【作者】 姬鸿云；

【导师】 王正中；

【作者基本信息】 西北农林科技大学 ， 水利水电工程， 2003， 硕士

【摘要】 混凝土的力学性能一直是学术界和工程界长期关心的问题，而混凝土的强度和变形又是混凝土力学性能中最重要的特性。随着近年来冬季施工在全国的迅速开展，混凝土在低温下的力学性能开始受到人们的重视，特别是南水北调西线工程中高寒强震地区的水工结构问题的研究，都与低温下混凝土的力学性能直接有关，它直接关系到在低温下结构的实际承载力以及安全状况。长期以来，国内外学者对混凝土及其构件在常温条件下的各种力学性能进行了比较系统而详尽的研究，提出了在各种受力情况下的破坏准则和本构模型，取得了大量的研究成果，并应用到工程实际当中。但是，由于混凝土材料组成结构的复杂性以及受外界荷载和其它因素的影响，对混凝土的力学性能还不能说完全准确掌握，特别是低温情况下混凝土的力学性能。混凝土在低温下的抗压强度、抗拉强度如何变化，弹性模量、峰值应变在低温条件下有什么样的发展规律，低温下和常温条件下各个力学指标有什么差异等问题。为此，本文针对混凝土在低温下的力学性能进行了试验，探讨了混凝土在低温条件下强度与变形的变化规律，为工程设计提供参考。 论文的主要研究工作与成果如下： 1．分析研究了混凝土的强度与变形以及前人提出的各种本构关系，探讨了混凝土的强度准则以及混凝土在各种受力情况下的破坏形态。 2．主要研究了低温对混凝土的强度与变形的影响。采用液压试验机和使用低温冷冻室，做了20组60个单轴受压试验和20组60个单轴受拉试验，得出了混凝土的受压和受拉应力—应变曲线、抗压强度与养护龄期以及抗拉强度与养护龄期的关系曲线。 3．通过对实验数据的分析，得出强度参数随温度的变化规律，以及温度对弹性模量、峰值应变的影响。在低温条件下混凝土拉压应力—应变曲线形状与常温下曲线形状相似。 4．在常温下一般不需考虑温度对混凝土性能影响。但若混凝土在养护期内没有达到抗冻临界强度受到低温作用，其强度将降低。试验还表明，当混凝土强度达到受冻临界强度后，随着负温值的增大其强度缓慢增长，弹性模量也有缓慢增长。混凝土应力达到峰值时的应变随负温值的增大而变小。应力—应变曲线形状随负温值的增大变得高而窄，曲线的下降段比常温陡直，混凝土的延性变差，脆性增大。更多还原

【Abstract】 The mechanical property of the concrete has always been a critical problem in the academic fields. However, the strength and deformation are most important property among all the mechanical capabilities of the concrete. With the rapid development of the winter construction, the mechanical performance under low temperature comes to draw people’s attentions for it has close relationship with the practical load and safety status of the structure under the low temperature.. During the decades, scholars in China and aboard have carried out comparatively systematic and elaborate study on all the mechanical performance of the concrete and its structure under normal temperature and point out failure Criterion and constitutive models in the different conditions, they have acquired great achievements and applied it in the engineering practice. But people still don’t master the mechanical property of the concrete comprehensively for the complex conditions, especially, in the low temperature, the mechanical capability , change of tensile and compression strength, elasticity module, the development law of poison ratio, the differential of all the mechanical indexes. To solve those issues, this article makes a full discussion about the strength and changing law of the concrete in the low temperature after carrying out a strict experiment on the mechanical property of the concrete. It provides a reference to the practical design.The following is the major research work and results:1. Analyzing the relation between the strength and deformation of concrete and all constitutive relations given by the vanguard specialists. Making a detail discussion on the strength guideline of the concrete and damage mode of the concrete of the in the conditions of different loads.2.This article focuses on the influence upon the strength and deformation of the concrete in the low temperature. Making use of the transformed pressure test machine and low-temperature refrigerator, 16 groups, 3 per group, uniaxial tensile experiments are carried out. It educed tensile , compression-strain curves of concrete, tensile strength-caring age curves of concrete and compressive strength-caring age curves of concrete.S.Throuth the thorough analysis, we can get the changing laws of the strength parameter with the variety of temperature and the temperature influence upon the elasticity module. The tensile and compression -strain curves, in the low temperatureconditions, are similar to the ones in the normal temperature. All kinds of physical and mechanical properties don’t change the original constitutive relation.4. Generally, we don’t have to consider the temperature influence upon the concrete performance. But during the caring age , if the concrete don’t experience the low temperature action of frost-resisting critical strength, its strength will decrease. The experiment also shows that after the concrete strength reach the frost-resisting critical strength, its strength and elasticity module will increase slowly with the decrease of the temperature. Only when the concrete strength comes to the peak value, the strain will reduce with the decrease of the temperature. The shape of stress-strain curves will become high and narrow with the decrease of the temperature. The descending part of the curves are much sharper than the ones under the normal temperature. The ductility of the concrete will also get worse and the brittleness will increase.更多还原