Meriam, Kraige & Bolton — Distributed Forces: Centroids and Centers of Gravity: Problem 5_177

⚡ Mecademy AIENG정역학 · ch5  Problem Statement The elements of a new method for constructing concrete foundation walls for new houses are shown in the figure. Once the footing is in place, polystyrene forms are erected and a thin concrete mixture is poured between the forms. Ties prevent the forms from separating. After the concrete cures, the forms are left in place for insulation. As a design exercise, make a conservative estimate for the uniform tie spacing if the tension in each tie is not to exceed . The horizontal tie spacing is the same as the vertical spacing. State any assumptions. The density of wet concrete is . Problem 5/177 (a) Determination of the uniform tie spacing ● Assumptions The "thin" wet concrete mixture behaves as a fluid, exerting a hydrostatic pressure distribution , where is the depth from the top surface. Atmospheric pressure acts equally on all external surfaces of the formwork and is therefore neglected. For a conservative estimate, the maximum hydrostatic pressure at the very base of the wall is assumed to act uniformly over the entire tributary area of the most critical (lowest) tie. The tributary area for one tie is a square of side (since horizontal and vertical spacings are equal), giving an area . ● Calculation Process 1. Present Final Formula: To find the minimum required spacing for a conservative design, we equate the maximum allowable tension in a tie to the force exerted by the maximum pressure at the bottom of the wall: FA BT d 6.5 kN 2