The Research On The NDT Testing Technology Of The Vertical Prestress Tension And The Grouting Compactness Of The PC Box Girder Bridge

The main purpose of vertical prestressing tendons on long-span prestressed concrete box girder bridge is to provide vertical pre-stress to inhibit the development of principal tensile stress, to get the purpose of preventing cracking of girder webs. However, there is always many cracks on girder bridges. On the one hand is due to incorrect construction, high location error of tendon, draw-in of anchorage and other causes; on the other hand is due to the long term prestress loss caused by reinforcement corrosion because of grouting uncompacted. On the other hand is due to the vertical prestressed pipeline pressure slurry density caused by vertical prestressed reinforcement corrosion resulting from lack of prestress loss in the actual tension reinforcement corrosion. Therefore, how to improve the construction quality of vertical prestressed reinforcement tension and reduce the long-term loss of operation to provide enough tensioning force become the focus of research In this paper, make some research on the detection method for the vertical prestressed reinforcement tension and pipe grouting compactness, achieved some results, and the main contents as follows:1) This paper introduced the purpose of the topic, the research status of domestic and foreign scholars on the nondestructive detection method of vertical prestressing and pipe grouting compactness.2) Based on the theory of structural dynamics, by the method of theoretical derivation and finite element numerical simulation, analysis the frequency characteristics of vertical prestressed reinforcement exposed segment.3) Through the model test, and get the empirical formula ofφ 32 finishing rolling rebar’s reality tensile and the increased stiffness coefficients.And the nondestructive method was used in real project, effectively improve the vertical prestressed construction quality.4) Brief introduced elastic wave, the basic principle of Impact-echo method and Fourier transform which used to transform time domain signal to frequency domain signal. At the same time, according to the propagation theory, the propagation path of longitudinal wave in five kinds of grouting compactness was detailed analysed.5) In the model test, different models with different grouting compactness of empty, 1/4dense, 1/2dense,3/4dense and fully dense are manufactured. The main frequency of model test and numerical simulation has a significant linear relationship with grouting compactness.6) According to the finite element numerical analysis results, the empirical formula of main frequency and grouting compactness is obtained. The quantitative evaluation of vertical prestrsess grouting compactness is taken by using this formula.