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PAPER 1: Broadening the Utilization of CSMIP Data: Double Convolution Methodology Towards Developing Input Motions for Site Response and Nonlinear Deformation Analyses by Renmin Pretell, Sumeet K. Sinha, Katerina Ziotopoulou, Jennie A. Watson-Lamprey, and Dimitrios Zekkos
[ABSTRACT - PAPER 1]
The double convolution methodology for the development of input motions for site response analyses and nonlinear deformation analyses is briefly presented. This methodology uses deep VS profiles and random vibration theory to modify ground motions recordings from top-of-soil stations (“reference site”) such that they are compatible with conditions at a neighboring location (“target site”) and some selected depth (halfspace), while preventing numerical errors associated with the inverse nature of a deconvolution analysis. The methodology can be particularly useful for obtaining input ground motions for the forensic investigation of case histories or further modified to meet some design criteria and used for site response analyses and the subsequent determination of hazard at the surface for the seismic performance assessment of structures. The proposed approach is termed “double convolution” as it uses two site response analyses (SRAs) to compute a desired transfer function (TF). The methodology is briefly presented followed by a demonstration of its implementation in an open-access webtool.
PAPER 2: Measurement and Identification Protocols for Horizontal-to-Vertical Spectral Ratio Peaks by Pengfei Wang, Paolo Zimmaro, Sean K. Ahdi, Alan Yong, and Jonathan P. Stewart
[ABSTRACT - PAPER 2]
Peaks in horizontal-to-vertical spectral ratios (HVSR) of Fourier amplitudes from three component recordings are used to identify site resonances, which are an important component of site response. We address two topics: (1) how should HVSR peaks be identified; and (2) are there appreciable differences in HVSR derived by using different instruments recording microtremors and seismic strong ground motions? We propose to identify peaks by considering peak amplitudes relative to neighboring ordinates and peak width. The procedure incorporates a regression tree algorithm that can be tuned to conform with user preferences toward relatively “conservative” or “liberal” peak identification (producing relatively few or many sites with peaks, respectively). Recommended parameters for both cases are provided. We then investigate the consistency of microtremor-based HVSR (mHVSRs) derived from seismometers and accelerometers, which show a high rate of false negatives (missed peaks) from accelerometers. In contrast, mHVSRs derived from co-located temporary and permanent instruments (optimized to record teleseismic signals) have about 60–80% consistency, with no apparent bias in peak assessments between instrument types. This indicates that mHVSR from accelerometers is not reliable, but that mHVSR can be reliably obtained with similar levels of quality from temporary or permanent seismometers. Lastly, we compare seismometer-based HVSR from microtremor and earthquake sources (mHVSR versus eHVSRs). Results are consistent for 60–70% of sites (i.e., both either do, or do not, have significant peaks; and when peaks are present, they occur at similar frequencies, <20% change). For sites with an mHVSR peak, the false-positive rate is nearly 50%, whereas for sites without an mHVSR peak the false-negative rate is relatively low (about 20%). The false positive rate is sufficiently high that the use of eHVSR to derive site response models is likely too optimistic (overestimates model effectiveness); mHVSR is preferred for consistency with information available in forward applications.
PAPER 3: Enhancing ASCE-41 Modeling Guidelines and Acceptance Criteria using Instrumented Reinforced Concrete Shear Wall Buildings by Laura L. Hernández-Bassal and Sashi K. Kunnath
[ABSTRACT - PAPER 3]
A preliminary set of evaluations on a low-rise reinforced concrete shear wall building is presented with the goal of assessing the modeling guidelines and acceptance criteria in ASCE-41 (ASCE/SEI 41, 2017). First, the ability of available commercial and open-source software to simulate the nonlinear flexural and combined shear-flexural response of experimentally tested walls is investigated. Next, a commonly-used commercial software, Perform-3D (CSI 2021) is utilized to conduct an assessment of a 3-story shear-wall building wherein all four analysis methods specified in ASCE-41 are applied. The simulation model is validated against instrumented data obtained during the 2010 Maricopa earthquake prior to its use in the ASCE-41 assessments. Results of the different assessments indicate that linear procedures are highly conservative with Collapse Prevention limits being exceeded whereas the application of nonlinear procedures suggest that the building performance is within Life Safety limits.
PAPER 5: Simulation of 0-7.5 Hz Deterministic Ground Motions for Maximum Credible Earthquake Scenarios at the Long Valley Dam, CA by Kim B. Olsen and Te-Yang Yeh
[ABSTRACT - PAPER 5]
We have used 3D 0-7.5 Hz deterministic wave propagation to model the seismic response of the Long Valley Dam (LVD) in central California. The velocity structure, anelastic attenuation model, and the properties of the dam were calibrated via simulations of a Mw3.7 event and the 1986 Mw6.3 Chalfant Valley earthquake. Our nonlinear simulations of a Mw6.6 Maximum Credible Earthquake scenario generate peak ground accelerations > 1 g at the LVD, where nonlinear damping (Drucker-Prager rheology) reduces PGAs predicted at the dam crest by a factor of 2.5. The simulations predict relative displacements of the dam material of ~ 10 cm.