Document RaBdq1yrq1zX7Qvq4eEBw5b3k

BUILDING CONSTRUCTION AND MAINTENANCE A=cross-secbonal area of Umber in square inches L=unbraced length of Umber in inches D=least cross-sectional dimension of timber m inches Shores or braces should be set at an angle not greater than 30 degrees from the hori zontal For excavations more than 16 ft deep or where heavy lateral pressures are encountered, interlocking steel sheet piling is recommended Ladders Construction of all ladders should con form to the provisions of state and local ordinances, if any, and the applicable ladder safety code Special-use climbing equip ment, such as the combination stepladderwork platform shown in Fig 15-8, also should be constructed to comply with the applicable codes. Ladder materials Wood for ladder construction should be straight-grained, thoroughly seasoned, free from large checks, shakes, decay, or inpinous knots Detailed requirements are listed in the wood ladder code This code estab lishes minimum requirements for ladder construction, but indicates that certain con ditions of use may necessitate somewhat more substantial construction Metal lad ders should be of adequate strength and rigidity also There is no standard yet de veloped for glass fiber ladders, so the pro visions of American Standard A142, Metal Ladders, should be applied Some provisions from the code for wood ladders are as follows (1) Side rails may be constructed of West Coast hemlock. Eastern spruce, Sitka spruce, or other woods in sizes that give equivalent strength Wood side rails should be dressed on all sides and should be free from sharp edges and splinters (2) Each step, whether a rung, tread, or cleat, should conform to the minimum di mensions and specifications given m the code (3) Wood rungs should be constructed of white ash or equivalent hardwood Neither Douglas fir nor Southern yellow pine should be used for rungs (4) Wood treads should be constructed of spruce or equivalent as indicated in the wood ladder code (8) Metal parts or fittings should be of steel, wrought iron, malleable cast iron, or equivalent metal adequate in strength lor the purpose intended and should be proper ly coated and protected so as to be rust resistant Types of ladders Smgle ladders should not be over 30 ft long Portable single ladders should be built with spread side rails, with the width Fig 15-6. Combinotion steplodder-work plotform equipped with costers for eosy moving. Front costers ore spring-loaded to ollow rubber feet to bo depressed to floor and hold device in place when mounted by worker --------"American Standards Association, 10 East 40th St, New York City, Safety Code for Portable Wood Ladders, A141; Safety Code for Portable Metal Ladders, A14 2, and Safety Code for Paced Ladders, A14 3. 15-13