Research On Nondestructive Testing Of Grouting Quality For Prestressed Concrete Beam

With the development of Chinese economy, the infrastructure has been built very well. Many large and medium-sized prestressed concrete bridges have been built. This made a contribution to the development of Chinese transportation construction. In the meantime, many problems appeared. One of them is the corrosion of prestressing tendon in the bridges which is a big potential safety hazard. The survey found that the main reason that caused prestressing tendon’s corrosion is the bad grouted density. Therefore finding a simple method to detect the grouted density becomes the present research hot spot.Impact echo method is a method using the stress wave caused by temporary impact to detect structures nondestructively. This paper mainly studied the detection of the grouted density using impact echo method based on laboratory test and finite element simulation. Some main achievements of this dissertation are described as follow:1. The principle of impact echo method is analyzed. And research status is introduced based on literature research at home and abroad.2. The characteristic of echo signal in different conditions is revealed based on laboratory test. And the effects of the grouted density, prestressing tendon, the thickness of concrete and the reinforcement are studied. The results show that:(1) The effects of prestressing tendon and the thickness of concrete on the time domain waveform are not obviously. (2) With the adding of reinforcement and the void in grouted duct, the time domain waveform is getting more and more disorganized. (3) With the void in grouted duct getting bigger, the frequency of main peak of frequency domain waveform is getting lower. (4) With the increase of the thickness of concrete, the frequencies of the peaks of frequency domain waveform are getting smaller. (5) When the prestressing tendon or reinforcement is added, noise wave or a small peak with a lower frequency appears.3. By systemic researching and finite element simulating experiment, it is confirmed that finite element simulation can be used to study the impact echo method and measure the void in grouted duct quantitatively and accurately.4. By simulating the grouted duct with different void, it is found that stress wave follows the same rule in finite element simulation. With the increase of the void in grouted duct, the only change is that the frequency of the main peak is getting lower. And after quantitative analysis of these data, a formula showing the relationship between the frequencies of main peaks and the rate of defects is fitted by MATLAB. Based on this formula and the data got by laboratory test, a new formula is fitted which can show the relationship between frequencies of main peaks and the rate of defects in laboratory test. And based on the second formula the rate of defect in laboratory test can be calculated on the condition knowing the frequency of main peak.