Hysteretic model of seawater and sea sand concrete-filled FRP- steel composite tube columns considering the confinement effectiveness

Aiming at the problems of marine infrastructure facing corrosion and complex load environments, a seawater and sea sand concrete-filled CFRP- steel composite tube (SFSCT) column structure was proposed: CFRP sheets are pasted on the inner and outer walls of the steel tube to provide corrosion resistance and improve yield capacity, and then the environment-friendly seawater and sea sand concrete is used to fill the steel tube. Based on pseudo-static tests, a fiber model was established based on OpenSEEs. The axial compression ratio, steel tube thickness, yield strength, shear span ratio, and CFRP layer were analyzed and collected as a database. The influence rules of the designed parameters were obtained. Combining experimental data and fiber model results, a complete hysteretic model was finally proposed based on the equal ratio superposition of parameters. The proposed model includes the parameter prediction methods such as peak load, drift ratio, and stiffness of the descending section, as well as the loading and unloading criteria. A trilinear skeleton curve model was established to predict the developing trends of various parameters. The confinement effectiveness of steel and CFRP was fully taken into considerations in the proposed model. The predicted results are in good agreement with the simulation results of SFSCT.