Imagine testing key design and performance issues and how well structural building components will stand up against an earthquake or hurricane without devastating loss and damage. That's the basic capability of a new Structural Building Components Research Institute (SBCRI) testing center that can replicate real-world performance of construction products and systems, using hydraulic actuators and monitoring sensors to collect force and position measurements.
This innovative facility is 5,730 sq ft, with a testing area large enough to build a 30 x 90 ft two-story house inside the facility for testing purposes. The lab structure is a series of steel columns and beams that enable hydraulic actuators to be precisely arranged around the component or structure being tested. The actuators provide exact loads, individually or simultaneously, to simulate any lateral or gravity combination and examine the integrity and cost efficiency of buildings.
The facility has the capability to test the complete structural framework with applied loads and pressure to simulate wind or seismic scenarios, snow and wind uplift. During tests, the hydraulic actuators apply loads simultaneously in vertical (gravity, uplift and cyclical) and horizontal (lateral and cyclic) planes that are parallel with or perpendicular to the roof framing components being tested.
For applications that require high force capability and precision control, hydraulic systems provide a viable alternative. Keith Hershey, director of research and development for SBCRI, turned to Ritter Technology LLC, a Parker Hannifin distributor, to help design a hydraulic system capable of applying force in three axes simultaneously to simulate both construction and environmental loads.
The initial design called for 52 Parker 2HX actuators mounted vertically to generate forces ranging from 8 to 15,000 LBF with 20-inch stroke lengths and precise position control down to 0.001 of an inch. Because the facility is pioneering new ways for testing building components and assemblies, control of these actuators needed to be easily modified and configured to meet unknown specifications.
Eight horizontal actuators control the applied load function in sinusoidal motion to simulate standardized earthquake loads as defined in ASTME 2126-05 Load Testing for Shear Resistance of Walls for Buildings. The engineering team also designed the hydraulic system with the capability to add up to 206 additional actuators, so the system can evolve as new testing configurations are developed.
A Delta Computer Systems' RMC75E motion controller was selected because of the unit's processing power and ease of integration with the hydraulic system. The team also developed a computer architecture and software package for test setup (calibration and actuator placement before tests), running specified tests, data collection and reporting, maintenance and alarms. Parker worked with controls integrator Adamation to develop the software. A distributed control system provides test parameter set-up, synchronous control of the actuators and collects all of the load distributions and deflections of the item being tested. Data is collected 100 times per second and stored on redundant hard drives for analysis.
The actuators are controlled by a panel on the rail system for easy movement throughout the testing facility. Currently, there are five control panels in total and 60 axes of position and force control, with room for growth if necessary. The testing system's motion controllers can be moved along the test lab's rail system to be near the actuators. Twelve cylinders are connected to each motion control enclosure. Actuators, cable harnesses and controllers have barcode labels enabling operators to scan in location, tuning and scaling parameters for each actuator, a process that can be performed at a PC workstation or wirelessly with a handheld pocket PC.