| In recent years,many high concrete arch dams have been built in the high earthquake intensity area of Western China,and their seismic safety has attracted much attention.In practical engineering,measures such as setting aseismic rebar on the dam surface will be taken to strengthen the aseismic performance of the dam.Due to the lack of earthquake damage case test,the seismic safety of concrete arch dam and the effectiveness of seismic rebar on dam surface need to be further studied and demonstrated.Supported by the national key research and development program(2017YFCC0404905),shaking table model test and Numerical Research on a domestic super high concrete arch dam project are carried out on the basis of comprehensive consideration of many factors,such as reservoir water dam dynamic interaction,geometric nonlinearity of transverse joints,model similar materials,foundation radiation damping and so on,This paper analyzes the failure mechanism and dynamic response law of concrete arch dam under seismic load,and discusses the feasibility and effectiveness of the technical measures of seismic rebar on simulated dam surface.The main conclusions of shaking table dynamic model test of concrete arch dam are:(1)In view of the fact that there is no simulated rebar material with similar scale in shaking table model test at present,this paper studies and discusses the material selection of simulated aseismic rebar and its realization form in shaking table test.The research shows that the selected simulated "aseismic rebar" material can better simulate the interaction between prototype rebar and concrete,The product of elastic modulus and cross-sectional area of rebar is used for equivalent similarity,which can meet the requirements of model similarity scale.The results of shaking table test show that macro cracks begin to appear in the dam with seismic rebar at 4.0 times of the design level,and finally through cracks occur at 6 times of the design level.Compared with the non seismic rebar model,macro cracks begin to appear at 3.0 times of the design level,and the cracking range of the dam body is smaller than that of the non seismic rebar model,which verifies the effectiveness of the aseismic rebar measures on the simulated dam surface.Although there are many damages in the middle and upper parts of the arch crown beam and the beam between the transverse joints after the test,the dam still maintains the static water retaining effect,which reflects the good aseismic safety of the test concrete arch dam.(2)According to the similarity principle,the results of model test can establish a precise physical relationship with the prototype structure.Because of the complexity of shaking table test,the model can not meet the requirement of similarity rate completely.At present,there is no systematic study on the influence of the discreteness of the boundary and material parameters of the shaking table model on the natural vibration characteristics of the dam.In this paper,the influence of the parameters of the above model,including dam material,foundation material and aseismic rebar on the natural vibration characteristics of the dam,is analyzed by finite element method,which provides a reference for the shaking table model test and numerical study of concrete arch dam.(3)In order to achieve the purpose of mutual verification between model test and numerical simulation,the dynamic time history analysis considering the damage plasticity of concrete is carried out based on the results of shaking table test and the study of material properties.The calculation shows that considering the effect of aseismic rebar has little effect on the natural vibration characteristics and dynamic response of the dam,and the arrangement of aseismic rebar on the dam surface can reduce the damage and cracking of the downstream dam surface,It can also slow down the development of macro cracks at the arch crown beam to the upstream,which has a certain effect on improving the aseismic performance of concrete arch dam. |
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