考虑时变因素修正的混凝土斜拉桥换索前初态模型

Analysis model before cable replacement construction of stay cable bridge with time-dependent effects

为准确掌握混凝土斜拉桥换索施工前的索力和主梁受力状态,建立的换索施工前的初态分析模型,需要对其运营期间混凝土收缩徐变、预应力索应力松弛、恒载性超载等因素产生的影响进行评估。而混凝土弹性模量、徐变、收缩及预应力筋松弛等因素具有与时间历程和应力历史紧密关联的材料非线性特征,采用有限元增量分析是合理的选择。为此,在时间历程划分的基础上,推导了考虑材料徐变、松弛、收缩影响的弹塑性有限元求解方程,建立了时间增量步内单元计入徐变、收缩、松弛影响的数值函数表达式,给出了斜拉索损伤刚度修正的具体措施和恒载性超载影响计入的分析方法,建立的初态模型分析技术进一步改善了混凝土斜拉桥运营期的桥梁状态评估方法。

In order to understand the cables forces and girder forces state of concrete cable-stayed bridge before the cable replacement construction,and to establish the analysis model of the bridge,the influence factors such as concrete creep shrinkage,stress relaxation of prestressing tendons,element damage,overload of dead need to be evaluated.Creep,relaxation and shrinkage are closely associated with the material nonlinearity which dependent on time and stress history so it＇s reasonable to adopt the finite element analysis technology based on elastic-plastic incremental load method.Based on the specified time intervals,the incremental elastic-plastic finite element equilibrium equation is deduced which includes the effect of creep,relaxation and shrinkage.For the time increment step,numeric expressions of creep,shrinkage and stress relaxation are established for beam element.Methods are proposed to analyze the influence of stay-cables damage and overload of dead.The methods will improve the structure state analysistechniques for the concrete cable-stayed bridge in service period.