Research On The Effects Of The Dynamic Characteristics And The Dynamic Bearing Capacity Under The Crack Of Concrete Gravity Dam

In practical engineering, no matter how to take crack control measures, the concrete gravity dam will still be working with cracks, Thus crack effect on the bearing capacity and the dynamic characteristics of the dam body become a problem must be considered. Fracture belongs to the category of the damage, This article mainly from the damage analysis, focuses on the relationship between damage of gravity dam and dam body dynamic characteristics and the bearing capacity. At present, in the earthquake high incident area, the linear elastic analysis of the dynamic characteristics and the bearing capacity of dam system is relatively mature, but based on the nonlinear dynamic characteristics and bearing capacity of concrete gravity dam damage analysis is still in the exploratory stage, the related research is less.This paper is based on general finite element software ABAQUS simulation, For dynamic damage analysis of DAMS first find out the dam damage range and any damage area of the region, and then gives damage area new material properties, to solve the free vibration characteristics of the dam before and after earthquake, and then contrast damage on dam natural vibration characteristics and obtain the influence. Then use the concrete damage plasticity constitutive model, use the simple harmonic excitation, the resonance failure pattern of concrete gravity dam and the corresponding ultimate plastic strain energy is calculated. Condition can be determined according to the damage, the dam seismic response is mainly according to the first mode vibration, according to the plastic energy dissipation can determine the damage degree of the dam. In this paper, with the rest of the plastic strain energy to represent the residual bearing capacity, analyzes the relations between the damage degree and the residual bearing capacity. This paper also studied the different frequencies and vibration mode of the relationship of dam damage. Analysis with Koyna gravity dam as an example, this paper suggests that:1)By loading different amplitude seismic load, observing the relationships between the changes of the size of the various frequencies and the damage. the first order and second order vibration frequency effected by the damage gravity dam is larger; For the same frequencies, the greater the earthquake acceleration amplitude, the greater the damage, the greater the gravity dam of frequency change before and after damage; For the high order frequency, gravity dam damage before and after the change is not too obvious.2) From damage analysis process can be seen that the earthquake duration influence of gravity dam damage is very large, the same seismic loading process, the damage extended by outside introversion, until completely destroyed.3) Different type resonance failure pattern caused by the different frequency.Load according to the first order frequency resonance corresponds to the minimum limit load amplitude, at the same time the dam’s plastic strain energy dissipation is the largest;Gravity dam damage is caused by the wave of near the first order natural frequency of vibration, such as a higher order of frequency of the second, third order wave cause dam damage need greater volatility, the forth order to achieve resonance destruction is impossible in the realistic society.4) The displacement variation and the vibration mode strain energy variation of the first order can discribe the damage state after the damage of the gravity dam5) Gravity dam obtain a certain ability to resist damage after damage, this ability under the condition of the little damage is not very obvious; the more serious he initial damage of the dam, the larger the plastic strain energy, the remaining bearing capacity of gravity dam is smaller, when the dam reaches a critical damage, the remaining bearing capacity is 0.6) Under the action of two different frequency at the same time, Gravity dam’s plastic strain energy is also larger than the sum of the individual’s plastic strain energy when the two separate order frequency effect, To the acceleration of different frequency amplitude superposition, the damage cracks is not equal to the sum of their damage superposition.This paper discusses the natural vibration characteristics of dam crack affect the characteristics of being hurt, And find out the rest of the bearing capacity and dam damage fracture corresponding relations, Discusses the applicability of the method used in the practical project, provide some valuable reference of the Damage to the dynamic analysis for dam.