Papers by Keyword: Shear Mechanism

Abstract: The shear behaviors of steel reinforced high strength and high performance concrete (SRHSHPC) composite frame columns are studied through the test on a number of SRHSHPC specimens with grade of concrete strength varied from C80 to C120 subjected to constant axial compression and cyclically varying horizontal load. Four influencing factors, namely, shear span ratio, axial compression ratio, stirrup ratio and concrete strength, are taken into consideration in the test, and strain gauges are respectively placed on steel web, stirrups as well as reinforcement bars to study the shear mechanism of SRHSHPC composite columns. According to test results, the shear failure patterns and shear mechanism of the specimens are discussed. By analyzing the contribution of the steel web, concrete, stirrups and reinforcement bars to the shear capacity, the shear mechanism of the SRHSHPC composite columns is figured out. Therefore, the influence of shear span ratio, axial compression ratio, stirrup ratios and concrete strength on shear behaviors of the SRHSHPC frame columns is clear. Finally, concrete truss model and principle of accumulation are applied to discuss the shear capacity and a calculation model for shear strength of the SRHSHPC composite columns is established. It is indicated that the shear behaviors of the SRHSHPC frame composite columns are excellent, and the calculated results of shear strength have good conformity with test results.

Abstract: To respond the need of industries to the new materials with higher specific modulus and lower density than those of the older Al alloys, aluminum- lithium alloys have been invented and improved. Aging process is one of the most important methods to improve the mechanical properties of aluminum- lithium alloys which are in the heat treatable category of aluminum alloys. Low temperature and natural aging processes cause the "short range diffusion" of Cu atoms in the aluminum and the formation of the GP zones. In this research, stability of GP zones and the effects of these areas on physical and mechanical properties of AA2090 alloy were investigated by hardness, electrical resistance, DSC (differential scanning calorimetric) and tensile tests. Results show that endothermic effect in the DSC diagrams of AA2090 alloy at 180°C to 240°C can be related to the enthalpy of GP zones dissolution. Formation of GP zones in the structure increases hardness, tensile strength and electrical resistance of Al- Li C u (2090) alloys.