“…Conte et al 4/23 (2003) proposed the use of 〈 , 〉, where is the ratio of the minimum yield strength required to limit the response parameter to , to the minimum yield strength required for the system to remain elastic. Bojórquez et al (2012) proposed 〈 , 〉, where is the square of ground motion acceleration integrated with respect to the duration of the ground motion, normalized to the product of PGA and PGV (peak ground velocity), and 〈 , 〉, where is the geometric mean of the spectral accelerations between the fundamental period and a higher period, normalized to . In all the aforementioned vector-valued IMs, the 'primary' parameter is , and the 'secondary' parameter is unitless.…”