47.5 MB - The Whole Building Design Guide

ASCE 7 refers to ASTM E 1996 for missile loads and to ASTM E1886 for the test method to be used to demonstrate compliancewith the E 1996 load criteria. In addition to testing impact resistance,the window unit is subjected to pressure cycling after testmissile impact to evaluate whether the window can still resistwind loads. If wind-borne debris glazing protection is providedby shutters, the glazing is still required by ASCE 7 to meet thepositive and negative design air pressures.Although the ASCE 7 wind-borne debris provisions only applyto glazing within a portion of hurricane-prone regions, it is recommendedthat all critical facilities located where the basicwind speed is 100 mph or greater comply with the followingrecommendations:m To minimize the potential for missiles penetrating exteriorglazing and injuring people, it is recommended that exteriorglazing up to 60 feet above grade be designed to resist thetest Missile E load specified in ASTM E 1996 (see text boxin Section 3.4.3.1). In addition, if roofs with aggregatesurfacing are present within 1,500 feet of the facility, glazingabove 60 feet should be designed to resist the test Missile Aload specified in ASTM E 1996. The height of the protectedglazing should extend a minimum of 30 feet above theaggregate surfaced roof per ASCE 7.Because large missiles are generally flying at lowerelevations, glazing that is more than 60 feet above grade andmeets the test Missile A load should be sufficient. However,if the facility is within a few hundred feet of anotherbuilding that may create debris such as EIFS, tiles, or rooftopequipment, it is recommended that the test Missile E load bespecified instead of the Missile A for the upper-level glazing.m For those facilities where glazing resistant to bomb blastsis desired, the windows and glazed doors can be designedto accommodate wind pressure, missile loads, and blastpressure. However, the window and door units need to betested for missile loads and cyclic air pressure, as well as forblast. A unit that meets blast criteria will not necessarily meetthe E 1996 and E 1886 criteria, and vice versa.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-105