Architectural Concrete

The concrete construction of the Los Angeles cathedral was an interesting case of combining architectural and mass concrete methods.

The Archdiocese of Los Angeles serves the largest community of Catholics in the United States. When the aging St. Vibiana's Cathedral was substantially damaged by the 1994 Northridge earthquake and subsequently condemned by the City, the Archdiocese decided to build a landmark, 21st century Cathedral that reflects the rich diversity and spirit of Los Angeles.

A 5.6-acre site in the heart of downtown Los Angeles was purchased by the Archdiocese from the County of Los Angeles. Taking shape atop a prominent hill between Grand Avenue and Hill Street alongside the Hollywood Freeway, the new cathedral is part of an ambitious urban renaissance to make downtown an exciting destination once again. Spanish architect and Harvard professor Jose Rafael Moneo was chosen to design the new $163 million complex, consisting of a new Cathedral, a conference center, a 156 ft. (47.5 m) campanile tower, carillon, a residence hall, a 2-1/2 acre grand plaza, and a subterranean parking structure. .
Lightly colored, sandblasted architectural concrete was selected for the 454,000 sq. ft (42,180 m2) of exterior and interior walls. The same architectural concrete was also chosen for the campanile, carillon, exposed parking structure walls, and the structural elements of the plaza. In total, the project is composed of an extraordinary 654,000 sq. ft ( 60,760 m2), 26,000 cubic yards (19,880 m3) of architectural concrete. Total volume of concrete for the project is 59,580 cubic yards (45,550 m3)..

The concrete work on the cathedral structure posed a number of significant technical challenges. Of the 454,000 sq. ft (42,180 m2) of architectural concrete, 70,000 sq. ft (6500 m2) of walls have a shingled pattern.. The walls vary in thickness from 1 to 5 ft (0.3 to 1.5 m) and pitch at angles ranging from vertical to 30o from horizontal. One of the most challenging aspects of this project is that no two cathedral walls intersect at 90o angles. Indeed, there are some 850 non-repeating corner conditions.

While the architectural concrete work at the parking structure was completing, the contractor was refining the forming techniques for the cathedral's intricate elements at an off-site mock-up. Unfortunately, the mock-up surfaces were exhibiting a high incidence of thermal-induced cracking, as well as interior to exterior thermal gradient cracking.

With just seven weeks until the first cathedral walls were to be cast, the contractor, Morley Construction Company together with the University of California at Berkeley embarked on a concurrent, iterative theoretical and field test program. Details of the solution can be found in the following paper:

D. Selna and P.J.M. Monteiro, Cathedral of Our Lady of The Angels: Combining Architectural and Mass Concrete, Concrete International, 2001.