Abstract
To build a more resilient city against strong earthquakes[1,2],it is quite significant to construct seismic resilient buildings[3,4].Lead viscoelastic damper(LVD)[5],demonstrated in Figure 1,was deemed as a novel resilient damper due to its self-recovery material properties(i.e.dynamic recrystallization of lead cords and superelasticity characteristic of viscoelastic materials),thus it can be incorporated in the buildings to improve their seismic resilience[6,7].
Figure 1 Configurations of LVD
Figure 2 Analytical RC frame model
This paper aims to assess the seismic performance,collapse-resistant performance and structural energy demands of reinforced concrete(RC)frame equipped with LVD subjected to strong earthquake.The investigations were applied to a 6-story 22.2 meter-height traditional RC frame and LVD-damped frame designed based on current Chinese codes[8-10]and simulated by Opensees[11].The simulated models of RC frame and LVD-damped frame were depicted in Figure 2 and Figure 3.
Figure 3 Numerical model of LVD frame
Time history analysis of the traditional RC frame(RCF),LVDdamped frame(LVDF)and its bare frame(i.e.without LVDs)were carried out to investigate the damping effect of LVDs installed in the structure.To assess structure seismic performance systematically,incremental dynamic analysis(IDA)[12]using ATC-63 recommended 22 far-field ground motion records[13],seismic fragility analysis and collapse assessment through the IDA results were conducted for the traditional RC frame and LVD-damped frame[14].In addition,to survey the contribution of LVDs on reforming structural energy dissipation mechanism,energy demands of RC frame and LVDdamped frame were statistically analyzed[15].Results of time history response investigation show that both the traditional RC frame and LVD-damped frame were available to meet the structural design requirements under designed earthquake.However,by adding LVDs,structure seismic performance was greatly improved compared with conventional RC frame and LVD-damped bare frame.Besides,as illustrated in Figure 4,the IDA results demonstrate that structural dynamic responses would be availably suppressed by installing LVDs,which could also reduce the undesirable dispersion of structural response making analysis results more reliable.
Figure 4 IDA results of RC frame and LVD frame
Structural damage evaluation consequences are shown in Figure 5 and Table 1.The analysis results reveal that exceedance probabilities of LVD-damped frame within different damage levels is lower than that of RC frame,showing that LVD designed frame can satisfyingly mitigate structural damage and increase collapse margin ratio(CMR)by 15%approximately.
Figure 5 Fragility and collapse probability curves
Specifically,the CMR was calculated based on ATC-63 method as follow:
Table 1 CMR calculat e results
In addition,it is also summarized from Table 2 that by dissipating a great percentage of structural input seismic energy under frequency earthquake(FE),design earthquake(DE),rare earthquake(RE)and very rare earthquake(VRE),constructing LVDs would be beneficial to generously reduce the plastic hinge rate,cumulative energy consumption and energy consumption ratio of the plastic hinge areas.In other words,furnishing LVDs could effectually mitigate structural damage of the RC frame and have a more stable structural energy dissipation mechanism under strong earthquake.
Table 2 Energy dissipation proportions of structura l components
