Influence Analysis Of Dam Seismic Performance Based On Dynamic Characteristics Of Concrete In Different Codes

With the successive introduction and implementation of the "Code for Seismic Design of Hydraulic Structures for Hydropower Engineering"(NB35047-2015)and "Standard for Seismic Design of Hydraulic Structures"(GB 51247-2018),several adjustments on the dynamic behaviors of concrete material and the regulations on the requirements for structural dynamic strength check have been made compared with the "Code for Seismic Design of Hydraulic Structures"(DL5037-2000).As for the standard value of the concrete's dynamic elastic modulus,it increases by 30% in 2000 Code to 50% in 2015 and 2018 Codes compared with the static standard value.As for the standard value of dynamic strength,the increasing ratio in 2000 Code was 30% higher than the static strength,that in 2015 code was adjusted to 20%,and the dynamic strength in 2018 Code was adjusted to a fixed value of concrete with different strengths.In order to study the influence of the dynamic behaviors of concrete on the seismic performance of concrete dams in different codes,it is important to study the impact of the seismic performance of gravity dams and arch dams on the seismic design and stability evaluation of the dam structure.Although scholars at home and abroad have conducted a series of studies on the dynamic properties of concrete,there are not many comparative analyses of dynamic elastic modulus and dynamic strength of concrete dams based on adjustments in different codes.In order to study furtherly the influence of concrete dynamic characteristics on the seismic response of dams under different specifications,this paper,a three-dimensional finite element analysis method and the large-scale general finite element software ANSYS are used to establish and analyze the static and dynamic results of the gravity and arch dam model.The research work are carried out and some results obtained are as follows:(1)Based on the adjustment of dynamic elastic modulus and dynamic strength in different codes,the analysis of concrete dynamic characteristics and concrete dam seismic design by domestic and foreign scholars are summarized.(2)The basic principles and solving steps of the finite element method in the large-scale general finite element software ANSYS are introduced,as well as the research method of the seismic response of the concrete dam.At the same time,the basic conditions of the gravity dam and arch dam are summarized,and the three-dimensional calculation model of the dam is established using the finite element software ANSYS.Based on the structural characteristics of gravity dams and arch dams and the requirements of design specifications for hydraulic structures,two seismic response research methods with different dam types are determined: the vibration mode decomposition response spectrum method under the massless foundation model is adopted for gravity dams,and the time history analysis method under viscoelastic foundation model is adopted for arch dams.(3)Using ANSYS to numerically analyze the three-dimensional gravity dam model established,the influence of the dynamic characteristics of concrete in different codes on the natural vibration characteristics,static and dynamic displacement and stress of the gravity dam and arch dam selected are studied and compared.At the same time,the seismic safety evaluation of the gravity dam is carried out.According to the calculation,the stress overrun volume and the anti-sliding stability coefficient are analyzed.The influence of the dynamic characteristics of concrete in different codes on the seismic performance of the gravity dam selected is analyzed.The analysis results show that the modification of the dynamic behaviors of concrete in different codes has a certain influence on the free vibration characteristics and static dynamic response of gravity dam.The requirements for seismic performance of concrete gravity dam in 2015 and 2018 Code have been improved to a certain extent compared with the 2000 codes.(4)Using ANSYS to numerically analyze the three-dimensional arch dam model established,the influence of the dynamic characteristics of concrete in different codes on the natural vibration characteristics,static and dynamic displacement and stress of the selected arch dam are studied and compared.At the same time,the seismic safety evaluation of the arch dam is carried out.According to the calculated stress overrun volume,point safety factor and the impact of the dynamic characteristics of concrete in different codes on the seismic performance of the arch dam are analyzed.The analysis results show that the modification of the dynamic behaviors of concrete in different codes has a certain influence on the free vibration characteristics and static dynamic response of arch dam.The requirements for seismic performance of concrete arch dam in 2015 and 2018 Code have been improved to a certain extent compared with the 2000 codes.