The bond-slip behaviors between shaped steel and concrete are investigated using comparative tests of pull-out,push-out,pull-push cycle, short-column and pull-out of the flanges or/ and webs insulated. Based on the experimental results measured in macroscopic and microscopic way, the relationship between internal microphysical state change and macromechanical response of the interface of shaped steel and concrete is discovered. The damage concepts are extended to characterize the microphysical state evolution and resulting in the bondslip failure of the bond interface of shaped steel and concrete. The mechanism of interfacial microcrack process and bond-slip failure between steel and concrete are investigated in fracture and damage mechanics. A failure model of bond interface of steel and concrete is proposed. The calculating method of fracture toughness of bond interface is provided,and the main parameters significantly affecting the fracture toughness are discussed. The characteristics of bond interface of shaped steel and concrete are analyzed. The influence of interfacial micro-crack process on bond-slip fracture toughness is researched. The model of banded micro-crack fracture process zone of bond interface of steel and concrete is put forward,and the sizes of fracture process zone are obtained from the banded fracture process zone model. In the light of the load-strain curves obtained in the bond-slip tests,the influence of fracture process zone on the bond-slip fracture toughness is modified using the critical fracture toughness. All these may contribute to the further analysis of bond-slip behaviors and the improvement of calculating theories in steel reinforced concrete composite structures.
