``A Computational and Communication Infrastructure for a High Performance Seismic Simulation Network''
Prof. Gregory L. Fenves
Pacific Earthquake Engineering Research Center
University of California, Berkeley
Berkeley, CA 94720-1710
E-mail: fenves@ce.berkeley.edu
URL: http://www.ce.berkeley.edu/~fenves

Background

Earthquake engineering is a multi-disciplinary field that creates technology to improve the seismic performance of civil systems (buildings, transportation and lifeline infrastructure, and industrial facilities). The range of scientific and engineering issues addressed in earthquake engineering is broad, ranging from fundamental behavior of advanced materials, earthquake response prediction and modification of soils, structural behavior and control, design methodologies, and public policy and economic decision making for seismic risk reduction.

Research in earthquake engineering is now oriented towards performance based engineering design. The objective of PBED is to provide a rational framework for owners and decision-makers to understand the tradeoffs between lifecycle cost and seismic performance. In this context, seismic performance is a complex and not yet fully defined metric of the probability that a system will meet the expected behavior in future earthquakes. In contrast with current design methodologies, which primarily protect life but not necessarily the system itself, PBED provides options for performance up to continued operation during an earthquake. Whereas understanding of system behavior associated with collapse of structural systems, important for protecting life safety, is fairly well established, the earthquake engineering research enterprise must be re-oriented to address higher levels of system performance such as limited damage. For this workshop, the tools for new research can be categorized as two broad initiatives:

1. High fidelity computational simulation of seismic performance
2. Advanced experimental simulation of seismic performance

Communication Infrastructure for the Seismic Simulation Network

The seismic simulation network will consist of a distributed physical testing facilities and computational resources. Testing facilities will include loading and control systems for simulating the deformations of large structural and geotechnical components and subsystems; earthquake simulators ("shaking table") to dynamically test subsystems and system models; centrifuges for testing soil systems with scaled gravity; and other testing methods under development (some described below). The utility of this "network" of facilities will be enhanced by a communication infrastructure. The objectives of the communication infrastructure are to: (1) allow collaborative design and conduct of experiments among participants in different disciplines and geographically dispersed; (2) disseminate and "mine" information from data that are expensive to collect; (3) provide opportunities for advanced testing methods; and (4) allow integration of physical testing with simulation by computational methods. Some of the scientific issues to be dealt with in the communication infrastructure are:

• Heterogeneous data. Testing data is very diverse and unique for each experiment. It can range from sampled analog data from instrumentation for displacement, acceleration, temperature, and other physical phenomena, to optical, acoustic, electrical field, and other emission data. High definition video images may be used in the future, with possibilities for direct measurement of some data from the images (e.g. crack formation, deformation fields, etc.), that bring in issues of image recognition.
• Advanced testing methodology. It is not possible to conduct an experiment on a large scale structure and it's supporting foundation and soil. New developments in on-line control of dynamic simulation will be an important feature of the network. Advanced communication will enable testing different components in different laboratories with the linking of experimental facilities. Components representing parts of a large system can be tested in different laboratories. One example is simulating the dynamic response of structure on a shaking table and the foundation in a centrifuge. The interface forces and deformations, with some processing, is transmitted between the controllers for the two testing facilities. Other possibilities may include using advancing sensing instruments, such as electron scanning microscopes, to observe phase changes, flaw propagation, and other changes in materials during severe cycles of deformation during a simulated earthquake. New testing methodologies will depend on a low latency, high reliability communication networks and protocols, in addition to development of the testing technology and methods themselves.
• Computational technology. The Turkiyyah position paper outlines the scientific needs for improving the computational simulation of earthquake behavior of civil systems. In regards to testing, a promising area is hybrid methods in which a portion of the system is modeled computationally and another portion is modeled and simulated physically in the laboratory. This is done now to simulate dynamic behavior in a "slow" loading environment. With improved computational speeds, communication speed, and new control systems, this can be done dynamically (which will avoid some of the scaling and velocity dependent problems with slow testing).
• Visualization. Another area which needs more attention in earthquake engineering simulation is visualization. The massive amounts of data generated during a test or computational simulation cannot be appreciated or fully understood with the current methods for plotting data. Much of what is interesting during a test is not visually observed. However, collected data (e.g. strain fields) can be visualized in real and simulated time. Visualization tools are needed that closely replicate the physical processes taking place during a test.
• Collaborative environments. As mentioned previously, a distributed experimental network will require a collaborative communication infrastructure to be effective. The environment should facilitate test specification, design, and conduct. It should allow participants to customize their view of the test and provide interfaces to specialized software.
• Data protocols. issues of quality assurance and control, ownership of data (intellectual property), liability, are not only technical issues but relate to how data are ultimately used in the design of buildings, transportation systems, and other civil systems. Society has high expectations that the data used in the design is reliable and interpreted correctly. A communication infrastructure for seismic simulation must go beyond exchanging uncorrupted data to providing mechanisms to assure the quality of the data and its interpretation.