For the past 3 years the ASCE/SEI Standards Committee on Seismic Rehabilitation has been working to combine ASCE 31-03 into ASCE 41-06 while also updating both standards. The result of that humongous effort is the soon-to-be released ASCE 41-13: Seismic Evaluation and Retrofit of Existing Buildings. The new combined standard has eliminated any inconsistencies that previously existed between the two standards. Now the user decides if they want to go forward with lower performance objectives traditionally used for existing buildings, as was the case within ASCE 31 or an equivalent hazard to a new building, similar to the Basic Safety Objective in ASCE 41. In addition, the Tier 1 checklists have been significantly modified and reorganized. The use deficiency-only procedures (Tier 2) have been greatly expanded to regular buildings of greater heights. Plus, there have been a number of significant technical changes including updated analysis provisions with more emphasis on nonlinear response history analysis, provisions for bucking restrained braced frames, expanded liquefaction provisions, a new foundation rocking analysis procedure, substantially updated URM provisions, and a full updated Chapter on Seismic isolation and Energy dissipation.

Some engineers suggest that current seismic design provisions, both for new buildings and for strengthened existing buildings, can improve resistance to blast loads and progressive collapse. However, there have been few attempts to quantify such improvement. To begin analyzing this possible relationship between seismic detailing and blast and progressive collapse resistance, the Federal Emergency Management Agency of the Department of Homeland Security sponsored a study at the U.S. Army Engineer Research and Development Center. The study was an analysis of the Alfred P. Murrah Federal Building, which was severely damaged in a 1995 terrorist attack. The building was first evaluated for seismic vulnerabilities as if it were located in a seismically active region. Three strengthening schemes were then designed for the vulnerabilities found during the evaluation: a pier-spandrel system and a new special concrete moment frame, both for the street face of the building, and a set of internal shear walls. In addition to these strengthening schemes, the original ordinary concrete moment frame on the street face of the building was redetailed to bring it into compliance with current building code provisions, without including a lateral load analysis. The three strengthening schemes and redetailed frame were then analyzed for their responses to the same explosion that occurred in 1995. Blast and corresponding progressive collapse analyses showed that the pier-spandrel and special moment frame schemes, as well as the redetailed original system, reduced the degree of direct blast-induced damage and subsequent progressive collapse, compared with the behavior of the original building. Internal shear walls, however, were not as effective in reducing the blast and progressive collapse damage. A key finding of the study was that strengthening the perimeter elements using current seismic detailing techniques improved the survivability of the building, while strengthening elements internal to the building envelope was not nearly as effective in reducing damage.

Degenkolb Engineers is completing its 62nd year of providing consulting structural engineering services in the design and construction industry. While the primary efforts have focused on the design of new structures and on seismic strengthening and rehabilitation, other important services include seismic evaluation, development of seismic hazard reduction programs, peer reviews, consultation and design of underpinning and shoring for deep excavations, as well as major participation in the development of seismic evaluation and rehabilitation standards. These services have been provided to private industry and business, universities, hospitals, governmental agencies, the insurance industry, and contractors, often, but not always, working with an architect. The firm is now in its fourth generation of leadership, headed by Chris D. Poland, President, CEO and Chairman of the Board. Copyright © 2003 John Wiley & Sons, Ltd.

The Structural Design of Tall BuildingsVolume 10, Issue 1 p. 1-7 InterviewFree Access Structural engineer to structural engineer: conversation with Steve Johnston Chris D. Poland, Corresponding Author Chris D. Poland Degenkolb Engineers, 225 Bush Street, #1000 San Francisco, CA 94104, USADegenkolb Engineers, 225 Bush Street, #1000 San Francisco, CA 94104 USA===Search for more papers by this authorJames O. Malley, James O. Malley Degenkolb Engineers, 225 Bush Street, #1000 San Francisco, CA 94104, USASearch for more papers by this author Chris D. Poland, Corresponding Author Chris D. Poland Degenkolb Engineers, 225 Bush Street, #1000 San Francisco, CA 94104, USADegenkolb Engineers, 225 Bush Street, #1000 San Francisco, CA 94104 USA===Search for more papers by this authorJames O. Malley, James O. Malley Degenkolb Engineers, 225 Bush Street, #1000 San Francisco, CA 94104, USASearch for more papers by this author First published: 07 February 2001 https://doi.org/10.1002/tal.159AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume10, Issue1March 2001Pages 1-7 RelatedInformation

Seismic provisions of building codes today are intended to provide structures with integrity, strength and toughness to provide life safe performance during large, infrequent earthquakes. However, even if a structure actually performs to this level in major seismic events, it may well end up too costly to repair; leading to its ultimate demolition. This is no longer a universally accepted end condition. The new performance based seismic engineering procedures and techniques now under development intend to design and rehabilitate structures to perform at appropriate levels for all earthquakes. By defining various performance levels, performance based seismic engineering allows property and business interruption losses after a seismic event to be controlled and, when appropriate, minimized.With the development of these new performance based seismic engineering techniques, building owners now have choices that were never available before. In the past, the seismic provisions of building codes were the only criteria to judge the adequacy of an existing structure. If an existing building was non-compliant, the only option was to "bring the building up to code." Building owners can now tailor the performance of their structures to their needs. Some building owners have achieved an adequate life-safe performance level without fully complying with today's codes. Hospitals, where the functionality of the facility after a major seismic event is more important than the actual structure, have used performance based seismic engineering to attain a higher performance level than basic life safety. Production companies such as hi-tech manufacturers and movie studios, where the value of the business is more important than the value of the buildings themselves, have been able to design and upgrade their facilities to maintain continued operations, even after a major earthquake. Finally, by defining short and long term goals, a university has used performance based seismic engineering to develop a long term seismic hazard reduction program for all of their buildings that, in the end, will allow them to systematically reduce their risk of loss in an orderly fashion as they work toward their ultimate goals.While these new opportunities have much potential, performance based seismic engineering also contains numerous pitfalls that need to be addressed. The multiple-tier performance level goes beyond the code provisions. Some clients and business owners have found these new levels and concepts too sophisticated to understand and incorporate in their long range plans. The performance levels themselves are subject to various degrees of interpretation. Performance criteria must be selected carefully and clearly defined or the desired the performance objective may not be met. The new techniques and tools associated with performance based seismic engineering are still being developed and may not fit certain needs or performance levels yet. The available techniques at times vary radically; different evaluation techniques often lead to different conclusions. Furthermore, without new data from seismic events, the calibration and verification of adequacy of these techniques is very difficult. Many of these techniques are unproven.Performance based seismic engineering is here to stay. It meets a significant need to be able to tailor structural design to target performance levels. It must be applied properly, however, with full recognition of its pitfalls, deficiencies and limitations. These problems must be among the research topics that are now being pursued.

While since 1973 the design and construction of new California Health Care Facilities have been regulated by special ordinances, pre-existing hospitals have remained largely non-compliant due to the prohibitive costs of upgrading. The special seismic design considerations that are needed for new and existing facilities, a program for assessing the projected performance of these facilities in terms of life-safety and ability to remain operational under various seismic conditions, as well as for developing effective, phased retrofit strategies to improve performance is discussed in this paper.

The Applied Technology Council (ATC) has developed and published a methodology, ATC-14, for evaluating specific buildings that is tailored for use by practicing structural engineers. ATC-14 was developed to be consistent with the latest building codes, but tailored to the often non-conforming characteristics of the variety of buildings in existence. As a portion of the 'Existing Structures' topic, one of the three major areas of research for the second year of the National Center for Earthquake Engineering Research (NCEER) five-year program, an investigation was performed to critically assess the applicability of ATC-14 to buildings in regions of low seismicity. The project has provided a large number of recommended additions and revisions to the original document. It is intended that these recommended revisions be included in any future editions of ATC-14, and the FEMA-sponsored ATC-22 project to develop a handbook for the seismic evaluation of existing buildings. The information presented in this report should serve as a supplement to ATC-14.