Large Scale Structures Laboratory
The Center for Sustainable Infrastructure is closely aligned with UA’s Large Scale Structures Laboratory (LSSL). Housed in the South Engineering Research Center, the LSSL contains a 75-foot by 40-foot test floor with a 3-foot thick strong floor, two 15-ton capacity overhead cranes, and 7-foot-by-4-inch by 7-foot-by-4-inch and 2-foot thick reconfigurable reinforced-concrete blocks that can be stacked and post-tensioned to the strong floor to provide reaction walls on the testing floor. The centerpiece of the LSSL is a 13-foot by 12-foot uniaxial earthquake simulator capable of exciting a 40,000-pound payload to a peak acceleration of 1.2 g, displacement of plus/minus 20 inches, and maximum velocity of 45 inches per second within a frequency range of 0 to 30 Hertz. In addition, the LSSL contains a 10-foot by 10-foot by 10-foot soil pit adjacent to the strong floor, with 5-ton capacity overhead crane, for geotechnical-related investigations including reduced-scale study of soil-structure interaction.
In addition to the earthquake simulator, the laboratory is equipped with a suite of eight MTS hydraulic actuators with large-flow servo valves, ranging in capacity from 35 to 330 kips, a high-capacity distribution system powered by an MTS Silent Flow Pump that can provide up to 720 GPM flow of high-pressure hydraulic fluid, service manifolds and several digital controllers. The LSSL is also well equipped with instrumentation including an OptiTrack optical motion capture device, accelerometers, LVDT’s, load cells, etc., and National Instruments high-speed data acquisition systems.
Advanced Materials Testing Laboratory
The Advanced Materials Testing Laboratory, located adjacent to the LSSL, contains nine materials testing machines. Both mechanical screw-driven machines and servo-hydraulic machines, many outfitted with hydraulic wedge grips, are available in a range of capacities from 5 to 220 kips. One 50-kip-capacity machine has tension-torsion capabilities and another is a thermo-mechanical test frame with an induction coil attachment and water-cooled collet grips.
Wind Hazard Simulation Testing Laboratory
In order to enhance the resistance of the built environment to extreme wind events, UA has completed construction of a boundary-layer wind tunnel facility for structural research. The Wind Hazard Simulation Testing Laboratory (WHSTL) is located in Hardaway Hall.
The wind tunnel, which has a 21-foot-long test section with a 5-foot by 5-foot cross section, is able to generate a maximum wind speed of 45 mph. The primary objective of WHSTL is to develop the hybrid test method for use in investigating the performance of large-scale structural and non-structural components to extreme wind loads. Real-time response data collected from an instrumented scale-model structure in the boundary-layer wind tunnel can be used as input to a nonlinear numerical model of the structure being subjected to simulated disaster loads on a high-speed computer. Computed response of the numerical model can provide instructions to the hydraulic control systems in the LSSL to introduce real-time displacement increments for full-scale structural elements or sub-assemblages being tested in the LSSL. Changes in the resistance of the structural components or sub-assemblages to the imposed displacements can be relayed to the nonlinear numerical model to update the properties of these critical elements.
UA researchers are further enhancing their capabilities for wind-hazard-related structural research with the addition of a debris cannon capable of firing projectiles at speeds of more than 150 mph at structural and non-structural components.
Pneumatic Debris Cannon
The Pneumatic Debris Cannon is nearing completion in Hardaway Hall.
More than 80 percent of the total building stock in the United States, and over 90 percent of the residential buildings in North America, can be described as light frame (wood-frame) construction. Many of these structures are in extreme wind, such as those from a hurricane or tornado, prone regions. Post extreme-wind event investigations show much of the residential damage come from debris impact, especially during a tornado. Damage because of debris impact not only causes the reduction of structural capacity, but also increases internal wind pressure, which may lead to successive structural damage. The importance of windborne debris protection to building envelopes during extreme wind events became quite evident to experts involved in investigations of building structures after the devastating effects of hurricanes such as hurricane Andrew in 1992 and hurricane Katrina in 2005, and tornadoes, such as those in Tuscaloosa, Alabama, and Joplin, Missouri, in 2011; and Moore, Oklahoma in 2013.
In recent years, several research centers at Florida State University, the University of Florida and Texas-Tech University have conducted a number of testing programs on windborne debris impact. In their experimental programs, the “missiles” used in tests were 2-by-4 inch wood studs with different weights of either 9 or 15 pounds. Most of these tests were conducted by shooting 2-by-4 inch wood studs into building external envelopes such as walls, roofs and shelters. The aim of these tests was to develop new requirements for design to ensure the integrity of the building envelope during extreme wind events. Because of these studies, several national and regional building codes have adopted the missile impact testing procedure for specification of acceptance criteria for minimum debris resistance of the external envelopes for buildings, for example ASCE-7 2002, SBC 200 and FBC 2001.
With the existing capability of the LSSL housed in SERC, it is possible to extend the research program on the effects of windborne debris impact. A hybrid testing system will allow us to simulate the building response under lateral dynamic loads. This will also allow us to study successive failures of the building envelope by shooting debris into building envelope components while the building model is being loaded with simulated wind force applied through the hybrid testing system.
The new pneumatic debris cannon was designed and fabricated during 2016 and is capable of firing up to a sequence of four projectiles, each weighing up to 20 pounds with muzzle speeds ranging to more than 150 mph. This debris speed is designed to represent tornado wind speeds up to 300 mph. The results from this research will allow us to calibrate the performance-based wind engineering design procedures currently under development. The performance-based wind engineering will allow engineers to design for new or retrofitted buildings subjected to high wind events to mitigate the losses due to damage of structural and non-structural components.