By Jim D’Aloisio | November 2021
The tragic collapse of Champlain Towers South in Florida has brought renewed attention to structural building condition reviews. Can they identify critical structural flaws in existing buildings? Can such a review determine if a structure is safe or stable? When should structural condition reviews be performed? These are simple questions, sometimes with not-so-simple answers.
Yes, a structural condition review, if properly executed, can identify conditions of structural concern. But there are limitations, depending on the nature and extent of the review, and the type of structural system. Traditionally, reviews were performed to determine the extent of structural damage, distress, and deterioration. However, confining observations to the identification of such visually evident conditions can miss some potentially serious conditions that may be present. Even worse, the lack of such conditions can lead to false confidence in the overall condition, or stability, of the structure.
A proper condition review begins prior to any field observations, with a review of existing documents. Any existing structural drawings, especially as-builts, as well as any renovation drawings and reports of prior reviews, if any, are useful to inform the structural engineer of critical observations. And the converse is true as well — the lack of availability of structural drawings sends up a flag that can inform and modify the protocol for the condition review.
During the field reconnaissance, in addition to evidence of damage, distress, and deterioration, a senior structural engineer should be on the lookout for unstable or unbraced conditions, irregular or incomplete load paths, or things that just don’t “look right.” Yes, the intuition of an experienced engineer has led to the discovery of serious existing building conditions that were best discovered before the occurrence of an unfortunate incident. One such condition was a long, tall cafetorium wall at a school in the Catskills, where neither the architect nor the structural engineer had considered wind load resistance. The wall exhibited no significant bowing or cracking, but our analysis suggested that it would have been unstable for wind loading in excess of 50 mph. Braced steel wind columns were able to be added without incident, since we realized that something was wrong, visually.
Mathematical analysis may be a part of a structural condition review, although it is not necessary in all cases. The analysis may determine if the elements are overstressed under code-required loading, or it may be a comparative analysis. A comparative analysis compares the original stress levels in the members to the member stresses under the new loading resulting from the proposed modification, for example, snow loading on a newly insulated and/or air sealed roof. By the way, the 2020 NYS Existing Building Code introduces an explicit requirement for such an analysis — a welcome clarification.
For decades now, New York SED’s Office of Facilities Planning has required Building Condition Surveys for all student-occupied buildings every five years. The newly modified plan calls for a rolling schedule, so each year a portion of the school districts must complete the survey. Although not a requirement of the program, it has always been our recommendation that the surveys be conducted by senior structural engineers. In the hundreds of school building reviews that we have performed in recent years, we have identified dozens of structural concerns — some of which have exhibited little or no visual signs of distress.
Vehicular parking garages are structures that should have regular structural reviews, especially because they are exposed to weather and de-icing chemicals that can cause progressive deterioration. The City of Syracuse has had a law in place for more than 20 years that obliges garage owners to perform annual condition reviews and a more extensive triennial condition assessment. This requirement was initiated as a result of the partial collapse of the MONY Towers garage in 1994. More recently, NYS has passed legislation requiring all garages in the state to undergo a review every three years. The impetus for this state law was the sudden collapse of Wilson North Parking Garage in 2015. Ironically, this garage collapsed as a result of a grossly inadequate 1970s design compounded by substandard construction and hidden deterioration that did not visually reveal itself. Based on this incident and experiences with other garages, we have developed a careful protocol for the reviews of parking garages, developed to minimize the potential for problems and increase the level of confidence that the structures are able to provide their intended function.
Bottom line: Buildings and other structures with undiscovered conditions of structural compromise are in our communities. A well-executed structural building condition review can frequently identify them so that they can be addressed before an unfortunate occurrence. Contact us to discuss and develop an appropriate protocol.