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90 The support for most basement walls is probably a condition that falls between Conditions 1 and 2, shown in Figure 11.2. However, by assuming the wall is simply supported, the resulting design will be conservative in that it will accommodate a larger positive moment than if one end were assumed fixed. In order to assume a fixed end for the bottom of the wall, the wall-to-footing connection must be designed to act monolithically. In such cases, a professional engineer should be consulted to consider all factors involved with the particular site and building. Construction of a monolothic wall-to-footing connection is not typical. Another area of concern would be the size of footing needed to resist the large moment created. The design guidelines in this chapter have been developed based on the assumption of sim- ply suppported end reactions. This means that the top and bottom of the wall must have support that resists inward movement. Because the floor structure is what provides that sup- port, it must be continuous between exterior walls. Also, the loading on opposite exterior walls must be approximately the same. If the conditions above are not met, a specialized design must be developed based on all the site and building conditions. For example, if there are large openings or many small openings in the first floor, due to such things as stairs or a split-level concept, there may be very little, if any, lateral support of the top of the basement wall. Another case where such lateral support is missing would be if one side of the house has a walk-out basement. If the other side of the building is acted upon by saturated soil pressure, the wall on the walk-out side could act as if hinged and failure would be imminent without a special design_ Figure 11.3 shows walls with and without adequate support. ",. . ,II ~ "... .'. ~.. ': ADEQUATE LATERAL SUPPORT INADEQJATE LATERAL ~UPPORT ... .. .;.# ." .-. .. ~ INADEQUATE LATERAL SUPPORT WHEN SOIL IS SATURATED, Figure 11.3. Adequate and inadequate lateral support.