CONSIDERATIONS FOR RETROFIT OF EXISTING STEEL BUILDINGS FOR RESISTING BLAST AND PROGRESSIVE COLLAPSE

One of the organizers of the proceedings, Mr. Faschan is a Partner at LERA and a Structural Engineer with twenty-five years of experience. He has worked on a wide range of cultural and commercial project types that have been recognized for achievements in structural design including high-rise buildings and long-span structures. Mr. Faschan is currently one of LERA's Project Director for the Shanghai World Financial Center, which will be the world's tallest building at 1614-ft. (492-m.). Mr. Faschan also has significant experience in design of blast resistant and collision resistant structures. He was the Project Director of the WTC Reconstruction efforts following the 1993 bombing. Mr. Garlock is a Senior Associate and a Structural Engineer with ten years of experience at LERA. He has worked on a large range of high profile public use facilities as well as low, mid, and high-rise buildings. His experience in high security projects has included a justice center and a bank for the Federal Reserve System. He managed LERA's efforts during the WTC Recovery Project and has also managed several projects for the Port Authority of New York and New Jersey. He is currently managing LERA's efforts for the NIST Investigation into the WTC Collapse. Richard B. Garlock P.E., M. S. Mr. Sesil is a Partner and a Structural Engineer with twenty years of experience at LERA. He has worked on award-winning projects both in the United States and abroad, spanning the entire range of building types. His expertise in the design of structural systems for high profile, high security and public use facilities includes courthouses, embassies and banks for the Federal Reserve System. Mr. Sesil, also an Adjunct Assistant Professor at Columbia University, has completed numerous landmark projects of international renown including the William Jefferson Clinton Presidential Center, Rock & Roll Hall of Fame, Miho Museum & Bridge in Japan and the Prada SoHo boutique in New York City. Daniel A. Sesil P.E., S.E., M. S. ABSTRACT Evaluation and subsequent strengthening of existing structures for extreme loading cases, such as blast, require a realistic and pragmatic design approach. Effective communication between Owner, Structural Engineer, Architect, Risk Analyst, Insurance Providers, and other stakeholders is paramount to a finished project that is satisfactory to all. The benefits of structural steel for use in the renovation of existing buildings are well documented and are applicable to the type of retrofitting required for resistance to blast and progressive collapse. The performance of steel construction during the 1993 bombing of The World Trade Center is further evidence. Combination of the existing conditions of the structure and the nature of the threat leads to strengthening techniques that may not be the first choice in the case of new construction. Less intrusive types of strengthening are favored. The general approach for strengthening of existing buildings starts with researching the original construction documents and then performing a condition assessment of the building. Vulnerability analysis is a multi-step process where there is constant dialogue about the possibilities of non-structural methods to decrease the threat on the building. With the goal of enhancing a building's performance under an extreme event, we have provided a range of upgrades from enhanced perimeter protection to structural hardening