核电厂钢筋混凝土结构基于双尺度结构分析的设计方法初探

PRELIMINARY RESEARCH ON DESIGN METHOD OF RC STRUCTURES IN NPPS BASED ON TWO-SCALE ANALYSIS

核电厂构筑物的钢筋混凝土结构以长墙、异形板为主,在结构有限元分析中以壳单元模拟,所得结果为单元的内力,但现行的设计沿用民用建筑中基于墙或板构件的整体内力进行结构设计的方法,结构效应和抗力所面对的对象并不匹配。基于宏观和细观双尺度结构分析的设计方法,首先利用标准大小的壳单元(如1 m×1 m)进行宏观尺度的整体结构分析,提取单元内力或位移;再对单元建立参数化的精细模型,混凝土采用实体单元,钢筋采用线单元,钢筋与混凝土之间通过非线性切向弹簧模拟黏结滑移关系,施加整体分析所得的单元内力或位移作为荷载-位移边界条件,进行细观非线性分析,基于混凝土材料的拉应变、钢筋的拉应变以及弹簧力作为指标,分别识别单元体的损伤状态,进而验算整体结构的安全性。通过对某核电厂厂房在500年一遇的基准地震工况(OBE地震工况)下的局部外墙构件进行双尺度设计方法验证,基于混凝土材料的拉压损伤指标识别单元体的损伤状态,进而验算这一外墙构件的整体安全性。

The reinforced concrete(RC)structure of nuclear power plant structures(NPPs)is mainly composed of long walls and irregular plates.The shell element is simulated by using FEM analysis,and the results are obtained as the internal force of the element.The current design specification is related to the method of structural design based on the overall internal force of the wall or plate member in the civil building,therefore,the objects of the effects and the resistant are different.To solve the problem,a design method based on macroscopic and mesoscopic two-scale structural analysis was proposed.Firstly,a standard size shell element(1 m×1 m)was used for macroscopic overall structural analysis,and the internal force and displacement of shell element were obtained.Secondly,a detailed shell element micros model with concrete and steel bars was established,the concrete was made of solid elements,the steel bars were line elements,and the nonlinear tangential spring was used to simulate the bond-slip relationship between the steel and the concrete.The mesoscopic nonlinear analysis was conducted on the internal force or displacement of the shell element obtained by applying the overall analysis as the load displacement boundary condition.Based on the tensile strain of the concrete,the tensile strain of the steel bar,and the spring force as indicators,the damage state of the shell element was identified,and the safety of the overall structure was checked.The mechanical properties of local external wall members of a NPPs under the 500-year operating-basis earthquake(OBE seismic condition)were verified based on two-scale analysis.The damage state of the shell element was identified based on the tensile and compression indicators of concrete.And then the overall safety of the exterior wall member was checked.