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APPENDIX B DEFINITIONS AND ABBREVIATIONS ~ _ For purposes of this report, the following definitions and abbreviations apply: Active Soil. A soil susceptible to volume changes due to change in moisture content. Deflection Ad. Difference in elevation of high and low points on a slab caused by deformations in the slab, i.e., differential settlement. Deflection Index ~/L). The maximum deflection differential which can be permitted to develop in a slab, divided by the slab length (L or L'). Liquid Limit. The moisture content at which soil passes from a plastic to a liquid state. Load-Bearing Partition. An interior partition which is expected to provide support for loads in addition to its own weight, such as ceiling joists, wall cabinets, bathroom fixtures. Non-Load-Bearing Partition. An interior partition which will not be re- quired to support any load other then its own weight, this not to exceed 500 plf. Plastic Limit. The moisture content at which a soil changes from a sem solid to a plastic state. This condition is said to prevail when the soil contains just enough moisture so that it can be rolled into threads of 1/8-inch diameter without breaking. Plasticity Index. The numerical difference between liquid limit and plastic limit. Soil Movement. The phenomenon of expansion or consolidation of cohesive soils due to change in moisture content. Stiffened Slab. A slab which will not deflect excessively when subjected to the design conditions; such a slab rests on and moves with volume changes in the soil9 and supports the entire structure. Structural Slab. A slab designed to be independent of soil support by having its load supported on piers or piles. 283

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2 84 APPENDICES Symbols used, in addition to those shown above, are as follows: As As = pbSd = Cross-sectional area of bottom reinforcing steel In each stiffening beam of Type III slab. = (pbSd-0.65 in.2) = Cross-sectional area of reinforcing steel placed in addition to reinforcement of surface slab at the top of each stiffening beam of Type III slabs. bs = Width of web of stiffening beam in Type III slab. b = Sum of widths be of all beams running parallel to the dimen sion ~ of Type m slab B = Sum of widths bS of all beams running parallel to the long direction (L) of Type III slab. B ' = Sum of widths bs of all beams running parallel to the short direction (L') of Type III slab. Support index representing quantitatively the degree to which the slab is supported in each of its principal directions. (Soils subject to lesser volume changes because of climate have a higher C factor.) Cm = Increased value of support index C because of special soil- moisture conditions. Cr = Reduced value of support index C because of compressible soils (for qu/w < 7.5~. Cw = Climatic factor representative of the anticipated degree of volume change of soils. C= (/allow E E' kips ksf K1 K2 K3 L L' d = Effective depth of stiffening beams in Type III slab (i.e., distance from center of bottom reinforcing steel to top of slab). Maximum allowable ratio ~/L in a slab. Modulus of elasticity of concrete, i.e., 3(10~6 psi. Effective modulus of elasticity of concrete finder sustained loading, i.e., 1.5(10~6 psi. Ultimate strength of concrete at 28 days (psi). Allowable steel design stress (20,000 psi normally, and 45,000 psi for Welded Wire Fabric to be used in Type II slabs). h = 0ver-all depth of a concrete stiffening beam (d + 3 inches). I = Moment of inertia of a cross section. j = Ratio of internal moment arm to effective depth of a stiffen ing beam (0.865 average value). k = Ratio of the depth of compression zone to the effective depth of a rectangular concrete beam. 1,000 pounds. Rips per square foot. Constant = 2vc = 150 psi. Constant = 8jfS = 2~10~7 psf. Constant = 48E(~/L) = 207~10~8 A/L psf. The longer side of a rectangular slab (ft). The shorter side of a rectangular slab (ft).

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APPENDICES 285 Q = Slab dimension (L or L') along which a Type III slab is analyzed or designed. I' = Slab dimension (L or L') normal to the dimension Q of a Type BI slab. Lw = Liquid limit. M = Bending moment Rips per It or lb per It). MmaX = Maximum value of bending moment (kips per It or lbs per It). n = The ratio of the moduli of elasticity for steel and concrete = 10. PI = Plasticity Index of a soil (dimensionless). p = Steel ratio of a concrete beam (dimensionless) = AS/bSd. pi = Steel ratio (p) as determined from deflection criterion (dimensionless). plf = Pounds per lineal foot. psf = Pounds per square foot. psi = Pounds per square inch. qu = Unconfined compressive strength of an undisturbed cohesive soil as obtained by standard soil testing laboratory method (ts0. t = Thickness of slab. tsf = Tons per square foot. V = Shear force Tipsy. Shear stress. Maximum allowable shear stress in concrete (75 psi). Maximum value of shear force Tipsy. Total dead and live load of slab reduced to uniform load per unit area (psfl. Ws = Total average dead and live superstructure load (psf). Wd = Average dead load of slab (psf). W = Total weight of structure, including slab dead weight and superstructure load Tipsy. w = Effective slab load = Woo (1-C) psf. Z = Steel ratio function = 1/3 ~3) + np~l-k)2 (dimensionless). up = Reduction factor for length of slab equal to 1.4- 0.4 (L/L') (but not < 0.5) when applied to long dimension (L) and equal to unity (1. 0) when applied to short dimension (L '). Vmax = =

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