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Smart Structures Laboratory - MAST hybrid testing facility

Overview | MAST System | Equipment | Staff

The Multi-Axis Substructure Testing (MAST) system represents cutting-edge technology that is used to test the integrity of new materials and structures.

The MAST system allows researchers to perform large-scale, three-dimensional experiments to stress-test structural components and materials and determine the structure or material's capacity to withstand extreme forces. Swinburne's advanced simulation architecture allows for cyclic testing and local/geographically-distributed hybrid simulations.

  • MAST system

  • Cruciform and actuators

  • Reaction wall

  • Servo hydraulic system

  • Simulation control system

  • Hybrid simulation utilising the Swinburne Green II Supercomputer

Cruciform

Non-linear Finite element simulations were performed to optimize the design of the MAST steel cruciform. The model included all relevant details such as: holes for base plate connections and stiffener plates. Zones of weakness at weld connections were considered by modeling local elements of lower strength/stiffness in the vicinity of welds Various load cases were considered to induce the highest possible flexure, shear and torsion within the structure.

Criciform characteristics

  • Four ±1 MN maximum stall capacity vertical actuators
  • Four ±500 kN maximum stall capacity Horizontal actuators
  • Crosshead – 1000 mm high – 3500 mm end to end arm length
  • 9 tonne crosshead
  • 20mm thick, Grade 450 MPa steel
  • 50mm base plate thickness in high bearing stress regions
  • Curved stiffener plates to reduce stress concentrations
  • Holes in internal stiffener plates to reduce weight
 

Strong floor and reaction wall

The hybrid testing facility introduces an array of possible loading conditions to both the strong floor and reaction wall, the strong floor is 1 metre thick and the 5 metre tall 'L' shaped reaction wall is also 1 metre thick.

Typically the load that can be applied to the strong floor is in excess of 1 MN. However, the loads which could be applied to the reaction wall were dependant on the height of the load, its distance from the wall edge and locations of neighbouring actuators. Over 100 load configurations have been evaluated to determine maximum allowable wall loading in any given scenario.

Servo hydraulic system

Actuators

The actuators and associated control systems will allow for the development of new testing methodologies, including cyclic quasi-static, dynamic, pseudo-dynamic hybrid and the effective force control testing methods, in which large structures could be directly subjected to dynamic excitations.

  • 2 MN (Qty. 1 set)
  • 1 MN (Qty. 4 sets)
  • 500 kN (Qty. 4 sets)
  • 250 kN (Qty. 4 sets)
  • 100 kN (Qty. 3 sets)
  • 25 kN (Qty. 3 sets)
  • 10 kN (Qty. 1 set)
 

Supporting Equipment

Equipment required to operate the actuators, included: a high-capacity, high-performance hydraulic supply and distribution system and numerous digital control systems:

  • Hydraulic Power Unit 21 MPa 600 lpm
  • 2 FlexTest 40 Test Controllers
  • 2 FlexTest 60 Test Controllers

Hybrid simulation

Hybrid Simulation, also known as the pseudo-dynamic test method, combines classical experimental techniques with online computer simulations. The components interact in real time resulting in cost-effective large-scale testing of structures subjected to extreme loading conditions generated by earthquakes, wind and ocean waves.

Hybrid simulation facilitates the study of structural response by experimentally testing only the critical elements of the structure while the remainder of the structure is modeled numerically in finite element simulations. While the physical portion of the overall hybrid model is tested in the laboratory using computer-controlled actuators, the numerical portion is analyzed on the computer.

Hybrid simulation reduces fabrication costs and the overall time for testing in the laboratory. Since the damage essentially starts as a local phenomenon, hybrid simulation allows the physical testing of only the critical portion of the structure where the damage is expected. The results of numerically analyzing the global structure are fed back to the actuators in real time producing an interactive real time feed-back loop.

Geographically-Distributed Hybrid Simulation

The popularity of the hybrid simulation technique amongst structural engineering researchers has grown in recent years. Due to limitations in available facilities, geographically-distributed testing has been developed from the use of sub-structure techniques and benefited from technological advances in data transfer and computing.

The concept of geographically-distributed testing is that individual substructures do not need to be within the same facility, but can be linked by either the internet or other methods of data transference. Therefore, laboratories with much larger capacities can be used to house experimental subassemblies.

There are also significant benefits in accessing more powerful super-computer facilities by remote to run more complex hybrid simulations, since distributed testing enables the computers running the analysis to be off site.

Hyrid Simulation Architecture

The hybrid simulation control system at Swinburne, uses xPCTarget and consists of a three-loop architecture.

The innermost Servo-Control Loop contains the MTS-Flex Test controller that sends displacement commands to the actuators while reading back measured displacements and forces.

The middle loop runs the Predictor-Corrector actuator command generator on the xPCTarget real-time digital signal processor (DSP) and delivers the command displacements to the Flex Test controller in real-time through the shared memory SCRAMNet. In order to bridge time scales, the xPC-Target’s Predictor-Corrector model predicts target displacements for the Flex Test controller until the next displacement arrives from the computational driver.

The outer Integrator Loop runs on the xPC-Host PC and includes OpenSees, MATLAB and OpenFresco that can communicate with the xPC-Target through TCP/IP network. The xPC-Host OpenSees model converges to the next command displacement at large and somewhat variable time intervals.

Information resources

  • PDF Document

    Up the MAST [PDF, 1.7MB]

    The first issue of Up the MAST showcases Swinburne's achievements with the Multi-Axis Substructure Testing facility.

 

Videos