The Wiltern Center Parking Structure - First Application of the DYWIDAG Ductile Connector System (DDC) in California
In May 1996, construction was completed on the Wiltern Center Parking Structure, a four story building in the center of Los Angeles. This is the first example of a revolutionary new precast structural system designed to survive, virtually without damage, an earthquake of catastrophic proportions, while still providing the designer and the owner with both functional and aesthetic freedom. From the brilliant idea of a ductile connector to the development of a new precast frame to the final realization of the structure, the complete development of this ambitious project required less than 4 years. lt is thanks to the close collaboration between the owner/developer and the design and construction teams that this project could be so successfully accomplished.
The DYWIDAG Ductile Connector (DDC) allows precast concrete beams to be bolted to a precast column, simplifying construction while at the same time improving seismic behavior. The DDC makes it possible for all joints (beam to column, column to foundation) to develop the flexural capacity and hysteretic behavior of equivalent monolithic connections.
The key element of the connector is represented by a high quality steel ductile rod in which the entire post-elastic behavior occurs, protecting the beam and column from any possible damage. The required inelastic response of the connection is provided totally by the remaining connector components.
Tests performed at the University of California, San Diego, showed that the DDC system has the ability to accommodate a story-drift of over 4% without significant loss of strength.
The Wiltern Center Parking Structure consists of four 64 x 58 m floors with a total floor area of 14,900 m. Eight ductile frames are evenly distributed throughout each floor plate. The entire load resisting system of standard precast concrete members was fabricated offsite and assembled merely by bolting the beams to the columns.
The erection process was simple. Precast columns were dropped over temporary guide studs inserted into the ductile rods that were cast in the footing. Shims were set to plumb the column at the appropriate height, and then the bolts were manually tightened. Once the columns were in place, precast beams were lowered into position. Two bolts were placed at the bottom of the beam and tightened using a calibrated torque wrench once the beam was properly aligned, The total erection time for each frame was between 5 to 8 hrs, so that the entire precast concrete system required only 16 working days to be completed. Further adjustments were possible but not necessary.
The successful completion of the Wiltern Center Parking Structure showed the ease of construction and cost-effectiveness of the prototype DYWIDAG Ductile Connector and is the first important step in establishing the new precast system not only for parking structures but for many types of high rise buildings. This project received the 1996 Harry H. Edwards Industry Advancement Award.