The Need for Revising the Seismic Resistance Requirements for Healthcare Facilities

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Herbert Weaver
6 years ago
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1 The following paper was prepared by Hassan Sughayer, P.E. from Earthquake & Structural Engineering Consultants (ESEC). Hassan is the preferred seismic consultant of D3G and is highly respected by his counterparts within the industry as well as HUD staff who have had the pleasure of working with Hassan. Hassan has over 30 years of experience in the evaluation of buildings for seismic resistance. We asked Hassan to discuss the issues he and his colleagues face when completing a seismic evaluation for a LEAN 232/223(f) project. I have summarized the issues below. Please take the time to read Hassan s paper as he provides technical insight and real concerns facing our industry. Summary: 1. There are no guidelines prescribed by HUD for the rehabilitation of a building in the event the building does not pass HUD s seismic requirements. 2. By removing the Life Safety (LS) evaluation requirements, HUD has increased the seismic resistance requirements, therefore, resulting in a greater number of buildings that will not pass the HUD seismic requirements. 3. There is opposition from HUD staff when the engineers use professional judgment in their evaluations. 4. There are no guidelines prescribed by HUD for the evaluation of ground failure in existing buildings. 5. HUD guidelines are not clearly written and are open for interpretation. Mike Ferguson, P.E. The Need for Revising the Seismic Resistance Requirements for Healthcare Facilities If you have reviewed a PCNA or LEAN report, you are bound to be familiar with the following statement that is included within D3G s reports: According to available information, the subject property is situated within a designated Seismic Zone 3, an area of moderate seismic activity. Consistent with the seismic requirements outlined in Standard and Poor s Property Condition Assessment Criteria for Multifamily Buildings, additional evaluation is warranted for structures which are within a Zone 3 or 4. According to the HUD MAP Guidelines, structures in Seismic Zone 3 or 4 must be capable of resisting ¾ of the seismic forces contained in ASCE/SEI If one looks at the image below of the United States Seismic Map, it is apparent that a LEAN Section 232/223(f) project could very well be located within zones 3 and 4, as sixteen (16) states, the territories of Guam and Puerto Rico, and the Caribbean and Virgin Islands are situated inside these zones. What is disconcerting, though, are the guidelines currently put forth by HUD need to be addressed as they can be misconstrued by seismic consultants. 1

2 Subsection IV.B.3.e of the LEAN Section 232/223(f) describess the Seismic Resistance Requirements as follows: Structures in seismic zones 3 and 4 must meet threee fourths (3/4) of the seismic force level resistance contained inn ASCE 31-02: Seismic Evaluation of Existing Buildings, American Society of Civil Engineers. A seismic hazard analysis of the building(s) must be made by a registered engineer familiar with lateral force design, where applicable code requirements at the timee of construction did not equal or exceed the referenced seismic standards. The evaluation mustt include an examination of the structure for continuity, ductility, and resistance to lateral forces. Structural elements and connections between elements must be strengthened and new elements installed as required, if the existing structure does not provide three fourths (3/4) of the seismic force level resistance required by this paragraph. It appears that Subsection IV.B.3.e was derived from Subsection 5.19D of the MAP Guide with the following changes: 1) Changes in the referenced standards: The referenced standards in Subsection 5.19D of the MAP Guide, which include FEMA 310, FEMA 356, and FEMA 274, weree replaced by ASCE Pleasee note that a document titled ASCE does not exist. Therefore, we assumed that the author was referring to ASCE ASCE is the standard that superseded FEMA 310. Both of these two standards provide guidelines for the seismic evaluation of existing buildings. Therefore, the 2

3 replacement of FEMA 310 by ASCE in the LEAN Section 232/223(f) is appropriate. Please note that ASCE provides guidelines for seismic evaluation only and does not provide guidelines for seismic rehabilitation in the event the buildings do not comply with the LEAN Section 232/223(f) requirements. The FEMA 356 and FEMA 274 standards do provide guidance for seismic rehabilitation. Without adding these two standards or any other equivalent standards, the LEAN Section 232/223(f) requirements are incomplete because there are no guidelines for the rehabilitation of existing buildings that do not comply with Subsection IV.B.3.e. It is recommended that the LEAN 232/223(f) requirements prescribe a standard for the rehabilitation of a building in the event that it does not comply with Subsection IV.B.3.e. Therefore, Earthquake & Structural Engineering Consultants (ESEC) strongly recommend adding standard ASCE to the LEAN Section 232/223(f) requirements. The standard titled ASCE has superseded both FEMA 356 and FEMA 274. Also, note that in the near future ASCE will be superseding both ASCE and ASCE The new ASCE will include requirements for both seismic evaluation and seismic rehabilitation. Therefore, this new document will replace all the documents that are mentioned above. 2) Removing the Life Safety Statement: Item 3 of Subsection 5.19D of the MAP Guide indicates that the objective of the seismic evaluation and rehabilitation is to prevent major failure, collapse, or loss of life due to earthquake forces; however, this requirement was removed from the LEAN Section 232/223(f). According to one HUD reviewer ESEC spoke with, this requirement was removed from the LEAN Section 232/223(f) requirements because the occupants of the buildings are less mobile in the event of an earthquake. Since this requirement is repetitive to what is stated in ASCE 31-03, keeping it or removing it will not impact the evaluation. The evaluating engineer will follow the ASCE requirement and will not consider this HUD life safety statement. Please note that ASCE has two levels of evaluation, the Life Safety (LS) level and the Immediate Occupancy (IO) level. The Life Safety (LS) level of evaluation permits for both structural and nonstructural damage during an earthquake, but does not allow for partial or full structural collapse. Also, the Life Safety (LS) level does not allow for nonstructural damage that may yield a life-threat. The Immediate Occupancy (IO) level of evaluation allows for non-life threatening structural and nonstructural damage that will permit the building to remain occupied after an earthquake, and also the earthquake damage can be repaired while the building is occupied. The Immediate Occupancy (IO) level of evaluation is appropriate for buildings that will be part of the emergency services during an earthquake, such as police stations, fire stations, and hospitals. This level of evaluation is more stringent than that of the Life Safety (LS) level of evaluation. 3

4 Based on this description, we conclude that the selection of the Life Safety (LS) level evaluation is more appropriate for the vast majority of the buildings that are covered by the LEAN Section 232/223(f). However, due to the large diversity in building use and function, the evaluating engineer should use his own judgment when using the Life Safety (LS) level or the Immediate Occupancy (IO) level. Please also note that the vast majority of healthcare buildings, especially older buildings, were most likely designed for Life Safety, not for Immediate Occupancy. Therefore, evaluating these buildings based on the Immediate Occupancy (IO) level may result in numerous buildings not passing the LEAN Section 232/223(f) requirements. Due to the gravity of this issue, serious consideration is strongly recommended. Other issues (related to ASCE and ASCE 41-06): It should be noted that the analytical and rehabilitation guidelines that are provided in ASCE and ASCE are designed to address common building types and building features. There are many unique building types and features that are not addressed or are inadequately addressed in both of these documents as shown in the Section 1.2 commentary on page 1-4 of the ASCE For example, I once evaluated two wood framed buildings that were situated perpendicular to each other and connected by elevated walkways at all floor levels. My evaluation revealed that the connections between the elevated walkways and the buildings were inadequate and the walkways were subject to collapse during a strong earthquake. In this case, the Tier 1 of the ASCE does not require these re-entrant corners to be evaluated since the joint between the walkways and the buildings are considered as re-entrant corners. During the 1994 Northridge Earthquake, I observed a similar building in which the elevated walkways had collapsed. There are also many inconsistencies between the various statements of the Tier 1 checklists in ASCE For example, the Wall Connection statement on Page 3-26 of ASCE requires shear walls to be connected through floors to transfer overturning force while the Hold-Down Anchors statement on Page 3-27 did not require hold-down anchors for life safety. In another example, the Load Path statement on Page 3-25 of ASCE allowed for one complete load path while the Redundancy statement on Page 3-26 requires two lines of shear walls. Please note that due to the above mentioned issues, both ASCE and ASCE encourage engineers to use their own judgment in evaluating buildings. When engineers deviate from the ASCE and ASCE requirements, there is an obligation to report any deviation in their report. However, in some instances engineers face strong opposition from HUD reviewers when the seismic consultant uses their professional judgment. It should be understood that the ASCE and ASCE encourage engineers to use their own professional judgment. In addition, LEAN Section 232/223(f) and Subsection 5.19D of the MAP Guide state the following: Both Structural elements and connections between elements must be strengthened and new elements installed as required, if the existing structure does not 4

5 provide three fourths (3/4) of the seismic force level resistance required by this paragraph. This statement is reasonable if the engineers complied with the code at the time of design. However, our experience indicates that many design engineers do not fully comply with codes. As a result, significant building damage during a strong earthquake may occur. As an example, significant damage was reported in a modern building during the 1994 Northridge Earthquake in Los Angeles. Many of these damages should not have occurred if the engineers complied with the code requirements at the time of design. Therefore, this evaluation statement needs to be thoroughly studied. ASCE and ASCE also do not allow for ground failure associated with fault rupture, soils liquefaction, or seismically induced landslides. However, these two documents do not provide guidelines for appropriate evaluation of ground failure for existing buildings. Therefore, evaluating engineers have no options other than to follow the requirements of the current codes for new buildings. We feel that applying new construction requirements to existing buildings when evaluating for ground failure is too restrictive and beyond the intended requirements of ASCE and ASCE The development of reasonable and safe requirements for ground failure (that will be similar to the reasonable and safe requirements for the structural elements in ASCE and ASCE 41-06) is strongly recommended. Since these standards do not currently exist, the evaluation requirement for ground failure needs to be studied. In conclusion, the LEAN Section 232/223(f) requirements and the Subsection 5.19D of the MAP Guide are not very clearly written and are open for interpretation among engineers. Therefore, major review and revisions are strongly recommended. 5

APPENDIX B: SEISMIC ASSESSMENT GUIDELINES

APPENDIX B: SEISMIC ASSESSMENT GUIDELINES PURPOSE Appendix B The following provide guidance for performing seismic assessments of stationary sources subject to the California Accidental Release Prevention