Sensitivity Analysis on Response Modification Factor of New Cable-Cylinder Bracing Systems

Abstract

ABSTRACTCable bracing systems have been increasingly investigated in recent years. The new cable-cylinder bracing system is made of bracings with two cables and one cylinder. In this system, the cables pass through the cylinder at their crossing region. For the first time in the present research, the overstrength factor, ductility factor, and response modification factor of this bracing system are evaluated using a two-dimensional model. For this purpose, incremental dynamic analyses are conducted on the system using 10 earthquake records. Based on the allowable stress design method, the values 2.33, 1.47, and 4.94 are obtained for the overstrength, ductility, and response modification factors, respectively. The response modification factor of the moment frame with cross-cable bracing is calculated and compared with that of the cable-cylinder bracing. Sensitivity analysis has been conducted on the dimensions of the cylinder, including its length and internal diameter, and pre-stressing stress of cables. According to the obtained results, under low pre-stressing stress, the response modification factor increasesby increasing the length and decreasing the diameter of the cylinder, in other words with increase in . Moreover, the response modification factor decreases with increase in pre-stressing stress of the cables. According to the results obtained from sensitivity analysis, the highest change in the response modification factor with different cylinder lengths, inner diameters of the cylinder, and pre-stressing stresses of the cables is 0.34, 0.377 and 0.612 respectively; i.e. the sensitivity of the response modification factor to the pre-stressing of cables is greater, compared to its sensitivity to the dimensions of the cylinder. Finally, an equation has been presented for calculating the values of response modification factor as per the dimensions of the cylinder and pre-stressing stress of cables.