工程类毕业论文.doc

工程类毕业论文
高等教育毕业论文(设计)
毕业论文(设计)题目
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完成时间: 2014 年 1 月
云南农业大学高等教育毕业论文(设计)评审表
摘要
混凝土是一种非均匀值脆性材料,由骨料、水泥石以及其中的气体和水组成。在温度和湿度变化的条件下,硬化并产生体积变化,由于各种材料变化不一致,互相约束而产生初始应力,造成在混凝土内出现微裂缝。这种微裂缝的分布不规则且不连贯,在荷载或应力作用下,裂缝开始扩展,并逐渐互相贯通,从而出现较大的肉眼可见的裂缝,成为宏观裂缝。
开裂发生的原因可能是原材料的选取与配合比的选择不当、施工方法和措施有误、建筑物所处的条件的影响以及结构不合理等。混凝土所产生的温度收缩、干燥收缩、不均匀沉降、结构应力集中等都可能或导致混凝土开裂。在实际工程中,往往是各种因素多重作用引起混凝土开裂。宽度
,叫做无害裂缝;而结构物的有害裂缝不仅会降低力学性能和承载力,而且直接影响结构耐久性,缩短使用寿命。施工中应采用措施式结构尽量不出现裂缝,或减少裂缝的数量和宽度,特别是避免出现有害裂缝。国内外对裂缝宽度都有相应的规定,ES01—2004《混凝土结构耐久性设计与施工指南》,;。混凝土由各种收缩引起的裂缝问题一直是混凝土结构物裂缝控制的重点和难点。
关键词:混泥土;裂缝;施工方法。
Summary
Concrete is a brittle material non-uniform value, the aggregate, cement, and one of the gas and in temperature and humidity conditions, the hardening and produce volume changes due to changes in various materials are inconsistent with each other constraints arising from the initial stress, resulting in micro-cracks in the irregular distribution of micro-cracks and not coherent, in the load or stress, the cracks began to expand, and gradually through each other, thus a greater visible cracks e macroscopic cracks.
Cracking reasons of the occurrence may be the selection of raw materials and the design of the improper selection, construction methods and measures in the wrong, building the condition the influence and unreasonable structure and so on. Concrete temperature shrinkage, produced by drying shrinkage, the uneven settlement, the structure stress concentration may or lead to concrete cracking. In practical projects, often is the various factors of concrete cracking caused by multiple roles. Width of less than or equal to mm to use function of crack usually no harmful, called harmless crack; The structures and the harmful cracks will not only reduce the mechanical properties and the bearing capacity, but also directly affecting the structure dur