Virtual Experiments for Teaching Hysteretic Structural Behavior Shirley J. Dyke, Nestor Castaneda, and Zach Feinstein Washington University in St. Louis (NEESR-CABER Project)

Outline Goals and Vision Instructional Objectives Framework for the “Virtual” Experiment Current Limitations and Future Plans Acknowledgements

Objective “Provide undergraduate students with an inquiry-based educational tool to understand the assumptions used in numerical modeling and their implications by performing a comparison of numerical and experimental data.”

Vision “Provide a unified framework to support the development of a series of virtual experiments created within the NEES network using the shared data repository and cyber-infrastructure capabilities.”

Instructional Objectives Users select the dimensions of the column they want to examine, e.g. the column geometry, section details, and material properties. Two different analysis methods (linear and non- linear structural behavior) are implemented to consider different modeling assumptions. A comparison between numerical and experimental results can be performed.

Framework for “Virtual” Exercise

NTCP communication protocol is used to send model parameters from client to the server site. Server site will perform analysis (openSEES) and send output files to RBNB by using FTP (File Transfer Protocol) Standard TCP/IP communication protocol is performed between RBNB and client site to send experimental and numerical data to the client. Visualization and further data analysis can be performed by using RDV interface.

Components: Experimental Data

Sample data provided from tested column Height= 3.6m, diameter=60cm Lateral loads applied using a hydraulic actuator Strains and displacements are measured

Components: OpenSEES One option (opensource and integrated with NEES cybertools) for modeling hysteretic structural behavior Used for the numerical simulation component of the virtual exercise Used to model the hysteretic structural behavior of reinforced concrete columns using a nonlinear and linear beam-column element.

Numerical Model Description Single 2-D non-linear Beam-Column element. 6 DOF – 3 Free – 3 Constraints (Base) Radial Fiber section - 23 and 4 rings in the core and cover, respectively, plus 20 wedges.

Numerical Model Description Concrete was modeled with “OpenSees Concrete 02 model”. Steel was modeled with “OpenSees Steel 02 model” Gravity effects are modeled applying a compression load at the tip of the column equivalent to the self-weight. No confinement and P-Delta effects are modeled.

Components: RDV –Control Panel A GUI is available for the students to set up, run and visualize the numerical simulation. Using RDV (real-time data viewer) students may plot and extract the numerical and experimental results for comparisons.

RDV Interface for Module

RDV Control Panel for Module

RDV Interface with Data

Implementation This experiment has been implemented by two sets of students, UConn and WashU. Feedback was solicited and is being incorporated into the tool.

Limitations Currently the system does not support multiple simultaneous OpenSees analyses. “Start” button re-enabled each 60 seconds, independently of actual run time for each simulation. Limits must be set for some model parameters within a reasonable range to ensure convergence.

Future Plans Video from the structural testing will be integrated into the tool in the future. Increase variety of experimental data sources to give students better variety for comparisons. Increase the number of numerical analysis options based on different modeling assumptions.

Future Plans Improve server capacities to run OpenSees using multiple simultaneous runs and avoid unnecessary delays. Implementation of a more robust communication protocol between RBNB and client site.

Integration with NEES EOT Cyberinfrastructure capabilities facilitate remote participation and operation of experiments or simulations, including geographically distributed and hybrid simulations. “Virtual” experiments may involve research tools, real-world data and cyberinfrastructure capabilities, encouraging students to gain experience with these capabilities. A broader set of students and institutions can access virtual tools, improving engineering education globally.

Acknowledgments Funding has been provided in part by NSF Grants CMS (NEESR Program) and CMS NSF Research Experiences for Undergraduates (NSF EEC– ). Prof. D.J. Belarbi, Dr. Sang-Wook Bae and Suriya Prakash for providing experimental data for this virtual exercise NEESit staff for technical support