including increment iterating method. The non-balance force at each node and the normal penetration of the two interfaces of each joint element are adjusted simultaneously in the code, and three testified examples prove it is reliable, precise and general. Furthermore, the actual gravity dam with longitudinal joints is numerical simulated, and the variation of the resultant deformation and stress distributions of the dam are analyzed definitely by changing different key mechanical parameters of the joint elements, and some valuable conclusions are obtained reasonably.In fact, analysis of the longitudinal joint in numerical simulation is a kind of nonlinear contact problem and the joints are always modeled by contact elements in FEM. However, it is a difficult problem to determine directly the mechanical parameters about these contact elements. Herein, a new displacement inverse method based on calculating intelligent method is provided to identifying the elastic parameters of the dam body and the frictional coefficients of the joints. During the inverse calculating process, the surface-to-surface contact element, which is developed in ANSYS solving by efficient iterating contact algorithm, has been used to simulate the longitudinal joint of the dam. Also, genetic algorithm (GA) is utilized in the inverse process since GA is a much more mature and more reliable one among many calculating intelligent methods. In the displacement inverse method, the surface-to-surface element and GA are two powerful tools assuring the whole inverse process is performed successfully and efficiently. The calculating results indicate that the inverse procedure is reasonable, efficient, and reliable, and can be successfully applied to obtain the frictional coefficients of the longitudinal joints of the actual gravity dam or other similar dams.A methodological system, which includes explicit time integration dynamic finite element method (developed in LS-DVNA3D codes), symmetric penalty method, visco-spring dynamic artificial boundary method, and method of static load response being calculated by dynamic codes, is introduced in detail and applied to solve the nonlinear static and dynamic responses of the structural system composed from the aging concrete gravity dam and the rock foundation, as a result that the combined action of dynamic and static loads is performed and the characteristic responses of these joints are obtained reasonably and easily. It proves that the methodological system can be used to settle the complex and large-scale engineering project feasibly and efficiently.Finally, a numerical simulation method of structural construction is provided about modeling constructing technique, constructing schedule, and as well as the variation of the boundary situation, loads and material behavior during process of construction for mass concrete structures. Based on the new reinforcing and regenerating technique for the long-term operating concrete dam and the numerical simulation method mentioned above, constructing process modeling and safety analyzing are performed utilizing the FE software, ANSYS, which has its own program design language, APDL, to make a constrction simulating program. The conclusion are drawn resonablly and the simulating method could provide suggestion about constructing treatments not only to this engineering but also to other similar projects since it can predict the systematic safety of dam construction and provide effective reference for technique of construction.