Spatiotemporal Pressure Loading Actuator

Maximum Chamber Size 7.6 m × 12.2 m (12 ft x 24 ft)
Minimum Chamber Size 3.6 m x 2.44m (12 ft x 8 ft)
Chamber Depth 0.25 m (10 in)
Number of Pressure Loading Actuators Up to 4
Variable Frequency Drive Power Range 1 – 550 Hp
Peak rated pressure 9.96 kPA (208 psf)
Peak rated air flow 51 m3/min (1,800 CFM)
Frequency Response 2 Hz
Pressure Transducers Up to 4
Pressure Transducer Range +/- 17.2 kPa (2.5 psi)
Compliance with Industry Standards ASTM E-1592, UL 580, FM 4470
Performance data View [pdf]
Drawings View [dwg]
Hardware Specifications View [pdf]
Standard Test Protocol View [pdf]
Calibration Certificates View [pdf]
Video of Experimental Test View [mp4]
Photo Gallery View [jpg]


Design methods for predicting component and cladding response relies upon full-scale testing because analytical approach is not able to predict performance. Roofing systems and wall components of a building are much more affected by the local, peak dynamic wind pressures that is the primary structural framing, and so industry-accepted wind uplift resistance test protocols (ASTM E1592, UL1897, FM 4470, UL580) are used to evaluate performance. These pneumatic pressure tests use uniform air pressure held for a fixed time or long period cyclic loading, to test specimens to failure. However, these test protocols do not truly replicate the spatial non-uniformity and rapid temporal variability of wind loading on buildings. A realistic wind pressure distribution is severely non-uniform, with extreme suction pressures at the building corners and the distribution itself changes rapidly with time. While testing with complete spatial pressure non-uniformity is still not feasible, the Spatiotemporal Pressure Loading Actuator uses four individual pressure loading actuators (PLAs) and a large re-configurable test bed to more closely approximate the pressure fluctuations on roof surfaces. The PLA was originally developed by the University of Western Ontario for the “Three Little Pigs” project to replicates the effects of the wind, the surface pressures, which vary with location and in time due to turbulence. Several studies internationally, have previously utilized combinations of PLAs for component and cladding testing for wall testing and roofing wind load studies

Capabilities and Principle of Operation

The key features of the Spatiotemporal Pressure Loading Actuator (SPLA) design is that it a) produces wind loads up to a Category 5 Hurricane (i.e. +5 kPa to -10 kPa range; b) can follow a pressure trace with high accuracy for a range of surface area; c) has a frequency response of up to of 4-6 Hz; d) can operate with substantial air leakage (12 – 60 m3/min) through cracks in the building materials; d) many PLAs can be simultaneously controlled to apply independent pressure traces. The performance characteristics of the PLA depend on the size of the test chamber used.

A Kollmorgen AKM-54H Servo Motor and single-axis servo-drive (model AKM-54H) controls the position of the rotating disc within each PLA which adjusts the pressure chamber. Each PLA is portable, and independently positioned depending on location of the sub-chambers for the experiment. A pressure transducer within each sub-chamber monitors the pressure and provides feedback to the each PLA. The four PLAs are networked together and controlled through a single PC-based control program. The SPLA computer terminal is a Dell Optiplex Model GX620 desktop computer (80 GB hard drive) that has all software installed (motion controller PCI card, data acquisition PCI-e card, LabVIEW and National Instruments software, and the Kollmorgen AKD software, Benchmark.) The LabVIEW program handles primary data acquisition using a X-series PCIe-6320 data acquisition (DAQ) card, by National Instruments. This general data acquisition card enables pressure data to be collected as well as structural loads and/or displacements in the experiment.

Equipment Specifications

The SPLA uses four pressure control valves developed by University of Western Ontario for the PLAs, mated to a single fan blower to produce the pressure and required airflow rates. The fan output is routed through four Greenheck Model HCD-120 air-balancing dampers to adjust the distorted air velocity profile immediately leaving the fan impellor and distribute the flow to each PLA. Polyester air filters with nine silencing tubes for sound attenuation, in a metal housing (model FS-245P-400) are connected in-line to each PLA. Control of the SPLA is achieved via state-of-the-art instrumentation, which includes the following:

  • 40 HP, 3-phase 460 V centrifugal blower rated at 10 kPa at a peak airflow of 1.44 m3/s (3050 CFM).
  • A Greenheck Model HCD-120 Heavy Duty Control Damper adjusts the distorted air velocity profile immediately leaving the fan impellor
  • Variable Frequency Drive (VFD), Model ACS550 with integrated PID controller regulates blower output airflow.
  • Polyester air filter in metal housing (model FS-245P-400) is mounted to the inlet on metal support frames above each pressure control valve. The filter includes sound attenuation devices to minimize noise pollution. Individual pressure control values are independently positioned depending on the experiment.
  • A 4-axis National Instruments Universal Motion Interface UMI 7774 Motion Controller board with encoder rates of 20 MHz communicates with the Variable Frequency Drive (VFD), the servo drives, and sends information to and from the motion controller card.
  • Four Kollmorgen AKM-54H Servo Motors, maximum mechanical speeds of 6000 RPM.
  • Four Kollmorgen AKD P600606 Servo Drives with position response loop time of 0.125 μs (8000 Hz).
  • Steel pressure chamber with maximum size of 7.3 m by 3.6 m by 0.25 m deep with transparent structural floor (15.9 mm thick), and anchor points to install load cells and other instruments.

Centrifugal fan and ducting for connecting the four PLAs


  • Four Omega MMCG pressure transducers with +/- 17 kPa range and response time less than 1 ms for real-time pressure feedback.
  • The PCI-7354 motion controller card, (by National Instruments) receives pressure data from the sub-chamber pressure transducer and generates a position command to be sent to the servo motor.
  • National Instrument PCI cards for data acquisition and software interaction through Labview interface.

Current Status and Planned Upgrades

The SPLA culminates the ongoing effort at the University of Florida to recreate more realistic load distributions for wind uplift testing of roofing systems [1,2,11]. The facility can be used for wood-framed construction, membrane roofing, and structural standing seam roofing systems. The physical transformation of the test chamber from horizontal to vertical orientations allows for roof and wall component testing. The size of the test chamber can be modified for any component size up to the maximum size of the full pressure chamber. The pressure chamber is configurable for use as a single large wall or roof specimen divided into up to four areas of individually controlled pressure time histories, or it can be used as three separate 2.4 m by 3.6 m. Control of the test protocol and data acquisition is handled within a common Labview interface so that a common trigger can initiate both testing sequence and data acquisition, ensuring time compatibility of the load and response data. The chamber size matches that of standard test protocols so direct comparison are possible with results. The recent upgrades will enable tests simulating corners wind loads on roofing systems, pressure equalization studies in multi-layer wall systems.


Associated Hardware and Software

Motion Control System 1 PCI-7354 Motion Controller Card Controls 4 axes of servo motion
1 UMI-7774 Universal Motion Interface Central hub unit for VFD, servo drives, pressure transducers, and computer
1 PS-15 Power Supply Supplies +24V/5A logic power for servo drives
4 AKD-P00606 Kollmorgen Single Axis Servo Drive Relative encoder; provides position feedback and communications for servo motor
4 AKM-54H Kollmorgen Servo Motor Rotates disc in the pressure control valve
Pressure Control Valve 4 UWO Prefabricated Valve Regulates air pressure into chamber
4 FS-245P-400 Inlet Air Filter Assembly Filters valve air intake and attenuates sound
4 Support Frame & Adaptor Plate Valve, servo motor and inlet filter attach to plate; plate is bolted onto frame
Test Chamber 1 Steel Pressure Chamber
Pressure Feedback 4 MMCG Omega Compound Range Pressure Transducer +/- 10 V output; 2.5 psi (360 psf) range w/ 0.03% accuracy
1* PCIe-6320 NI Data Acquisition (DAQ) Card Syncs with motion controller card and allows for pressure data collection via hardware time
Air Supply System 1 1240-SS Spencer Centrifugal Blower Generates airflow rated up to 40” wc at 3000 cfm
1 ACS550 Variable Frequency Drive (VFD) Controller Varies blower motor’s input current to regulate the blower’s output airflow
1 Galvanized Steel Ducting Transfers blower airflow into lab
4 HCD-120 Greenheck Control Damper Adjusts contraction flow for uniformity
1 TR T-7 Flexaust Flexible Ducting Transfers air to and from pressure control valves
Miscellaneous 1 NEMA enclosures, electrical cables, pipe clamps, pressure tubing, etc.

Performance Curves

Phase Shift as a function of Input Signal Frequency and Leakage