This wiki provides a list of resources within the NEEShub related to hybrid simulation (HS) and real-time hybrid simulation (RTHS) for earthquake engineering. These technologies are enabling researchers to conduct a wide array of experiments to examine the behavior of structures under realistic loading conditions.
'''HYBRID SIMULATION (HS):''' Hybrid simulation is a cost-effective experimental technique to evaluate the dynamic performance of large or full scale civil structures. In hybrid simulation, the rate-dependent behavior of a civil structure, including inertial and damping effects, is simulated numerically while the displacement-dependent behavior is evaluated through experimentation. Furthermore, through the technique of substructuring, a structure (total or reference structure) can be partitioned into, (1) a physical (or experimental) substructure, which usually includes the more complex components and (2) a numerical (or computational, analytical) substructure, which usually includes well-understood behavior that can be captured by numerical models. The coupling between the two substructures is achieved by enforcing equilibrium and compatibility at the interface using a transfer system such as servo-hydraulic actuators.
'''REAL-TIME HYBRID SIMULATION (RTHS):''' Advances in embedded systems with hard real-time computing capabilities have facilitated the use of real-time hybrid simulation methods. Compared to HS, RTHS offers the capability of accurately representing the rate-dependent behavior of the physical components while examining the global performance (the reference structure) and local performance (the physical substructure). In RTHS, the interface interaction between the substructures is enforced by servo-hydraulic actuators or a shake table which act as the transfer system. A transfer system must be controlled to ensure that all interface boundary conditions are satisfied in real time. Performance of RTHS are functions of four major factors (1) the overall dynamics of the total structure (2) the accuracy of the numerical substructure (3) how the total structure is partitioned into numerical and physical substructures (4) how well the interface boundary conditions are achieved by the transfer system.

[[Image(RTHS.GIF, 500px, align=center)]]

A typical RTHS system consists of cyber and physical components.

'''A. Cyber Components:'''
These components execute user programmed digital functions (numerical model and transfer system motion control scheme) and while communicating with the physical world through I/O and analog sensing and actuation systems. A real-time kernel is included to meet the time scale constraints of RTHS. Cyber components include,

• Numerical Substructure: Portion of the total structure included in the numerical model.

• Transfer System Control: Digital controller is included to enable synchronization between numerical and physical substructures.

• Visualization and Control Dashboard: User interfaces and data logging components facilitate operation and visualization results during a hybrid experiment.

'''B. Physical components:'''
This term refers to the portions of the reference structure that are present in the laboratory, as well as the sensors and transfer system that are used for performing the experiment. In RTHS, measured responses are fed back to the cyber components in real time. Physical components include,

• Physical Substructure: Portion of the reference structure included in the physical specimen.

• Sensing System: In RTHS, sensors, e.g. accelerometers, LVDTs, force transducers, etc., are used to measure the restoring force and local response for transfer system control feedback of the physical substructure and monitor the performance.

• Actuation System: The interface interaction between the substructures is enforced by servo-hydraulic actuators or a shake table which acts as a transfer system.

= List of Resources =

== Projects ==
* [ Behavior of Braced Steel Frames With Innovative Bracing Schemes - A NEES Collaboratory Project ]
* [ Real-time Fast Hybrid Testing Steel Frame Test ]
* [ Hybrid Simulation and Shake-Table Tests on RC Buildings With Masonry Infill Walls ]
* [ International Hybrid Simulation of Tomorrow's Braced Frame Systems ]
* [ Semiactive Control of Nonlinear Structures ]
* [ Advanced Servo-Hydraulic Control and Real-Time Testing of Damped Structures ]
* [ Framework for Development of Hybrid Simulation in an Earthquake Impact Assessment Context ]
* [ Performance-Based Design and Real-Time Large-Scale Testing to Enable Implementation of Advanced Damping Systems ]
* [ Development of a Real-Time Multi-Site Hybrid Testing Tool for NEES ]
* [ Collapse Simulation of Multi-Story Buildings Through Hybrid Testing ]
* [ Development and Validation of a Robust Framework for Real-time Hybrid Testing ]
* [ Real-Time Hybrid Simulation Test-Bed for Structural Systems with Smart Dampers ]

== Tools ==
* [ NHCP ]
* [ OpenFresco ]
* [ UI-SimCor ]
* [ RT-Frame2D ]

== Publications ==
* [ Real-time Hybrid Simulation Benchmark Study with a Large-Scale MR Damper ]
* [ Comparison of 200 KN MR Damper Models for use in Real-time Hybrid Simulation ]
* [ Evaluation of Structural Control Strategies for Improving Seismic Performance of Buildings with MR Dampers Using Real-Time Large-Scale Hybrid Simulation ]
* [ A Tracking Error-Based Adaptive Compensation Scheme for Real- Time Hybrid Simulation ]
* [ Servo-Hydraulic Actuator Control for Real-Time Hybrid Simulation ]
* [ Accommodating MR Damper Dynamics for Control of Large Scale Structural Systems ]
* [ Real-Time Hybrid Testing of an MR Damper for Response-Reduction (Dissertation) ]
* [ Hybrid Simulation Evaluation of Innovative Steel Braced Framing System ]
* [ Increasing Resilience in Civil Structures Using Smart Damping Technology (Dissertation)]
* [ Evaluating Modeling Choices in the Implementation of Real-time Hybrid Simulation ]
* [ Model-Based Framework for Real-Time Dynamic Structural Performance Evaluation ]
* [ Development of a Robust Framework for Real-Time Hybrid Simulation: from Dynamical System, Motion Control to Experimental Error Verification (Dissertation)]
* [ Development and validation of a real-time computational framework for hybrid simulation of dynamically-excited steel frame structures (Dissertation)]

== Reports ==
* [ NEES Vision Report on Computational and Hybrid Simulation (Committee Report) ]
* [ Development and Validation of a Robust Actuator Motion Controller for Real-time Hybrid Simulation Applications ]
* [ Development and Validation of a Computational Tool for Real-time Hybrid of Steel Frame Structures ]
* [ Hybrid Testing in NEESR Projects ]

== Workshops ==
* [ CU/NEES Fast Hybrid Testing Workshop ]
* [ Hybrid Simulation Workshop at NEES@Berkeley ]
* [ Advances in Real-Time Hybrid Simulation Workshop at NEES@Lehigh ]

== Multimedia ==
* [ NEES@Berkeley project highlight: NEES TIPS Seismic Isolation Hybrid Simulation ]
* [ NEES@Berkeley project highlight: International Hybrid Simulation of Tomorrow's Braced Frame ]
* [ NEES@Berkeley project highlight: Hybrid Testing of Squat RC Shear Walls ]
* [ Pseudo-dynamic Hybrid Simulation of a Six-Story Building with Self-Centering Energy Dissipating (SCED) Braces ]
* [ Small-scale Hybrid Simulation ]
* [ Non-contact Instrumentation (CABER) ]
* [ UI-SimCor ]
* [ Multi-Site Soil-Structure-Foundation Interaction Test ]
* [ Hybrid Simulation of Semi-rigid Frames ]
* [ Controlled Rocking of Steel Frame ]
* [ CABER - Hybrid Simulation of a Curved 4-Span Bridge under Complex Earthquake Motion ]