Study On Axial Compression Behavior Of Concrete Filled GFRP Tubular Stub Columns In Saline And Alkali Environment

GFRP tube concrete short column is a new type of composite column with high strength,high rigidity and good durability.Compared with the conventional concrete-filled steel tubular stub column,the corrosion resistance of GFRP tube concrete short column is better in the harsh and complex environment,such as saline alkali area,seaport area,etc.It is necessary to do a lot of research on the mechanical properties degradation of GFRP tube concrete short column in the complex corrosive environment.In this paper,the GFRP tube concrete short columns with inner diameter of 100 mm,wall thickness of 3 mm and height of 300 mm are selected as the research objects.The degradation of mechanical properties of GFRP tube concrete short columns immersed in saline and alkali solution at different temperatures（20 ℃,40 ℃,60 ℃）and different periods are studied.Based on the corrosion mechanism of GFRP tube concrete short columns in saline and alkali solution,the internal concrete defects of GFRP tube concrete short columns before and after immersion are detected by using metal ultrasonic detector,and the degradation of mechanical properties of GFRP tube concrete short columns is analyzed.In this paper,the failure process and failure mode are discussed.Meanwhile,the effects of immersion temperature and immersion time on the ultimate bearing capacity and stress-strain curves of the short columns are analyzed,and the degradation law of mechanical properties of GFRP tube concrete short columns in saline and alkali environment is obtained.The test results showed that the corrosion of saline and alkali solution led to the degradation of mechanical properties of plain concrete short columns and GFRP tube concrete short columns to a certain extent.The failure process and failure mode of plain concrete short columns and GFRP tube concrete short columns were different in axial compression test.The longer the immersion time and the higher the immersion temperature were,the more obvious the degradation of mechanical properties was.Under the same conditions,the internal defects of plain concrete short columns were significantly higher than that of GFRP tube concrete short columns,which indicated that GFRP tube not only improved the bearing capacity of internal core concrete column,but also extended the service life of internal core concrete column.The corrosion of the external saline and alkali solution on the internal core concrete was slowed down;the immersion temperature had a great influence on the mechanical properties of GFRP tubular concrete short columns,and the temperature effect was significantly greater than the time effect in the short term;the stress-strain model of GFRP tubular concrete short columns corroded by saline and alkali solution was no longer bilinear under normal condition.