47.5 MB - The Whole Building Design Guide

funds are not available for strengthening orreplacement, it is important to minimize therisk of injury and death by evacuating areasadjacent to weak non-load-bearing walls,weak glass curtain walls, and areas belowlong-span roof structures when winds above60 mph are forecast.As a result of building code changes andheightened awareness, some of the commonbuilding vulnerabilities have generally beeneliminated for facilities constructed in themid-1990s or later. Components that typicallyremain vulnerable to high winds are thebuilding envelope and exterior-mounted mechanical,electrical, and communicationsequipment. Many failures can be averted byidentifying weaknesses and correcting them.Critical facilities sometimes occupybuildings that have changed their originaluse (see the case of Hancock County EOC,discussed in Section 4.4). Buildings thatwere not designed for a critical occupancywere likely designed with a 1.0 ratherthan a 1.15 importance factor, and henceare not as wind-resistant as needed. Itis particularly important to perform avulnerability assessment if a facilityis located in a building not originallydesigned for a critical occupancy,especially if the facility is located in ahurricane- or tornado-prone region.By performing a vulnerability assessment, items that need to bestrengthened or replaced can be identified and prioritized. A proactiveapproach in mitigating weaknesses can save significant sumsof money and decrease disruption or total breakdown in criticalfacility operations after a storm. For example,a vulnerability assessment on a school such asthat shown in Figure 3-105 can identify weaknessof exterior classroom walls. Replacingwalls before a hurricane is much cheaperthan replacing the walls and repairing consequentialdamages after a storm, and proactivework avoids the loss of use while repairs aremade.A comprehensive guide for remedial workon existing facilities is beyond the scope ofthis manual. However, the following are examplesof mitigation measures that are oftenapplicable.Before beginning remedial work, it isnecessary to understand all significantaspects of the vulnerability of a facilitywith respect to wind and wind-driven rain.If funds are not available to correct allidentified deficiencies, the work should besystematically prioritized so that the itemsof greatest need are first corrected. Forexample, at a building such as that shownin Figure 3-105, had the windows beenretrofitted with shutters, that effort wouldhave been ineffective, because the wallsthemselves collapsed. Mitigation effortscan be very ineffective if they do notaddress all items that are likely to fail.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-133