Rising seventeen stories above the Seattle skyline, the Norton Building was the city’s first modern office tower. Completed in 1959, the open floorplan was supported by 238 modified prestressed concrete I-beams, 32” deep x 70’ long.
The building owner did not believe that concrete beams could be used without increasing the total building height to an undesirable level. To prove the effectiveness of shallow prestressed concrete members, Concrete Technology Corporation fabricated, and load tested, a prototype beam to four times the design load. When the test loads were removed, the beam rebounded, and resultant cracks disappeared. The owner promptly approved the use of prestressed concrete beams in their building.
The prestressed concrete beams used both pre- and post-tensioning. 24 pre-tensioned straight strands were installed in the lower flange, while another 24 strands were post-tensioned through two draped tendons. Long girder spans created large open floor plates without obstruction, providing the owner tenant flexibility. |