DYWIDAG Micropiles secure Skyscraper in Philadelphia, USA
At the end of 2007, construction work began on Philadelphia’s new architectural landmark: Cira Centre South, located between University City and Center City Philadelphia.
The project includes the construction of two modern skyscrapers with offices, condominiums, a four-star hotel and shops, as well as a 2,400 car parking garage. The first phase, which is to be completed by August 2010, includes the construction of a 14-level parking garage using “Green” construction technology. The second phase is not expected to be completed until 2013; this includes the construction of a 47-story tower known as the Walnut Street Tower and a 24-story tower known as the Chestnut Street Tower. All of these were designed by the famous architectural firm of Pelli Clarke Pelli, which also designed Kuala Lumpur’s Petronas Twin Towers.
Cira Centre South is designed to be an extension of the existing 32-story Cira Centre office tower located at Amtrak’s 30th Street Station along the banks of the Schuylkill River. When completed in 2005, this tower was the tallest building ever constructed outside of Center City Philadelphia. Both the existing Cira Centre tower and new Cira Centre South parking garage were LEED (Leadership in Energy and Environmental Design) certified. LEED certification is awarded to construction projects that are environmentally friendly and sustainable.
In accordance with the design by consulting engineers Pennoni Associates in Philadelphia, loads had to be transferred to the foundation via individual footings and reinforced strip footings. In order to augment ultimate loads, A.P. Construction reinforced the strip footings by installing more than 400 DYWIDAG Micropiles, using 46mm (1-3/4") Ø and 65mm (2-1/2") Ø, St 830/1035 (Grade 150) THREADBAR® with respective hardware consisting of hex nuts, couplers and steel bearing plates. DSI supplied over 8,800m (29,000ft) of 46mm (1-3/4") Ø St 830/1035 (Grade 150) THREADBAR® that were coupled in the field, installed into the center of the tubular piles, and grouted afterwards. Additionally, a total of 2,000m (6,800ft) of Ø 65mm (2-1/2") St 830/1035 (Grade 150) THREADBAR® were attached to the bottom 20’ of each Ø 46mm (1-3/4") THREADBAR® center bar to further reinforce the rock socket portion of each Micropile.
As the Micropiles had to be installed within a very aggressive time schedule, DSI had to supply a large portion of the THREADBAR® in less than 30 days. This required continual communication not only with numerous DSI plants throughout North America, but also with the customer. DSI USA would like to thank everyone involved in making this project a success.