Versatile Hybrid Testing System Capable of  RTHS, dRTHS and slow HS Experiments

            Lab Diagram


NEW feature of distributed Real-Time Hybrid Simulation (dRTHS) was added in 2017!

LESS @ WMU is a state-of-the-art facility for simulating earthquakes and the effects on small scale structures.  The major equipment in the LESS includes a uni-axial seismic simulator (commonly called shake table), two 3 kips hydraulic actuators with the supporting hydraulic power supply and advanced real time controller. The shake table has a dimension of 3 ft. x 3 ft. and can subject a specimen with maximum weight of 500 lb to an earthquake time history with peak acceleration up to 4 g. Structural dynamic properties and its response when attacked by an earthquake will be obtained through such shake table test. Instrumentation available in the lab consists of accelerometers and linear variable displacement transducer (LVDT) and a set of wireless sensor network. Through these equipments, various seismic experiments can be performed, including shake table test, effective force test, pseudodynamic test in real time and with substructuring.   

Shake Table     (Top)    

Table size:

Maximum specimen mass:
Frequency of operation:
Maximum specimen mass:
Supporting frame:


3 ft. x 3 ft. x 2 in. aluminum plate

500 lbf (228 Kg)

0~20 Hz

4g (with 500lbf specimen)

+/- 3in.

3 ft. x 4 ft. x 1 in. steel plates (x2)

                        Shake Table
NI-Controller and Data Acquisition     (Top)
8-Slot 3U PXI Chassis Controller
   Integrated SCXI Chassis: 4 Signal Conditioning Module Slots
   2.53 GHz Dual Core Embedded Controller
PXI Modules
   PXI-6229:  16-Bit, 32 AI, 48 DIO, Multifunction M Series DAQ
   PXI-6221:  16-Bit, 16 AI, 24 DIO, Multifunction M Series DAQ
SCB-68 (x3)
   68-Pin Shielded Desktop Connector Block
Hydraulic Power Supply     (Top)
20 Horsepower TEFC Motor
  380-480 V, 3 phase, 50/60 Hz power
  Local and remote control, 24 VDC control voltage
  High/low pressure controls
    Hydraulic Power Supply
Hydraulic Linear Actuators    (Top)
Shore Western 91 Series Dynamic Actuators



  Stroke cushion:

  Swivel base and end rod:

  Servo valve:

  Load cell:

±  3,240 lbs at 3000 psi

6 inch, +/- 3 inch

±  0.5 inch cushions

± 90 degree swivel, ± 7 degree tilt

10 Gpm at 1000 psi

2.5 kip fatigue rated 300% overload capacity

Hydraulic Linear Actuators
Hydraulic Control System    (Top)

Shore Western SC6000 Control System

  2 channel, desktop enclosure

  2.13 GHz Processor

Linear Variable Differential Transducer (LVDT)     (Top)
Schaevitz Sensors DC-EC 5000 (x3)    LVDT

  Input voltage: 

  Linear range: 

  Frequency response:  

  LVDT Specification and calibration

± 15 V DC

±  5 in

200 Hz

PSD 4-15 DC LVDT Power Supply (x1)                            LVDT Power Supply
Input voltage range:
Input frequency:
Output current:
Overall dimension:
Operating temperature:
115/ 230 VAC  ±10%
47to 63 Hz
±15 V DC  ±10%
100 mA continuous
2.00 x 4.31 x 0.90 inches;
–25°C to 70°C
Accelerometers     (Top)
(Wired) Crossbow Technology CXL04GP3 (x5)      Accelerometer
Iput range:   +/- 4g
Measurement:   x-/y-/z-axes (3-axis)
Size: 0.95” x 2” x 1.2”
Accelerometers specification & Calibration:
1.62 oz

1, 2, 3, 4, 5

Wireless Accelerometer Network Set
  IIB2400 interface board        Wireless Accelerometer
  Size: 1.9" x 1.4" x 0.6"

  IPR2400 Intel Mote 2 (Imote2) processor/radio board with external antennae

    Size: 1.4" x 1.9" x 0.35"

  Structural Health Monitoring Accelerometer (SHM-A) sensor board

  IBB2400CA battery board with on/off switch

   3-axis Measurement  
   Input Range: +/- 2g

   Operation software: ISHMP Services Toolsuite, Version 3.0.0

   Developed by: Illinois Structural Health Monitoring Project (ISHMP)


Instrumentation Frame     (Top)
4' 3" tall braced frame with three slots corresponding to story heights of structure specimen (see below). This allows for adjustment of instrumentation height.  Instrumentation Frame
Structure Specimen     (Top)

Three story shear-type building specimen

  Structure Specimen
  Number of stories:        
  Story height:                
  Structure height:            
  Column cross section:  
  Story weight:               
  Structure weight:          
  Story Stiffness:              
  Natural frequencies:      



41 1/2"

1/8" x 1 1/4"

12.6 lbf

37.7 lbf

0.164 kip/in

5.04Hz, 14.10Hz, 20.30Hz

  Three possible hybrid testing configurations


Substructure Specimen     (Top)
Cantilever Column with Idealized Plastic Hinge Connection  Substructure Specimen
  Section: HSS 3"x1.5"x1/8"
  Length: 3'
  Base plate: 5"x12" steel plate with 1/2" thickness

The plastic hinge emulates nonlinear behavior and can be easily replaced after yielding without permanent damage to the specimen.
Friction Based External Damper    (Top)
  Maximum Damping Ratio: 1.699%  Friction Base External Damper
  Design Based On: Tekton and Sumitomo Dampners' Inner-Outer Rod Design

The friction damper is activated by a simple process. When the structure is excited by the input excitation, the lower plate moves before the upper plate and a delay, caused a diffrence in relative velocities, forcing the inner rod to move after the outer rod, creating the desired friction.

Acknowledgment : The LESS would like to thank Heather Schmitt, Johnathan Holtz, Justin Poel for their hardworking in building the shake table and the reaction frame.
    Western Michigan University ---- Department of Civil and Construction Engineering
Laboratory of Earthquake and Structural Simulation ---- Last Updated: 9-21-2021