【作者】 何盛东；

【导师】 刘立新；

【作者基本信息】 郑州大学 ， 结构工程， 2012， 博士

【摘要】 混凝土是我国工程建设的主要建筑材料之一,随着基础设施建设的快速发展和环境保护的加强,配制混凝土可利用的天然砂资源的日趋匮乏,优质的天然砂资源也越来越少,已不能满足工程建设规模日益扩大的需要,与建筑业蓬勃发展的矛盾日益突出。使用机制砂代替天然砂配制混凝土对节约资源保护环境有重要意义,已成为必然趋势,机制砂的开发、研究和应用也日益受到重视。目前机制砂混凝土虽然在房屋建筑、水电和水运工程中有一定应用,但因对其性能的研究尚不够深入,应用还不广泛,尤其是在用砂量巨大的公路、铁路预应力混凝土桥梁工程中的应用方面,十分有必要对机制砂及机制砂混凝土的性能作进一步的研究。本文结合机制砂在预应力混凝土桥梁工程中应用的需要,对机制砂和机制砂混凝土的物理力学性能进行了较系统的试验研究,研究了机制砂预应力混凝土梁在静力和疲劳荷载下的受力性能,分析了机制砂混凝土和机制砂预应力混凝土梁的受力特点,提出了相应的设计方法,为机制砂在工程建设中的广泛应用,尤其是在预应力混凝土桥梁工程中的应用提供依据。论文的主要工作和成果有：1、对机制砂和天然砂的物理力学性能进行了较全面的对比试验研究,表明正规生产的机制砂可实现良好级配,其物理力学性完全能满足普通混凝土的使用要求。普通混凝土配合比的计算方法同样适合机制砂混凝土的配制,为提高机制砂混凝土的和易性和工作性能,建议在制配制机制砂混凝土时加入适量粉煤灰,并适当延长拌制。2、对机制砂混凝土和普通混凝土的基本力学性能进行了系统的对比试验研究,表明机制砂混凝土的立方体抗压强度、轴心抗压强度、劈裂抗拉强度和弹性模量均随着替代率的增大而增大,而收缩变形则随着替代率的增大变化不大,完全适用于预应力混凝土。建立了机制砂混凝土的立方体抗压强度与轴心抗压强度、劈裂抗拉强度、弹性模量的换算关系式,为机制砂混凝土在预应力混凝土桥梁工程中的应用提供了参考依据。3、对8根机制砂预应力混凝土简支梁(折线先张梁5根,曲线后张梁2根和直线后张梁1根)制作工程中钢绞线、混凝土应变(应力)的监测,以及预应力损失的分析表明,机制砂预应力混凝土梁的各项预应力损失均可按现行规范的公式或原则进行计算,且总预应力损失小于普通混凝土预应力梁。4、通过5根预应力混凝土梁(3根折线先张梁、2根后张梁)在静力荷载作用下受力性能的试验研究,对比分析了机制砂混凝土和普通混凝土预力梁从加载开始到破坏过程中混凝土、非预应力筋和钢绞线的应变、裂缝开展以及挠度变化的特点。结果表明在相同条件下机制砂预应力混凝土梁的裂缝宽度和挠度小于普通混凝上预应力梁。机制砂预应力混凝土梁的受弯承载力、裂缝宽度和挠度均可按现行规范的相关公式计算,计算结果偏于安全或有较大的保证率。5、通过3根预应力混凝土梁(2根折线先张梁、1根后张梁)在疲劳荷载作用下受力性能的试验研究,对比分析了机制砂混凝土和普通混凝土预力梁在疲劳受力过程中以及疲劳后静载受力过程中裂缝和挠度变化的规律。结果表明机制砂预应力混凝土梁的疲劳受力性能优于普通混凝土预力梁,疲劳加载后的剩余承载力以及裂缝和挠度仍可按现行规范的相关公式计算,具有足够的安全度和保证率,为机制砂混凝土预应力梁在承受疲劳荷载的桥梁工程中的应用提供了依据。6、在试验研究的基础上,基于正截面理论提出了机制砂预应力混凝土梁受力性能分析方法,编制了相应的数值分析程序,数值分析结果与试验实测结果趋势一致符合良好,可应用于机制砂预应力混凝土梁和普通混凝土预应力梁受力性能的分析。更多还原

【Abstract】 Concrete is one of the main building materials in engineering construction. With the rapid development of infrastructure construction and more attention being paid to environmental protection, and the available and high quality natural sand resources dwindling, nowadays natural sand can not meet the need of increasing engineering construction. This becomes an increasingly prominent conflict in the construction industry. Using the manufactured sand rather than natural sand in the concrete is very important to resources conservation and environment protection. Thus the development, research and application of manufactured sand has been paid much more attention to. Manufactured sand concrete has been used to a certain amount in housing construction, hydropower, water transportation and other fields, but the study on its property is not deep enough and its application is not extensive, especially in pre-stressed concrete bridge projects of highway and railway construction which needs huge amount of sand. Therefore it’s very necessary to further study the performance of the manufactured sand and manufactured sand concrete. In this paper, a systematic experimental research on the physical and mechanical properties of the manufactured sand and manufactured sand concrete by combing the need of applications of manufactured sand in the pre-stressed concrete bridge. The experimental researches of the mechanical properties of manufactured sand pre-stressed concrete beams under static and fatigue loads are done, and the mechanical characteristics of the manufactured sand concrete and the manufactured sand pre-stressed concrete beams are analyzed. An appropriate design methods is also proposed. All these provided the basis for the extensive application of manufactured sand in engineering construction, especially in the pre-stressed concrete bridge engineering. The main work and achievements in this paper are shown in the following.1. The physical and mechanical properties of the manufactured sand and natural sand are compared in the experiment. The result shows that the formal made manufactured sand could achieve good gradation and its physical property could meet the requirements of ordinary concrete The mixture ratio calculation method of ordinary concrete was also suitable for the manufactured sand concrete. In order to improve the workability and work performance, it is recommended to add appropriate amount of fly ash and extend the mixing time about 10 seconds.2. By systematic comparison test on the basic mechanical properties of the manufactured sand concrete and ordinary concrete, it is found that the cubic compressive strength, axis compressive strength, split strength and elastic modulus increased with the replacement rate increasing, and shrinkage deformation decreased as the replacement rate increased. The manufactured sand concrete was fully applicable to pre-stressed concrete. The relationships between concrete cube compressive strength and the axial compressive strength, splitting tensile strength, modulus of elasticity were established, which provides a reference for the application of manufactured sand concrete in pre-stressed concrete bridge engineering.3. Eight simply supported beams of manufactured sand pre-stressed concrete (5 of them are fold line pre-tensioned beams,2 of them are parabolic line post-tensioned beams and 1 was linearity post-tensioned beam) were designed. The load and strain of pre-stressed reinforcement tendon and concrete with manufactured sand were monitored during the whole production process, and the prestress loss of test beams was analyzed. All these indicated that the prestress losses of pre-stressed manufactured sand concrete beams can be calculated by the current formulas or principles in the Code. And the total prestress of pre-stressed manufactured sand concrete beams was less than that of pre-stressed concrete beams with natural sand.4. Through the experimental study of the mechanical properties of 5 pre-stressed concrete beams (3 of them are fold line pre-tensioned beams,2 of them are post-tensioned beams) under static load, the strain of concrete, non-pre-stressed bars and steel strand, the condition about cracks developing and changes of deflection between manufactured sand concrete pre-stressed beam and normal concrete pre-stressed beam are comparatively analyzed in every phase. The results show that under the same conditions the crack width and the deflection of manufactured sand concrete pre-stressed beams are smaller than normal concrete pre-stressed beams. The bending capacity, crack width and deflection of the manufactured sand concrete pre-stressed beam can be calculated by using the current formulas in the code and the calculated results are reasonable and have large guarantee rate.5. Through the experimental study of the mechanical behavior of three pre-stressed concrete beams(2 fold line pre-tensioned beams and 1 post-tensioned beams) under the condition of fatigue load, the cracks and the laws of deflection change between manufactured sand concrete and common concrete pre-stressed beams in the process of fatigue force and static load are compared and analyzed. The result shows that the mechanical behavior of manufactured sand concrete pre-stressed beams is superior to the common concrete pre-stressed beams. For the mechanical property of manufactured sand concrete pre-stressed beams, the related formula in current specifications can also be applied to the calculation of their residual bearing capacity, cracks and the deflection. They have enough reliability and guarantee rate. The study offers basis for the applications of manufactured sand concrete pre-stressed beams to bridge engineering under fatigue load.6. Based on the experimental study and the normal section theory, the analysis method of the pre-stressed manufactured sand concrete beams is proposed and the according program is compiled. The results of numerical analysis are in line with experimental results closely. The numerical analysis could be applied to the analysis of mechanical property of pre-stressed concrete beams with manufactured sand as well as pre-stressed concrete beams with natural sand.更多还原