受腐蚀钢筋混凝土墩柱抗侧向冲击性能研究

发布时间：2018-08-15 14:04

【摘要】：随着我国交通基础建设的飞速发展,全国各地兴建或规划建设大量内河和跨海桥梁。对于大型桥梁,车辆、船舶或海上漂浮物撞击桥墩的事故时有发生。同时,处于海洋环境中的跨海大桥桥墩受到氯离子的侵蚀导致混凝土构件中的钢筋腐蚀,耐久性退化而提前失效,其规律有待深入研究。因而研究受腐蚀钢筋混凝土墩柱的抗侧向冲击性能具有重要的工程意义和学术价值。本文通过快速腐蚀和落锤冲击试验完成8根不同腐蚀率的钢筋混凝土墩柱的抗侧向冲击性能的试验研究;通过考虑混凝土墩柱的材料率效应,钢筋腐蚀力学性能退化,钢筋混凝土腐蚀粘结性能退化以及冲击侵彻性能,分析得到腐蚀钢筋混凝土墩柱的极限状态计算方法;利用ANSYS/LS-DYNA对试验进行数值模拟,通过钢筋力学性能的退化模拟钢筋腐蚀作用,综合分析获得腐蚀率对钢混墩柱抗侧向冲击性能的影响。在此基础上进行拓展,分析支座形式以及混凝土强度对其抗侧冲击性能的影响。得到以下主要结论:(1)随着腐蚀率的增加,钢筋混凝土墩柱的初始锈胀裂缝宽度和长度增加明显。(2)不同腐蚀率试件在冲击荷载作用下呈现不同破坏形态。低腐蚀率试件的破坏模式为冲击处混凝土侵彻压碎并由弯剪裂缝开展导致弯剪破坏,高腐蚀率试件破坏模式为冲击处混凝土侵彻压碎以及无预警的剪切脆性破坏。腐蚀率的增加降低墩柱抗侧冲击延性。(3)高腐蚀率的混凝土墩柱的平均冲击力和峰值冲击力在低冲击工况下大于低腐蚀率墩柱,在破坏工况下,高腐蚀率墩柱的平均冲击力和峰值冲击力均小于低腐蚀率试件,腐蚀率影响试件的最终破坏模式,同时降低试件的冲击承载力。(4)高腐蚀率试件的拉区钢筋的峰值应变和平均应变较低腐蚀率试件出现明显降低。主要原因是钢筋的腐蚀导致钢筋与混凝土的粘结性能退化,使钢筋应变滞后。使用钢筋应变滞后系数?考虑钢筋腐蚀作用导致的应变滞后,计算结果与试验结果接近,误差在6.8%。(5)腐蚀钢筋混凝土墩柱的冲击极限状态计算方法主要考虑材料的率效应,腐蚀钢筋的力学性能退化,腐蚀钢筋的应变滞后,冲击区域的混凝土侵彻退化。计算结果与试验结果误差在5.27%。(6)有限元分析中,观察试件的冲击主拉应力分布可以发现两端简支试件在冲击部位两侧各1/3处为试件冲击剪切破坏的薄弱部位;一端固支,一端简支的试件,主拉应力集中区域偏向固支端,试件跨中冲击区域靠近固支端侧1/3跨处成为试件的薄弱部位。同时试件的墩帽角部为受压薄弱部位。(7)高强度的混凝土峰值冲击力大于低强度的混凝土。由于混凝土材料的率敏感性,在冲击速度较低时,混凝土的冲击力涨幅较小,冲击速度较高时,混凝土的冲击力涨幅明显变大。
[Abstract]:With the rapid development of transportation infrastructure in China, a large number of inland rivers and cross-sea bridges are built or planned throughout the country. Accidents occur when large bridges, vehicles, ships or floating objects hit the pier. At the same time, the corrosion of bridge piers caused by chloride ions in the marine environment leads to the corrosion of steel bars in concrete members, the durability degradation and early failure, the law of which needs to be further studied. Therefore, it is of great engineering significance and academic value to study the lateral impact resistance of corroded reinforced concrete pier columns. In this paper, the lateral impact resistance of 8 reinforced concrete pier columns with different corrosion rates is studied by rapid corrosion test and drop hammer impact test, and the corrosion mechanical properties of reinforced concrete columns are degraded by considering the material rate effect of concrete pier columns. The ultimate state calculation method of corroded reinforced concrete pier column is obtained by analyzing the degradation of corrosion bond property and impact penetration property of reinforced concrete, and the numerical simulation of the test is carried out by ANSYS/LS-DYNA. The influence of corrosion rate on lateral impact resistance of steel concrete pier column is analyzed synthetically through the degradation of steel bar mechanical properties to simulate the corrosion of steel bar. On this basis, the influence of bearing form and concrete strength on lateral impact resistance is analyzed. The main conclusions are as follows: (1) with the increase of corrosion rate, the initial corrosion crack width and length of reinforced concrete pier columns increase obviously, and (2) the specimens with different corrosion rates show different failure patterns under impact loading. The failure mode of low corrosion rate specimens is concrete penetration and crushing at impact site and bending shear failure caused by bending shear crack. The failure mode of high corrosion rate specimen is concrete penetration crushing at impact site and shear brittle failure without warning. The increase of corrosion rate reduces the lateral impact ductility of the pier column. (3) the average impact force and peak impact force of the concrete pier column with high corrosion rate are larger than those of the low corrosion rate pier column under the low impact condition, and under the failure condition, The average impact force and peak impact force of the pier column with high corrosion rate are smaller than those of the low corrosion rate specimen, and the corrosion rate affects the ultimate failure mode of the specimen. (4) the peak strain and average strain of steel bar in tensile zone of high corrosion rate specimens are obviously lower than those of low corrosion rate specimens. The main reason is that the corrosion of steel bar leads to the degradation of bond property between steel bar and concrete, which makes the strain of steel bar lag behind. Using strain lag coefficient of steel bar? Considering the strain lag caused by the corrosion of steel bar, the calculation result is close to the test result, and the error is 6.8. (5) the impact limit state calculation method of corroded reinforced concrete pier column mainly considers the rate effect of material, and the mechanical properties of corroded steel bar degrade. The strain of corroded steel bar lags behind, and the penetration of concrete in impact area degenerates. The error between the calculated results and the test results is 5.27. (6) in the finite element analysis, observing the main tensile stress distribution of the specimens, it can be found that the specimens with simple supports at both ends are the weak parts of the impact shear failure at each third of each side of the impact site, and one end is clamped, For simply supported specimens with one end, the main tensile stress concentration area is inclined to the fixed support end, and the impact area in the middle span of the specimen is close to the end / side of the fixed support end to the third span, which becomes the weak part of the specimen. At the same time, the corner of the pier cap of the specimen is weak under compression. (7) the peak impact force of high strength concrete is greater than that of low strength concrete. Because of the rate sensitivity of concrete material, when the impact velocity is low, the increase of impact force of concrete is smaller, and the increase of impact force of concrete is obviously larger when the impact velocity is high.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU375

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