Retaining walls; their design and construction . members, termedloosely, counterforts. See Fig. 46. These serve a function similar to that performed by the gussetplate on a through girder, an-choring the wall and base slabto each other. This combination of counter-fort, wall and footing, forms astructure quite difficult toanalyze exactly and, generally,no such exact analysis is at-tempted. The usual modes oftreating the wall and base slabsof the counterfort wall are as Fig. 46.—Stresses in !i rouutor- c ^^ fortedwall. follows: (a) The wall and the footingslabs are treated as composed of a seri
Retaining walls; their design and construction . members, termedloosely, counterforts. See Fig. 46. These serve a function similar to that performed by the gussetplate on a through girder, an-choring the wall and base slabto each other. This combination of counter-fort, wall and footing, forms astructure quite difficult toanalyze exactly and, generally,no such exact analysis is at-tempted. The usual modes oftreating the wall and base slabsof the counterfort wall are as Fig. 46.—Stresses in !i rouutor- c ^^ fortedwall. follows: (a) The wall and the footingslabs are treated as composed of a series of independentlongitudinal strips, freely supported at the ends, , at thecounterforts. The bending moment is then WL/S. W is thetotal weight acting upon the strip in question. (6) The wall and footing arc treated in strips as above, but thesupports are taken as fixed at the counterforts. Although, ex-actly speaking, for this condition, the moment at the support isWL/12, and that at the center of the beam is WL/24, the moment Jx(i+Cx)g. REINFORCED CONCRETE WALLS 97 is assumed alike at the center and at the support and of valueWL/12. Method (b) is the one generally used in the design of the slabsforming the counterfort wall and will be used in the present text. The design of the counterfort itself is a matter of much con-troversy and practice is far from uniform here.^ It may be takenas a tension brace, simply anchoring, by means of the rods con-tained in it, the base slab and the wall slab to each other, theconcrete merely acting as a protection to the steel; as a cantileverbeam, anchored at the base and receiving its load from the wallslab, or as the stem of a T beam. In the following work thecounterfort will be treated as a cantilever beam. Prof. Cain hasmade an exact analysis of a beam of this wedge shape (see hisEarth Pressures, etc.) but the theory of retaining walls and ofearth pressures does not seem to justify such refinements ofdesign. Not only are all of the m
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