Damping Scaling Factors for Elastic Response Spectra for Shallow Crustal Earthquakes in Active Tectonic Regions: “Average” Horizontal Component

Abstract

Ground motion prediction equations (GMPEs) for elastic response spectra are typically developed at a 5% viscous damping ratio. In reality, however, structural and nonstructural systems can have other damping ratios. This paper develops a new model for a damping scaling factor ( DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE for damping ratios between 0.5% to 30%. The model is developed based on empirical data from worldwide shallow crustal earthquakes in active tectonic regions. Dependencies of the DSF on potential predictor variables, such as the damping ratio, spectral period, ground motion duration, moment magnitude, source-to-site distance, and site conditions, are examined. The strong influence of duration is captured by the inclusion of both magnitude and distance in the DSF model. Site conditions show weak influence on the DSF. The proposed damping scaling model provides functional forms for the median and logarithmic standard deviation of DSF, and is developed for both RotD50 and GMRotI50 horizontal components. A follow-up paper develops a DSF model for vertical ground motion.

Damping Scaling Factors for Vertical Elastic Response Spectra for Shallow Crustal Earthquakes in Active Tectonic Regions

“…The validity of the resulting model for longer distances was examined by residual analysis of the remainder of records. We observed that the general trends seen between DSF V and potential predictor variables-damping ratio, spectral period, duration, magnitude, distance, and site conditions-are similar to what was observed in Rezaeian et al (2014) for the horizontal component scaling factor, DSF H . Damping ratio was directly included in the model as a predictor variable.…”

“…The DSF was used to scale pseudo-response spectral accelerations (PSA) at a 5% damping ratio to PSA at other damping ratios. The "average" horizontal component, which hereafter will simply be referred to as the horizontal component, was represented in two ways: (1) GMRotI50 horizontal component, as defined by An alternative approach taken by most researchers, dating back to the classic work of Newmark and Hall (1982) and also used in Rezaeian et al (2014), is to develop models of multiplicative factors (i.e., DSF) that scale the 5% damped spectral ordinates predicted by any GMPE to ordinates for other damping ratios. The advantages of this approach are that it does not require interpolation between discrete damping ratios and can be easily applied to GMPEs other than those from which the model was derived.…”

Pseudo-Spectral Damping Reduction Factors for the Himalayan Region Considering Recorded Ground-Motion Data

“…The values of DRF have been plotted as a function of period at various levels of damping in Fig 6 . The DRF values tend to become unity at lower and higher periods because the forces in a very stiff or very flexible structure are relatively independent of the damping ratio [ 1 ]. This trend is observed in the DRF derived from the PSA irrespective of period and damping.…”

“…Most ground-motion prediction equations are available for a reference damping of 5%. The damping ratio depends on the structure, type of material, and ground shaking, among other characteristics [ 1 ]. In reality, however, structural systems may have a damping ratio other than 5%.…”

“…Cardone et al [ 17 ] reviewed the models from existing studies and found that the most accurate DRFs were those proposed by Wuand Hanson [ 12 ], and Lin et al [ 8 ], which depend on both the damping ratio and the period of vibration. Hatzigeorgiou [ 18 ] developed a model in terms of damping and period alone, while Rezeian et al [ 1 ] developed a reduction factor from the pseudo-acceleration response and formed a model in terms of moment magnitude, distance, and damping at specific periods.…”