SCEC Award Number 19150 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Validation of SCEC BBP nonlinear soil module
Investigator(s)
Name Organization
Pedro Arduino University of Washington Ertugrul Taciroglu University of California, Los Angeles Mahdi Taiebat University of British Columbia (Canada) Luis Bonilla Universite Paris-Est (France)
Other Participants
SCEC Priorities 4a, 4b, 4c SCEC Groups GM, CXM, EEII
Report Due Date 04/30/2020 Date Report Submitted 09/23/2022
Project Abstract
 Effects of soil nonlinearity are crucial in controlling the behavior of seismic wave propagation and seismic response of soil-structure systems. Validation studies of constitutive models of soils is an important task and demands special attention. In this project, we thoroughly validate the SCEC BBP nonlinear soil module, where a multi-axial bounding surface plasticity model is implemented. A stiffness-proportional viscous damping is integrated at the constitutive level of the nonlinear soil model. Then site response analysis of the Lotung site s performed by using the 1D-3C soil column with calibrated material properties. Through comparisons between the SCEC BBP nonlinear soil module and other finite element platforms as well as measured field data, excellent agreement is obtained in both single element material level tests and site response analysis.
Intellectual Merit Propagation of seismic waves in soils is a complex phenomenon requiring advanced models to capture the response of harder geological units and advanced material models to represent the inelastic response of the upper soft soil layers. Extensive work has been—and continues to be—carried out in the development and validation of numerical tools for the simulation of synthetic motions in hard geological units. Full utilization of such tools by the broader earthquake engineering community is not possible unless their capabilities are extended to include wave propagation in soft inelastic soil layers. This requires the use of finite element/difference platforms featuring advanced constitutive models to represent the wave propagation in inelastic soils and coupling to existing broadband earthquake generation tools.
In this context, this project aims contribute in this line of work by extending the capabilities of the SCEC Broad Band Platform (BBP) to include the nonlinear response of soft soil layers near the surface. The upgraded tool with proper validation could be very useful for the estimation of synthetic ground motions. This is a multiyear project of which this is the second phase.
In this phase we completed the validation of the constitutive model at the element level and at the FEM level through the evaluation and analysis of propagating waves in layered soils.
Broader Impacts This project stimulated the creation of an independent teaching module on bounding surface plasticity and kinematic hardening. For this purpose, several educational matlab scripts were created including a variety of loading conditions. The scripts were translated into python and Jupyter notebooks were created to be used in the classroom. One postdoctoral scientist worked in the validation phases. One master student worked in the Jupyter notebooks.
The project has helped strengthen cooperation between the UW and UCLA research groups.
This project adheres to the initiative for a Technical Activity Group to coordinate SCEC research on nonlinear shallow crust effects. In this context, this project prompted cooperation and coordinated research activities between project 18020 led by Domniki Asimaki and our group. The Asimaki group used the same constitutive model but implemented in the Hercules framework.
Exemplary Figure Figure 2: Schematic con guration and material properties of the constructed nite element model
for validation study.

Figure 3: Comparison of accelerations in EW direction between the recorded signals and the
predictions using OpenSees and ABAQUS models.
Credits: W. Zhang, F. Ghahari, P. Arduino, and E. Taciroglu