The paper presents the analysis of stress in steel and concrete in CFST composite elements subjected to push-out tests. Two analytical models of stress distribution are presented. The bond at the interface between steel and concrete in the initial phase of the push-out test is provided by the adhesion. Until the force reach a certain value, the slip between both materials does not occur or it is negligibly small, what ensures full composite action of the specimen. In the first analytical model the full bond between both materials was assumed. This model allows to estimate value of the force for which the local loss of adhesion in given cross section begins. In the second model it was assumed that the bond stress distribution is constant along the shear transfer length of the specimen. Based on that the formulas for triangle distribution of stress in steel and concrete for the maximum push-out force were derived and compared with the experimental results. Both models can be used to better understand the mechanisms of interaction between steel and concrete in composite steel-concrete columns.
1. Burak, E., Tuncan A.: Determination of frictional behavior between concrete and steel tube interaction, Proceedings of the 7th European Conference on Steel and Composite Structures Eurosteel, 521-522, Italy, 2014.
2. Cameron, B.: Bond behavior in concrete filled tube composite
3. columns, Ms thesis, University of Washington, Seattle, 1997.
4. EN 1994-1-1 Eurocode 4: Design of composite steel and concrete structures. Part1-1: General rules and rules for buildings, 2004.
5. Hunaiti, Y.M.: Bond strength in battened composite columns, Journal of Structural Engineering, 117, 3 (1991) 699-714.
6. Hunaiti, Y.M.: Aging effect on bond strength in composite sections, Journal of Materials in Civil Engineering, 6, 4 (1994) 469-73.
7. Ke, X.J., Sun, Y.H., Yang, Z.: Calculation on Bond Strength of High-Strength Concrete Filled Steel Tube, Proceedings of the 4th International Conference on Sensors, Measurement and Intellgent Materials, 995-999, China, 2016.
8. Khodaie, N.: Effect of the Concrete Strength on the Concrete-Steel Bond in Concrete Filled Steel Tubes, Journal of the Persian Gulf, 4, 11 (2013) 9-16.
10. Szmigiera, E., Woyciechowski, P.: Influence of the compaction method on the bond between steel and concrete in composite columns, Periodica Polytechnica-Civil Engineering, 57, 2 (2013) 129-137.
11. Szmigiera, E., Woyciechowski, P., Szadkowska, M.: Badania przyczepności betonu do stali konstrukcyjnej w słupach zespolonych, in: Beton i Konstrukcje z betonu-badania, Seria Monografie Zakładu Konstrukcji Betonowych i Zakładu Inżynierii Materiałów Budowlanych 2015, 111-127.
12. Virdi, K.S., Dowling, P.J.: Bond strength in concrete filled circular steel