Experimental Study And Theoretical Analysis On Bond-Slip Performance Between Shaped Steel And High Concrete In Srhc Structures

Because of the high bearing capacity, enough stiffness and excellent durability, steel reinforced high concrete composite (SRHC) structure are increasingly widely applied in the practical engineering in recent years. SRHC, which place shaped steel into high concrete, can not only give full play to the excellent mechanical properties, but also have ability to avoid the obvious brittleness problem of high concrete, therefore high concrete could possible be used in multi-storey buildings, thus the goals that diminishing sectional dimension, reducing structure weigh and increasing the effective clearance of construction were achieved. Bond-slip performance of interface between shaped steel and high concrete is the one of basic research area of SRHC structures, which excellent mechanical properties could be fully exerted by meeting the requirements of the interfacial bonding strength, that support establishment of series of reasonable calculation methods about strength and rigidity.In order to determine the relations between the main influencing factors-concrete strength, concrete cover thickness, shaped steel embedment length and the ratio of the transverse hoops-and the nature bold-slip performance of SRHC structures,12push-out test specimens were designed, among them some test specimens were devised to the analysis the advantage by setting the shear stud on the flange, web and total cross-section of shaped steel. For comparing the mechanical performance about the before and after damage of SRHC,8test specimens derived from the push-out test which has better configuration of surface were loaded under the axial pressure. The displacement control loading system were used for the time, compared with the force control system of loading, the obtained data are more accurately reflect the whole process of the bond-slip damage, the problem that hard to obtain the data of specimen after peak load by using traditional force control system of loading was solved. By observing the failure patterns of push-out text specimens, the mechanics characteristics corresponding different failure patterns were analyzed, the distribution regularity of bond strength and slip were identified. The relationships between bond strength and slip at each stage were formulated by the obtained load-slip curves. The influence of five factors (concrete strength, concrete cover thickness, shaped steel embedment length, the ratio of the transverse hoops and shear stud) to the bond-slip performance of text specimens were identified. By analyzing the transmit mechanism of shear, the proportion of the three component for bond strength (chemical bond stress, occlusal stress, frictional stress) were achieved. The balance equations of force at interface between shaped steel and concrete were established, on the basic of the obtained data by the resistance strain gauge placed on the shaped steel, the change curves of slip and embedment length were acquired. By using linear regression methods, the computational formula on the effective bond strength, the initial bond strength, the ultimate bond strength and the residual bond strength were deduced, furthermore, the gray incident theory were applied to optimize the above formulas, the simplified calculation formulas, which have good accuracy, were achieved according to the coefficient of correlation. Relying on the dimensionless bond-slip curves, the constitutive equations were established. Form the perspective of energy, the proportion of elastic deformation energy and plastic deformation energy were calculated when the text specimens bear the ultimate load. The stiffness and equivalence principle of slip were exerted to establish damage variable and the calculation formulas for damage variable were worked out, what is more, the relationships between influencing factors and damage level were formulated. At the end of the paper, some calculation methods from different codes were introduced, and the advantages and disadvantages of each method on SRHC under the axial load were analyzed, the relations between factors and the mechanical performance (the ultimate bearing capacity, elastic modulus, coefficient of deformation and Energy dissipation) of SRHC column.Some relative research results in the paper about bond-slip performance of interface between shaped steel and high concrete in SRHC structures may contribute to engineering application, and it provides theoretical support for the establishment of reasonable calculation method.