The Wave Propagation In Damaged Prestressed And Reinforced Concrete Media

The prestressed and reinforced concrete structures are used extensively in the engineering. The path, phase, amplitude, time, energy attenuation and frequency of wave propagation are changed by the consistency, uniformity, constituent, strength, damage and micro cracks etc. in the concrete structure. Because the characteristic information of concrete can be carried from the received wave, the strength and the damaged degree of concrete can be gained by studying this information. There are extensive prospects of application for the wave propagation theory in the prestressed and reinforced concrete structures.The theory of wave propagation in concrete media with local damage is the basis of the study in this paper. The time-displacement curve of the received wave is calculated. The strong influence of the degree, location and length of damage on the amplitude and the delaying time of the first wave are analyzed. Therefore, the damage is considered necessary in the nondestructive test of concrete structure.There may be damage in concrete structure when the prestress is loaded. The local damage may be produced in the interior of concrete structure by the other factors. The quantitative relationships between wave propagation and damage, prestress and other parameters are given.According to the experiment, the elasticity and viscosity can be changed by the damage in concrete media. A damage theory with double parameters is presented which use both elastic and viscous parameters as description of the damage, and the damaged degree and the materials properties in damaged concrete are exactly described by this theory. The influence of the damaged length and degree on the wave propagation is analyzed in the viscoelastic concrete media, and the corresponding influence curves are given.The influence of the reinforcing steel bar on the path, time and amplitude of the wave propagation are strong. The transformation of the form of wave in course of propagating is analyzed and the wave form is calculated by addition method. The quantitative influence relationships between the diameter of reinforcing steel bar, the distance (between reinforcing steel bar and the probe) and the amplitude of wave are analyzed.The influence of every factor in the prestressed and reinforced concrete structures on the wave propagation is studied in this paper. The quantitative relationships between every factors and form, amplitude, delaying time of the first wave are gained, the dependable basis is provided for further quantitative study of inversion and nondestructive test.