Document zzLBe8KO8KdKN4o7G0JxL9wkR

24I Ida 14 A 1820 22 24 M ^M HEIGHT OF WALL IN FEET ww-m WS =5 2 2 S - - -- <*N M g N MM* w A #| p * I* ** 4 4 4 4 4 4 4 4 * NUMBER OF 6" COURSES M M 40 ** FiC 17-4 --Wind velocities that can be withstood by concrete block walls of varying height Courtesy The Travelers Insurance Companies Extenor masonry walls, especially of either load-bearing or nonload-bearing type what ever their height, are subject to wind loads be yond their designed capacity pnor to the final set of the mortar or final tie into the structure These wind loads have caused walls or sec tions of walls to break offand fall, causing both personal injury (sometimes fatal) and property damage Masonry walls should follow the erection of permanently installed structural members so that adequate lateral stability is provided If this is impossible or impractical, temporary bracing should be placed until structural members can be installed Usually the architect will include in his de sign pilasters as well as the requirements for anchors and ties Also local building codes require that during erection ofwalls the proper bracing and supporting shall be provided The question is, what is proper During construction of extenor masonry, two external forces should be considered --the weight (vertical) and the wind load (horizon tal) Because the vertical load is supported by spandrels and relieving angles, the cntical consideration is the honzontal load Pro tection or bracing for this load must be pro vided either by screening or by simple shoring Codes and other engineering data indicate the thickness and height of walls which will withstand specific wind loads while unsup ported These specifications should be checked against the local wind conditions and bracing provided when required (See R W Armstrong citation m "References ") The National Building Code (1967 Edition) requires the following Dunng erection masonry walls shall not be built higher than 10 times their thickness unless ade quately braced or until provision is made for the prompt installation of permanent bracing at the floor or roof level immediately above the story under con struction 431