Many participants noted that to enable the development of more accurate structural models, a networked set of equipment that replicates the effects of corrosion, accelerated aging, and fatigue is needed for the characterization of subsystems, components, and materials. Such a facility could have the capability for multi-axial loading, high-temperature testing, and high pressures. It would need to be able to test full-sized or close-to-full-scale subsystems and components under fully realistic boundary and loading conditions, including rate effects to avoid issues with scaling, and would need to be supported by a comprehensive set of high-performance instrumentation. Such a facility could enable the development of high-fidelity physics-based models for incorporation into simulations of complete structures. It could also enable the characterization of the full lifetime performance and sustainability of structural elements and materials and allow the development of appropriate retrofit and strengthening techniques for existing aging infrastructure.
A significant proportion of the losses following an earthquake are the result of indirect damage to the contents of buildings, rather than damage to the structural frame. A number of participants noted that the requirements of the current seismic qualification codes cannot be fully met with existing facilities,1 highlighting the need for a high-performance multi-axis facility with the frequency range and levels of motion necessary to investigate and characterize the performance of non-structural elements (e.g., partitions) and other content (e.g., shelving, IT equipment, lighting, electrical and mechanical equipment) within a building or other infrastructure. Such a facility would need to deliver very high displacements, velocities, and accelerations so that it could simulate the behavior of floors at any point within a building; however, it may not need to have a very high payload capacity because most non-structural items within buildings are relatively light. Such a facility could permit the development of complete building models, including the building content, and also the development of more robust non-structural elements and equipment that would be significantly less likely to be damaged in an earthquake.
A mobile facility for in situ structural testing, as described by participants in the “design of infrastructure” group, could be equipped with a suite of highly portable testing equipment including shakers, actuators, sensors, and high-resolution data acquisition systems that could be used to test structures, lifelines, or geotechnical systems in place. Examples include modal shakers to introduce dynamic loads on structures, bridges, and soil systems. Additional capability could include large-capacity broadband dynamic seismic wave sources coupled with improved sensing capabilities to allow the high-resolution subsurface characterization essential for regional modeling. Hydraulic actuators capable of in situ lateral loading could provide an experimental capability of testing structures. Intentional and repeatable dynamic loading of buildings, bridges, and other structural systems could allow systems to be dynamically characterized for improved modeling capabilities. Dynamic excitation of geotechnical systems could improve understanding and the modeling of liquefiable soils.
1 For example, IEEE Standard 693-1997, which contains recommended practices for seismic design of substations, cannot be met without significant filtering of the low-frequency content of the signal (Takhirov et al., 2005).