考虑徐变的预应力约束混凝土承载性能研究

发布时间：2019-07-04 15:49

【摘要】：随着基础设施建设工业化要求的提高,预制拼装混凝土结构体系得到了长足的发展。预制拼装混凝土结构需要足够的预加力锚固预制的构件,正常服役过程中应力水平较高,存在较为显著的混凝土徐变现象和预应力松弛现象。近年来,约束混凝土构件越来越多地用作这一结构体系的主要承压构件,而考虑徐变和松弛耦合作用的约束混凝土性能研究尚存较大空缺。基于此背景,本文分别针对钢管混凝土和FRP约束混凝土所涉及的相关问题,在理论模型的研究和分析工具的开发两个方面开展了较为系统的研究,主要内容和创新性贡献如下:(1)基于OpenSees的纤维单元技术,实现了分析工具的开发。一方面,完成了OpenSees新材料的二次开发,为有效嵌入任意自主开发的材料单轴本构提供了接口;另一方面,建立了节段式混凝土桥墩的通用纤维单元模型,为预制拼装混凝土结构提供了精确、高效的数值分析工具。(2)针对钢管混凝土和FRP约束混凝土,完成了单轴本构模型的开发和改进。提出了一种形式简洁、物理意义明晰的单参指数型钢管混凝土本构模型,改进了混凝土下降段的表达;基于Lam和Teng的FRP约束混凝土本构模型,提高了模型对高强混凝土和不同类型FRP材料的通用性。将本文模型通过二次开发嵌入OpenSees,结合多种工况下的试验,对其准确性进行了数值验证。(3)针对钢管混凝土,提出了轴压作用下耦合徐变和松弛的长期变形分析模型,实现了对其任意目标时刻应力和应变状态的高效、准确预测,在保证精度的基础上相比经典模型提高了10-15倍的计算效率;提出了考虑徐变和松弛的钢管混凝土本构模型,从本构关系的角度描述了徐变和松弛耦合作用对其力学性能的影响机理。参数研究表明,徐变和松弛耦合作用可能造成高达25%-30%的预应力损失,对结构的正常使用极限状态存在较为显著的负面影响。(4)针对FRP约束混凝土,考虑FRP的材料特性,提出了考虑徐变的预应力FRP约束混凝土构件的长期变形分析模型,提出了考虑徐变和松弛的FRP约束混凝土本构模型,从本构关系的角度描述了FRP徐变、混凝土徐变和预应力松弛等效应对其力学性能的影响机理。结合相关试验,验证了本文提出的长期变形分析模型和FRP约束混凝土本构模型的有效性。
[Abstract]:With the improvement of the industrialization of the construction of the infrastructure, the pre-assembled concrete structure system has been developed rapidly. The precast and assembled concrete structure requires sufficient pre-stressing and pre-stressed components, and the stress level in the normal service process is high, and the concrete creep phenomenon and the pre-stress relaxation phenomenon are obvious. In recent years, more and more constrained concrete components are used as the main pressure-bearing components of this structural system, and there are still large gaps in the performance of the confined concrete considering creep and relaxation coupling. Based on this background, the paper has carried out a systematic study on the development of the theoretical model and the development of the analytical tools, and the main contents and the innovative contributions of this paper are as follows: (1) The development of the analysis tool is realized based on the technology of the fiber unit of OpenSees. On the one hand, the secondary development of the new materials of the OpenSees is completed, which provides an interface for the effective embedding of the single-axis constitutive model of any self-developed material; on the other hand, a general fiber unit model of the segmental concrete pier is established, so that the pre-assembled concrete structure is provided with precision, An efficient numerical analysis tool. (2) The development and improvement of the uniaxial constitutive model were completed for CFST and FRP-confined concrete. The constitutive model of a single-parameter-type steel tube with simple form and clear physical meaning is proposed, and the expression of the concrete section is improved. The constitutive model of the FRP-confined concrete based on Lam and Teng is used to improve the universality of the model to the high-strength concrete and the different types of FRP materials. In this paper, the model of this paper is embedded in OpenSees through secondary development, and the accuracy of this model is verified by the test under various working conditions. (3) Aiming at the concrete of the steel pipe, the long-term deformation analysis model of the coupling creep and the relaxation under the action of the axial compression is put forward, and the high-efficiency and accurate prediction of the stress and the strain state at any target moment is realized, and the calculation efficiency of 10-15 times is improved compared with the classical model on the basis of ensuring the accuracy; The effect of creep and relaxation coupling on the mechanical properties of a steel-filled steel-filled concrete constitutive model considering creep and relaxation is put forward. The parametric studies show that creep and relaxation coupling may result in a pre-stress loss of up to 25% to 30%, which has a significant negative effect on the normal use limit state of the structure. (4) For FRP-confined concrete, considering the material properties of FRP, a long-term deformation analysis model of the prestressed FRP-confined concrete member considering creep is put forward, and the constitutive model of the FRP-restrained concrete considering creep and relaxation is put forward, and the creep of the FRP is described from the constitutive relation. The effect of concrete creep and stress relaxation on the mechanical properties of the concrete. In this paper, the long-term deformation analysis model and the validity of the FRP-confined concrete constitutive model are verified in the paper.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU378

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