Nonlinear Seismic Response Analysis Of High Arch Dams With Joints

With the development of economy, Many arch dams such as Xiao wan, XiLuodu and so on whose height are more than 300m are going to be constructed inwestem regions of China. The arch dams locate at such areas which have highmoUnain, deep valley, steep slope, narrow riverway and high seismic intensity.The aseismic capabilities of high arch dams have relationship with lives andproperties of people and productions of industry and agriculture, so the eanhquakebecomes the main factor of arch darns design. Arch dams are built by parts, andeach of parts has vertical contraction joints spaced regular intervals. The dynamictensile stresses of earthquake may balance or exceed to the precompressionstresses due to static watef, this may arouse opening of joints along the normaldirection. If the altemate actions of earthquake join, the joints may behave gradualopening and closing. The effect of opening and closing of joints will weaken theintegral stiffness of arch dams, prolong their vibration periods and remarkablyreadjusting of stresses. In general, the nonlinear character of joints is thesignificant factor of the analysis of high arch dams seismic response. Reasonablytaking into account nonlinear character of dynarnic model has very importantsignificance of theory and engineering.Nonlinear dynamic analysis of high arch dams is carried out considering theopening of joints and the effect of traveling wave with engineering background ofXi Luodu arch dam whose height is 278 meteL Based on the theory of interactionof fluid-solid, the coupled FEM equation considering compressible water isdeduced. In order to reduce the equation complexity and adapt to complicaiednonIinear ana1ysis of high arch dams with joints, finite element treatments areused with incompressibIe water and massless foundation. The added mass ofwater and added stiffness of foundation are respectively used to substitute theinfluence of water and fOundations. The efficiency in the computations isimproved by means of static condensation. Fenves' 3-D joint element modeI andits constitutive relations are demonstrated and used to simulate the opening,closing and sliding of joints,and the initial pressure and tensile strength at theinterface. In order to control the propagation of errors and enhance the accuracy ofnumerical solution, the wilson- 0 method is modified and the numerical stabilityof modified wilson- e method is analyzed. Because of need of much iteration ineach time step while carrying on nonlinear numerical anaIysis, the incremefltalequilibrium formulation and its equivalent iterative equation of the constantaverage acceleration Newnark method are deduced. The theory of traveling waveinput is discussed, and the dynatnic response of linear whole dams is analyzed byuse of single-direction traveling wave model. The difference and commonnessbetween cross-direction and longitude direction traveling wave that exists in theresponse and distribution of dam displacement and stress are obtained. Thedynamic seismic response of Xi Luodu dam is studied. The difference andcommonLness between dams with joints and without are analyzed. The magnitudeand distribution of acceleration and stress of dams with joint and without possessmany differences. The influence of different water depth on seismic response ofdams with joint is studied, the conclusion in term of opening width, opening depthand opening frequency is attained. The characteristics about the magnitude anddistribution of stress, the width and depth of joint and time sequence of jointopening are compared on condition of different traveling wave directions. Thedifference between general unifOrm wave input and traveling wave inPut is alsocompared. Though the above analysis, some conclusion are drew as followings fl. The computational results show that the assumptions of incompressiblewater and massless fOundation can considerably simplify the complexity ofequation...