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91 -~ - 11.4.4 Slab Support Condition The basement floor slab, like the basement wall, is a~sumed to be simply supported at the junction with the wall. In order to accommodate wldt~lS for typical houses. it is assumed that there is a center, longitudinal bearing wall in the bas~ment to which the slab spans for sup- port at mid-house location. --~. ----:-- . p f)' I> p' , , ~ '.' .'. p .,' '- . ...- -',6 PO:. :_. ", ~ '..~', 0. .. ~.' . D ' '. ~.~..p t t .'. " 'r.T: .- '-,1 " . b " ": 'C'>-:~0~' ; (> ',. t .1~J__L , 'b . t!> .. . P D . p' . - 1>. '0,. . ff' '0. SPAN ~ BEARING WALL SPAN WITHOU:~E:!_~~__ WAl_L Figure 11.4. Bearing wall iln~ slab support. This breaks the total width into two shorter spans., Without the bearing wall, practical slab designs would only allow very narrow basements_. Figure 1L5 shows fOLJr different kinds of bearing walls. The curves established for slab de5lg~ conSider three different span Widths. A bearing wall or some other type of structural mid-s~an support. must be incorporated into the design of a basement floor slab is using the guideli~es in this chapter. It is further assumed that the slab edge is tied to the exterior basement fNalls 50 that the connection is not the weakest point of the slab. Soil beneath the slab is assumed to be undrained. In other words, for this location it is not practical or desirable to us'e a surnp pump to keep water away from the basement walls. 11.4.5 Design Control Parameter The design control parameter was chosen so that lhi!, forces causing the loading on the wall can be easily related to the design of the wall. The w~lll design is based on the bending moment created within the wall. The bending rnolTre~t with the wall is due to the external soil and water loading. Chapter VI gives the methodology for determining the equivalent fluid weight (Yeq) that represents the soil and water Ibading condition. In Section 11.6, wall design equations are set up in terms of the working I~)ad equivalent fluid weight (yw). The working load equivalent fluid weight can also be refe(red to as the allowble equivalent fluid weight for any particular wall design. Thus, in the fina,1 analysis the actual equivalent fluid weight yw can be used to select a wall design or the !allowable equivalent fluid weight yO) for a specific wall design is compared with Yeq so that Y~q does not exceed YO), 11.5 Computation of Loadings Two approaches to the design of a basement wall arid slab are possible. The first approach would be a detailed design computing a lateral and uiplitt forces in accordance with Chapter VI and then using the ACI codes referenced for calcu'lation of the bending moment and then design of the wall and slab.