The Large High Performance Outdoor Shake Table (LHPOST) has been designed with performance characteristics that permit the accurate reproduction of strong near-source earthquake ground motions for the seismic testing of structural and soil-foundation-structure interaction (SFSI) systems at full-scale or very large-scale. The facilities at the NEES @ UCSD site are being used to investigate structural and geotechnical performance issues related to the area of Critical Infrastructure Protection (CIP). Potential research areas include:
- the effects of passive and semi-active energy dissipating systems on building response;
- large-scale testing of dynamic soil-foundation-structure interaction;
- seismic response of nuclear waste dry storage casks, including soil-structure interaction and the interaction between casks;
- loss estimation of buildings, including the interaction between their components;
- seismic response of full-scale wood-frame construction including school buildings;
- response of building diaphragms, where the presence of a distributed mass constrains the testing to be performed solely under dynamic conditions;
- assessment of liquefaction mitigation mechanisms;
- seismic response of tall wind turbines, high-voltage towers and industrial chimneys; and
- the study of the complex interaction between interconnected components of electrical substations, such as high-voltage transformer-bushing systems.
The LHPOST became operational in October 2004 and is managed as a national NSF sponsored shared-use equipment site as part of the George E. Brown Jr., Network for Earthquake Engineering Simulation (NEES). With close collaboration between NEES Headquarters and other NEES equipment sites, NEES @ UCSD provides tele-participation capabilities allowing remote researchers support and access to the shake table. Originally built as a single degree-of-freedom system, the LHPOST was designed to be readily upgradable to a 6-DOF. An initial phase of this upgrade to 4-DOF was completed in December 2009. Although this table is not the largest of its kind in terms of size in the world, the velocity, frequency range, and stroke capabilities make it the largest table outside Japan. The facility adds significant capabilities to existing United States testing facilities.
The LHPOST facility components include:
- a moving steel platen (7.6 m wide by 12.2 m long) with an estimated mass of 144 ton,
- a reinforced concrete reaction block,
- two servo-controlled dynamic actuators with a combined horizontal force capacity of 6.8MN
- a platen sliding system consisting of six hydrostatic pressure-balanced bearings (replaced by six vertical actuators in December 2009),
- an overturning moment restraint system consisting of two nitrogen-filled hold-down struts,
- a yaw restraint system consisting of two pairs of slaved hydrostatic pressure-balanced bearings, and
- cover plates to protect the actuators.
After an extensive set of table commissioning tests in October 2004, many major large-scale experiments have been conducted on the NEES @ UCSD shake table. The results of these tests with extremely large simulated ground excitations are having a major impact on the understanding of the earthquake response of structures and on the development of seismic codes. Although the LHPOST is a shared-use facility, the shake table was fully booked with NEES research projects during the FY 2007-08, FY 2008-09, and FY 2009-2010. Additional NEES projects are scheduled continuously until July 2013.
In addition to research projects, the shake table is available for industry related testing at a recharge rate. Please contact us for more information.