A System for Multi-Axial Subassemblage Testing (MAST)

The George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Program is a project funded under the NSF Major Research Equipment Program. This cooperative agreement, under the NEES Program, establishes a NEES large-scale, laboratory earthquake engineering research experimentation site at the University of Minnesota-Twin Cities campus. The University will design, purchase, construct, install, commission, and operate a Multi-Axial Subassemblage Testing (MAST) system for structural earthquake engineering experimentation. This equipment will be operational by 2004 or earlier and will be managed as a national shared-use NEES equipment site, with teleobservation and teleoperation capabilities, to provide new earthquake engineering research testing capabilities through 2014. This NEES equipment site will be connected to the NEES collaboratory through the University's Abilene connection, with Gigabit Ethernet capabilities. Shared-use access and training will be coordinated through the NEES Consortium. This award is an outcome of the peer review of proposals submitted to program solicitation NSF 00-6, 'NEES: Earthquake Engineering Research Equipment.' The Multi-Axial Subassemblage Testing (MAST) system provides an integrated approach to the simulation of structural response of buildings and bridges in moderate and large-scale earthquakes, linking large-scale testing of structures with three-dimensional nonlinear analyses of structural components and systems. The MAST system enables multi-axial cyclic and pseudo-dynamic tests of large-scale structural subassemblages, such as portions of beam-column frame systems, walls, bridges, and piers. The MAST system consists of high performance actuators, cross heads (large steel weldments for the top and bottom reaction surfaces, a digital controller with six degrees-of-freedom (DOF) software (control system), a hydraulic distribution system, and an L-shaped reaction wall system to provide lateral load resistance for the horizontal actuators. The MAST system uses the six DOF controller to position the top cross head using eight actuators (four vertical and two horizontal pairs of orthogonal actuators) to apply realistic states of deformations and loading in a straightforward and reproducible manner. The six DOF control software employs advanced control technology to locate the position of the cross head through real-time simultaneous control of the eight cross head actuators. This system not only enables control of the position of a point in space, but also of a plane in space. This feature makes it possible to apply biaxial control of structures such as multi-bay subassemblages or walls. It also enables the application of pure planar translations, as well as the possibility of applying gradients to simulate overturning (e.g., axial load gradient in the columns of a multi-bay frame or wall rocking). With this system, a full six DOF loading condition can be imposed on the test structure, thus providing a new large-scale testing capability that will enhance the earthquake engineering community's understanding of complex failure states. The MAST system will be located in the Structural Engineering Laboratory in the Department of Civil Engineering on the University of Minnesota, Twin Cities campus. The University has committed to $875,000 in cost sharing for laboratory infrastructure improvements to accommodate the MAST system. The University of Minnesota will integrate the MAST system into its research program and undergraduate and graduate curricula, implement a MAST collaboratory for researchers, practitioners, and industry professionals to facilitate experimental, computational, and technology transfer aspects of the MAST system, and provide training opportunities for outside researchers.