混凝土拱坝地震非线性响应中的应变率效应研究

Strain rate effect in seismic nonlinear responses of concrete arch dam

通过引入多轴有效硬化函数和S型率相关强度准则,改进了混凝土损伤塑性(concrete damage plasticity,CDP)模型,称为S-CDP模型,能够更加合理地反映混凝土材料的应变率效应和三维塑性变形行为。基于S-CDP模型建立了大岗山拱坝的率相关数值模型。利用所建的率相关数值模型,分析了地震作用下坝体混凝土的应变率分布规律、动态增长因子的变化规律以及混凝土应变率效应对坝体动力响应的影响。结果表明,S-CDP模型能够合理反映受拉区混凝土材料的率效应,在地面峰值加速度为0.557g,0.663g,0.836g的地震动荷载作用下,拱坝坝体混凝土的动强度增长最多能达到23%,然而并不能保证坝体混凝土的动强度始终提高20%及以上。在水工建筑物抗震设计时,若将混凝土的动强度提高固定的20%,可能会造成计算的损伤结果与实际的损伤有所偏差,动强度提高固定的20%计算得到的损伤结果相较于该文中采用S-CDP模型计算得到的损伤结果偏大。因此在水工建筑物抗震设计时,推荐选用合适的混凝土率相关本构模型进行计算,以尽可能的保证计算的精确度。

Here,introducing multi-axis effective hardening function and S-type rate correlation strength criterion,the concrete damage plasticity(CDP) model was improved,and known as S-CDP model.This model could more reasonably reflect the strain rate effect and 3D plastic deformation behavior of concrete materials.Based on S-CDP model,the rate correlation numerical model for Dagangshan arch dam was established.The established rate correlation numerical model was used to analyze strain rate distribution law,dynamic growth factor(DIF) variation law and effects of concrete strain rate effect on dynamic responses of dam body under earthquake action.The results showed that S-CDP model can reasonably reflect rate effect of concrete material in tensile zone;under seismic loads of peak ground acceleration(PGA)=0.557g,0.663g,and 0.836g,respectively,dynamic strengths of arch dam body concrete can increase by up to 23%,but this model can't guarantee dynamic strength of dam body concrete always increasing by 20% or more;in aseismic design of hydraulic structures,if dynamic strength of concrete increases by a fixed 20%,it may cause deviations between calculated damage results and actual damage results;damage results calculated through increasing dynamic strength by a fixed 20% are larger than those calculated using S-CDP model here;in aseismic design of hydraulic structures,it is recommended to choose appropriate concrete rate correlation constitutive model for calculation so as to ensure calculation accuracy as much as possible.