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The bond-slip behaviors of self-stressing steel slag concrete filled steel tubes (SSSSCFST) are investigated by carrying out the push-out tests. The influence of thickness to diameter ratio, confining parameter and expansion ratio of steel slag concrete (SSC) on bond-slip performance are analyzed. Investigations of the failure modes of each specimen indicate that the shear failure of the bond interface dominates the failure of the specimen. Further, three stages of the load-slip relationship curve of bond slip was observed, i.e., the loading stage, descending section and constant load section. In the loading section, with the increase in thickness to diameter ratio or confining parameter, the interface bonding force of specimen improves firstly and then decreases. Besides, the interfacial bond strength increases with enhancement of the expansion ratio. In the descending section, the interfacial bonding force raises with improvement of diameter-thickness ratio, while decreases as the confining parameter and expansion ratio increase. Moreover, the influence of considered parameters on the ultimate interface bond load is analyzed. Finally, a theoretical model for the bond-slip behaviors of SSSSCFST is proposed by accounting for the non-uniform distribution of interface bond strength. It indicates that the theoretical model can well capture the main features that are exhibited during the whole process of push-out test.

Objective. Compare the effects of three sampling methods on the microbiological monitoring results after reprocessing of gastrointestinal endoscopes, providing scientific basis for improving the monitoring quality of gastrointestinal endoscope cleaning and disinfection. Method. Gastrointestinal endoscopes after reprocessing were selected randomly at the gastrointestinal endoscopy center of a tertiary hospital in Shanghai from October 2018 to February 2019. The endoscopes selected were all sampled in three different methods under continuous sampling and intermittent sampling respectively. Methods used includes, the biopsy channel group (Group A), the entire channel group (Group B), and the disc brush group (Group C). Then the colony forming units (CFU/piece) were counted in the laboratory. Results. A total of 12 endoscopes were sampled by using continuous sampling approach, in which the detection rate of bacteria in disc brush group (33.3%) and entire channel group (33.3%) was higher than biopsy channel group (8.3%). Among the 12 endoscopes sampled with intermittent approach, the detection rate of bacteria from high to low was the disc brush group (50%), the entire channel group (41.7%), and the biopsy channel group (8.3%). Conclusion. Different sampling methods will lead to the difference of microbiological culture results after reprocessing of gastrointestinal endoscope, indicating that the improved sampling method is beneficial to objectively reflect the endoscope cleaning and disinfection effect, and improve the monitoring quality of endoscope disinfection.