Reliability analysis of two archetype RC buildings with hysteretic dampers

Assessment of Non-Linear Analyses of RC Buildings Retrofitted with Hysteretic Dampers According to the Italian Building Code

“…Therefore, the structures are immediately accessible after a main earthquake correspondent to the LLS according to the IBC [30], characterized by return period T R of 475 years, with a probability of non-exceedance of 10% for nominal life V N = 50 years of a residential building (cu = II). Figure 6 shows the capacity curves of the case study buildings and the relative d p s which correspond to the ending point of the elastic branch, or at most at the beginning of the second branch relevant to the cracked concrete [43]. In this study, the two structures are retrofitted by using hysteretic steel dampers installed into diagonal steel braces (Figure 7), which is a common configuration for frame buildings [1,5,6,[43][44][45]].…”

“…Figure 6 shows the capacity curves of the case study buildings and the relative d p s which correspond to the ending point of the elastic branch, or at most at the beginning of the second branch relevant to the cracked concrete [43]. In this study, the two structures are retrofitted by using hysteretic steel dampers installed into diagonal steel braces (Figure 7), which is a common configuration for frame buildings [1,5,6,[43][44][45]]. An elastic-perfectly plastic constitutive behavior is assumed for the dampers, similarly to other studies [1,6,41,43,44].…”

“…In this study, the two structures are retrofitted by using hysteretic steel dampers installed into diagonal steel braces (Figure 7), which is a common configuration for frame buildings [1,5,6,[43][44][45]]. An elastic-perfectly plastic constitutive behavior is assumed for the dampers, similarly to other studies [1,6,41,43,44]. Four units on each floor in both X and Z directions are installed in the external bays according to the layout shown in Figure 7.…”

“…The mechanical properties of each diagonal steel brace and the encased hysteretic steel damper form an in-series system can be expressed as a combination of the properties of the linear elastic brace (B) and of the elasto-plastic damper (D), as shown in Figure 8, where K B and K D are the elastic stiffnesses of the brace and of the damper, V y is the maximum force of the damper, d y, d bd and d 2 are the yield displacement, the design seismic displacement calculated at LLS and the ultimate displacement of the damper at CLS, respectively. Damper ductility µ D , defined as the ratio between d bd and yield deflection d y , for standard steel hysteretic dampers typically ranges between 4 and 16 [1,15,41,43]. The properties of the single damped brace (DB), in terms of stiffness K DB , ductility µ DB , and damping capacity ξ DB , are determined through the Equations ( 6)-( 8), where ratio K B /K D between the stiffnesses of the steel brace and the damper should be taken ≥2 in order to guarantee that the largest part of the deformation of the story is concentrated in the damper [45,46].…”

“…The properties of the single damped brace (DB), in terms of stiffness K DB , ductility µ DB , and damping capacity ξ DB , are determined through the Equations ( 6)-( 8), where ratio K B /K D between the stiffnesses of the steel brace and the damper should be taken ≥2 in order to guarantee that the largest part of the deformation of the story is concentrated in the damper [45,46]. Typical values of µ DB and ξ DB for damped bracing systems according to current practice are reported in Table 1 [15,43,44]. Therefore, in the study, the seismic upgrade of the case study buildings is performed considering damped brace systems characterized by values of ductility µ DB ranging from 3 to 13.5; more specifically, µ DBs equal to 3, 5, 7, 9, 11, and 13.5 are assumed.…”