Multi-Hazard Mitigation Plan: 17. Shelters

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Chapter 17:Shelters Building A would classify as a Type B hurricane shelter in its existing condition. Essentially, a Type B hurricane shelter is possible because the exterior doors and windows, exterior dormer louvers, and interior doors are all estimated to be capable of providing protection for an ASTM-E-1996 Level A missile. The analysis of the standing seam metal roof indicates that the roof panels are not adequate to resist the wind uplift pressures required for a Type A hurricane shelter. Nonetheless, given that the peak gust wind velocity associated with the capacity of the standing seam metal roof (120-mph) is close at hand with the upper bound peak gust wind velocity required for a Type A hurricane shelter (130-mph), it is recommended that a more in depth analysis be made based on the specific properties of the standing seam metal roof used in Building A. Upon verification that the standing seam metal roof is capable of resisting the wind pressures required for a Type A hurricane shelter, it would be necessary to retrofit the multi-purpose dining hall exterior windows and dormer openings so that an ASTM-E-1996 level C missile protection is provided inconformity with such shelter designation. The interior doors in the multi purpose dining hall would not have to be upgraded to resist an ASTM-E-1996 Level C. While retrofits to the exterior windows and dormer openings in the multi purpose dining hall are required to attain a Type A or better shelter qualification, the main-wind-resisting-system and other secondary structural components are theoretically capable resisting wind loads that correspond to an EHPA type shelter. The analysis of the main-wind-force-resisting-system and secondary structural components suggests that the capacity of Building A to resist hurricane wind loads is most likely governed by the capacity of the steel tapered columns that form part of the interior gable rigid frames. This value of velocity corresponds to a very high Category 4 hurricane and almost borderline Category 5 hurricane. It is important to note that an enclosed condition was not evaluated or considered in the recommendations because in order to prevent pressurization of the interior spaces (including the eave cavity and ceiling plenum) it would be required to seal off all window and vent openings temporarily or permanently. Since Building A is a naturally ventilated building, it would be necessary to condition the interior spaces mechanically— a very costly retrofit. Therefore, prevention of interior pressurization is considered economically impractical. A summary of the retrofits recommended above,based on Shelter Type, is as follows: • All Types: Remove or mitigate the possible debris sources indicated in this report. • Type A Shelter: Upon verification that the standing seam metal roof is adequate for the wind loads required for a Type A Shelter(based on project specific data),provide impact protection for all exterior windows and dormer openings at the multi-purpose dining hall (ASTM-E-1996 Level C Missile or better. 17-9 Hawaii County Multi-Hazard Mitigation Plan