Mechanical Properties Of Steel Beam-Square Steel Tube Filled With Reinforced PP ECC Joints

With the rapid development of the city, natural disasters especially earthquake occurs frequently, building to the development of large space、ultra-high-level direction, so people pay more and more attention to the structural requirements of the building. Square steel tube steel reinforced concrete structure have many advantages with strength, superior seismic performance, good ductility, short construction time. These advantages promote the development of square steel tube filled with steel-reinforced concrete structure more and more widely. The key to the application of the square steel tube filled with steel-reinforced concrete structure is its joints, so it has important theory and application value to research the connections between the concrete filled square steel tube columns and steel beams for the development and application of the concrete filled square steel tube column frames. The polypropylene fiber engineering cement composite materials (hereinafter referred to as PP ECC), modified polypropylene fibers were added to the ECC. PP ECC have many features with compressive strength, low price, light weight, durability, toughness, fine cracks, impact resistance.The research is using square steel tube filled with PP ECC instead of C60concrete, the PP ECC filled with steel reinforced, these three make up square steel tube filled with steel-reinforced PP ECC, which is a combination of new materials and new overloaded column. The compressive strength of the PP ECC is larger than C60concrete compressive strength, PP ECC and steel reinforced square steel tube work together, it will further improve the bearing capacity of the pillars. The structure play the advantages of the two materials and avoid weaknesses. The PP fiber has crack resistance and toughening, it could continue to work with wound and inhibit the development of cracks when cracks appear. In this paper, ANSYS is used to analysis the combinations column joint. Build the square steel tube filled with steel-reinforced concrete and PP ECC beam-column joints models,and analysis the static and cyclic loading respectively.The validity of the model is validated by comparison of test and simulation. By comparing the performance of the CFRT joints with or without reinforcement ring, it has shown that the beam-column joints with reinforcement ring deformed smaller, by the interaction between the two, reducing the stress of the beam-column joints, improving the bearing capacity of the joints. By contrasting different materials built in square steel tubes,the performance of the PP ECC which is built in square steel tubes beam-column joints is stronger than the C60concrete beam-column joints. PP ECC has a greater advantage on the reciprocating loads, especially for the earthquake zone and the high-rise building structure. By comparing stiffness degradation and displacement ductility factor of the two joints, the ductility of PP ECC joint is better than C60joint, the stiffness degradation of PP ECC joint is slower. The PP ECC and C60concrete are similar on price, it is an equivalent quality replacement. In addition, changing the structure parameter, such as changing the size of the square steel tube, changing the wall thickness, and changing the level of concrete, studying the mechanical properties of the steel beams and columns combination joints. The research has shown that it is obvious to the bearing capacity of the plastic stage when increasing the pipe wall thickness, increasing the concrete level and increasing the size of the square steel tube.