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MAST Laboratory
2525 4th St SE
Minneapolis, MN 55455

612-626-9561 main
612-624-5964 fax

Dept. of Civil Engineering
500 Pillsbury Drive SE
Minneapolis, MN 55455

612-625-5522 main
612-626-7750 fax
cive@umn.edu

Facilities › MAST System

MAST System

The Multi-Axial Subassemblage Testing (MAST) System at the University of Minnesota allows researchers to test the strength of structural components up to two stories high at full scale or higher at partial scale.

Integrated with advanced six degrees-of-freedom control technology, the MAST System can twist, compress or stretch test specimens. Its aim is to improve how buildings, bridges and other man-made structures withstand the impact of earthquakes, hurricanes or even deliberate attacks.

The MAST system is capable of applying up to 1.32 million pounds of vertical force and nearly 900,000 pounds of horizontal force. Structures up to 28.75 feet (8.7 m) in height and 20x20 feet (6.1x6.1 m) in plan can be tested at the MAST Laboratory.

Key features of the MAST System include:

Versatile large-scale structure testing apparatus
MAST system
  • Ability to conduct multi-axial quasi-static cyclic testing, quasi-static pseudo-dynamic testing, and continuous pseudo-dynamic testing on large-scale structural subassemblages including portions of beam-column frame systems, walls, bridge piers, abutments, towers, and other structures.
  • Accommodates test specimens up to approximately 20 ft. (6.1 m) long and 28.75 ft. (8.7m) high. Longer test specimens may be managed by placement along the diagonal.
  • Displacements of up to ±20 inches (±508 mm) and loads up to ± 1,320 kips (±5,900 kN) can be achieved in the vertical direction. Displacements of up to ±16 inches (±406 mm) and loads up to ±888 kips (±3,900 kN) can be achieved in each of the two horizontal directions.
Sophisticated control with ease of use
  • Advanced six-degrees-of-freedom (6-DOF) servo-hydraulic control system, designed by MTS Control Systems, allows researchers to control the crosshead and specify the three translational three rotational DOFs in either displacement or mixed-mode control. DOFs may be constrained by a master-slave relation to be a linear combination of the values of other DOFs.
  • Customized hydraulic control software is powerful yet simple to use, providing a comprehensive interface for researchers to interact with the MAST hardware controller.
Crosshead loading element
  • The 6-DOF forces are transferred through the rigid steel crosshead (94,000 pounds) to the specimen, which is bolted to the underside of the crosshead and the strong floor. The actuators move the crosshead to apply desired loads and deformations.
  • Strategically positioned mounting holes at the bottom of crosshead allow maximum flexibility for attaching test structures.
Actuator system
  • Four ± 330 kip vertical actuators connect the crosshead and the strong floor and have a stroke of ± 20 inches. Vertical spacers can be used to vary the height of the crosshead.
  • Four ± 440 kip horizontal actuators connect the crosshead and the L-shaped strong wall, with one pair in the lateral Y direction and one pair in the longitudinal X direction. Each pair provide lateral loads up to 880 kips in the orthogonal directions with strokes of ± 16 in.
  • Four ± 220 kip (± 975 kN) ancillary actuators with a displacement range of ± 10 inches (± 254 mm) permit displacements or loads at other locations on the test specimen.
Highly configurable reaction system
  • The MAST reaction system is composed of an L-shaped strong wall and a strong floor, each seven feet thick and designed to accommodate a wide range of test structures. A prefabricated steel grid was used in their design, permitting precise placement of the holes used to tie down specimens.

Six Degrees-of-Freedom Control Technology

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6DOF
Six Degrees of Freedom: isometric of crosshead positioned in strong walls

The MAST System's 6-DOFs (vertical, lateral, longitudinal, yaw, pitch, and roll) are driven by a sophisticated MTS controller. The controller seamlessly converts controls in six degrees-of-freedom space into drive commands for each of the eight actuators, accounting for geometric nonlinearity.

The controller provides mixed-mode control, which allows each DOF to be controlled either in displacement or force control. Moreover, the controller can slave any DOF to any combination of other DOFs. This technology opens up a wide range of testing possibilities. For example, the mixed-mode control features can be used to specify a lateral displacement history in the horizontal plane while maintaining a constant gravity load or varying axial load on the subassemblage to simulate overturning load effects.

In addition, moments can be controlled about orthogonal axes to simulate specified moment-to-shear ratios that would correspond to assumed lateral load distributions on the structural subassemblage. Rotation or moment about the vertical axis can be controlled to eliminate or simulate limited torsional effects on the test structure. Furthermore, the MAST System can test planar assemblies in a straightforward manner, which in traditional laboratory setups often requires cumbersome ancillary lateral framing schemes to constrain out-of-plane effects. At the MAST Lab, the 6-DOF control can be used to eliminate out-of-plane deformations.

Hydraulic Control Computer (HCC)

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HCC
In-house developed hydraulic control software, specialized for ramp and hold type test

Hydraulic control software (HCC) was developed in-house as the principal means of controlling the MAST System actuators. The HCC interfaces with the control software provided by MTS Systems to present a heads-up display of the system status and to enable control of the system using a ramp and hold protocol.

The target endlevels describing the new position or force level of the crosshead and ancillary actuators are input along with the time period to reach those levels. The MAST System operator then sets the move command and ramp function in order to achieve the desired endlevels.

Features of HCC include:

  • Heads-up status display that puts key system information into an easily understood format:
        Feedbacks (crosshead DOFs, ancillary and individual actuators)
        Errors (crosshead DOFs, ancillary actuators)
        Crosshead shear and warp
        Limit detector settings
        Modes (interface also supports mode switching)
        Slaving matrices
  • Target endlevels may be input from several sources:
        Operator console input
        Read pre-determined endlevels from a file
        Remote researcher input
  • Remote researcher control is juried for safety. The local MAST system operator has exclusive power to start a ramp movement after reviewing target endlevels (see Telepresence Software)
  • A single, consistent user-defined coordinate system is provided throughout the test.

System Capacity

Total System Capacity
Vertical Forces:±1,320 kips (±5,900 kN)
Lateral Forces:±880 kips (±3,900 kN)
Lateral Displacements:±16 inches ( ±406 mm)
Vertical Displacements:±20 inches (±508 mm)
Subassemblage size (W x L x H):20’-0" x 20’-0" x 28’-9” (6.1 m x 6.1 m x 8.7 m)

Non-concurrent Capacities of MAST DOFs

Axis DOF - Degree of Freedom Load Stroke / Rotation
X Translation ± 880 kips ± 16 inches
Rotation ± 8,910 kip-ft ± 7 degrees
Y Translation ± 880 kips ± 16 inches
Rotation ± 8,910 kip-ft ± 7 degrees
Z Translation ± 1,320 kips ± 20 inches
Rotation ± 13,200 kip-ft ± 10 degrees

Main Actuators

Type Vertical Actuator Horizontal Actuator
Quantity:44
Static load capacity: ±330 kips (±1,470 kN) ±440 kips (±1,960 kN)
Piston stroke: ±20 inches (508 mm) ±16 inches (±406 mm)
Swivels at actuator ends: Low-friction hydrostatic bearings, ±30° travel Low-friction mechanical U-joint style swivels, ±25° travel

Ancillary Actuators

Specifications
Quantity:4
Static load capacity:±220 kips (±980 kN)
Piston stroke:±10 inches (±250 mm)
Swivels at actuator ends:Low-friction, tilt angle at lower swivel ±16°; at upper ±90°
Equipment Documentation
Technical Drawings Ancillary Actuator Specifications
Ancillary Actuator Specifications (CAD Drawing)
Wall-Floor Attachment Bracket

Crosshead

Specifications
Box section: 56 x 65 inches
Tip to tip: 29.3 feet
Weight: 94 kips (47 tons)
Standard positions: 18'-3", 19'-9", 21'-3", 22'-9", 24'-3", 25'-9", 27'-3", 28'-9"
Equipment Documentation
Photos: View from bottom
Y translation
RY rotation
Plan Views: Bottom Flange
Other documents: Crosshead Translation and Rotation Limits
Prop System: Ancillary Support System (CAD Drawing)
Prop Specifications

Strong Wall

Load capacity of horizontal wall holes
Each threaded hole: ±125k lateral & 125k shear, simultaneously
9ft wide edge strip: V=470k/ft & M=2,160 ft-k/ft
Each wall:
  • ±880 lateral at 16ft elevation
  • ±880k lateral at 32ft elevation
  • 1,760k shear, simultaneously
Lateral capacity - vertical strips in each wall
Overall: V=1,760k & M =43,600 ft-k
Distributed Shear: 195 k/ft
Distributed moment: 2,115 ft-k/ft
Equipment Documentation
North Wall: Photo
Plan View
West Wall: Photo
Plan View

Strong Floor

Load capacity of vertical holes
Each threaded hole: ±125k vertical & 125k horizontal, simultaneously
Groups of 8 holes off cruciform area: ±1,000k vertical & 1,000k horizontal, simultaneously
Groups of 12 holes on cruciform area: ±1,500k vertical & 1,500k horizontal, simultaneously
Each end of cruciform: ±330k vertical & 330k horizontal, simultaneously
Vertical load capacity - horizontal strips in each direction
Overall: V=2,200k & M=43,950 ft-k
9ft wide edge strip: V=470k/ft & M=2,160 ft-k/ft
Groups of 12 holes on cruciform area: ±1,500k vertical & 1,500k horizontal, simultaneously
9ft wide middle strip: V=470k/ft & M=1,635 ft-k/ft
17ft wide wall strip: V=470kft & M = 1,090 ft-k/ft  
Equipment Documentation
PDF Documents: Photo
Clearance and Interference
Plan View
Threaded Adapters: Specifications and Inventory

Overview Literature

Manuals & Guides

CAD Drawings

Below are links to as-built CAD drawings of the MAST System components. The files are either dwg or dxf format. CAD software such as AutoCAD or Autodesk is required to view these files.

Geometric Limits of Crosshead Movement

We have prepared several Excel spreadsheets (one for each crosshead position) to help users calculate the geometric limits of the crosshead.

Because of the interactions between actuators due to the large possible movements, the reachable movement limits in the six-degrees-of-freedom space may be less than the limits for the individual actuators. The limits depend on the number of spacers in the vertical actuators.

Introductory Videos

MAST Overview Video These introduction videos were put together to showcase the capabilities of the MAST system.
  • MAST Laboratory Video Presentation - 15 MB
  • Capabilities Overview - 20.6 MB

Time Lapse Videos

MAST Videos
These time lapse videos demonstrate the six degrees-of-freedom control motions of the MAST system. The video speed is about 16 times normal speed. These videos are available in both their original format and zipped up files to reduce file size.

Animations

MAST Animations
Animated clips of the MAST system in motion. These animations demonstrate the six degrees-of-freedom control motions of the MAST system. These motions allow the MAST system to recreate virtually any real world earthquake forces with not only brute force, but with extreme precision.