【作者】 段旻罡；

【导师】 张社荣；

【作者基本信息】 天津大学 ， 水工结构工程， 2004， 硕士

【摘要】 钢筋混凝土材料的应力-应变非线性以及混凝土开裂是钢筋混凝土结构的主要非线性反应之一。本文以南水北调天津干线大型输水钢筋混凝土箱涵为工程背景,采用大型有限元软件ANSYS及其中的SOLID65单元作为建模和计算的工具,在引入混凝土线弹性开裂模型一种弹性类本构关系和多线性等向强化模型、Drucker-Prager模型两种塑性类本构关系以及修正了的Willam-Warnke五参数破坏准则的基础上对钢筋混凝土箱涵进行非线性有限元分析,同时引入钢筋混凝土弥散固定式正交裂缝模型对钢筋混凝土箱涵进行开裂模拟研究,得到如下结论:(1)钢筋混凝土箱涵随着输水压力的不断增加,管身混凝土处于多轴受拉以及主拉应力较大的多轴拉-压应力状态下,当达到混凝土破坏面时相继在管身两边孔底角内倒角面、两边孔顶角内倒角面、中孔底板底部和两侧墙外壁中部出现开裂现象。裂缝首先出现在最薄弱截面垂直于σ1的方向上并逐渐展开,在各开裂区域出现一次开裂后随着应变不断增大该点大主应力都处于下降状态,不会出现二次开裂的情况,属于典型的拉断破坏。(2)钢筋混凝土箱涵在正常工作状态下管身处于双轴或三轴受拉状态,混凝土的受拉破坏以脆性为主,在裂缝出现之前应力-应变基本为线性关系,其对本构关系的敏感性不强,因而不同钢筋混凝土本构模型的选用对开裂区域和开裂应力水平的预测差别并不大。但线弹性开裂模型由于受应力重分布的影响从而在预测后继开裂区的过程中可能会产生误差;Drucker-Prager模型由于其理想弹塑性的特征,在进入塑性区后应力水平增长较低,当使用应力空间的破坏准则时会产生较大的误差,建议Drucker-Prager模型在模拟受拉为主的结构时应与定义在应变空间上的破坏准则共同使用。更多还原

【Abstract】 The nonlinear stress-strain relationship and the cracking of concrete are importantresearch domains of the nonlinear response of reinforced concrete structure with loadsapplied. In this dissertation, three constitutive relationships, the linear elasticity model,the multiple linear isotropic hardening model and Drucker-Prager model, and onefailure criterion, the modified Willam-Warnke model with five parameters, areintroduced to describe the nonlinearity of the reinforced concrete multiple box culvert(RCMBC), which is one of the pipes used in the Tianjin main line of the South-to-northwater transfers project. In the same time, the cracking behavior of RCMBC is simulatedby the way of applying the RC smeared orthogonal fixed crack model to the analysis. Inthe course of research, the ANSYS software and its element SOLID65 involved areemployed as the tools of modeling, meshing, and computing. The conclusion is asfollows:(1)In the effect of the RCMBC normal water pressure, the tube concrete stressenvironment is a multiaxial tensile stress state and multiaxial tensile-compressive stressstate with a larger principal tensile stress. With the ascent of the water pressure, the tubeconcrete could be failure and there are cracks one after the other in the points which isthe outer bottom fillet surfaces of two side culvert, the outer top fillet surfaces of twoside culvert, the outside surface of middle culvert bottom board, and the outside middlesurfaces of two flank wall. The cracks appear firstly at the plane of weakness in adirection normal to the σ1 and spread slowly. Subsequently, in the every area ofcracking, the first principal stress is declined with the increment of strain so as toeliminate the probability of cracking in another direction.(2)The tube concrete of the RCMBC has a brittle cracking when the tensile stressreaches the failure surface. Therefore, the stress-strain relationship of concrete beforethe cracking is linear, which has a lower sensibility to using different constitutiverelationship in the model, in the same words, the prediction of the cracking area andcracking stress has a little difference applying the different RC constitutive model.When the linear elasticity model is implemented, the tensile stress in the subsequentcracking area could be evaluated incorrectly because of the effect relating to the stresstransferring in the first cracking area. As the elastic-perfectly plastic material model, theDrucker-Prager model could be improper to predict the cracking stress of the RCMBC,which should be implemented according to the failure criterion defined by the principalstrains.更多还原