SECTION 721 CALCULATED FIRE RESISTANCE

721.3.1 Equivalent thickness. The equivalent thickness of concrete masonry construction shall be determined in accordance with the provisions of this section.

721.3.1.1 Concrete masonry unit plus finishes. The equivalent thickness of concrete masonry assemblies, Tea> shall be computed as the sum of the equivalent thick­ness of the concrete masonry unit, T" as determined by Section 721.3.1.2, 721.3.1.3, or 721.3.1.4, plus the equivalent thickness of finishes, Tel' determined in accordance with Section 721.3.2:

     (Equation 7-6)

T, = Vn/LH = Equivalent thickness of concrete masonry unit (inch) (mm).

 

where:

Vn = Net volume of masonry unit (inch3) (rnm3).

L = Specified length of masonry unit (inch) (mm).

H = Specified height of masonry unit (inch) (mm).

 

721.3.1.2 Ungrouted or partially grouted construction. T, shall be the value obtained for the concrete masonry unit determined in accordance with ASTM C 140.

 

721.3.1.3 Solid grouted construction. The equivalent thickness, Te, of solid grouted concrete masonry units is the actual thickness of the unit.

721.3.1.4 Airspaces and cells filled with loose-fill material. The equivalent thickness of completely filled hollow concrete masonry is the actual thickness of the unit when loose-fill materials are: sand, pea gravel, crushed stone, or slag that meet ASTM C 33 requirements; pumice, scoria, expanded shale, expanded clay, expanded slate, expanded slag, expanded fly ash, or cin­ders that comply with ASTM C 331; or perlite or vermiculite meeting the requirements of ASTM C 549 and ASTM C 516, respectively.

All Rights Reserved. This 2006 International Building Code® is a copyrighted work owned by the International Code Council, Inc. Without advance written permission from the copyright owner, no part of this book may be reproduced, distributed, or transmitted in any form or by any means, including, without limitation, electronic, optical or mechanical means (by way of example and not limitation, photocopying, or recording by or in an information storage retrieval system). For information on permission to copy material exceeding fair use, please contact: Publications, 4051West Flossmoor Road, Country Club Hills, IL 60478-5795. Phone 1-888-ICC-SAFE (422-7233). Trademarks: “International Code Council,” the “International Code Council” logo and the “International Building Code” are trademarks of the International Code Council, Inc.