Ultrasonic Computerized Tomography Imaging Method With Combinatorial Optimization Algorithm for Concrete Pile Foundation

Abstract

Concrete pile foundations are the main load-carrying and aseismic structures for many largescale building structures. Their structural quality will have a great impact on the safety of building structures. However, the imaging results still cannot easily meet practical demands in current ultrasonic Computerized Tomography (CT) imaging tests of concrete structures. In view of the current difficulties, a combinatorial optimization tomographic imaging method is proposed. First, a quadric broadening objective function with a clear physical meaning is established according to the characteristics of ultrasonic propagation in concrete. Then, a new CT imaging method of concrete pile foundation is formed by combining fast adaptive optimization search ability of Genetic Algorithm (GA) with the global search control ability of Simulated Annealing Algorithm (SAA). The numerical simulation experiments have shown that the usage of the correct priori information and the excellent characteristic of the Simulated Annealing Genetic Algorithm (SAGA) in searching for the global minimum value of the function have produced accurate and effective results with stable numerical values. Finally, the imaging method is verified by experiment, where results show that SAGA requires fewer iterations, has faster computation speed and gives more accurate imaging results compared with the single GA.INDEX TERMS Concrete pile foundation, ultrasonic CT, inversion imaging algorithm, combinatorial optimization algorithm, SAGA.

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