高强钢筋钢纤维混凝土梁疲劳性能试验研究

发布时间：2019-04-10 16:43

【摘要】：工程实际中,承受交变荷载的钢筋混凝土结构越来越多,其疲劳性能一直备受关注。随着工程结构向高强、轻质方向发展,势必对钢筋和混凝土的强度提出更高要求。目前,高强钢筋和混凝土已普遍应用于工程中,但由于高强混凝土结构延性差,脆性特征明显,在循环荷载作用下疲劳问题更加突出,不少学者提出将钢纤维加入高强混凝土结构中以提高其整体刚度和韧性。由于国内外对高强钢筋钢纤维混凝土结构疲劳性能的研究还比较少,同时现行规范也缺乏其疲劳性能的计算方法和设计规定,因此,本文制作了5根HRB500级高强钢筋钢纤维混凝土梁,其混凝土强度等级为CF60,梁长1200mm,截面尺寸120mm×200mm,纵筋配筋率0.94%。其中1根梁做静载试验,其余4根梁进行等幅疲劳试验,应力水平分别为0.5、0.6、0.7、0.8,重点研究应力水平对梁裂缝、挠度、应变、刚度及疲劳寿命等的影响,主要结论如下:(1)静载和疲劳荷载下高强钢筋钢纤维混凝土梁的试验过程和破坏形态差异显著。静载荷载下梁的延性较好,破坏前有明显征兆;疲劳荷载下梁为脆性破坏,但钢纤维的加入有效抑制了裂缝发展,提高梁截面的抗弯刚度,改善梁的破坏形态。(2)随着应力水平的提高,高强钢筋钢纤维混凝土梁的疲劳寿命和疲劳强度显著下降,破坏过程和形态相似,呈现明显的三阶段规律:前期发展迅速,增幅较大,一般在1万次疲劳循环之前;中期疲劳特征值稳定均匀增加,增幅减缓,持续时间最长,约占整个疲劳寿命的80%左右,后期疲劳特征值达到临界值,突然发生失稳破坏。(3)以粘结-滑移理论为基础,提出了静载和疲劳荷载下高强钢筋钢纤维混凝土梁裂缝宽度的计算公式;根据累积残余应变与循环次数双曲线的线性相关,提出了高强钢筋钢纤维混凝土梁受压区混凝土累积残余应变的计算方法。(4)通过对试验数据的拟合,得到高强钢筋钢纤维混凝土梁S与lgN的疲劳寿命曲线。同时,结合刚度损伤量分数值D,预测高强钢筋钢纤维混凝土梁的疲劳寿命,为高强钢筋钢纤维混凝土梁疲劳设计提供依据。
[Abstract]:In engineering practice, there are more and more reinforced concrete structures subjected to alternating loads, and their fatigue performance has been paid more and more attention. With the development of engineering structure to the direction of high strength and light weight, it is bound to put forward higher requirements for the strength of reinforcement and concrete. At present, high-strength reinforcement and concrete have been widely used in engineering, but because of the poor ductility and brittleness of high-strength concrete structure, fatigue problem is more prominent under cyclic load. In order to improve the stiffness and toughness of high-strength concrete structures, many scholars have proposed adding steel fibers into high-strength concrete structures. Because the research on fatigue behavior of high strength steel fiber reinforced concrete structure at home and abroad is still relatively little, at the same time, the current code also lacks the calculation method and the design regulation of its fatigue performance, therefore, In this paper, five HRB500 steel fiber reinforced concrete beams are made. The concrete strength grade is 1200mm long, 120mm 脳 200mm, and the ratio of longitudinal reinforcement is 0.94%. The concrete strength grade is 1200mm, the cross-section size is 120mm 脳 200mm, and the longitudinal reinforcement ratio is 0.94%. One beam was subjected to static load test, and the other four beams were subjected to constant amplitude fatigue test. The stress levels were 0.5, 0.6, 0.7, 0.8, respectively. The effect of stress level on the crack, deflection, strain, stiffness and fatigue life of the beam was mainly studied. The main conclusions are as follows: (1) the test process and failure pattern of high strength steel fiber reinforced concrete beams under static load and fatigue load are significantly different. The ductility of the beam under static load is better, and there are obvious signs before failure. Under fatigue load, the beam is brittle failure, but the addition of steel fiber effectively inhibits the development of cracks, improves the flexural stiffness of beam section, and improves the failure pattern of beam. (2) with the increase of stress level, the failure pattern of beam is improved. The fatigue life and fatigue strength of high strength steel fiber reinforced concrete beams are significantly decreased, and the failure process and shape are similar, showing an obvious three-stage law: the development of the early stage is rapid, the increase is relatively large, generally before 10,000 fatigue cycles; The mid-term fatigue eigenvalues increase steadily and uniformly, the increase slows down, and the duration is the longest, accounting for about 80% of the whole fatigue life. The fatigue eigenvalues reach the critical value at the later stage and suddenly occur instability failure. (3) based on the bond-slip theory, the fatigue eigenvalues reach the critical value at the later stage. The calculation formula of crack width of high strength steel fiber reinforced concrete beam under static load and fatigue load is put forward. According to the linear correlation between cumulative residual strain and cycle number hyperbolic curve, the calculation method of accumulated residual strain of concrete in compression zone of high strength steel fiber reinforced concrete beam is put forward. (4) by fitting the test data, The fatigue life curves of high strength steel fiber reinforced concrete beam S and lgN are obtained. At the same time, the fatigue life of the high strength steel fiber reinforced concrete beam is predicted by combining the stiffness damage value D, which provides the basis for the fatigue design of the high strength steel fiber reinforced concrete beam.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU37

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