NEES Equipment Site University of Minnesota http://nees.umn.edu

1. NEES Equipment SiteUniversity of Minnesotahttp://nees.umn.edu MAST 6 Degree-of-Freedom Testing Machine The University of Minnesota Multi-Axial Subassemblage Testing (MAST) system enables multi-axial quasi-static cyclic tests of large-scale structural subassemblages, including portions of beam-column frame systems, walls, and bridge piers. Six-degree-of-freedom control technology, employed by the MAST system, advances the current state of technology in which boundary effects are often reduced to simple uniaxial loading configurations because of difficulties encountered in imposing multiple-degree-of-freedom states of deformation and load using conventional structural testing means. The system is unique in size and scope and greatly expands the large-scale earthquake experimentation capabilities both nationally and internationally. As shown in the photograph above, the MAST system employs a stiff steel crosshead in the shape of a cruciform, which is controlled with six-degree-of-freedom control technology. Four ± 1470 kN (± 330 kip) vertical actuators, capable of applying a total force of ± 5870 kN (± 1320 kips) with strokes of ± 510 mm (± 20 in.) mount between the crosshead and the strong floor. Two sets of actuator pairs with strokes of ± 400 mm (± 16 in.), provide lateral loads up to ± 3910 kN (± 880 kips) in the horizontal orthogonal directions. The actuator pairs are secured to an L-shaped strong wall with universal type swivels. The vertical clear distance permits specimens up to 8.8 m (28 ft. 9 in) in height to be tested. The horizontal clear distance between the vertical actuators can accommodate specimens up to 6.1 m (20 ft.) in length in the two primary orthogonal directions. Larger specimens may be oriented along the diagonal directions. The stiff steel crosshead and six-degree-of-freedom control technology enable control of the position of a plane in space. This feature makes it possible to apply 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). Any degree-of-freedom may be programmed in either displacement control or load control, and degrees-of-freedom may be constrained in a master-slave relation to be a linear combination of the values of other degrees-of-freedom. As an example, using the mixed-mode control capabilities of the MAST system, it is possible to program any lateral displacement history, and at the same time specify overturning moment as a constant times the lateral force, while simultaneously maintaining an independent history of axial load on the test specimen. The system is also equipped with four ± 980 kN (± 220 kip) ancillary actuators with strokes of ± 250 mm (± 10 in.), which can be used to apply lateral loads at intermediate story levels, gravity loads, or simulated specimen boundary conditions. An example of a test incorporating the ancillary actuators to simulate a simple boundary condition for a slab-column connection test is shown in the figure to the right. In addition to quasi-static ramp and hold testing protocols, the MAST laboratory also supports hybrid testing using either a local or remote (user provided) computation engine for local or distributed testing. The equipment is capable of supporting Simcor and OpenFresco protocols. The MAST laboratory has a wide array of instruments including LVDTs, string potentiometers, tiltmeters, and load cells. These instruments are seamlessly integrated into MAST’s data acquisition system with a variety of custom designed quick connect boxes. The data acquisition system allows for any combination up to 248 ¼-bridge strain sensors and 172 voltage (@±10V) channels to be sampled simultaneously at a rate of up to 10Hz. MAST also offers the use of a Metris (formerly Krypton) K600 optical dynamic measuring machine. The K600 system is a CCD camera-based system that is used to monitor the position of infrared LEDs in 3D space. Where traditional instruments are typically limited to one or two measurable degrees of freedom, the advantage of the K600 system is the ability to measure 3D positions of single points on a specimen and rotations of planes on a specimen. MAST has 41 LEDs which can be run simultaneously @ 100Hz. In conjunction with the contributions of NEESit Cyberinfrastructure software, the teleobservation/teleoperation infrastructure provides relevant information needed for both monitoring and interpretation of experiments. As such, this facility incorporates real-time teleobservation of all visual monitoring information (video feeds) during an experimental run and real-time transmittal of all acquired sensor data. Full real-time teleoperation of 10 video cameras and 8 still image cameras, and limited real-time teleoperation of hydraulic equipment is available. The MAST facility fits into an integrated data-centric approach for experimentation, computation, theory, databases, and model-based simulation facilitated through the NEEScentral collaboratory. One of the most powerful features of this integrated approach to model-based simulation is an accumulated database of experimental results, which features the ability to “replay” tests and to couple experimental responses with computer simulations. The project team for the operational phase of the facility includes Carol Shield (PI), Catherine French, Paul Bergson, Drew Daugherty, Angela Kingsley, Jon Messier, and Jane Zirbes, (Dept. of Civil Eng.), and Douglas Ernie (Dept. of Electrical and Computer Eng.) Researchers examined the damage of a 8.3m (27'-3") tall tee-shaped concrete wall that was subjected to a series of multidirectional deformations at the MAST facility. Multi-Axial Subassemblage Testing (MAST) 6 Degree-of-Freedom (DOF) Control Technology Ability to test large-scale structural subassemblages Teleoperation of hydraulic equipment Real-time data and visual information sharing via telepresence Testing of a Slab-Column Connection MAST Control Room – supports teleparticipation Carol Shield Principal Investigator This equipment site receives operational support from the National Science Foundation under Cooperative Agreement No. CMS-0402490. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the view of the National Science Foundation.