Experimental and numerical study on out-of-plane post creep buckling behavior of concrete-filled steel tubular arch

Long-span concrete-filled steel tubular (CFST) arches have gained widespread use due to their high strength, excellent seismic resistance, and ease of construction. However, these arches are susceptible to out-of-plane buckling, particularly when the creep of the concrete core significantly reduces buckling load resistance. This is primarily caused by increased deformation of the arch and early yielding of the steel tubes under lower load levels-a phenomenon known as post-creep out-of-plane buckling, which has not yet been experimentally studied. In this research, a 9-meter span CFST slender arch was first subjected to a sustained load for 356 days and then tested to failure without unloading to investigate the effects of creep-induced pre-buckling deformation on the out-of-plane buckling behavior. The confinement effect of the concrete core during both the sustained loading phase and the post-creep buckling stage was analyzed based on the test results. A finite element (FE) model, incorporating the nonlinear creep effects of concrete, was developed to simulate the post-creep out-of-plane buckling behavior of CFST arches. The model's accuracy was validated against the experimental data, and the comparative results demonstrated its capability to reliably predict both the long-term and post-creep buckling behavior of CFST arches.