Excellent refresher course
I just wanted to thank Structural Engineer and David Fanella, Ph.D., S.E., P.E., for the feature "How to determine structural loads—Part 1" in the July 2008 edition the magazine. It is a thorough explanation of using the 2006 International Building Code in load requirements, and made for an excellent refresher course! I am already looking forward to future issues for the continuation of this series.
Ed Levy

Note that Fanella’s "How to determine structural loads—Part 2" begins on page 18. This series will continue with articles on seismic and wind load determination this fall. Look for parts 3 and 4 in the November and December issues of Structural Engineer.
Jennifer Goupil, P.E.

Are the structural upgrade triggers in the IBC and IEBC morally defensible?
In 2003, the International Existing Building Code (IEBC) introduced into national model building codes the concept of requiring structural upgrades when repairs are being performed. These so-called "triggers" force building owners to structurally upgrade their buildings when certain thresholds of damage—based on a "loss of structural capacity"—are reached. Similar triggers based on loss of structural capacity have now been tentatively approved for inclusion into the 2009 International Building Code (IBC), which is the model building code for nearly the entire United States. These new triggers are problematic for a number of reasons, as described below.

Loss of structural capacity—Upgrade triggers in the IEBC (and soon the IBC) are governed by "loss of structural capacity", but no commonly accepted definition of "loss of structural capacity" exists; the term can mean different things to different engineers. Linking upgrade requirements to an undefined term will necessarily increase the likelihood of disagreement between building owners, building officials, engineers, FEMA, and insurance companies; will result in difficulty in determining standard-of-care; and will dramatically increase structural engineering and architectural design fees. According to a recent study by the Structural Engineers Association of Northern California (SEAONC, 2008), triggers based on loss of structural capacity are difficult to implement, are onerous, are essentially unenforceable, are subject to manipulation by engineers to obtain the results they desire, can dramatically delay repair and recovery efforts after a natural disaster, and often make little sense (particularly where the cause of the damage is unrelated to the structural upgrades that are being required).

Economic implications—According to the Handbook to the Uniform Building Code: An Illustrative Commentary (ICBO, 1998), upgrade triggers that add to the cost of maintenance/repairs provide a disincentive to performing maintenance/repairs and have been found to contribute to deterioration and net loss of existing building stock. Furthermore, requiring upgrades in order to repair a building adversely affects building owners, who must fund not only the repair but also the upgrade, which can cost many times the cost of repair-only. The specific seismic upgrade triggers in the IBC and IEBC have not really been tested in a high seismic zone; however, the City of Oakland, California adopted similar "loss of structural capacity" upgrade triggers after the 1989 Loma Prieta earthquake. Although well intentioned, the Oakland upgrade triggers had a number of unanticipated and unintended consequences. In a study of eight large buildings affected by the Oakland Earthquake Ordinance (Searer et al., 2006), engineers were unable to accurately determine "loss of structural capacity" and a majority appeared to manipulate the calculation to reach the answer they or their clients desired; costs to upgrade and repair averaged more than six times the cost of repair-only; multi-year litigation ensued regarding two of the eight buildings; buildings were demolished (including a historic building); and the ordinance contributed to a major economic downturn, where damaged buildings remained in their damaged condition—vacant and unrepaired—for more than a decade.

Lack of rationality—There is also a lack of rationality in the upgrade triggers in the IBC and IEBC. If upgrading were to cost a small percentage of the repair-only scope, upgrading at a time when significant repairs are being performed can make economic sense. However, since there are no cut-offs, rational tests, or economic considerations for the additional upgrade costs, the upgrade triggers can result in wildly disproportionate costs when compared to repair-only, as shown by the five-fold increase in costs observed in the Oakland Ordinance study.

Furthermore, there is no logical cause-and-effect relationship between the damage that triggers upgrading and the required seismic upgrades. These upgrade triggers require seismic upgrades of structures damaged by any and all causes if the substantial structural damage trigger is exceeded in moderate or high seismic zones, but this makes little if any sense. For example, assume that a building is significantly damaged by termites. Is it logical to require a seismic upgrade of the structure to obtain a permit to repair the termite damage? Yet according to the upgrade triggers, there is no consideration of the relationship (or lack thereof) between the cause of the damage and the requirement to seismically strengthen the damaged structure. Given that damage to structures typically results from decay and deterioration, vehicle impact, and fires—and typically not earthquake—and given that other hazards (including fire) kill many more people per year than earthquakes, the preoccupation of these triggers with forcing seismic upgrades is unwarranted.

Seismically nonsensical—Even when considering earthquake hazards, these upgrade triggers fail the logic test: suppose that a large, design-level earthquake (the "big one") occurs in a city. Based on even the most modern design criteria, it is reasonable to expect that large numbers of buildings will experience significant damage and significant "loss of structural capacity" as a result of the earthquake. Yet despite the fact that damaged non-code-conforming buildings may have performed within the expectation of the current code (i.e. structural damage but no collapse), the proposed upgrade triggers would require further potentially massive and costly upgrades beyond the repairs already needed, because the upgrade triggers in the IBC and IEBC do not permit any consideration of the intensity of the earthquake shaking responsible for the damage. Why would any engineer conclude that a city full of buildings that went through a major earthquake but protected life safety should be seismically upgraded? Why would any community want to mandate those upgrades? Why should the federal government, insurance companies, building owners, or taxpayers pay for those upgrades?

Upgrades required without damage—Recent changes to the IEBC go even further, requiring partial upgrades of the seismic- and wind- resisting systems even when no damage has occurred. For example, a recent change approved for the IEBC mandates upgrade of the roof-to-wall connections in rigid-wall-flexible-diaphragm buildings (such as tilt-ups) in high seismic zones be strengthened to meet at least 75 percent of current code when the buildings are reroofed. While the authors concede that older tilt-ups are often vulnerable to significant damage and collapse due to failure of roof-to-wall connections during an earthquake, requiring upgrade of these connections during reroofing simply does not make sense, since roof-to-wall connections in tilt-ups are typically strengthened from below the roof diaphragm. Similarly, the IEBC is now poised to require upgrade of roof-to-wall connections in high wind zones—again as a consequence of reroofing, and which again makes little sense. In this case, upgrades are required even if only slight theoretical overstresses are present in the structural connections and even if the building has performed adequately for decades.

Conclusion—Changes to the 2009 IBC and IEBC that require structural upgrades have already been tentatively approved and are about to be accepted in ICC Final Action Hearings; these changes make little engineering sense, make even less sense economically, and will discourage maintenance and repair of buildings. Is this really the path that the structural engineering community wishes to pursue?

The authors believe that the IBC and the IEBC are being manipulated in a way that will drive up structural engineering consulting fees but will not necessarily benefit society—or pass any rational benefit-cost analysis. If a local jurisdiction wants to mandate strengthening of a particular vulnerable class of buildings, it should do so via a local ordinance and can already do so without the changes that are about to be adopted. Such an ordinance can have a compliance timeline that will give owners time to plan for the cost of upgrading their buildings, and the ordinance can be debated and weighed by all interested parties within that particular jurisdiction, including building owners, tenants, and the public, to ensure that a sound public policy is being implemented. Sneaking upgrade triggers into technical portions of the code is simply not fair to building owners or society in general.

Based on the above, we urge rejection of the numerous upgrade trigger provisions that are being considered at the ICC Final Action Hearings in Minneapolis, in September.
Gary R. Searer and Terrence F. Paret

References
International Conference of Building Officials (ICBO), Handbook to the Uniform Building Code: An Illustrative Commentary, 1998, Whittier, CA.

Searer, G.R., Paret, T.F., Freeman, S.A., and Gilmartin, U.M., "Evaluation of the Effects of Oakland’s Earthquake Damage Repair Ordinance," 8th US Conference on Earthquake Engineering, 2006, San Francisco, CA.

Structural Engineers Association of Northern California (SEAONC), "SEAONC’s SFBC Structural Damage Repair Study Group Report and Recommendations," 2008, http://www.seaonc.org/member/ftp/files/Study%20Group%20Report-WTH.pdf

Correction
In the June issue of Structural Engineer magazine, the Project Spotlight article "A value proposition for bridge projects: Delivering safe, functional infrastructure efficiently and economically," by Craig Finley, P.E., cited an incorrect photo credit for the model of the Miami Intermodal Center on page 32. The photo credit should have been Florida Department of Transportation, MIC Program. We apologize for the error.