【作者】 邓雷飞；

【导师】 赵冲久； 赵利平；

【作者基本信息】 长沙理工大学 ， 港口、海岸及近海工程， 2011， 硕士

【摘要】 残余预应力是反映预应力混凝土构件工作性能的重要指标之一,但它本身就是一个未知参数,若能找到一种方法能较精确的检测出钢筋残余预应力,无论是对在役混凝土结构的性能评估、修复加固还是对拟建结构的设计、施工都具有指导意义。本文在有限元分析的基础上,利用钻孔法对高桩码头预应力构件残余预应力检测进行研究,试图寻找一种既简单实用又稳定可靠的方法检测钢筋残余预应力,为在役预应力梁工作性能作出较准确的评估。本文主要进行了以下工作:1.建立预应力薄板模型分析预应力、孔尺寸及板尺寸与应力释放扰动值之间的关系,得出结论为:孔口扰动值与预应力大小无关;它在一定范围内随孔尺寸增大而增大;构件尺寸越大孔口扰动值越小,并且受构件最短边的影响最大。2.基于有限元ANSYS建立预应力混凝土简支梁模型,采用生死单元法、2次加载法和位移平衡法。分析在预应力混凝土梁底钻孔(梁不受外荷载作用)时梁底混凝土表面应力释放规律。通过改变钻孔参数(孔径和深度),分析出钻孔孔径和孔深都为50 mm时,由梁底中心轴距钻孔中心100 mm处的应变计算得的钻孔中心应力与实际施加应力吻合。由此确定钻孔的最佳孔径和深度都为50 mm,应变测量最佳贴应变片位置为梁底中心轴向距钻孔中心100 mm处,贴片方向为梁轴向工作应力方向。该结论对预应力梁残余预应力检测具有指导意义。3.以钻孔法现场检测某高桩码头在役混凝土轨道梁残余预应力为例,描述了钻孔法检测残余应力的基本过程。根据实际情况对测得的平均应变进行了修正,然后计算出梁底中心混凝土正应力,并通过线性回归的方法计算出预应力梁钢筋残余预应力。最后将其与规范法计算出的钢筋残余预应力进行比较验证。4.根据轨道梁残余预应力计算出最大开裂荷载,然后通过现役单、双门机包络图的计算,对轨道梁门机作业健康状况作出评估。根据包络图可知第1跨和第8跨跨中为轨道梁最不利位置,由此也可以确定轨道梁钻孔位置应选取在第1跨和第8跨跨中,因为这两跨的最易产生钢筋疲劳及裂缝。但其最大弯矩均未超出轨道梁的最大开裂荷载,因此判定该轨道梁在门机正常工作时是安全的。更多还原

【Abstract】 Residual prestress is one of the important indicators of prestressed concrete components. It is a necessary work to find a way to detect the residual prestress more accurately and conveniently, both for the performance evaluation, design of repairing and strengthening work of existing concrete structures and design of new structures. In this paper, the residual prestress of a beam in a high pile wharf is detected by hole-drilling method, based on finite element analysis. The following works are involved.1. The relationship among residual prestress, hole depth, plate size and the prestress disturbance beside the hole, in the model of prestressed concrete thin plate. The disturbance value is independent of prestress, increases with the growth of hole depth, and decreases with the growth of the plates size.2. A model of prestressed concrete beam is established based on general finite element ANSYS, with birth-death element method and 2 times loading method. Release of stress beside the hole is studied in Simulation drilling at the prestressed concrete beam without external load, By changing the drilling parameters which is diameter and depth. It is found that when diameter and depth are both 50 mm, the calculated stress and measured stress are in good agreement which is 100mm away from center of the hole. Therefore, the diameter and depth of drilling are both 50 mm and the strain gauge affixing point is 100mm from hole center at the bottom of the beam, and the direction of which is the axial stress direction of the beam. This conclusion is instructive for the Detection of residual prestress prestressed beam.3. Residual prestress of existing prestressed concrete track beams in high-piled wharf is conducted by hole-drilling method.4. The maximum cracking load of prestressed track beams is calculated according to the residual prestress detected, then health assessment about the track beam is done through calculating the envelope diagram of the portal crane moving. The envelope show that the most unfavorable position are cross 1 and cross 8, but it did not exceed the maximum of cracking load, so the track beam is safe when the portal crane normal working. And it can be determined that the position of the hole should be cross 1 and cross 8, because the two cross most likely to be fatigue failure and cracking.更多还原