Materials Performance

NOV 2014

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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S FEATURE ARTICLE Mitigating Structural Steel Corrosion Protects Decorative Façade of the Historic Elks Veterans Memorial Preserving History with Cathodic Protection Several years ago, the limestone soffit and entablature of the historic Elks Veterans Memorial in Chicago, Illinois, owned by The Benevolent and Protective Order of Elks of the United States of America (Elks), showed signs of distress due to masonry damage caused by corrosion. The limestone soffit stones, which sit on top of the colonnade that encircles the neo-classical rotunda, had experienced hairline cracking caused by stress from corrosion products forming on the steel support system components; and a sheer fracture of one of the soffit stones resulted in a portion of the stone breaking off the entablature. The steel corrosion of the memorial is an instance where the oxidation (rust) didn't affect the structural integrity of the steel— none of the steel frame was replaced—but created a material preservation issue and a safety concern stemming from the deterio- ration of the decorative limestone façade. Harboe Architects, the Chicago-based architectural firm hired by the Elks to deter- mine the condition of the structure and identify the underlying cause of the stone breakage as well as make repair recom- mendations, retained NACE International members and corrosion consultants Gina Crevello, principal of Echem Consultants, LLC (New York, New York) and Paul Noyce, principal of Axieom, LLC (New York, New York), to inspect the memorial's steel frame and diagnose the corrosion problems. Their ensuing investigation and corrosion assessment determined that an impressed current cathodic protection (ICCP) system for the rotunda's steel support system would provide the optimum solution for protecting it from corrosion and preserving the integ- rity of the historic masonry. Implementing the installation of the ICCP system as part of the exterior masonry restoration project, however, was not without challenges. The Historic Structure Construction of the Elks Veterans Memorial started in 1923 and the building was completed in 1926. According Crevello and Noyce, the memorial integrated the best building technologies that were available at that time. The rotunda is comprised of 24 bays with a 360-ft (110-m) diameter entab- lature supported by 24 ionic columns that Gina Crevello, Echem Consultants, Paul Noyce, Axieom, and Kathy Riggs Larsen, MP Associate Editor are 30-ft (9-m) tall. An embedded rolled-steel beam frame sits on the limestone colonnade and supports the rotunda's entablature and dome. It features 24 spans, and each comprises a 15-ft (4.6-m) long by 5.375- in (137-mm) wide center beam with two inward-facing steel channels located 3 in (76 mm) from the outer edges of the center beam flanges. Welded to the outer face of the channels are 5 by 3.5 by 0.5 in (127 by 89 by 13 mm) L-angles. The steel frame is welded at base plates that rest on the columns, with the steel spans going from one column centerline to another. The original construc- tion specifications called for steel with a tensile strength of 60,000 psi (414 MPa) and an elastic limit of 30,000 psi (207 MPa), and shop-coated with Dereka Metal Paint. The 15-ft soffit stones on the lower course of the entablature are single units of limestone. The ends of the stones are compressed between the columns and other masonry components of the entablature. To support the soffit stones, lug anchors were set within the soffit stones at six locations per bay and bolted to the L-angles on the steel beam. Steel shims were installed on the 26 NOVEMBER 2014 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 53, NO. 11

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