Repair of an Earthquake Damaged Building Facade in Coordination with FEMA: A Case Study Including Stabilization, Evaluation, Historically Sensitive Restoration, and Hazard Mitigation

摘要

The Nisqually Earthquake struck Washington State in February 2001, damaging the facade of the historic Bush Hotel, located in Seattle's International District. During the seismic event, sections of exterior cement plaster parge cladding and clay block infill fell from the structure onto the sidewalk below. This paper outlines the failures of the 1920s era concrete frame and hollow-core clay block infill exterior wall assembly, the multi-faceted approach designed to implement a historically sensitive repair in coordination with FEMA regulations, and addresses mitigation of potential future hazards. Prompt evaluation of the life safety threat was conducted, and sprayed-in-place polyurethane foam was used as a unique method to stabilize and temporarily weatherize portions of exterior walls. Various techniques were used to evaluate exterior walls and quantify the extent of damage including hammer sounding, invasive testing, mapping, and CAD-assisted measurements in a rigorous process to meet FEMA funding requirements. Damage to the exterior walls included delamlnated and cracked stucco cladding, crushed hollow-core clay block infill panels, and cracked and spalled concrete. A multitude of factors were addressed in the Construction Documents including: restoring exterior walls to pre-earthquake conditions; maintaining the historical fabric of the building's appearance; coordination with FEMA and historic review agencies; repair to hollow-core clay block without in-kind material readily available; restoration of an exterior mural; performing work in a busy downtown setting with the building fully occupied; and addressing removal of lead-containing coatings. Importantly, a plan for mitigation of potential hazards was designed and Implemented utilizing anchors to secure clay block infill panels to the structure, in order for wall sections to better resist possible future earthquakes. Methodology and examples for the synthesis of well-coordinated Contract Documents for such a complicated project are addressed. Evaluation of successes and challenges in coordination with FEMA, design, and repair methods are also provided.