Method and characteristics of band gap of periodic pile row structures based on domain decomposition and nullspace technology

Aiming at the problems such as complex structure of displacement function, high calculation cost, and difficulty in waveform fitting caused by the distortion of pile-soil parameters when the traditional energy method is used to solve the band gap of periodic row pile structures, the traditional energy method is improved based on the idea of regional decomposition, and the pile and the soil are modeled separately in independent coordinate systems to overcome the distortion of pile-soil parameters. Then the nullspace technology is used to deal with various boundary constraints, which overcomes the boundary dependency problem in type function construction and greatly improves the computational efficiency. The results show that compared with the wave number finite element method, the proposed method is accurate and reliable, and has efficiency advantages. In addition, the elastic modulus of soil and the filling ratio of row piles are the main factors affecting the band gap. Compared with the square periodic row piles, the hexagonal arrangement can obtain higher starting frequency, cut-off frequency and band gap width.