Abstract: A method for quantitative analysis of a cavity at the top of a concrete-filled steel tube is disclosed. By substitution of the determined inner radius of the steel tube, the thickness of the steel tube wall and the propagation speed of ultrasonic waves in the steel tube and in the concrete, the propagation time of the ultrasonic wave between the top and the bottom of the concrete-filled steel tube enables calculation of the height of the cavity. The method can be used to quantify the cavity height at the top of the concrete-filled steel tube, with small relative errors and high accuracy.

Abstract: The invention provides a method for quantitative analysis of cavity zone of the top of the concrete-filled steel tube, comprising the following steps: By substitution of the determined inner radius of the steel tube, the thickness of the tube wall and the propagation speed of the ultrasonic wave in the steel tube, the propagation speed of the ultrasonic wave in the concrete, and the starting time of the first wave when the ultrasonic wave propagating between the top and the bottom of the concrete-filled steel tube into the calculation model of the cavity height of the top of the concrete-filled steel tube, to obtain the cavity height of the top of the concrete-filled steel tube; the calculation model of the cavity height is: t = ( x 1 + d 2 + 2 ? x 2 ? ( d + r ) v s + 4 ? r 2 + d 2 + 4 ? rd - 2 ? r ? h - 2 ? hd - d 2 + 2 ? x 2 ? ( d + r ) v c ) ; wherein, x1 and x2 are both calculation variables, and their values are: x 1 =