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NEWS RELEASE

Contacts:
UC San Diego: Denine Hagen
(858) 534-2920, dhagen@ucsd.edu

40-foot tall, five-story building test at UC San Diego evaluates new earthquake-resistant concrete construction systems

Editor’s Note: Images available on the web. Video images available upon request.

August 5, 1999 (San Diego, Calif.) In a project that could have a major impact on construction of office buildings, hospitals, and apartment towers in seismic regions like California, UC San Diego structural engineers are subjecting a five-story building to a series of simulated earthquakes. The goal of the research is to validate new precast concrete construction systems for earthquake-prone regions.

The building, which weighs 500 tons and has 91 precast components is erected in the Charles Lee Powell Structural Research Laboratory on the UC San Diego campus. At 40-feet tall and 900 square-feet per floor, the building is the largest structural model ever tested in the U.S. The test is the culmination of a 10-year research program called PRESSS (Precast Seismic Structural Systems) involving collaboration of more than a dozen university research teams across the country in partnership with industry.

"The building is a composite of five different structural systems, so we are effectively testing five different buildings. There is one wall type and four frame types, within this large-scale model," said Nigel Priestley, UC San Diego professor of structural engineering and principal coordinator of PRESSS. "Each of the building types incorporates new connections between the precast concrete elements. These connections are designed to make the building ductile and dissipate seismic energy so that it withstands an earthquake without major damage." Priestley says most of these connections also include a pre-compression mechanism that allows the building to sway with an earthquake and then self-center to the building’s original position.

In current practice, cast-in-place concrete or steel is used in construction of tall buildings in seismic areas. Use of precast, or prefabricated, concrete has been limited in seismic regions of the U.S. because of poor performance of inappropriate connection details in past earthquakes.

However, precast concrete is an attractive alternative to steel or cast-in-place concrete because it is relatively inexpensive, and quick and easy to install. In addition, there is more quality control in manufacturing because components are prefabricated in a controlled environment. Architectural design features can also be incorporated into the precast elements.

"Our ultimate goal is to construct precast concrete buildings that withstand earthquakes with minor (if any) damage and damage that can be repaired easily without displacing people and/or commerce in the building," said Doug Mooradian, Precast/Prestressed Concrete Manufacturers Association of California. "We believe through PRESSS, we have come up with new construction concepts that not only will protect the life and safety of building occupants, but will also perform better and cost less."

Throughout the PRESSS program, structural engineers have investigated several new types of connections including the five selected for the large-scale test. The UC San Diego project is the first experimental evaluation of these systems as part of a complete building model. PRESSS will use the results of the UC San Diego test to recommend a set of new design guidelines for precast concrete frame and wall buildings in seismic zones.

The UC San Diego research team are subjecting the test building to a series of simulated earthquakes of increasing intensity, culminating in an earthquake level which exceeds the most stringent California design requirement. Forces and displacements (back and forth movement) simulating the effects of the earthquake on the building will be applied by 10 computer-controlled hydraulic actuators, two at each floor level, capable of applying forces up to 100 tons, and displacements up to 48 inches. Instrumentation on the building enables this computer controlling the test to measure the structural performance of the building during the earthquake simulation. Forces and displacements can be modified at 1/100th to 1/1000th of a second time intervals depending on the condition of the building.

Financial support for the PRESSS program has been provided by the National Science Foundation, the Precast/Prestressed Concrete Institute, and the Precast/Prestressed Concrete Manufacturers Association of California.


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