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Properties Of Wall Assemblies Fire Protection Data, Sound Data, And Energy Data For Masonry Walls
1) Fire Protection Data
2) Sound Data
3) Energy Data
4) Data Tables
1. Fire Protection Data
A fire wall is a fire-resistive barrier which will prevent the passage of fire from either side to the other side under the most adverse conditions. Cutoff walls of less fire resistance have often been called fire walls and there is, consequently, much misunderstanding about the broad subject of fire subdivision.
Automatic sprinklers are basic protection for the continuity of production. Damage and lost time from a fire is seldom very great if sprinklers are functioning properly. However, something could go wrong. Most catastrophic fires result from (1) either entire lack of sprinklers or incomplete sprinkler protection, or (2) the sprinklers being prevented from functioning as intended. A failure of the human element or an accident usually prevent proper functioning of sprinklers.
For instance, a sprinkler valve may have been closed to make repairs or to extend a sprinkler system and, due to faulty valve supervision, left closed and forgotten; or a valve may have been closed too soon before the fire was out. A fire may occur after a plant's fire-protection system has been partly damaged in an explosion, wind storm or flood. Then damage can be heavy. It is a time to save as much as possible. That is the real function of the fire wall -- to stop the fire -- a defense against catastrophe.
The resistance of masonry walls to fire has been evident for a long time. Their value in defense against fire was recognized more recently as manufacturing plants grew from simple structures into huge connected complexes. Plant owners came to realize that they could not afford to lose their entire production unit. Replacement of buildings and machinery was a time-consuming process. Part of the answer were barriers to prevent the passage of fire. Fire experience has proven the value of this conclusion.
Despite disaster on one side, this masonry wall
remained in place to protect the balance of the plant.
When a plant establishes parallel production facilities at widely separated locations, it effectively safeguards a part of the production from a fire catastrophe or other disaster. When it is more desirable to have many important operations under one roof, fire walls serve much the same purpose as separation by distance. Fire walls are solid barriers against fire, a last ditch defense, when all other protection fails.
Fire walls can help greatly to shorten the interruption of production resulting from a serious fire. Saving part of the plant usually allows prompt resumption of at least partial production, and in any case reduces the amount of rebuilding necessary. A plant which cannot continue to supply its customers is in a very unfavorable position. Its business will go to competitors and is not easily regained.
ANSI/NFPA 101 Standard (Life Safety Code) recognizes an urgent need to compartmentise such buildings having educational, health care, detention, apartment etc. occupancies, by requiring fire and smoke barriers. See Section 6.2 and Section.6.3 of the Life Safety Code and UBC for fire rating requirements.
1.1 Fire resistance ratings of CMU assemblies.
Fire-resistance ratings of concrete masonry walls are based on fire tests made at Underwriters' Laboratories, Inc., National Bureau of Standards, Portland Cement Association, and other recognized laboratories. Methods of test are described in ASTM E119 "Standard Method of Fire Tests of Building Construction & Materials." The test consists of exposing one side of a wall to a fire of controlled intensity for a time equal to or greater than its rated fire-resistance time. Immediately, the hot face of the wall is subject to a fire hose stream. Bearing walls also carry a load equal to 80 psi based on gross wall area. The wall must withstand the fire test without passage of flame or gases. Heat transmission must be limited to less than 250F gain in temperature.
Since testing every conceivable design possibility of concrete walls is unfeasible, rational methods of estimating fire-resistance ratings have been developed. These are discussed here.
The fire resistance ratings of most concrete masonry walls are determined by heat transmission measured by temperature rise on the cold side. Few walls fail due to load during the fire test or during cooling under the fire hose. Fire endurance can be calculated as a function of the aggregate type used in the block unit, and the solid thickness of the wall, or the equivalent solid thickness of the wall when working with hollow units. Results of research relating fire resistance in hours to the equivalent thickness of hollow concrete masonry of various aggregate types is shown below.
Equivalent thickness of hollow units is calculated from actual thickness and the percentage of solid materials. Both needed items of information are normally reported by the testing laboratory using standard ASTM procedures, such as, ASTM C140 "Methods of sampling and testing concrete masonry units." When walls are plastered or otherwise faced with fire- resistant materials, the thickness of these materials is included in calculating the equivalent thickness effective for fire resistance.
Estimated fire resistance ratings are for fully protected construction in which all structural members are of incombustible materials. Where combustible members are framed into walls, equivalent solid thickness protecting each such member should be not less than 93 percent of the thicknesses shown. Plaster is effective in increasing fire resistance when combustible members are framed in a concrete masonry wall if it is applied on the fireside of the wall, opposite the combustible member. Fire resistance of hollow unit concrete masonry walls can be increased also by filling core spaces with various fire resistant materials.
1.2. Clay and CMU walls are classified In Table 43.B (UBC) as follows.
"Reproduced from the Uniform Building Code, with permission of the publisher, the International Conference of Building Officials."
TABLE NO 43-B
and Notes to Table 43B
The NW Masonry Guide Table of Contents
Masonry Institute of Washington
Washington State Conference of Mason Contractors
